MARCH 2008 ANNUAL SUMMARY 1201 Eastern North Pacific Hurricane Season of 2005 RICHARD D. KNABB,LIXION A. AVILA,JOHN L. BEVEN,JAMES L. FRANKLIN,RICHARD J. PASCH, AND STACY R. STEWART Tropical Prediction Center/National Hurricane Center, NOAA/NWS/NCEP, Miami, Florida (Manuscript received 3 November 2006, in final form 30 April 2007) ABSTRACT The 2005 eastern North Pacific hurricane season is summarized, the individual tropical cyclones are described, and official track and intensity forecasts are verified and evaluated. The season’s overall activity was, by most measures, below average. While a near-average 15 tropical storms formed, many of them were relatively weak and short-lived. Seven of these storms became hurricanes, but only one reached major hurricane status (an intensity of 100 kt or greater on the Saffir–Simpson hurricane scale) in the eastern North Pacific basin. One of the hurricanes, Adrian, approached Central America in May but weakened to a tropical depression prior to landfall. Adrian was the only eastern North Pacific tropical cyclone to make landfall during 2005, and it was directly responsible for one fatality. 1. Overview squares of the 6-hourly intensities (maximum sustained surface winds in knots) of all tropical cyclones while at Similar to the preceding two years, tropical cyclone tropical storm or hurricane strength. The ACE index activity in the eastern North Pacific basin (the area during 2005 in the eastern North Pacific was 75 (units north of the equator between the American continents are 104 kt2) or about 66% of the long-term (1971–2004) and 140°W longitude) was below average during 2005, mean value of 114. The 2005 ACE value is the ninth- especially in terms of hurricanes and major hurricanes lowest since 1971 (when reliable tropical storm and hur- [category 3 or stronger on the Saffir–Simpson hurricane ricane data began in the basin), although the values for scale (Saffir 1973; Simpson 1974)]. Sixteen tropical cy- 2003 and 2004 are even lower. The relatively low ACE clones formed during the season, and all but one of value shows that, while the total numbers of tropical these cyclones reached tropical storm strength. Seven storms and hurricanes were not drastically different of the fifteen tropical storms eventually became hurri- from their corresponding long-term averages, many of canes (Table 1, Fig. 1). The corresponding averages the storms were relatively weak and short lived. The during the period 1971–2004 are 15 tropical storms and 2005 season extended the period of mostly below- 9 hurricanes, while the previous 10-yr averages are 13 average activity that began in the eastern North Pacific and 7. Kenneth was the only major hurricane, although Jova reached category 3 intensity in the central Pacific basin in about 1995. In general, cooler-than-average sea basin (west of 140°W) after having reached category 2 surface temperatures (Fig. 2) across much of the basin in the eastern Pacific. The occurrence of only one major during the peak months of the 2005 season appear to hurricane is well below the 1971–2004 average of four have contributed to the below-average activity. and the 10-yr (1995–2004) average of three. The season began early, with the first tropical cy- A useful measure of the season’s overall activity is clone forming on 17 May, which is the fourth-earliest the accumulated cyclone energy (ACE) index, which tropical cyclone in the basin since 1971. The median reflects the combined intensity and duration of the en- date during 1971–2004 for the first tropical cyclone was tire season’s storms. It is calculated by summing the 29 May. The first cyclone of 2005 became Hurricane Adrian, which was also the only cyclone to make land- fall during the season, although it did so as a tropical Corresponding author address: Dr. Richard D. Knabb, National depression. Despite weakening prior to landfall, Adrian Hurricane Center, 11691 SW 17th Street, Miami, FL 33165. was directly responsible for one fatality in Nicaragua. E-mail: [email protected] Following Adrian, a full month passed before the next DOI: 10.1175/2007MWR2076.1 Unauthenticated | Downloaded 09/29/21 11:33 PM UTC MWR3545 1202 MONTHLY WEATHER REVIEW VOLUME 136 TABLE 1. Eastern North Pacific hurricanes and tropical storms The tropical waves, with their focused source of low- of 2005. level vorticity, propagated into the eastern North Pa- Max cific throughout the hurricane season as usual. How- 1-min Min ever, they led to the development of more tropical cy- wind pressure Direct clones during the upper-level divergence phases of the Storm Classa Datesb (kt) (mb) deaths MJO, which provided an environment more conducive Adrian H 17–21 May 70 982 1 for convection. A summary of the life cycle of each of Beatriz TS 21–24 Jun 45 1000 0 the 2005 season’s tropical cyclones is provided in sec- Calvin TS 26–29 Jun 45 1000 0 tion 2. Section 3 provides verification statistics on offi- Dora TS 4–6 Jul 40 1003 0 cial National Hurricane Center (NHC) forecasts of Eugene TS 18–20 Jul 60 989 0 Fernanda H 9–16 Aug 75 978 0 these cyclones. Greg TS 11–15 Aug 45 1000 0 Hilary H 19–25 Aug 90 970 0 Irwin TS 25–28 Aug 45 1000 0 2. Tropical cyclone summaries Jova H 12–25 Sep 85c 973c 0 The individual cyclone summaries in this section are Kenneth H 14–30 Sep 115 948 0 Lidia TS 17–19 Sep 35 1005 0 based on NHC’s poststorm meteorological analyses. Max H 18–22 Sep 75 981 0 These analyses result in the creation of a ‘‘best track’’ Norma TS 23–27 Sep 50 997 0 database for each cyclone, consisting of 6-hourly rep- Otis H 28 Sep–3 Oct 90 970 0 resentative estimates of the cyclone’s center location, a T ϭ tropical storm, wind speed 34–63 kt (17–32 m sϪ1); H ϭ maximum sustained (1-min average) surface (10 m) hurricane, wind speed 64 kt (33 m sϪ1) or greater. wind, and minimum sea level pressure. The best track b Dates are based on UTC and include the tropical depression identifies a system as a tropical cyclone at a particular stage but exclude the remnant low stage. time if NHC determines that it satisfies the following c Jova later had maximum winds of 110 kt and a minimum pres- definition: “A warm-core, non-frontal synoptic-scale sure of 951 mb in the central Pacific basin. cyclone, originating over tropical or subtropical waters with organized deep convection and a closed surface tropical cyclone formed in the basin. Four tropical wind circulation about a well-defined center” (NWS storms formed from late June through late July, but 2006). The life cycle of each cyclone (corresponding to none of these became hurricanes. Following another the dates given in Table 1 for the season’s tropical break in activity for about three weeks, the middle-to- storms and hurricanes) is defined to include the tropical late portions of August were fairly active, with four depression stage, but it does not include the remnant more tropical storms, two of which became hurricanes. low stage. The tracks for the season’s tropical storms Although the first two weeks of September were quiet, and hurricanes, including their tropical depression and six tropical storms formed during the three-week pe- remnant low stages (if applicable), are shown in Fig. 1. riod from 12 September to 3 October, and four of these Other than for Hurricane Adrian, no damages or casu- became hurricanes. No tropical storms formed after alties were reported in association with any of the tropi- that period. cal cyclones described in this section. The episodic nature of the 2005 eastern North Pacific Observations of eastern North Pacific tropical cy- season can be attributed in part to the Madden–Julian clones are mostly limited to satellite data, primarily oscillation (MJO; Madden and Julian 1972). Analysis of from the Geostationary Operational Environmental 200-mb-velocity potential anomalies (Fig. 3) indicates Satellites (GOES). GOES-East and GOES-West pro- that the extended periods without tropical cyclones co- vide the visible and infrared imagery that serves as in- incided with the upper-level convergence phases of the put for intensity estimates via the Dvorak (1984) tech- MJO over the tropical eastern North Pacific. Con- nique. This imagery is supplemented by occasional mi- versely, periods dense with activity tended to occur dur- crowave satellite data and imagery from National ing the upper-level divergence phases, although no Oceanic and Atmospheric Administration (NOAA) tropical cyclones formed during the upper-level diver- polar-orbiting satellites, Defense Meteorological Satel- gence phase in early June. Using satellite data analysis lite Program (DMSP) satellites, the National Aeronau- techniques described by Avila et al. (2003), the genesis tics and Space Administration (NASA) Tropical Rain- of most of the tropical cyclones in the eastern North fall Measuring Mission (TRMM), and the NASA Quick Pacific during 2005 can be attributed, at least in part, to Scatterometer (QuikSCAT). While passive microwave one or more westward-moving tropical waves that imagery is useful for tracking tropical cyclones and as- originated from Africa and crossed Central America. sessing their structure, QuikSCAT retrieves estimates Unauthenticated | Downloaded 09/29/21 11:33 PM UTC MARCH 2008 ANNUAL SUMMARY 1203 . 1. Tropical storms and hurricanes of 2005 in the eastern North Pacific basin. IG F Unauthenticated | Downloaded 09/29/21 11:33 PM UTC 1204 MONTHLY WEATHER REVIEW VOLUME 136 FIG. 2. Sea surface temperature anomalies (°C) in the eastern North Pacific basin, from the National Centers for Environmental Prediction (NCEP) reanalysis, averaged during the period July–October 2005.