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Irma ravages South Florida

Conditions to deteriorate overnight in Northeast Florida, Southeast Georgia


JACKSONVILLE, Fla. – Hurricane Irma continues tracking up Florida’s west side, and even though its eye is still more than 200 miles south-southwest of Jacksonville, it is important to remember that this is a very large storm -- much, much larger than Hurricanes Andrew and Charley.

Although Irma’s core looks less impressive on radar than earlier Sunday (in fact, the southern eye has opened up), hurricane hunters flying inside Irma Sunday evening reported 105 mph winds in its southeast quadrant.  Doppler radar velocity data also shows similar strength wind aloft. So the National Hurricane Center’s official 11 p.m. update keeps Irma at Category 2 status, with 100 mph wind. It continues moving to the north, at 14 mph.

Despite the slow weakening, this is still a very dangerous storm that will have a significant impact on The Sunshine State.

Irma’s outer rain bands have already wreaked havoc on the northern half of Florida.  The tornado threat is increasing, and a number of tornado warnings (including some touchdowns) have occurred.  Wind gusts have been increasing, as well. Hurricane Irma passed over the Florida Keys as a Category 4 storm Sunday morning, and made landfall at Marco Island this afternoon as a Category 3 storm with 115 mph winds.

The Weather Authority’s forecast philosophy remains unchanged: Irma will continue on a path right up the western side of the state, with its track bending slightly to the northwest as it approaches northern Florida. An in-house RPM model has now incorporated the data from Sunday evening’s critically important 8 p.m. weather balloon launches, and the raw output images below show the storm’s progression nicely:

4 a.m. Monday

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8 a.m. Monday

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12 p.m. Monday

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4 p.m. Monday

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The RPM also gives us projections of the storm’s wind field. These maps show the model’s wind forecast. The light blue color is tropical storm to Category 1 (39-73 mph) force winds, and the cyan shade represents Category 1 to Category 2 winds (74-96 mph):

4 a.m. Monday

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8 a.m. Monday

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12 p.m. Monday

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4 p.m. Monday

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Notice the patch of cyan color that shows up over the ocean just off Florida's coast. This suggests that hurricane force winds are possible offshore during the first half of the day on Monday, with conditions diminishing to tropical storm force by late afternoon.

Even more important is the wind direction: Those strong winds are blowing toward the coast, which means that water will be pushed inland. This storm surge will cause significant flooding in coastal locations of northeast Florida into southeast Georgia. Also notice that by late afternoon, the wind over Jacksonville is blowing from the south. That will push St. Johns River water northward, causing a significant flood potential for downtown Jacksonville, depending upon how strong that wind is when the directional shift to the south occurs.

Some people are asking if any other major hurricane (Category 3 or higher) has taken the same path that Irma is. We checked historical maps dating back to the mid-1800s, and there was only one major hurricane that even comes close: a storm in the 1930s that crossed the Keys and traveled parallel to the state’s west coast, but well offshore. So, in essence, no major hurricane in recorded history has taken the path that Irma has.

Major Hurricane Tracks: 1930-1939
Source: National Atlas (USGS)

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Earlier Sunday:

The Category 4 strike on the Keys, following Hurricane Harvey's landfall on the Texas coast as a Category 4 storm, makes this the first year in recorded history in which two Category 4 storms hit the United States.

Here are some peak wind gusts reported thus far around the state:

Earlier Sunday, the National Weather Service in Key West reported a 10-foot storm surge on Cudjoe Key, with inland water levels reaching 10-14 feet.

Irma continues its march up the state's west coast. We just received a report that all bridges in the Tampa area have now been closed. This will be the first direct hit by a hurricane on the Tampa area in nearly a century. The National Hurricane Center's 5 p.m. update reflects some weakening due to land interaction and increasing wind shear, as expected. However, Irma remains a very dangerous Category 2 storm with 110 mph sustained winds near the center.

The tornado threat has increased over the Florida peninsula from south to north, and there have been a number of tornado warnings throughout the day.

Conditions in northeast Florida/southeast Georgia will continue to deteriorate through Sunday night into early Monday. We continue to expect possible hurricane force wind gusts developing primarily west of I-75, with widespread tropical storm-force gusts east of there. As mentioned in the previous update, winds ahead of Irma from the east and northeast will promote coastal flooding, while the inevitable wind shift to the south on Monday will drive St. Johns River waters northward, creating a significant flooding hazard for downtown Jacksonville. As for the western side of the state, those east winds ahead of the storm do not pose their flood threat. Rather, once the eye passes north of them, vicious west winds on the bottom side of the storm will drive Gulf of Mexico waters inland -- this storm surge will be very destructive.