About Jeff Masters
Dr. Masters co-founded wunderground in 1995. He flew with the NOAA Hurricane Hunters 1986-1990. Co-blogging with him: Bob Henson, @bhensonweather
By: Dr. Jeff Masters , 1:22 PM GMT on August 28, 2006
The hurricane season of 2006 has claimed its first victim, a woman washed away by Ernesto's storm surge in Haiti yesterday. However, it appears that we have not had a repeat of the massive flooding disaster of 2004, when Hurricane Jeanne brushed Haiti, killing 3000. Ernesto is still pounding Haiti and the Dominican Republic with relentless heavy rains as it moves ashore into Cuba this morning. Rainfall amounts of 8 inches have been reported in Barahona, Dominican Republic, and amounts as high as 20 inches may have fallen in Haiti. Cuba is receiving its own torrential rains, but is being spared a significant storm surge or high winds. Ernesto is barely a tropical storm, and I expect it will be a tropical depression Tuesday morning when it pops off the coast of Cuba into the Florida Straits. Given the great success of Hispaniola and Cuba at weakening the storm, the threat to Florida is now much reduced. Let's analyze the possibilities.
Figure 1. Surface wind analysis at 9:30pm EDT last night shows Ernesto had maximum winds of only 40 knots (45 mph) in a small circle (lightest blue color) between Cuba and Haiti.
Ernesto and Florida
The NOAA jet flew last night, and last night's 00Z (8pm EDT) set of model runs have come into much better agreement on a track into South Florida Tuesday night or Wednesday morning. Two model runs are available from the latest 6Z (2am EDT) model cycle, and continue the trend of pushing the forecast tracks to the east. The GFS and GFDL models have virtually identical tracks for their 72-hour forecasts, with Ernesto as a Category 1 hurricane with 75 mph winds and a pressure of 983 mb when it hits Key Largo Tuesday night or early Wednesday morning. This more easterly track is believable given Ernesto's recent northwesterly track.
Wind shear remains low and is forecast to remain low for the duration of Ernesto's life, so the key factor controlling his intensity will be interaction with land. To get an idea of how quickly Ernesto might reintensify once emerging into the Florida Straits, it is helpful to search the historical record. I found two storms similar to Ernesto that crossed the tip of Haiti, hit Cuba as hurricanes, then emerged into the Florida Straits. Hurricane Inez of 1966 hit Cuba as a Category 3 hurricane, then weakened to a tropical storm when she emerged into the Florida Straits. It took three days before she was able to re-intensify into a Category 2 hurricane in the Gulf. The August 1894 Category 2 hurricane that hit Cuba took only one day to re-intensify from a tropical storm into a Category 2 hurricane once it emerged into the Florida Straits. This storm hit Ft. Myers as a Category 2 storm. Dissipation of Erensto is also possible, as happened to a 1916 tropical storm that hit Cuba on a similar track and died as it emerged into the Florida Straits. A 1928 tropical storm following a similar path never regained hurricane strength, despite spending two full days over the Gulf after encountering Cuba. So, history is against Ernesto becoming anything stronger than a Category 1 hurricane upon landfall in South Florida, and I believe landfall as a tropical storm is more likely. If Ernesto does take a more westerly track up the west coast of Florida towards Sarasota, landfall as a Category 1 hurricane could occur.
Ernesto is a more significant threat to the Carolinas
While much of the focus of attention has deservedly been on Ernesto's impact on Florida, I believe the best chance of Ernesto hitting the U.S. as a Category 2 or 3 hurricane will come in the Carolinas. The GFDL model has Ernesto as a borderline Category 1 or 2 hurricane with a pressure of 975 mb Thursday night upon landfall in South Carolina. The GFS, UKMET, and Canadian models predict that Ernesto will stall off the Carolina coast, as the trough of low pressure drawing it northeastwards accelerates away. High pressure will then build in, forcing Ernesto back to the west towards the Carolina coast. If this happens, Ernesto will have plenty of time over the warm Gulf Stream, and could easily reach Category 2 or 3 strength before making landfall in the Carolinas. The NOGAPS model depicts a similar scenario, but predicts Ernest will stall further north, then move west, threatening the Mid-Atlantic states.
I'll have an update late this afternoon when the 12Z (8am EDT) model runs are in. I will also post an explanation of which models to trust, and where to get plots of the output from the various models. The Hurricane Hunters have gone home; they will not be flying the storm while it is over Cuba, so there will be nothing new to report from them.
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