At 500 PM AST (2100 UTC), the eye of Hurricane Irma was located near latitude 18.8 North, longitude 65.4 West. Irma is moving toward the west-northwest near 16 mph (26 km/h), and this general motion is expected to continue for the next couple of days. On the forecast track, the extremely dangerous core of Irma will pass just north of Puerto Rico tonight, pass near or just north of the coast of Hispaniola Thursday, and be near the Turks and Caicos and southeastern Bahamas by Thursday evening. –ADVISORY LINK–
Maximum sustained winds are near 185 mph (295 km/h) with higher gusts. Irma is a category 5 hurricane on the Saffir-Simpson Hurricane Wind Scale. Some fluctuations in intensity are likely during the next day or two, but Irma is forecast to remain a powerful category 4 or 5 hurricane during the next couple of days.
Hurricane-force winds extend outward up to 50 miles (85 km) from the center and tropical-storm-force winds extend outward up to 185 miles (295 km). A wind gust to 62 mph (100 km/h) has been recently reported at San Juan, Puerto Rico.
The estimated minimum central pressure based on Air Force reconnaissance aircraft data is 914 mb.
Bryan Norcross – Wednesday update: Incredible HURRICANE IRMA is mauling the northern Leeward Islands this morning. There is reason to fear tremendous damage and loss of life on those islands. Top winds are still estimated at 185 mph, and the area covered by damaging winds is slowly expanding.
Irma will track over or very near the Virgin Islands and Puerto Rico this afternoon and tonight. The center of the storm will be close enough to those islands that full preparations are required, and extreme caution is necessary.
The northern parts of the Dominican Republic and Haiti are likely to be hit hard, especially due to the interaction of the circulation with the tall mountains producing mudslides. But the current thinking is that the center of Irma will be far enough offshore that the mountains will not dramatically weaken the storm.
Tomorrow (Thursday) the winds will pick up in the Southeastern Bahamas. The models indicate that the worst of Irma’s winds will move through the Southeastern and Central Bahamas on Friday. Strong winds will be felt throughout the island chain.
Then Saturday things get murky. Irma’s forecast track is a bit slower than it was yesterday. The storm is still expected to slow down Saturday near or over the west-central Bahamas or Cuba and then ease into the Florida Straits well south or southeast of the Keys late in the day. When storms move slowly, the forecast immediately becomes more difficult. And, of course, we’re talking about the location of the eye 3 or 4 days in the future.
All indications continue to be, however, that a very large and powerful hurricane will move over or near the Keys and head north on Sunday. There is no certainty and nobody knows if the core of the storm, where the strongest winds are, will track close to the east coast, west coast, or go right up the center of the peninsula, in which case it would affect both coasts.
There are, however, changes to the model forecasts this morning, not that they are conclusive.
Your government – specifically NOAA – is throwing all of their resources at making the best possible forecasts. They are collecting double the usual data over the U.S., detailed upper-air data around the storm, and essentially continuous data from inside the hurricane itself. All of this data is fed into the computer models, but still we are left with significant uncertainty due to the number of factors that can still affect the storm before it gets to Florida.
The consensus of the models that ran overnight that took advantage of the data fed into them last evening, has shifted east, so more possible tracks are slightly offshore of the east coast. Previously, they were spread across the state. The National Hurricane Center is always suspicious of large model shifts in just one run, because sometimes they shift back after more data is collected.
Therefore, the official NHC morning forecast brings Irma over the Florida Keys and north into the peninsula on Sunday. Irma is expected to be a large, powerful hurricane at that time, although some weakening from it’s incredible Category 5 self is anticipated. Remember that the average forecast error 5 days out is over 200 miles, so moves by the models from one side of the state to the other is within that range. We have to wait for more data and more model runs to see how the details change. And the difference between the east coast and west coast of Florida is a detail at this point.
Today is the day that governments across the southern part of Florida are going to have to make final hard decisions. If a reasonably imaginable forecast would produce life-threatening conditions – especially due to the ocean, Gulf, or Florida Bay rising up and inundating the land – they have to move people out of the way well in advance of that happening. That means ordering evacuations while the forecast is still uncertain.
A key part of the forecast challenge is even more difficult than predicting where the worst of the winds will track. That’s where the worst storm surge will occur. The height of the water rise at any one place is dependent on the angle the storm is moving, the strength of the wind, the length of time the wind blows from the same direction, and other factors. Since the storm surge is the deadliest threat from the hurricane, it’s critical that people are out of areas where the water may inundate neighborhoods, not to mention evacuation routes. This is the most difficult aspect of preparing a community for a hurricane.
The west coast of Florida – including the Ft. Myers/Cape Coral/Naples area and Tampa Bay – are spectacularly vulnerable to storm surge. Much more so than the east coast, which still has many threatened areas.
If the storm looks like it could go up the west coast, evacuations are going to be required there, which will create an epic movement of people through the State of Florida. If this happens, and you are in an evacuated area, do not dawdle. Do not even think about dawdling. Immediate action will be required.
Every day that goes by in the ramp up to a hurricane gets more difficult because people get more frantic, stores run out of supplies, and the traffic gets worse. This storm presents an elevated level of difficulties because it may affect the entire peninsula with dangerous weather. The means that early preparation is more crucial than normal, and it’s always a good idea.
If you didn’t see yesterday morning’s prep list, check it out in the post below. Now is the time to set yourself up to deal with the storm. And crucially, be sure you know your evacuation status – are you in an evacuation zone and have you been ordered to leave? – and make a plan for where you will go. The closer to home the better, though some areas will require a significant drive.
This complex situation will require all Floridians to pay especially close attention to instructions from local officials starting immediately. Be informed. Be ready. Take action. (Facebook Link)