Average hurricane season foreseen by CSU, but TSR predicts an active season

[phantom power]

A near-average Atlantic hurricane season is on tap for 2009, according to the latest seasonal forecast issued today by Dr. Phil Klotzbach and Dr. Bill Gray of Colorado State University (CSU). The Klotzbach/Gray team is calling for 12 named storms, 6 hurricanes, and 2 intense hurricanes. An average season has 10-11 named storms, 6 hurricanes, and 2 intense hurricanes. The new forecast is a step down from their December forecast, which called for 14 named storms, 7 hurricanes, and 3 intense hurricanes. The new forecast calls for a near-average chance of a major hurricane hitting the U.S., both along the East Coast (32% chance, 31% chance is average) and the Gulf Coast (31% chance, 30% chance is average). The Caribbean is also forecast to have an average risk of a major hurricane.

The forecasters cited several reasons for reducing their forecast from an active season to an average season:

1) Sea surface temperature (SST) anomalies in the tropical Atlantic have cooled considerably since December. In fact, these SST anomalies are at their coolest level since July 1994. Cooler-than-normal waters provide less heat energy for developing hurricanes. In addition, an anomalously cool tropical Atlantic is typically associated with higher sea level pressure values and stronger-than-normal trade winds, indicating a more stable atmosphere with increased levels of vertical wind shear detrimental for hurricanes. Part of the reason for the substantial cooling since December is because a stronger than average Bermuda-Azores High drove strong trade winds. These strong winds acted to evaporate more water from the ocean, cooling it. Higher winds also increase the mixing of cool waters to the surface from below. However, in March, the Bermuda-Azores High weakened. The resulting weaker trade winds may allow SSTs to warm to above average levels by the coming hurricane season, if this weaker Bermuda-Azores High persists.

2) Hurricane activity in the Atlantic is lowest during El Niño years and highest during La Niña or neutral years. The CSU team expects current weak La Niña conditions to transition to neutral and perhaps weak El Niño conditions (50% chance) by this year's hurricane season. April and May are typically the months when the atmosphere will swing between El Niño and La Niña, which makes any seasonal forecasts of hurricane activity during April low-skill. The current computer models used to predict El Niño (Figure 1) mostly favor neutral conditions for the coming hurricane season. These models are primarily based on statistical methods that observe how previous El Niño events have evolved. Three of the newer computer-intensive dynamical models (similar to the GFS model we use to make weather forecasts) do predict an El Niño event by hurricane season. The reliability of all of these models is poor.

http://www.wunderground.com/blog/JeffMasters/comment.html?entrynum=1207&tstamp=

[Nicholas D Wolfwood]

1. Is it just me, or does it seem odd that a state with almost no impact from hurricanes...

would have leading experts on the issue residing there... :shrug:

[RaleighNCDUer]

3. well, why not?

After all, they're starting out way up there with the clouds at eye-level.

[Nicholas D Wolfwood]

4. Damn, I knew Colorado was pretty high up there...

I didn't know it was THAT high!! :crazy:

[liberal N proud]

2. Colorado State University?

A hurricane prediction from the mountains?