Pacific ENSO Update
3rd Quarter, 2007 Vol. 13 No. 3
TROPICAL CYCLONE ACTIVITY
The PEAC archives western North Pacific tropical cyclone numbers, track coordinates, and 1 minute average maximum sustained wind taken from operational warnings issued by the Joint Typhoon Warning Center (JTWC) of the U. S. Air Force and Navy, located at Pearl Harbor, Hawaii. Western North Pacific tropical cyclone names are obtained from warnings issued by the Japan Meteorology Agency (JMA), which is the World Meteorological Organization's Regional Specialized Meteorological Center (RSMC) for the western North Pacific basin. The PEAC archives South Pacific tropical cyclone names, track coordinates, central pressure, and 10 minute average maximum sustained wind estimates from advisories issued by the Tropical Cyclone Warning Centers at Brisbane, Nadi, and Wellington. The numbering scheme and the 1-minute average maximum sustained wind estimates are taken from warnings issued by the JTWC. There are sometimes differences in the statistics (e.g., storm maximum intensity) for a given tropical cyclone among the agencies that are noted in this summary.
Second Quarter 2007 Summary
The 2007 typhoon season cyclone season is off to a slow start with a total of 4 cyclones (three typhoons and one tropical storm) numbered by the JTWC through late July. All four of the JTWC cyclones were given names by the JMA: Kong-Rey, Yutu, Toraji, and Man-Yi. Typhoon Man-Yi affected Guam and Yap when it was a tropical storm (see island summaries), and later blasted Okinawa with high winds and torrential rains as a very intense typhoon. Normally, the JTWC numbers 5 or 6 cyclones in the western North Pacific basin during the first half of the year. By July, this basin is typically on a rapid upswing in activity, and 4 or 5 numbered cyclones usually occur in this month. By the end of July, the JTWC typically numbers 10 or 11 cyclones. Thus, with only 4 numbered cyclones through late July, the season is indeed off to a slow start. The number of early season tropical cyclones in the western North Pacific is strongly related to El Niño, with more occurring during the onset of El Niño and fewer of them occurring during the year that follows El Niño. Forecasts for typhoon activity in the western North Pacific for all of 2007 are for below normal activity. With a normal of 30 numbered cyclones, however, a below normal season in this basin is not to be taken lightly.
The hurricane season in the eastern north Pacific is near normal in numbers of cyclones (six through late July), but only three of these cyclones passed beyond the depression stage and were named by the National Hurricane Center in Miami: Alvin, Barbara, and Cosme. Hurricane Cosme (weakened to a depression) passed south of the Big Island in late July bringing some gusty winds to the Hawaiian Island chain. In contrast to the 2007 North Atlantic seasonal hurricane outlook, experts at the NOAA Climate Prediction Center are projecting a 70 percent chance the East Pacific hurricane season will be below normal, a 25 percent chance that the season will be near normal, and only a five percent chance the season will be above normal. Tropical storm activity in the Central Pacific basin is also expected to be below average, with only two to three tropical cyclones expected to form or cross into the area during the 2007 season.