Pacific ENSO Update

3rd Quarter, 2007 Vol. 13 No. 3


The PEAC tropical cyclone outlook for the upcoming typhoon season of 2007 is for overall activity in the basin (e.g., numbers of tropical storms, numbers of typhoons, and numbers of intense typhoons) to be below normal. The track distribution should be near normal. 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 considered to be low during 2007. From Guam and the CNMI westward through Yap State and the Republic of Palau, the late summer and fall will likely bring 3 or 4 typhoon threats that will necessitate gale warnings and high-seas advisories for some or all of the islands. The risk of a direct hit by a damaging typhoon for Guam and the CNMI will be 10 to 15%; the risk of a direct hit by a damaging typhoon in Yap and its northern atolls will be on the order of 5 to 10%; and in the Republic of Palau the risk will be around 5% (1 in 20 odds). This level of threat for these locations is normal.

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, University College London, Tropical Storm Risk (TSR) research group, UK, led by Dr Adam Lea and Professor Mark Saunders.

Both the Hong Kong Center and the TSR consortium anticipate that the 2007 Northwest Pacific typhoon season will see slightly below average activity. They are expecting a small (15%) reduction in all categories: annual number of tropical cyclones, annual number of typhoons, annual number of intense typhoons, and the accumulated cyclone energy (ACE). ACE is a measure of the total energy expended by a tropical cyclone during its life. These forecasts span the full Northwest Pacific season from January to December. The activity so far in 2007 has been below normal.