PEAC'S TROPICAL CYCLONE OUTLOOK SUMMARY

The PEAC tropical cyclone outlook for the second half of 2006 is for tropical cyclone development and movement patterns within Micronesia to be displaced toward the west and north through August, and then resume a more normal spatial distribution from September through the remainder of the year. The overall numbers of tropical storms and typhoons in the basin should be near normal . An observed shift of tropical cyclone tracks to the west of normal through early July should relax by fall, and thus the threat of a typhoon for Guam, the CNMI, Chuuk State, Yap State, and the Republic of Palau should be what is typical for these islands (see local variability summaries below). Islands from Pohnpei eastward into the RMI experience tropical storms and typhoons primarily during El Niño, so the risk of a damaging tropical cyclone in these locations is low.

The PEAC forecast considered input from two seasonal outlooks for tropical cyclone activity in the western North Pacific basin: (1) The City University of Hong Kong Laboratory for Atmospheric Research, under the direction of J. C-L. Chan, and (2) The Benfield Hazard Research Centre, UCL (University College London), Tropical Storm Risk (TSR) research group, UK, led by Dr Adam Lea and Professor Mark Saunders.

The Hong Kong group posted the following on its web site in June.

The predicted number of all TCs (Tropical depressions, tropical storms and typhoons, (TD+TS+TY)) is 31.
The predicted number for tropical storms and typhoons (TS+TY) is 28.
The predicted number of typhoons (TY) is 18.
With these changes, the average predictions from all the potential predictors therefore call for a near-normal year for all TC categories for the entire WNP.

[The mean numbers for these statistics from the JTWC are 31, 28, and 18 for (TD+TS+TY), (TS+TY) and (TY), respectively.]

The UK group posted the following on its web site in June

June Forecast Update for Northwest Pacific Typhoon Activity in 2006, issued: 7th June 2006.

The TSR (Tropical Storm Risk) June forecast update for Northwest Pacific typhoon activity in 2006 anticipates a season with slightly above-average activit y. The forecast spans the full Northwest Pacific season from 1st January to 31st December 2006 (95% of typhoons historically occur after 1st May) and is based on data available through the end of May 2006. … TSR’s main predictor for overall activity is the forecast anomaly in August-September 2006 Niño 3.75 sea surface temperature (SST). We anticipate this will be 0.13±0.43ºC warmer than normal and thus slightly enhancing for activity. Monthly updated forecasts for intense typhoon numbers and the [Accumulated Cyclone Energy] ACE index will be issued through to early August 2006.

The PEAC tropical cyclone outlook for Micronesia is for tropical cyclone development and movement patterns to be displaced toward the west and north through August, and then resume a more normal spatial distribution from September through the remainder of the year. The overall numbers of tropical storms and typhoons in the basin should be near normal. An observed shift of tropical cyclone tracks to the west of normal through early July should relax by fall, and thus the threat of a typhoon for Guam, the CNMI, Chuuk State, Yap State, and the Republic of Palau should be what is typical for these islands (see local variability summaries below). Islands from Pohnpei eastward into the RMI experience tropical storms and typhoons primarily during El Niño, so the risk of a damaging tropical cyclone in these locations is low.

For Hawaii, the forecast for the rest of the tropical cyclone season (through November 30th) continues to be for a slightly below average cyclone season with 2 or 3 tropical cyclones in the Pacific basin.

An update on the South Pacific cyclone season will be provided in the next newsletter. At this time, the forecast conditions for SST indicate a possible busier than normal tropical cyclone season for Samoa.