VoluO:? 8 NlJJ:lbec 1 EASTERN NORTH PACIFIC TROPICAL CYCLONES A 23 Year Survey 01 Minimum Measured Central Pressures. Tropical Weather 1957 - 1980 Stephen M. Blumel (1) National Weather Association Tropical Meteorology Committee P.O. Box 2424 Ft. Myers, FL 33902 Abstract in., occuring on Oct. 25, 1939, off the west coast of Mexico. However, a review A review of available ship & aircraft reconnais­ of data contained in Table 1 indicate the sance reports for Eastern North Pacific hur­ frequency & intensity of hurricanes in ricanes, period 1957 thru 1980, reveals two main this Region are much greater than pre-1970 points. One, that hurricanes occurring in this date would indicate. Frequent monitoring part of the world dre both more n~erous & more of these hur r icanes by aer ial reconnais­ intense that pre-1966 data would indicate. Th1O, sance during the 1970's has revealed that that a good, long term & consistent data base does central pressures below 28.00 in. are not exist [or this reg101, the inverse of that quite common, & that intense ·supe~_hur!i­ available Eor the Atlantic & Western North Pacific canes· (central pressure 27.50 in. or Oceans. This brief report will serve to examine less) are not the extrem~ rare events reasons for this lack of both qualitative and previous climatologies would indicate. quantitative meteorological data, to reveal the Further, hurricanes of such intensity as very violent degree to which these hurriccwes may Ava in 1973, with a minimum pressure of intensiEy, and to document the available minimum 27.02 in., are also likely more common central pressure data which exists for the most than the current data indicate. See Fig­ intense of these storms, occuring within the ure 2 for annual minimum pressure since aforementioned study period. 1957. 1. INTRODUCTION The principal reason for the uncertainties in hurr icane climatology for this Region The study area covered by this report lies in the lack of an annual, consistent (F igure 1), extends from the Mexican aircraft reconnaissance program. This in pacific Coast on the northeast, longitude turn is a result of lack of funds for a 90 0 W to the southeast, westward across the dedicated research program involVing the Eastern pacific north of the equator, to very detailed, but expensive observations longitude 140 o W. Annual tropical cyclone only aircraft can provide. While it is reports prepared for the Eastern North true that Eastern North pacific hurricanes Pacific Ocean for the period 1957 thru seldom present a m~jor threat to the SW 1980 served as the main data base. Good, coast of North AmerIca, with the vast ma­ consistent data before this time were not jority travelling west or northwest and available. Ship reports constituted the dissipating over the cool ocean waters sole source of minimum pressure data be­ east of Hawaii, those that do recurve fore 1970, while aircraft reconnaissance north & northeast can and do wreak severe supplied all data from 1970 onward. With damage to Mexico, Baja California and the the adventof the first fully operational S\'l United States. An excellent and very meteorological satellite system by the recent example of this is Hurricane Paul­ U.S. in 1966, ship routing became more ef­ sept. 1982 Paul formed SW of Guatemala in f ici ent, hence the frequency of sh ips sud­ the pacific, & described a parabolic denly and unexpectedly encountering these course a few hundred miles offshore of the hurricanes, & consequently acquiring pres­ pacific west coast of Mexico. Recurvature sure data simultaneoulsy with eye passage, to the north and northeast, in response to has become virtually nil. This accounts a 500 mb. trough over the western U.S., for the sudden drop-off of data (in the brought the well-def ined • eye· across the eye) from ships by 1970 (Figure 2). extreme SE tip of Baja Calif. on Sept. 29. Maximum sustained winds at this time 2. DISCUSSION were estimated near 120 mph. Cabo San Lucas, located on the sw tip of Baja mea­ The first recorded category 5 hurricane sured peak wind gust of 127 mph., in the (see Table iTin- the Eastern North pacific ·weaker· left-front quadrant of the hur­ Ocean occured in June 1973 (Table 1, Hur­ ricane. Continuing NNE across the Gulf of ricane Ava), during the course of a spe­ California, the center again made landfall cial NOAA Research Flight Facility aerial near Loss Mochis, Mexico. This station reconnaissance monitoring of this storm. measured wind gust of 98 mph. The hurri­ Prior to this time, the lowest observed & cane cant inued inland, turning NE & moving reported sea-level pressure occuring in a into southern New Mexico as a dissipated Eastern North pacific hurricane was 27.45 surface system, but maintaining an excel- 41 National Weather Digest lent, satellite-defined, comma-shaped mid Table 1 and upper-level circulation/cloud system. LOWEST , Torrent ial rains accompained Paul's tran­ STORM !'lEAS. PRESSURE E sit across this rugged, mountainous ter­ YEAR NO. NAME DATE MILLIBARS INCHES r rain, with water up to four feet deep in 1957 09 Oct. 20-21 28.32 S 1958 10 Sept. 29-0ct.04 ",960 28.35 S highway underpasses at EI paso, located in 1959 12 Oct. 22-21 9S8 28.29 S 1960 Not Available extreme SW Texas, near the New Mexico/ 1961 Mexico border. 1962 1963 08 Mona Oct. 17-18 961. 4 28.39 S 1964 Not Available From a purely meteorological standpoint, 1965 1966 routine detailed quantitative data are 1967 16 01 iva Oct. 05-14 939.0 27.73 S highly desirable, with the aim of com­ 1968 17 Rebecca Oct. 05-11 965 28.50 S 1969 Not Available piling a truly quantitative climatology 1970 12 Lorraine Aug. 15-27 ,,, 28.44 R for tropical cyclones of the Eastern North 1971 15 Olival Sept. 20-30 ,,, 27.99 R (Irene) Pacific Ocean. 1972 07 Gwen Aug. 21-31 941 27.79 R 1973 01 A"" June 01-12 915 27.02 R 1974 13 Magqie Aug. 26-Sept. 01 27.40 R 3. SUMMARY 1975 Not AVailable 1976 01 Annette JUne 03-14 925'" 27.32 R 1977 Not Available With today's round-the-clock satellite 1978 surveillance of the Eastern North Pacific 1979 09 Ignacio Oct. 23-30 937 27.67 R 1980 Not available allowing evasive ship-routing, & budget KEY -R Reconnaissance Report (Measured Data) restraints ever-increasing in the atmo­ S Ship Report (Measured Data) spheric sciences, compilation of an in­ Oliva/ depth, qualitative & quantitative climato­ (Irene) pacific Name was Oliva, Atlantic Name was Irene. logy of hurricanes/tropical storms oc­ Table 2 cur ing in this Region on a regular, sea­ (Saffir/Simpson Dlaster Scale) sonal basis will have to await future Category Maximum Sustained Minimum Central Maximum Storm technological advances in satellite-born ~ Winds(MPH} Pressure(IN.) Surqe(FT.l microwave/radiometric sensors. 74 " 28.94 0< Above - 5 ACKNOWLEDGMENTS 110 28.50 28.93 - 8 111" 130 27.91 28.49 12 This report was funded soley thru per­ 131 155 27.17 - 27.90 13 - 18 sonal, out-of-pocket funds. Over 155 Below 27.17 Over 18 I would 1 ike to express my sincere thank s to Mr. Dick DeAngelis, meterologist -- Na­ (It.) ~ 61 67 71 73 75 77 tional Oceanographic Data Center, Wash., CEN'!'R.I.L DC, and Dr. Leonard Snellman Chief, PRESSURE Sci. Services Division, NWS Western Re­ ".m> gion, Salt Lake City, UT, who both sup­ plied much of data upon which this report is based. Additionally, I would like to acknowldge the work of the staff of Mar i­ 28.50 ner's Weather Log for their excellentde­ dication to documenting, for the marine & meteorological/oceanographic community, meteorological and oceanographic data that 26.00 are both timely & invaluable; Mr. Vernon Dvorak, National Earth Satellite Service­ Wash., DC, for his pioneering work towards • satellite wind-speed intensity estimates 27.~O of hurricanes; and the National Climatic Center for the excellent documentat ion, as • prepared by the E. pacific Hurricane Cen­ ter, of the annual hurricane summaries for 27.00 this Region since 1956, in the publication ~Climatalogical Data-National summary, An­ nuals 1956 thru 1980' (terminated with the 1980 issue due to government bUdget cuts). AIRCRAfT 26.50 ( • SHipS ( • ,I 26.00 Figure 2. Annually-measured minimum cen­ tral pressures, Eastern North Pacific Ocean, 1957 - 1980. 42 Volume 8 Number 1 FOOTNOTES AND REFERENCES 1. Stephen M. Blumel has worked as a Hydrological 4. Gunther, E.B. & Staff. Annual Data & Verifi­ Technician employed by the U. S. Geological Survey cation Tabulation, Eastern North Pacific Tropical at Ft. Meyers, Florida. He has been a cooperative Cyclones 1979, NOAA TM NWS-wn 150 1980. Salt Lake observer in the Central Florida severe weather City, UT. network since 1966. He has also been an acti ve NWA member and published previously in the Nation­ 5. Gunther, E.B. & Staff. Annual Data & Verifi­ al Weather Digest. cation Tabulation, Eastern North Pacific Tropical Storms and Hurricanes 1980, NOAA TM NWS-WR 165, 2. National Oceanographic Data Service Mariner' s 1981. Salt Lake City, Utah. Weather Log, Vol. 1-24, 1957-1980 Wash., DC. 6. Court, Arnold. Tropical Cyclone Effects on 3. National Climatic Center Climatalogical Data­ California. NOAA TM NWS-w.R 158, 1980. Salt Lake National Summary, Annuals, Vol. 7-31, 1956-1980 City, UT. Ashevill, NC. Figure 1. Map of Study Area-Eastern North Pacific Ocean. " J-- Degrees CA ~ AZ ( -/--. r,atitude -( f I.M I l N 200 "I-_r~-__ J TX ........ """I \ \..r\ Mexico \ 10 43 .