Hurricane dynamics

By: Jeff Masters and Bob Henson , 3:04 PM GMT on July 18, 2016

The Eastern Pacific's unending parade of tropical cyclones continues. The latest member of the show is Hurricane Estelle, which got its name Friday night. Joining the party Tropical Storm Agatha started on July 2 have been Category 4 Hurricane Blas, Category 2 Hurricane Celia, Category 3 Hurricane Darby, and soon-to-be Category 1 Hurricane Estelle (Estelle was a high-end tropical storm with 70 mph winds at 11 am EDT Monday.) This puts us well ahead of climatology: the Eastern Pacific usually does not see its fifth named storm until July 22, its fourth hurricane until August 12, and its second major hurricane until August 19. An average season has 15 named storms, 8 hurricanes, and 3 major hurricanes.

•••••

The Atlantic remains quiet--but beware of this year's ocean heat content!

As is usually the case when the Eastern Pacific is active, the Atlantic is quiet. This inverse correlation in activity occurs because the conditions over the Eastern Pacific driving this July's bounteous activity--surface low pressure and rising air--creates a compensating area of sinking air over the tropical Atlantic. This sinking air creates surface high pressure and dry weather--the antithesis of conditions needed for tropical cyclone formation. There are no tropical cyclone threat areas in the Atlantic to discuss today, and none of the reliable models for tropical cyclone formation is predicting development during the coming five days. Don't expect to see much activity in the Atlantic until the Eastern Pacific's burst of activity slows down. When we finally do get the surface low pressure, rising air, low wind shear, plentiful low to mid-level moisture and an African tropical wave needed to spawn an Atlantic hurricane, watch out. Record to near-record levels of heat energy are in the Atlantic in the Caribbean, Gulf of Mexico and waters surrounding the Bahamas (Figure 2), exceeding even the heat energy that was available during the notorious Hurricane Season of 2005. This year's high levels of ocean heat content in the Atlantic increases the odds of dangerous rapidly-intensifying major hurricanes if the other conditions needed for intensification are present.

•••••