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Posted at 12:30 PM ET, 08/24/2012

Tropical Storm Isaac stronger, set to cross Haiti and Cuba on path to U.S.

Visible satellite image of Tropical Storm Isaac in the Caribbean from this morning. (NOAA/NESDIS)
Isaac has not reached hurricane intensity yet, but as of 11 a.m. EDT, the maximum sustained winds are 60 mph. This is the strongest the storm has been so far. The threshold for becoming a hurricane is 74 mph. It still does not appear to be poised to rapidly intensify – the deep convection (strongest thunderstorms) is mostly off to the south, and a developing storm “prefers” to have the strongest thunderstorms persistently form over the center. Hurricanes love symmetry.

If you’re tracking along, I have several radar loops covering Isaac’s journey through the Caribbean, and will add more sites as it heads for the U.S. The one from Gran Piedra, Cuba should be of particular interest today.

Link: Hurricane Tracker

Forecast rainfall totals from Isaac beginning this morning and ending on Wednesday morning. The bright yellow contours depict the 8-9” range. Localized higher amounts are likely. (NOAA/HPC)
Regardless of what exact intensity the storm is, there are dangers associated with any tropical cyclone.

The primary one for now is rain, and the associated flooding, mudslides, etc. Much of southern Florida could receive 6-9” in the next few days, with locally higher amounts. Areas in Haiti and Dominican Republic could see 10-20” of rain, with 6-12” in Jamaica and eastern Cuba. Besides flooding, additional threats include coastal storm surge, tornadoes, and of course, winds from the storm itself.

The suite of track models valid at 8 a.m. EDT. The two southern outliers aren’t dynamical models, they are basic climatology/persistence guidance. (UW-Milwaukee)
The track guidance as of 8 a.m. EDT today remained tightly clustered. All models show a turn to the west-northwest then northwest, taking Isaac over or near Haiti today, then along the spine of Cuba on Saturday into Sunday, before emerging into the Florida Straits (between Cuba and Florida) on Sunday morning.

Isaac should make its closest approach to southern Florida on Monday morning. Once the storm re-emerges over water on Sunday morning, we should see some intensification, but the exact amount will depend on how much it gets beaten up by traveling near Haiti and Cuba. It looks very likely that Isaac will spend Monday and Tuesday over the very warm eastern Gulf of Mexico in a low-shear environment as it heads toward the northern Gulf coast.

Probability of tropical storm force winds over the next five days. View larger. (NOAA/NHC)
Based on the 11 a.m. EDT advisory package from the National Hurricane Center, Key West has a 47% chance of experiencing tropical storm force winds in the next 5 days, Miami is at 26%, and Tampa is at 31%. Raising the bar to hurricane force winds, Key West stands at 5%, Miami at 0%, and Tampa at 1%.

If Isaac recovers from the trek over Cuba and begins to re-organize on Monday, it could become a dangerous situation for the entire eastern Gulf coast, from Louisiana to Florida. Stay tuned, and if you’re in any of those areas, it’s not a bad idea to calmly make some preliminary preparations. Finally, following up on yesterday’s discussion about the RNC in Tampa, not much has changed; Tampa is still expected to experience adverse weather conditions, and some minor storm surge, during the first half of next week.

Brian McNoldy is a senior researcher at the University of Miami’s Rosenstiel School of Marine and Atmospheric Science.

By Brian McNoldy  |  12:30 PM ET, 08/24/2012

Categories:  Tropical Weather, Latest

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