Comparing June with last year, plus July 2006 outlook

[phantom power]

Nice graphics over at the link.

A look at June 2006
An opposite trend in surface pressures occurred in June 2006, compared to June 2005 (Figure 3). The Bermuda High has averaged 7 mb stronger than normal this month--and a full 12 mb stronger than last year's June Bermuda High. Low pressure has dominated the Eastern U.S., thanks to a persistent dip in the jet stream that has brought rain, floods, and relatively cool weather to the Eastern U.S. This dip in the jet stream has also brought much higher levels of wind shear to the Gulf of Mexico and Caribbean than we saw last year in June.

As a result of the stronger Bermuda High this June, the trade winds blowing across the tropical Atlantic are much stronger than they were last year in June. These stronger winds have cooled the ocean, and SSTs are only 0.5 - 1.0 degrees C warmer than average this June, compared to 1 -2 degrees above normal in June 2005. This year's SST anomaly is still quite high, but probably not enough to support major hurricanes in July, like we saw last year with Dennis and Emily.

Outlook for July 2006
The two-week forecast from the GFS model continues to show the jet stream dipping over the Eastern U.S., and a stronger than normal Bermuda High. This pattern favors a continuation of the cool, rainy weather over the Northeast U.S., and hurricane strikes on Florida and the East Coast of the U.S.--or recurvature out to sea. The Gulf Coast has lower than average odds of a strike. This jet stream pattern should act to keep wind shear high over the main breeding grounds for July tropical cyclones--the Gulf of Mexico, Bahamas, and western Caribbean. If a hurricane does manage to develop and dodge the shear, it is unlikely it will become a major hurricane, due to the relatively cool ocean waters expected this July, compared to July 2005. Thus, July 2006 will not be a repeat of July 2005, which had five named storms, three hurricanes, and two intense hurricanes. If the current upper-level jet stream pattern holds in place, I think we can expect one or two named storms in July, one of them being a hurricane (not major). Will the current jet stream pattern hold? We are not very good at anticipating when these "blocking patterns" in the large scale atmospheric flow will change. Sometimes they can last for an entire season. If the pattern breaks in the last half of July, we could see more activity than I am forecasting here. In any case, I am still anticipating that August and September will be very busy again this year, so enjoy the relatively quiet start to hurricane season!

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