East PAC season starts today

The tropical season in the Eastern Pacific begins today, May 15th. The season starts earlier in the Eastern Pacific than it does in the Atlantic Basin or even in the Central Pacific, both of which begin on June 1st. The Western Pacific can be active essentially all year long.

The Eastern Pacific typically has more named storms than the Atlantic does. 2009 was a rather busy year with 18 named storms including 7 hurricanes, 4 of which became major Cat 3 or greater. The primary reason for such a strong season was the presence of El Nino which shifted warm sea waters to the eastern portions of the Pacific Basin.

Meteorologist Erin Jordan from KOLD in Tuscon, AZ points out that average seaons in the Eastern Pacific have a greater number of storms than both El Nino and La Nina years do. This could be due to increases in wind shear during these peorids (I'm guessing, I certainly do not know that for a fact), but the expectation is that this year's hurricane season for the Eastern Pacific is expected to be milder that normal.

East Pacific Hurricane Season starts Saturday (KOLD)

With El Nino officially gone from the equatorial East Pacific, the water temperatures are not as favorable for tropical storm development.
However, the data from the last 50 years shows that an average year has more named storms than both La Nina or El Nino years.

If a La Nina forms, cooler than average sea surface temperatures dampen the formation of tropical storms even more than in El Nino years.

Right now, the equatorial East Pacific is in the neutral phase with near average sea surface temperatures.

However, some of the global models that forecast swings in El Nino and La Nina are predicting a swing towards La Nina, which are cooler than average sea surface temperatures.

If this happens, less tropical storms may form and we may not see as many Gulf of California moisture surges to rev up our afternoon monsoon storms.

On the flip side, the overall monsoon circulation is more favorable for day to day storm development over the Southwest.

There is much debate right now as to whether La Nina will form or not. If La Nina does develop, cold water will shift towards North America which will result in even less activity in the Eastern Pacific.