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Observations and Forecasts from the Landfall of Tropical Cyclones John, Lane, and Paul (2006) over Northwestern Mexico

LUIS M. FARFA´ N Unidad La Paz, Centro de Investigacioń Cientı´fica y de Educacioń Superior de Ensenada, B.C., La Paz, Baja California Sur, Mexico

ROSARIO ROMERO-CENTENO AND G. B. RAGA Centro de Ciencias de la Atmo´sfera, Universidad Nacional Auto´noma de Me´xico, Mexico City, Mexico

(Manuscript received 22 September 2011, in ﬁnal form 4 June 2012)

ABSTRACT

This study focuses on track and intensity changes of three tropical cyclones that, during the season of 2006, developed in the eastern North Pacific basin and made landfall over northwestern Mexico. Observational datasets, including satellite and radar imagery and a rain gauge network, are used to document regional- scale structures. Additionally, gridded fields are applied to determine the large-scale environment. John made landfall as a category-2 hurricane on the Saffir–Simpson scale and moved along the Baja California Peninsula during more than 40 h, resulting in total rainfall of up to 506 mm. The largest accumulations were located over mountains and set new records with respect to daily rates from the 1969–2005 period. Later in the season, Lane and Paul made landfall over the mainland and brought moderate rainfall over the coastal plains. Lane became a category-3 hurricane and was the third strongest hurricane to make landfall since 1969. In contrast, Paul followed a recurving track to reach the coastline as a weakening tropical depression. Strong wind shear, associated with a midlatitude trough, is found to be related to the intensity change. Examination of the official forecasts reveals that first inland positions were predicted several days before the actual landfall events. An assessment of the forecasts issued 1–3 days prior to landfall shows large track errors associated with some of the above tropical cyclones and this resulted in a westward bias. It is suggested that the track errors are due to an inadequate representation of the large-scale environment that steered the tropical cyclones.

1. Introduction conditions in the southwestern United States (Smith 1986; Garza 1999). The west coast of North America routinely experiences Northwestern Mexico is defined as the geographical landfalling tropical cyclones (TCs) from the eastern North region located north of 208N and west of 1048W (Fig. 1), Pacific basin, located east of 1408W. During recent including Nayarit, Sinaloa, and Sonora on the mainland decades, several studies have focused on TCs that made as well as the Baja California Peninsula. In 2005, Mexico landfall over the coastal areas of Mexico. Serra (1971) had 103 million inhabitants and 10% of them lived in the analyzed track information from the period 1921–69 northwest (INEGI 2011b). Table 1 provides the top five to document that TCs crossing onshore had maximum communities in Sinaloa and Baja California Sur (BCS, frequency from August through October. Jaúregui south of 288N) and their geographical locations are (2003) found that, between 1951 and 2000, 54% of the shown in Fig. 1. Sinaloa had a population over 2.5 mil- basin landfalls occurred over the northwest coast of 2 lion and the highest density (45 inhabitants km 2) while the country. Some of these TCs continued moving BCS had both the lowest population and density (7 in- northward and, eventually, they influenced the weather 2 habitants km 2) in the region. Therefore, upon TC landfall, major differences should be expected between Corresponding author address: Luis M. Farfań, CICESE, Unidad the impacts upon the population from mainland tracks La Paz, Miraflores 334, La Paz, Baja California Sur 23050, Mexico. and from tracks moving across the peninsula. Since BCS E-mail: [email protected] has coastlines along both the Pacific Ocean and the Gulf

DOI: 10.1175/WAF-D-11-00108.1

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FIG. 1. Geographical area of northwestern Mexico and topographic contours (m, shaded) given in the vertical bar. Specific locations mentioned throughout the text are the states of Baja California Sur (BCS), Sinaloa (SIN), Nayarit (NAY), and Sonora (SON). Circled letters are the five largest communities in BCS and SIN, as shown in Table 1. Dots represent landfall positions from tropical cyclones during the period 1969–2006. The dashed box outlines the area shown in Fig. 10. of California, this makes it highly susceptible to TC im- season of 2006. This includes three landfall events and pacts from the surrounding seas. our specific objectives are the following: During the 2006 season in the eastern North Pacific, d to discuss track and structure changes that occurred from 27 May until 20 November, 18 named TCs de- during landfall; this discussion is based on satellite and veloped and 10 of them reached hurricane strength. radar observations as well as on upper-air soundings These numbers are slightly above the 1971–2005 average and gridded data; estimated by Arnt et al. (2010). In 2006, two hurricanes d to determine the associated rainfall patterns from a made landfall in northwestern Mexico. Strong winds and regional network operated by the Servicio Meteorolo´gico heavy rainfall affected coastal communities by causing extensive property damage and nine deaths (Pasch et al.

2009). Later in the season, Paul arrived as a weakening TABLE 1. Population (inhabitants) from Baja California Sur tropical depression and this event was associated with and Sinaloa, Mexico and the five largest cities per state. The city four deaths. Comprehensive information on the TC evo- identification (CI) is used to show the corresponding geographical lution is provided by the U.S. National Hurricane Center location in Fig. 1. (NHC), through the corresponding reports and season CI State/city CI State/city summary (Pasch et al. 2009). However, our study strives Baja California Sur (512 170) Sinaloa (2 608 442) for a more detailed discussion of TC evolution prior to A La Paz (189 176) A Culiacań (605 304) and at landfall with emphasis on the impact over popu- B Cabo San Lucas (56 811) B Mazatlań (352 471) lated areas. C San Jose´ del Cabo (48 518) C Los Mochis (231, 977) The present study focuses on TC impact over Baja D Ciudad Constitucio´ n (37 221) D Guasave (66 793) ´ California and the mainland during the relatively active E Loreto (10 283) E Guamuchil (61 862)

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Nacional (SMN) of Mexico; a comparison is made over the global basins (e.g., Jiang and Zipser 2010). Radar with respect to records from other events during the imagery from stations in BCS and Sinaloa is used to doc- period 1969–2005; and ument the reflectivity and rain rate, respectively. These d to assess the ability of official forecasts, issued by NHC radars are operated by SMN and they were extremely from 1–3 days before landfall, in the prediction of the useful for TC monitoring during the season of 2006 (Pasch actual track and intensity; an extended survey, cover- et al. 2009). To determine spatial coverage and intensity ing the seasons from 1988 through 2009, was also patterns of selected precipitation episodes, a ground-based performed. network of rain gauges is used. The network records are available as 24-h accumulations and are archived by SMN. This paper is divided into six sections. Section 2 de- To set a climatological reference, records from the period scribes observational sources used to document TC evo- 1969–2005 are examined and they are compared against lution. A climatological perspective and individual case those from the landfalls in 2006. studies are described in section 3 while official forecast The three-dimensional structure of the flow is derived performance is discussed in section 4. Finally, a discussion from gridded reanalyses issued by the National Centers is presented in section 5 while section 6 provides a sum- for Environmental Prediction–National Center for Atmo- mary and our conclusions. spheric Research (NCEP–NCAR; Kalnay et al. 1996) and analyses from the Global Forecast System (GFS). They are used to resolve large-scale circulation patterns and 2. Methodology and datasets provide a reasonable representation of the environment Tropical cyclone position and intensity are taken from surrounding the TCs. Isobaric plots and vertical cross the (NHC) best-track database while the development sections are constructed to identify relevant circulations of convective features and moisture patterns are derived through the atmosphere. Upper-air soundings, from SMN from satellite imagery. During the last few decades, sat- and the National Oceanic and Atmospheric Administra- ellite surveillance has become an important source of ob- tion (NOAA), are examined to identify relevant charac- servations and, in many cases, is the only available method teristics in the environment over Mexico and the United for estimating TC structure, motion, and intensity (Velden States. et al. 2003). Digital imagery from the Geostationary Operational Environmental Satellite-11 (GOES-11) infrared and 3. Results water vapor channels is provided by the Space Science a. Climatological overview and Engineering Center at the University of Wisconsin— Madison. The imagery is available at 30-min intervals and Examination of records from the eastern North Pacific is used to determine cloud-cover structures and moisture reveals the development of 579 named TCs during the patterns. Infrared images have 4-km resolution and they period 1969–2006 and, approximately, 10% of them supply a measure of cloud-top temperature with the made landfall in northwestern Mexico. The majority of coldest (highest) tops associated with deep convection. these landfalls were along the coasts of BCS and Sinaloa The water vapor imagery (8-km resolution) is useful for with almost equal numbers of strikes per state. Figure 2 monitoring changes in the moisture patterns during the displays the tracks that were identified to make first evolution of mid- to upper-level systems such as troughs, landfall over either the peninsula or the mainland. In- ridges, and cutoff circulation patterns (Dvorak and Mogil serts show the temporal frequency of incidence that was 1994). In addition, a set of animations is available online determined by dividing each month into three periods of (http://met-bcs.cicese.mx/2006) in which the infrared im- 10 or 11 days. ages cover 3-day periods while the water vapor images Figure 2a shows 28 tracks that first moved over Baja display the whole TC life cycles. California. Incoming systems approached the peninsula To identify the extent of accumulated TC rainfall over from the south and almost 90% of them occurred from late sea and land, data from the Tropical Rainfall Measuring August through early October. Thirteen tracks had a sec- Mission (TRMM) are used. The data are from product ond strike, either over the northern peninsula or the 3B42 version 6, which derives precipitation estimates mainland. During the same period, 27 TCs tracked only from various satellite systems and, when possible, from over the mainland (Fig. 2b). This group developed later in rain gauge data over land (Huffman et al. 2007). The the season, with the highest frequencies occurring in the gridded output has spatial resolution of 0.25830.258. last third of September and most of October. The tracks This product provides good coverage over the tropics and are similar to distinct groups identified by Romero-Vadillo has proven to be useful in determining TC contributions et al. (2007; see their Fig. 9) and by Ritchie et al. (2011;

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FIG. 2. Tracks of tropical cyclones that made first landfall over the (a) Baja California Peninsula and (b) the mainland. Tracks are derived from the 1969–2005 seasons and thick lines are tropical cyclones from 2006. The large dot represents Isla Socorro. Temporal frequency (percentage) of landfall strikes is shown in upper-right inserts. The lower-left lists provide the 2 five strongest hurricanes at landfall: name, year, and maximum winds in m s 1 (Saffir–Simpson- scale category). Small dots are initial locations of the strongest tropical cyclones. their groups 1 and 2) for late season tracks affecting the A relatively large set of mainland TCs moved across northwest. The change in direction from northwest the state of Sinaloa, and Fig. 1 shows distinct clusters through north to northeast, into the midlatitude westerlies, around Mazatlań (site B) and Los Mochis (site C). This is known as recurvature (e.g., Dobos and Elsberry 1993). result agrees with findings from Blake et al. (2009) of

Unauthenticated | Downloaded 10/02/21 03:28 AM UTC DECEMBER 2012 F A R F A´ NETAL. 1377 a significant concentration of hurricane-strength landfalls along Sinaloa. Further investigation suggests that, when compared with peninsular hits, stronger TCs tend to make landfall over the mainland. This is likely due, in part, to warmer sea surface temperature in the Gulf of California with respect to the cooler California Current in the Pacific. Information on relatively strong TCs at landfall is shown in the lower-left inserts of Fig. 2. Four out of 12 hurricanes were classified as major (category 3 or stronger on the Saffir–Simpson scale) hurricanes while moving across the mainland. In contrast, only one of 10 hurricanes crossed the peninsula with category-3 strength. Farfań (2004) examined general features of the large- scale environment associated with a sample of six TCs that made landfall over Baja California. The author found that the mean 500-hPa flow showed a midlatitude trough traveling eastward across the western United States and an anticyclonic circulation was located over the Gulf of Mexico. A similar analysis was performed for the landing tracks during the period 1969–2005. Figure 3a shows that when landfall occurs over the peninsula, there is a weak trough within 1108–1308W, the flow over western Mexico is from the south, and, in agreement with the steering concept, there is northward TC motion. In contrast, during mainland landfall, there isamoreintensetroughandnortheastwardmotion (Fig. 3b). As in Ritchie et al. (2011), the 584-dm contour is chosen as a practical aid to demarcate the base of a midlevel trough and is located close to 208N. This is accompanied by a distinct region of large wind shear 21 (.20 m s ) northwest of the anticyclone. Examination FIG. 3. Mean geopotential heights (dm) at the 500-hPa level from of composites 24 and 48 h prior to landfall indicates the NCEP–NCAR reanalysis and selected cases from Fig. 2. eastward propagation of the trough. These facts are Tropical cyclones, at time of landfall, over the Baja California Peninsula and the mainland from 1969–2005 are considered. consistent with results discussed by Corbosiero et al. Contour interval is 10 dm and the 584-m contour is thicker. Light 2 2 2 (2009) on the large-scale environment that steered TCs (10–20 m s 1), medium (20–30 m s 1), and dark ($30 m s 1) affecting the southwestern United States. shadings represent 850–200-hPa wind shear. The dotted line rep- 2 resents the 5 m s 1 wind shear. The black dots are mean positions b. The season of 2006 of TCs, from the best tracks at 12, 24, and 48 h prior to landfall as well as 12 and 24 h after the strike. Mean landfall locations are Tracks of TCs that made landfall over northwestern represented by asterisks. Mexico are shown in Fig. 4. The tropical depression, which eventually became Hurricane John, was first detected near the Gulf of Tehuantepec. John moved par- is likely due to the passage over the Sierra Madre Oc- allel to the coast and experienced slow weakening over cidental. Finally, similar to the cases in Fig. 2b, Paul BCS. This is related to lower terrain elevations, the re- followed a recurving track just west of Isla Socorro and duced width of the peninsular mountains, and the mar- quick dissipation occurred during landfall. ginal presence of the relatively warm Gulf of California 1) SYNOPTIC-SCALE CIRCULATIONS at the right side of the low-level circulation. Later, Lane was associated with a relatively short track during its life Figure 5 displays the GFS analyses at landfall. The cycle and moved over the southern gulf to cross the fields shown in Fig. 5a indicate that, during John’s ar- mainland in Sinaloa. As soon as Lane made landfall, the rival, the large-scale flow was controlled by a midlevel 2 intensity decreased from category-3 strength (57 m s 1) anticyclone over the U.S.–Mexico border. The anticy- 2 to become a tropical storm (18 m s 1) in only 12 h. This clone’s southern edge provided steering flow from the

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FIG. 4. Tracks of 2006 TCs John (28 Aug–4 Sep), Lane (13–17 Sep), and Paul (21–26 Oct). Positions are marked every 6 h, and numbers are dates of fixes at 0000 UTC with initial and final positions represented by storm name and the first letter of the name in lowercase letters, respectively. Location of maximum intensity (MAX) and recurvature initiation (REC) are 2 indicated. Inserts show sustained wind speed (m s 1), maximum intensity, and time of 2 landfall (vertical line). Dashed lines are the tropical storm (17 m s 1) and hurricane 2 (33 m s 1) intensity thresholds. southeast, which is consistent with TC displacement (geopotential height . 590 dm) over the Gulf of Mexico toward Baja California. The wind shear was relatively that is associated with southerly flow over central Mexico. 2 low, in the range of 5–10 m s 1; therefore, the environ- Figure 5c is useful in determining that Paul’s weakening ment was favorable for TC intensification (e.g., Kaplan trend was due, in part, to the presence of an unfavor- et al. 2010). The corresponding precipitable water field able environment including large wind shear, along (not shown) depicts a maximum around John and a sec- with a midlatitude system off Baja California, north of ondary moisture concentration that is located to the west, the TC center. This system is accompanied by north- associated with the development of another TC (Kristy). eastward, humid flow from the equatorial Pacific into With the 584-dm contour about 2000 km to the northwest western Mexico. of the landfall suggests no direct influence on John from More information on the three-dimensional structure the midlatitude environment. Note that, simultaneously, of the environment, during the landfall of the three case an Atlantic system (Ernesto) was developing over the studies, is determined from a set of vertical cross sections eastern United States. constructed over the Gulf of California and southern In contrast to the above setting, during Lane’s landfall California. The examination was also performed during (Fig. 5b) the 584-dm contour is closer to the TC, there is TC approach (24 and 48 h prior to landfall), although, for moderate shear over northern Mexico, and these features the sake of brevity, the corresponding figures are not are associated with the passage of a midlatitude trough. shown. For the environment associated with Lane and Additionally, there is a relatively strong anticyclone Paul, the cross sections depicted northward advection of

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humid air below the 700-hPa level and trough passage with strong westerly winds at upper levels. The cross sections capture well-deﬁned jets within the 400–100-hPa layer, along with a signiﬁcant decrease in low-level humidity over southern California, after the trough passage. These structures are consistent with the lack of cloud cover and rainfall over the northern gulf, a subject to be discussed below.

2) SATELLITE AND RADAR IMAGERY At landfall, infrared imagery from John (Fig. 6a) and Lane (Fig. 6b) shows well-defined areas of high cloud tops around the circulation centers and minimum temperatures below 2608C. The corresponding water vapor imagery (Figs. 6d and 6e) shows the extent of the dry air over the Pacific Ocean and a portion of northwestern Mexico. High-resolution (1 km) visible images areusedtoidentifyspiralbandsandaneye,whichare consistent with their hurricane strength. In contrast, Paul arrived as a weakening low-level circulation with a reduced area of high cloud tops (Fig. 6c) although a more humid environment was present over northern Mexico (Fig. 6f). While interacting with the peninsula, John’s infrared imagery indicates that intense clusters developed around the circulation center (http://met-bcs.cicese.mx/2006/john_ ir.gif). A set of convective systems developed farther north, in the southwestern United States, within a moderately moist environment (precipitable water from 25 to 40 mm) detected by the sounding network. Note the missing data from Mexican stations in Fig. 6, an issue to be discussed in section 5. As the storm approached BCS, the Cabo San Lucas radar range and temporal frequency were changed from 540 to 240 km and from 15 to 5 min, respectively. This fact allows us to identify a 15-km diameter eye surrounded by a ring of relatively intense reflectivity and a distinct spiral band located south of the circulation center. In addition, intense cells developed over the eastern flank of the core and the potential for major damage was also present in a region 100–200 km off the coast (Fig. 7a). The mainland radar is used to provide complementary monitoring of John’s passage over La Paz. This imagery (not shown) displays several features, including curved bands over the gulf and intense clusters along the eastern flank of the core. FIG. 5. GFS analyses at the 500-hPa level at times closest During Lane’s development, the animation of the water to landfall: (a) 0000 UTC 2 Sep, (b) 1800 UTC 16 Sep, and (c) vapor imagery (http://met-bcs.cicese.mx/2006/lane_wv.gif) 0000 UTC 26 Sep 2006. Solid lines represents 500-hPa geopotential height with 10-dm contour interval; 584 and 590 dm are shown by is convenient tool for identifying the arrival of a large area 2 2 thick lines. Light (10–20 m s 1), medium (20–30 m s 1), and dark of dry air from the southwestern United States while the 2 ($30 m s 1) shadings represent the 850–200-hPa wind shear. The infrared images indicate that, prior to landfall, deep con- 2 dotted line represents the 5 m s 1 wind shear and dashed lines en- vection developed over the southern gulf. The Guasave 3 25 21 close areas of relative vorticity above 5 10 s . Large dots and radar allowed more detailed monitoring of an eye as the single letters are the corresponding best-track positions for TCs John ´ (J), Kristy (K), Ernesto (E), Lane (L), Miriam (M), and Paul (P). TC moved near Mazatlan and curved bands of heavy

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FIG.6.GOES-11 (left) infrared and (right) water vapor imagery at landfall from (a),(d) Hurricane John, (b),(e) Hurricane Lane, and (c),(f) Tropical Depression Paul during 2006. Landfall positions are given by symbols as in Fig. 4 and the vertical scale in (b) indicates a cali- brated scale of cloud-top temperature (8C). Numerical values indicate precipitable water (mm) from upper-air soundings closest to the imagery times and crosses represent missing soundings. rainfall developed over central Sinaloa (Fig. 7b). The of cloud clusters moved northeastward into Sinaloa and GOES infrared imagery (Fig. 6d), along with the cor- Nayarit. The Guasave radar detected heavy precipita- responding visible image (not shown), indicate that the tion along the mainland plains and a feature of interest is core had a 300-km width. This is consistent with the the rainfall and cluster location to the east (ahead) of 345-km diameter of tropical storm winds estimated, 4 h the circulation center. Since cloud tops near the TC prior to landfall, by NHC. center were in the range of 108–158C, it is assumed that The animation of satellite imagery determines rele- the circulation is representative of the layer below vant features from Paul’s life cycle. Prior to landfall, 1500 m. This height assignment is derived from a tem- high cloud tops developed ahead of the TC. This activity perature comparison between dropsonde observations occurred on 24–25 October over the southern gulf, while taken during a reconnaissance mission from the U.S. the circulation was south of Cabo San Lucas and a set Air Force and estimates from the GOES infrared

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FIG. 8. Rainfall accumulation from TRMM during the periods (a) 28 Aug–4 Sep, (b) 13–17 Sep, and (c) 21–26 Oct 2006. The vertical gray scale indicates accumulation (mm). Best-track positions are given at 6-h intervals.

imagery. The low-level circulation remained active as it moved across the gulf and reached the mainland near Culiaca´n (Fig. 7c).

3) ACCUMULATED RAINFALL Figure 8 shows the distribution of accumulated rainfall from TRMM. While moving over the ocean and south of the Mexican coast, accumulations above 200 mm are estimated around John’s core (Fig. 8a). In contrast, FIG. 7. Reﬂectivity (dBZ) from the Cabo San Lucas radar at (a) amounts below 150 mm are estimated along most of 2 0203 UTC 2 Sep and rain rate (mm h 1) from the Guasave radar at BCS. No rainfall over the peninsula or over Sonora was (b) 1918 UTC 16 Sep and at (c) 0401 UTC 26 Oct 2006. Images are associated with the passage of Lane but an enhanced area selected from the closest times to landfall and the white dot rep- is conﬁned to the southern Gulf of California, west of resents radar location. Nayarit (Fig. 8b). Paul constituted a source of limited rainfall for northwestern Mexico (Fig. 8c), associated

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FIG. 9. Total rainfall (mm) in Baja California Sur from the period 31 Aug–4 Sep 2006. Top-10 reports are circled and given in Table 2. Best-track positions (large dots) and intensities (hurricane, HR; tropical storm, TS; tropical depression, TD), associated with John, are indicated. Terrain elevations (m, shaded) are at 300-m intervals. Asterisk is the landfall site for John and triangles are the strongest hurricanes (name initial and last two digits of the year) from Fig. 2a. with weakening and recurving motion while the circula- rainfall affected the majority (67%) of the BCS pop- tion approached the mainland. ulation that these communities comprise. Another out- Actual rainfall amounts from John’s passage over land, standing aspect is that maximum rain rates from John 2 based on SMN data, are shown in Fig. 9, and Table 2 (270–449 mm day 1) set new records at several stations presents the 10 largest accumulations. The pattern of with observations since 1969. Previous maxima were enhanced accumulation along the mountains and lack of associated with TC approach or landfall between 1976 rainfall over the central peninsula, west of 1138W, is and 2003. Positions of the strongest landfalls in southern consistent with TRMM estimates (Fig. 8a). However, in BCS (Fig. 9) indicate preferred arrival south of 248N, situ observations are used to determine that substantial across the Gulf coast. This represents an important amounts were underestimated by the TRMM-based re- weather threat to a small area that, during the last few trieval algorithm. While maximum estimates are below decades, has been affected by four category-2 and one 200 mm, in situ observations reported totals between 287 category-3 hurricanes. John moved over land for more and 506 mm. The reasons for this difference are unclear than 40 h to become a unique case among TCs that and beyond the scope of this study, however. moved over the peninsula (Fig. 2a). Extraordinary rainfall was recorded at stations 1–4, The combined information from GOES and TRMM with less than 300 inhabitants each. In contrast, the ﬁve satellites, as well as SMN radars, suggests favorable largest communities listed in Table 1 received totals in conditions for heavy precipitation from Lane’s landfall. the range 49–265 mm. This fact suggests that moderate Data collected by the rain gauge network (Fig. 10a and

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TABLE 2. Total rainfall accumulations (mm) associated with TC John from stations in BCS, during the period 31 Aug–4 Sep 2006. 2 2 Maximum daily accumulation (MAXDAY, mm day 1) is from the period, record of maximum daily rainfall (MAXREC, mm day 1)is from 1969 through 2005, and tropical cyclone (name, month, and year) is associated with the previous record. Asterisks are daily maxima greater than previous long-term record. The station identiﬁcation (SI) is used to show the corresponding geographical location in Fig. 9.

SI Station name Total MAXDAY MAXREC TC 1 San Bartolo 506 449* 425 Liza (Sep 1976) 2 San Javier 480 400* 250 Marty (Sep 2003) 3 El Huatamote 456 436* 229 Ignacio (Aug 2003) 4 Agua de San Antonio 447 295 360 Isis (Sep 1998) 5 Santa Gertrudis 360 198 300 Isis (Sep 1998) 6 Los Planes 360 300* 240 Juliette (Sep 2001) 7 San Jose´ de Magdalena 353 313* 170 N/A 8 San La´zaro 340 270* 264 Marty (Sep 2003) 9 San Antonio Norte 290 290* 124 Marty (Sep 2003) 10 Guadalupe 287 222 227 Lester (Aug 1992)

N/A 5 no tropical cyclone associated with this maximum.

Table 3) show maxima above 250 mm (stations 1 and 3) an official forecast is released at four initial times (0000, in southern Sinaloa, while secondary maxima (46– 0600, 1200, and 1800 UTC) and contains projections valid 211 mm) occurred over the central portion of the state at 12, 24, 36, 48, 72, 96, and 120 h (Rappaport et al. 2009). (stations 2 and 4–10). The largest precipitation rates This product is an important tool available from hurri- 2 were in the range 220–260 mm day 1, while the center cane specialists with responsibility in the Atlantic and of circulation was making landfall. Inspection of in- eastern North Pacific basins. dividual soundings released at Mazatlań reveals that the a. Forecast selection thermodynamic conditions supported deep convection. These conditions include 1) high precipitable water, Section 3 described observations from the evolution .55 mm; 2) nearly saturated air, with relative humidity of TCs that had an impact in northwestern Mexico in .75%, below the 900-hPa level; and 3) an unstable at- 2006. Now, and by using official forecasts, we wish to mosphere given by the lifted index ,218C. provide an examination of the operational products is- According to TRMM (Fig. 8c), limited rainfall oc- sued prior to landfall. A survey of all the official fore- curred over most of the mainland, and scattered areas of casts indicates that the first available predictions with light precipitation developed over the southern Gulf and a position over land were issued 62 h (John), 60 h (Lane), east of Paul’s best track. Despite its limited strength, and 114 h (Paul) before the actual events. Therefore, we considerable accumulations were collected by in situ choose to inspect a sample of forecasts issued within stations around the landfall area. According to Fig. 10b 5 days from their respective landfall times. In particu- and Table 4, more than 200 mm were reported by sta- lar, as shown in Fig. 11, only the following forecast tions 1–4, on the coastal plains of north-central Sinaloa. cycles are inspected: 1) 0000 UTC from 30 August to 2 The largest rate was 200 mm day 1 at the closest station 1 September, 2) 1800 UTC from 13 to 15 September, to the landfall position. Inspection of daily records and 3) 0000 UTC from 23 to 25 October. These fore- indicates that most of the rainfall was collected on casts were issued between 1 and 3 days from landfall 25 October, when intense cloud clusters were developing and they were associated with timely warnings as well ahead of Paul’s low-level center of circulation. as valuable information for emergency management decisions before strong winds and heavy rainfall arrived at populated areas. 4. Official forecasts Figure 11a shows that the first of John’s official fore- Forecasts are the result of human experience and casts generated a track that was misplaced over the careful assessment of the model guidance. Track and Pacific Ocean, away from land. John was expected to intensity forecasts are routinely issued during the entire become a category-4 hurricane with no impact over life cycle of every TC and they are derived from a de- northwestern Mexico and, with respect to the best track, tailed examination of simple prediction techniques as there was a westward bias in the motion. Subsequent well as from deterministic and ensemble models (Heming forecasts resulted in a weaker hurricane with brief and Goerss 2010). Current guidance is based on products landfall and potential impact over the relatively large from meteorological centers around the world. At NHC, communities in southern BCS. The first forecast for

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TABLE 3. Total rainfall accumulations (mm) associated with TC Lane from selected stations in Sinaloa, 14–16 Sep 2006. SI is used to show the corresponding geographical location in Fig. 10a.

SI Station name Total 14 Sep 15 Sep 16 Sep 1 Siqueiros 297 27 49 223 2 San Lorenzo 268 5 3 260 3 Mazatla´n 257 1 9 247 4 El Dorado 211 6 205 N/A 5 La Cruz 208 2 7 199 6Lo´ pez Portillo 140 24 4 112 7 Sanalona 139 21 1 117 8 Culiaca´n962093 9 Badiraguato 66 0 0 66 10 Lo´ pez Mateos 46 0 0 46

N/A 5 not available.

Lane had a northwestward track while later predictions suggested a northward path over the Gulf and landfall, as a category-1 hurricane, over the peninsula or over northern Sinaloa (Fig. 11b). Again, the ﬁrst forecast had a westward bias. Finally, Paul was expected to follow a recurving track, near Isla Socorro (Fig. 11c). The corresponding forecasts had some position changes and kept the landfall site over central Sinaloa and, in contrast to the previous cases, these tracks appeared to have no lateral bias. As a baseline level of accuracy to determine forecast skill, predictions from the Climatology and Persistence (CLIPER) model are incorporated and compared with the above set of forecasts. In general, CLIPER tracks followed a northwestward displacement and only a few of them indicated passage across the Mexican coast. In addition, tracks from three global-scale models were examined from the operational forecasts issued 3 days prior to landfall (Figs. 11d–f). These tracks are derived from the GFS model, the Geophysical Fluid Dynamics

TABLE 4. Total rainfall accumulations (mm) associated with TC Paul from selected stations in Sinaloa, from 24 to 26 Oct 2006. SI is used to show the corresponding geographical location in Fig. 10b.

SI Station name Total 24 Oct 25 Oct 26 Oct 1 Pericos 224 0 200 24 2 San Juan 222 0 148 74 3 Presa Buelna 215 0 163 52 4 Guamu´ chil 215 0 163 52 FIG. 10. Total rainfall (mm) in Sinaloa from the periods (a) 14–16 5 Diaz Ordaz 147 0 101 46 and (b) 24–26 Sep 2006. Top-ten reports are circled and given in 6 Badiraguato 136 0 104 32 Tables 3 and 4. Best-track positions (large dots) and intensities 7 Culiaca´n 131 0 113 18 (hurricane, HR; tropical storm, TS; tropical depression, TD), as- 8Lo´ pez Mateos 120 0 82 38 sociated with Lane (a) and Paul (b), are indicated. Terrain eleva- 9 Culiaca´n 103 N/A 89 14 tions (m, shaded) are at 300-m intervals. Asterisks are the landfall 10 Andrew Weiss 95 0 80 15 sites and triangles are the strongest hurricanes (name initial and N/A 5 not available. last two digits of the year) from Fig. 2b.

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FIG. 11. Best-track (thick line) and ofﬁcial forecast (OFCL) positions for TCs (a) John, (b) Lane, and (c) Paul. Initial dates are given in the lower-left inserts (symbol, day, and month). Forecasts are at 12, 24, 36, 48, 72, 96, and 120 h. Model forecasts are from GFS, GFDL, and NOGAPS with initial times at (d) 0000 UTC 30 Aug, (e) 1800 UTC 13 Sep, and (f) 0000 UTC 23 Oct 2006.

Laboratory (GFDL) model, and the Navy Operational Most of the corresponding tracks are in agreement with Global Atmospheric Prediction System (NOGAPS) the ofﬁcial forecasts for John, Lane, and Paul; however, model. According to Rappaport et al. (2009), they are the GFS tracks take the TCs farthest west (left) away among the leading models in accuracy and are a key from the corresponding best tracks. Therefore, we choose component of several ensemble models at the NHC. to examine forecasts from this model only.

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TABLE 5. Official, GFS, and CLIPER errors (km) from track largest departures among the selected models (Table 5 forecasts issued 3 days prior to the landfall of 2006 tropical cyclones and Figs. 11d–f), we perform an examination of the in northwestern Mexico. Errors larger than the CLIPER forecast output fields associated with forecasts issued 3 days are shown with boldface numbers. before landfall. The GFS fields are taken from the Time and date TC name Forecast time (h) National Operational Model Archive and Distribution (forecast source) 24 48 72 96 120 System (NOMADS; available online at http://nomads. 8 0000 UTC 30 Aug John (Official) 55 89 242 451 789 ncdc.noaa.gov) on a 1 global grid and 6-hourly in- John (GFS) 148 245 392 596 914 tervals. The examination includes 500- and 200-hPa John (CLIPER) 120 291 335 421 578 heights as well as 850–200-hPa wind shear and sea level 1800 UTC 13 Sep Lane (Official) 11 187 504 N/A N/A pressure. Lane (GFS) 84 334 672 N/A N/A Figure 12a shows that John’s forecast initiated with Lane (CLIPER) 96 147 391 N/A N/A 0000 UTC 23 Oct Paul (Official) 211 364 528 N/A N/A a midlevel anticyclone (A) over northern Mexico and Paul (GFS) 223 221 N/A a couple of cyclonic circulations over the Pacific, south Paul (CLIPER) 129 514 1082 N/A N/A of 208N. One of them corresponds to John (J) and another, to the west, is consistent with the early stages of N/A 5 not available. Kristy (K). An Atlantic TC (Ernesto, E) was present far to the east of the anticyclone and heading north into the b. Forecast errors Florida Peninsula. During the first 24–48 h into the GFS We used an NHC database to examine track and in- run, the anticyclone remained essentially in place and its tensity errors from the official forecasts shown in Figs. southern flank favored westward displacement of the 11d–f. This database is available online (http://www.nhc. Pacific TCs. At 72 h (Fig. 12d), the circulation associ- noaa.gov/verification/verify7.shtml) and track error is ated with John is located approximately 400 km south- defined as the distance between the forecast and best- southwest of the peninsula. The forecast location was track positions at a given verification time. Table 5 determined from the sea level pressure minimum, below shows that, as expected, the forecast errors increase with the 500-hPa circulation, and these fields are shown in time. Beyond 72 h, the errors from John’s forecast were Figs. 13a and 13b at full resolution. Note that, with re- above 400 km and since the official forecast errors are spect to the best track, John’s circulation is in the wrong larger than those from CLIPER, this is considered to be location. The circulation associated with Kristy weak- a relatively poor forecast with no skill at 96 and 120 h. A ened and was shifted toward the display’s western edge, similar situation occurred during Lane’s forecast at 48 450 km away from the actual position. and 72 h in the verification. In contrast, improved skill is A similar situation occurred when Lane’s forecast was associated with Paul’s forecast that followed a recurving initialized as a tropical storm close to the coast and with track around Isla Socorro. Beyond 72 h, Lane and Paul an elongated anticyclone to the north, from 1408 to 758W have no error assignments because the observed TCs (Fig. 14a). This feature did not change significantly had already dissipated. during the next few days (Figs. 14b and 14c). At 72 h into For intensity, as a counterpart to CLIPER, the Statis- the model run, the height configuration resulted in tical Hurricane Intensity Forecast (SHIFOR) is a simple steering flow from the southeast, which kept the circu- intensity model that assesses forecast skill. Intensity er- lation associated with Lane south of 208N, over open sea rors, defined as the difference between forecast and best- (Fig. 14d). The more detailed fields (Fig. 13c) show that track maximum winds, were also analyzed but not shown. the contour orientation, over the actual landfall area, is 2 Relatively large (.25 m s 1) errors occurred at 96 and not from south to north, as is shown in the analysis (Fig. 120 h of John’s official prediction, with no skill relative to 5b). A weak circulation that resembles Miriam de- SHIFOR, due to the failure to forecast landfall in BCS. veloped and it is located at about 1258W (Figs. 13c and Similarly, Lane’s forecast was not able to anticipate the 13d), 1000 km west of the actual position. The westward category-3 strength reached just prior to landfall and this motion remained active and at 120 h the circulation resulted in underpredictions in the forecasts. In contrast, associated with Lane was located farther away from the Paul’s official forecast did a better job of predicting the continent, at 208N, 1208W. intensity just prior to landfall with errors under the cor- To identify specific patterns in the forecast fields, which responding SHIFOR forecast. may be critical to determining the correct TC track, a comparison with respect to the corresponding analyses c. GFS forecasts is performed. This examination involved several forecast In an attempt to understand the nature of the track times, vertical levels, and scalar fields; however, as shown errors for John and Lane and, since the GFS had the in Figs. 12 and 14, the discussion concentrates on the

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FIG. 12. GFS ﬁelds at (a) initialization (0000 UTC 30 Aug 2006) and (b) 24, (c) 48, and (d) 72 h into the model forecast. Solid contours are the 500-hPa geopotential heights at 10-dm intervals with 584 and 590 dm shown by thick lines. Positive differences (m, forecast heights . than the analyses) are shaded and dashed lines depict negative differences. Features discussed in the text are given by dots and letters which indicate corresponding best-track positions for TCs John (J), Kristy (K), and Ernesto (E), as well as the anticyclone (A).

500-hPa geopotential heights at 24, 48, and 72 h. Dif- the anticyclone in the zonal band 208–308N and, when ference heights from John’s forecast indicate that, compared with the analysis (Fig. 5b), the westward during the first 48 h into the model run, moderate de- steering flow is a likely error source in the missed track. partures developed west of 1008W (Figs. 12b and 12c). Therefore, it appears that the westward track is likely These differences, up to 40 m, suggest that the anticy- due to an inaccurate representation by the GFS model clone over northern Mexico extends farther to the west of the midlevel anticyclone extent over northern Mex- with respect to the analyses. The differences cover ico, reducing the northward component of the steering a large area from the west coast of North America to flow and, therefore, missing the landfall position over the central Pacific, centered at 408N, 1308W. At 72 h, northwestern Mexico. Since similar forecast tracks the well-defined maximum over southern BCS is related were derived from the NOGAPS and GFDL models to John’s missed landfall from the GFS. A similar dis- (Fig. 11e), we suggest that the problem may be related tribution of height differences was also detected in the to the initial fields and, as discussed in section 5, this heights at the 400-, 700-, and 850-hPa levels as well as in may originate from a limited number of upper-air the sea level pressure. observations. The spatial distribution from Lane’s forecast has a d. Additional seasons (1988–2009) relatively large area of positive departures west of 1008W (Figs. 14b and 14c), as well as an error maximum To have a larger dataset of official forecasts, we con- around the landfall site in Sinaloa (Fig. 14d). These ducted an extended survey to cover landfall events from features are consistent with the westward extension of other seasons. Besides the 2006 events, we identified 21

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FIG. 13. GFS ﬁelds at 72 h into the forecasts initialized at (a),(b) 0000 UTC 30 Aug and (c),(d) 1800 UTC 13 Sep 2006. At 500 hPa, solid contours are the geopotential heights at 10-dm intervals with 584 and 590 dm shown by thick lines; the dashed line depicts relative 2 2 vorticity at 5 3 10 5 s 1. At the surface, solid contours are sea level pressure at 2-hPa intervals; the dashed line depicts relative vorticity 2 2 at 5 3 10 5 s 1. Features discussed in the text are given by dots and letters indicate the corresponding best-track positions for TCs John (J), Kristy (K), Lane (L), and Miriam (M).

cases from 1988 through 2005 and 6 additional cases from during their approach to the mainland. Maximum rainfall 2 the period 2007–09. This makes a total of 30 cases that rates, in the 360–449 mm day 1 range, are associated with were classified, depending on the motion prior to landfall, straight tracks while most of the rates below the average 2 into recurving or (approximately) straight-moving tracks. (242 mm day 1) were supplied by recurving or weak TCs 2 This classification resulted in 13 tracks that completed moving north. For example, the lowest rate (35 mm day 1) recurvature while 10 of the straight tracks had a large is from Nora of 2003, a recurving tropical depression than component of northward motion, such as Lane in 2006. moved more than 500 km during the day prior to landfall. Table 6 lists specific information, including TC intensity Plots of the official forecasts issued 1–3 days before and rainfall rates at landfall. It is interesting to note that landfall were created and they were useful in identifying 70% of these cases moved onshore through BCS. In the occurrence of distinct patterns with respect to the agreement with the information displayed in Fig. 2, most of best track. One pattern is associated with westward de- the landfalls occurred in the second half of the season. partures such as those from John (Fig. 11a) and Lane Some recurving tracks experienced extreme intensification (Fig. 11b), and they tend to be larger in the first predi- or weakening, such as Kenna in 2002 and Rick in 2009, ction. To determine performance, for the above tracks,

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FIG. 14. GFS fields at (a) initialization (1800 UTC 13 Sep 2006) and times at (b) 24, (c) 48, and (d) 72 h into the model forecast. Solid contours are the 500-hPa geopotential heights at 10-dm intervals with 584 and 590 dm shown by thick lines. Positive differences (m), forecast heights larger than the analyses, are shaded and dashed lines depict negative differences. Features discussed in the text are given by dots and letters, which indicate corresponding best- track positions for TCs Lane (L) and Miriam (M), as well as the anticyclone (A). we selected the 72-h verification time from the forecast systems over the study area. Note that anticyclones cen- issued 3 days prior to landfall. Then, the NHC database tered over northern Mexico or the southwestern United was used to compute average errors from the official States are associated with TCs tracks predicted to move forecasts and a summary is shown in Fig. 15. Relatively away from the continent but, when compared with the large errors (180–1230 km) are from recurving TC best track, they were incorrect. The steering flow seems to forecasts, while the straight TCs have lower errors (44– favor northwestward displacement of the TCs and in- 818 km). Errors from John and Lane were below and spection of the model guidance, available when issuing above the long-term average, respectively. A compari- the official forecasts, suggests that some of the models did son to the corresponding CLIPER forecast errors sug- not anticipate environmental changes that resulted in gests that the official forecasts had, in most cases and a larger component of northward motion. Additionally, including Paul, some skill in predicting track changes some of the recurving tracks (Figs. 16b and 16f) occurred due to recurvature. In contrast, straight tracks were during the passage of midlatitude systems and large er- easier to predict, as the official and CLIPER forecast rors may be due to an inaccurate prediction of the along- errors have similar averages. track component of motion. The large-scale environment was examined on an individual basis and fields from cases with the largest track 5. Discussion errors are shown in Fig. 16. The 32-km North American Regional Reanalysis (NARR; Mesinger et al. 2006) was This study analyzes landfalling TCs over northwest- used to determine the setting of tropical and midlatitude ern Mexico and provides documentation from existing

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TABLE 6. Eastern North Paciﬁc tropical cyclones making landfall in BCS, Sinaloa (SIN), or Nayarit (NAY) from 1988 through 2009. Intensity is TD, tropical depression; TS, tropical storm; or HN, hurricane category N on the Safﬁr-Simpson scale. Text in boldface represents recurving tracks. Rainfall is the maximum daily rate 2 (mm day 1) from stations at landfall.

Landfall Year Name date Intensity* Rainfall State 1989 Kiko 27 Aug H3 302 BCS 1989 Raymond 4 Oct H3/TS 106 BCS 1990 Rachel 2 Oct TS 240 BCS 1992 Lester 23 Aug TS/TS 142 BCS 1993 Calvin 7 Jul TD/H2 186 BCS 1993 Hilary 25 Aug H2/TS 128 BCS 1993 Lidia 13 Sep TS/H2 320 SIN 1994 Rosa 14 Oct TS/H2 227 SIN 1995 Henriette 4 Sep H2 221 BCS 1995 Ismael 15 Sep H1 234 SIN 1996 Fausto 13 Sep TD/H1 411 BCS 1997 Nora 25 Sep H3/H1 85 BCS 1998 Isis 2 Sep TS 360 BCS 1999 Greg 7 Sep TD 105 BCS FIG. 15. Track errors (km) at 72 h from the official (OFCL, gray) 2000 Norman 22 Sep TD 147 SIN and CLIPER (CLP5, black) forecasts issued 3 days before landfall 2001 Juliette 30 Sep H3/TS 387 BCS in northwestern Mexico. Shown are tracks from (top) recurving 2002 Kenna 25 Oct TS/H4 232 NAY and (bottom) straight storms. The corresponding TCs are from the 2003 Ignacio 25 Aug TD/H1 364 BCS 1988–2009 period and they are labeled by the first letter of the 2003 Marty 22 Sep TS/H2 323 BCS storm’s name and the last two digits of the year, as listed in Table 6. 2003 Nora 9 Oct H1/TD 39 SIN The dotted lines represent error averages for each of the forecast 2004 Javier 19 Sep H3/TD 95 BCS sources. No bar indicates that the corresponding TC verification 2006 John 2 Sep H3/H2 449 BCS was not available at 72 h. 2006 Lane 16 Sep TD/H3 260 SIN 2006 Paul 26 Oct H1/TD 200 SIN 2007 Henriette 4 Sep TS/H1 415 BCS there are some limitations that are important to con- 2008 Julio 25 Aug TS 273 BCS 2008 Lowell 11 Sep TS/TD 132 BCS sider. For example, 1) satellite imagery from GOES 2008 Norbert 11 Oct H1/H2 226 BCS platforms is available from the 1974 season with rela- 2009 Jimena 2 Sep H2/H2 440 BCS tively low spatial and temporal resolutions; 2) the Cabo 2009 Rick 21 Oct H5/TS 201 SIN San Lucas and Guasave radars started operations in the * First entry is the intensity 3 days before landfall and second (or early 1990s while their digital imagery is archived only only) entry is the intensity at landfall. since 2000; 3) upper-air observations have been variable, as only one station has been in operation since 1948 while the most recent site started in 1991; and 4) the GFS regional datasets. Satellite and radar imagery are used to analysis–forecast system is available from 2002. These identify convective features while environmental flow facts suggest that the documentation of events prior to patterns are determined from gridded analyses and 2000 is more difficult to fully accomplish. upper-air soundings. Previous studies identified the key The density and reliability of upper-air observations role of the topography in Baja California and the large- in Mexico may play a critical role in the correct initial- scale flow in the motion, intensity, and structural changes ization of the large-scale environment in the operational of the incident TCs. However, the present research found models. As part of this study, we made a simple survey that, during the most active portion of the 2006 season, of the observations taken during selected periods from there were TCs hitting the peninsula and the mainland. the 2006 season. For example, prior to John’s landfall, These TCs made landfall over regions with different only 20% of the maximum number of standard sound- environmental conditions and contrasting population ings (66) was released at the 11 operational sites west of densities. 988W. Few soundings were taken at inland stations Assuming availability of the observations, an ex- and there were no releases at Isla Socorro, La Paz, or tended study may be performed to document 1969–2009 Guaymas (Sonora). The sounding coverage increased to landfalls, when more than 50 TCs made landfall in the 38% and 41% before Lane’s and Paul’s landfall, re- northwest, and to derive more general results. However, spectively, with more stations active along the west

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FIG. 16. NARR fields at the 500-hPa level for TCs with relatively large track errors. Contours are geopotential heights with 20-dm intervals and shading is used for values above 584 dm. Thick lines represent the 584- and 590-dm contours. Plus signs are positions at 24, 48, and 72 h from the official forecasts issued at the time shown in the top label. Dots are the corresponding best-track positions, including TC location at the initial time. coast. An increased number of soundings should better end of section 4. However, an important element is to represent the location, extent, and intensity of the large- realize that during the last few decades the performance scale circulations that are used to initialize the model of numerical models has improved and it is difficult to forecasts. However, there are still questions about the compare model versions (such as those from the GFS) quality control and model assimilation from these ob- that have been upgraded over the course of several servations that need to be carefully examined, and this is years. This is an important factor to be considered when recommended as part of a subsequent research study. assessing a model’s ability to simulate TC tracks. We recognize that our results are derived from the The official forecasts are also useful for estimating the analysis of a few TCs and they do not include enough fraction of the population that may be directly affected seasons to lead us to expect that the findings will become by the TC approach or landfall. We computed the representative of long-term statistics. To generalize population fraction, with respect to the total population, these results and, as part of an ongoing research study, from communities located along the forecast tracks. The we are performing an extension of the official forecast influence area is estimated from the radius of specific error analysis, with some of the results discussed at the wind speeds prior to and during landfall, which is among

Unauthenticated | Downloaded 10/02/21 03:28 AM UTC 1392 WEATHER AND FORECASTING VOLUME 27 the NHC products released in real time. Based on the d John had a track similar to that of TCs developing population census from 2005, we determined the pop- during late August or the month of September. It was ulation to be affected by the selected set of official steered by an anticyclone, made landfall as a category- forecasts for John (Fig. 11a): nobody would have been 2 hurricane, and moved along the peninsula for several affected by the first forecast, while subsequent fore- days. This resulted in large amounts of total precipi- casts ranged from 30% to 35% of the total BCS pop- tation over the mountains with maximum rates that ulation (Table 1). Likewise, no impact was derived were comparable to, and in some cases larger than, from Lane’s first forecast and 15%–40% of the state previous records. of Sinaloa’s population would have been affected by d Lane developed as a midlatitude trough approached the next forecasts (Fig. 11b). This particular applica- the western United States and an anticyclone was in tion is still under development but we envision it to place over the Gulf of Mexico. The TC moved over the be an extremely useful tool to be used by emergency southern Gulf of California and made landfall near managers and decision makers while designing pro- large communities in Sinaloa. Its passage provided tection plans. moderate accumulations of rainfall and daily rates in Information derived from the most recent census the coastal plains. (INEGI 2011a) reveals that the population in Mexico d Paul was the only recurving TC and its track is has increased dramatically and, currently, there are nine consistent with past TCs that developed late in the million more inhabitants than in 2005. The fastest-growing season. Convective activity, ahead of the storm center, state in the northwest is BCS and the largest rates are resulted in moderate rainfall over north-central Sinaloa. concentrated in San Jose´ del Cabo and Loreto (see Fig. 1 Its recurvature was linked to the development of a mid- and Table 1 for locations). These facts, plus the rela- latitude system and strong wind shear that was, in part, tively large coastal length and the frequent approach of responsible for weakening over the Gulf of California. eastern Pacific TCs, suggest that these cities require Our results indicate that the first official forecast, with special attention to prevent major storm impacts on the an inland position, was issued as early as over 4 days and population and infrastructure. One promising way to as late as 60 h before the actual landfall. A selection of accomplish this task is by providing better long term the forecasts issued 3 days prior to landfall was exam- (3–5 days) forecasts, which are essential for giving ad- ined and an assessment revealed general characteristics vance warning of landfall events. However, an important of the track errors. Predicted tracks for John and Lane human dimension aspect to consider is the correct in- showed a westward bias, which suggested reduced im- terpretation of graphical products widely adopted by the pact on the population of northwestern Mexico. By in- local media to communicate forecasts. Incorrect in- specting the GFS model, we showed that the incorrect terpretations may lead to incorrect conclusions with re- spatial extent of anticyclones throughout the model run spect to track, size, intensity, and impact region (Broad is associated with westward flow and a limited compo- et al. 2007). We propose training actions focused on nent of northward motion to steer the TCs into the con- awareness and education for specific groups, such as the tinent. A survey examining additional seasons revealed effort described by Farfań et al. (2010) in which Latin that similar environmental conditions were present dur- American students are offered short courses on scien- ing the approaches of other TCs for which the official tific aspects of TC landfall as well as their corresponding forecasts were also unable to anticipate landfall. social and economic impacts. In conclusion, our analysis of case studies that made landfall during the season of 2006 represents a contri- 6. Summary and conclusions bution to the knowledge of TC impact on northwestern Mexico. More recent landfall events, from 2007 through The goal of this study was to document TC track and 2009, confirm the need to continue examining TC de- structure changes, before and during landfall in north- velopment along with an evaluation of the official western Mexico, from the relatively active 2006 season. forecasts. Further events are likely to occur and their Based on the best-track dataset, three of the eastern impact will become more important given the rapid North Pacific TCs were selected for analysis: John, Lane, growth of coastal populations and their corresponding and Paul. Two of them became the third-strongest TCs infrastructures. hitting the northwest since 1969. They brought strong winds and heavy rainfall that affected populated areas, and our inspection of data from satellites, radars, gridded Acknowledgments. This work was carried out with the fields, and a rain gauge network resulted in the following aid of the Inter-American Institute for Global Change set of key findings: Research (IAI, Grant CRNII-2048) which is supported

Unauthenticated | Downloaded 10/02/21 03:28 AM UTC DECEMBER 2012 F A R F A´ NETAL. 1393 by the U.S. National Science Foundation (Grant GEO- Heming, J., and J. Goerss, 2010: Track and structure forecasts of 0452325), and from the National Council on Science and tropical cyclones. Global Perspectives of Tropical Cyclones Technology in Mexico (CONACYT, Grant 23448). SMN from Science to Mitigation, J. C.-L. Chan and J. D. Kepert, Eds., World Scientific Series on Asia–Pacific Weather and personnel supplied the rainfall observations (Alejandro Climate, Vol. 4, World Scientific, 287–323. Gonza´lez and Adolfo Portocarrero), radar imagery Huffman, G. J., and Coauthors, 2007: The TRMM Multisatellite (Modesto Mendoza), and upper-air soundings (Victor Precipitation Analysis (TMPA): Quasi-global, multiyear, Ramos). The NHC error database was provided by James combined-sensor precipitation estimates at fine scales. J. Hy- Franklin. The authors wish to thank the three anonymous drometeor., 8, 38–55. INEGI, cited 2011a: Census of population and housing 2010 (in reviewers for comments that improved the manuscript. Spanish). [Available online at http://www.censo2010.org.mx/.] ——, cited 2011b: General census of population and housing REFERENCES (in Spanish). [Available online at http://www.inegi.org.mx/est/ contenidos/proyectos/ccpv/cpv2005/Default.aspx.] Arndt, D. S., M. O. Baringer, and M. R. Johnson, 2010: State of the Jaúregui, E., 2003: Climatology of landfalling hurricanes and climate in 2009. Bull. Amer. Meteor. Soc., 91, s1–s222. tropical storms in Mexico. Atmo´sfera, 16, 193–204. Blake, E. S., E. J. Gibney, D. P. Brown, M. Mainelli, J. L. Franklin, Jiang, H., and E. J. Zipser, 2010: Contribution of tropical cyclones T. B. Kimberlain, and G. R. Hammer, 2009: Tropical cyclones to the global precipitation from eight seasons of TRMM data: of the eastern North Pacific basin, 1949-2006. Historical Cli- Regional, seasonal, and interannual variations. J. Climate, 23, matology Series 6-5, National Climatic Data Center, 162 pp. 1526–1543. Broad, K., A. Leiserowitz, J. Weinkle, and M. Steketee, 2007: Kalnay, E., and Coauthors, 1996: The NCEP/NCAR 40-Year Re- Misinterpretations of the ‘‘cone of uncertainty’’ in Florida analysis Project. Bull. Amer. Meteor. Soc., 77, 437–471. during the 2004 hurricane season. Bull. Amer. Meteor. Soc., 88, Kaplan, J., M. DeMaria, and J. A. Knaff, 2010: A revised tropical 651–667. cyclone rapid intensification index for the Atlantic and eastern Corbosiero, K. L., M. J. Dickinson, and L. F. Bosart, 2009: The North Pacific basins. Wea. Forecasting, 25, 220–241. contribution of eastern North Pacific tropical cyclones to the Mesinger, F., and Coauthors, 2006: North American Regional rainfall climatology of the southwest United States. Mon. Wea. Reanalysis. Bull. Amer. Meteor. Soc., 87, 343–360. Rev., 137, 2415–2435. Pasch, R. J., and Coauthors, 2009: Eastern North Pacific hurricane Dobos, P. H., and R. L. Elsberry, 1993: Forecasting tropical cyclone season of 2006. Mon. Wea. Rev., 137, 3–20. recurvature. Part I: Evaluation of existing methods. Mon. Rappaport, E. N., and Coauthors, 2009: Advances and challenges at Wea. Rev., 121, 1273–1278. the National Hurricane Center. Wea. Forecasting, 24, 395–419. Dvorak, V. F., and H. M. Mogil, 1994: Tropical cyclone motion Ritchie, E. A., K. M. Wood, D. S. Gutzler, and S. R. White, 2011: forecasting using satellite water vapor imagery. NOAA Tech. The influence of eastern Pacific tropical cyclone remnants on Rep. NESDIS 83, 42 pp. the southwestern United States. Mon. Wea. Rev., 139, 192–210. Farfań, L. M., 2004: Regional observations during the landfall of Romero-Vadillo, E., O. Zaytsev, and R. Morales-Pe´ rez, 2007: tropical cyclone Juliette (2001) in Baja California, Mexico. Tropical cyclone statistics in the northeastern Pacific. At- Mon. Wea. Rev., 132, 1575–1589. mo´sfera, 20, 197–213. ——, G. B. Raga, and F. Oropeza, 2010: Training on tropical cy- Serra, S., 1971: Hurricanes and tropical storms of the west coast of clones and their passage across the border. Border Climate Mexico. Mon. Wea. Rev., 99, 302–308. Summary, The University of Arizona, 12 pp. [Available online Smith, W., 1986: The effects of eastern North Pacific tropical cyclones at http://www.climas.arizona.edu/files/climas/pdfs/periodicals/ on the southwestern United States. NOAA Tech. Memo. NWS BorderClimateSummary_Jun10.pdf.] WR-197, 229 pp. Garza, A. L., 1999: 1985–1998 North Pacific tropical cyclones im- Velden, C., J. Simpson, W. T. Liu, J. Hawkins, J. Brueske, and pacting the southwestern United States and northern Mexico: R. Anthes, 2003: The burgeoning role of weather satellites. An updated climatology. NOAA Tech. Memo. NWS WR-258, Hurricane! Coping with Disaster, R. Simpson, Ed., Amer. 83 pp. Geophys. Union, 217–247.

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