Tropical Storm Risk on ‘Remarkable’ 2010 Hurricane, Typhoon Seasons

December 3, 2010

To mark the end of the 2010 Atlantic hurricane season, Tropical Storm Risk (TSR), which provides resources for predicting and mapping tropical storm activity worldwide and is co-sponsored by Aon Benfield, has issued a series of reports summarizing the 2010 Atlantic hurricane and the 2010 Northwest Pacific typhoon seasons. TSR announced that both seasons had been record (or near-record) breaking but in very different ways.

Speaking at the Aon Benfield Japan Seminar in Tokyo, Professor Mark Saunders of TSR highlighted the following features of these two remarkable seasons.

2010 Atlantic Hurricane Season:
— One of the most active on record with 19 tropical storms and 12 hurricanes. Only 2005 has seen more hurricanes (with 15), and only 2005 and 1933 have seen more tropical storms (with 28 and 21 respectively).
— No US land falling hurricane. This is unprecedented for a season with at least 10 hurricanes.
— Fifth year in a row with no major hurricane strike on the US. The only previous time this has happened was in 1901-1905.
— Two hurricanes – Igor and Julia – occurred simultaneously at Cat 4 intensity. This last happened in 1926.

2010 Northwest Pacific Typhoon Season:
— Very likely to be the least active season since reliable records began in the mid 1960s.
— Currently just 14 tropical storms and 8 typhoons. The previous records for the least number of tropical storms and typhoons in a year were 17 and 9 respectively set in 1998.
— Experienced fewer tropical storms than the North Atlantic in 2010. Apart from in 2005 this has never happened before. A ‘normal’ typhoon season experiences nearly three times more storm activity than the North Atlantic.
— No Japanese-mainland land falling typhoon. This is only the second such occurrence since 1988.

Saunders added: “The very active Atlantic hurricane season was caused primarily by record-breaking warm sea surface temperature anomalies in the tropical North Atlantic, combined with weaker than normal vertical wind shear caused by La Niña.

“These factors helped to energize and sustain storms. The exceptionally low Northwest Pacific typhoon season was caused by La Niña reducing cyclonic vorticity over the Northwest Pacific where typhoons form. This made it difficult for storms to spin-up.”

He also noted that forecasts had pretty well predicted the high North Atlantic hurricane activity from the previous December, but had not anticipated the unprecedented lack of US land falling hurricane activity.

The low Northwest Pacific typhoon activity had also been pretty well forecast in updates after May 2010.

Source: Aon Benfield

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