• Judith Curry

Hurricane Irma eyes Florida

(Reno, NV) Cat 5 Hurricane Irma is one for the record books; it’s eye is on Florida.

Irma is predicted to strike the SW coast of Florida as a Cat 4 early Sun a.m., with a northward track covering the entire length of the state and into Georgia.

We’ve been monitoring this storm for two weeks, since the wave emerged from Africa.

Irma became a hurricane on 8/31. In a matter of a few hours, Irma became a major hurricane. The surprising thing about this development into a major hurricane was that it ocurred over relatively cool waters in the Atlantic – 26.5C — the rule of thumb is 28.5C for a major hurricane (and that threshold has been inching higher in recent years).

So why did Irma develop into a major hurricane? We can’t blame 26.5 C temperatures in the mid Atlantic on global warming. The dynamical situation for Irma was unusually favorable. In particular, the wind shear was very weak. Further, the circulation field (e.g. stretching deformation) was very favorable for spinning up this hurricane.

Irma intensified to Cat 5 on 9/5. This intensification was initially picked up by the models on 8/31, but at this point it was mostly a case of ‘right answer for the wrong reason’, since the models hadn’t yet settled down regarding track. Astonishingly, Irma has hung on to its Cat 5 status through the time of this writing.

The track forecast for Irma has been challenging because of:

  • a predicted sharp northward turn in the Caribbean

  • FL is challenging target for a northward moving tropical cyclone, because of its geography as a peninsula

A Florida landfall has been the favored prediction from CFAN’s calibrated ECMWF tracks since 9/03. ECMWF has been on target so far with the predicted tracks, with CFAN’s calibrations providing considerable value.

This blog post [link] provides forecast history for Irma and the latest predictions from Climate Forecast Application Network (CFAN).

About CFAN

Climate Forecast Applications Network (CFAN) develops innovative forecast tools that give longer and more accurate warnings of extreme weather events, so clients can better prepare and recover. CFAN’s staff applies the latest research to a wide range of customer challenges, helping businesses and government around the world. Our advanced prediction tools provide clients with the confidence to make complex and difficult decisions about weather risks.

CFAN was founded in 2006 by Judith Curry and Peter Webster and launched under the Enterprise Innovation Institute’s VentureLab program at Georgia Tech. Its research has been assisted by grants from NOAA, NASA, and the Department of Energy.

Contact Information

Dr. Judith Curry, President (404) 803-2012

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