Hellish Intensification — Maria’s Winds Jump 50 mph to CAT 5 Strength in Just 12 Hours

A special statement from the National Hurricane Center reports that Maria has reached Category 5 intensity — with maximum sustained winds of 160 mph and a minimum central pressure of 924 mb. This is, perhaps, one of the most rapid intensifications the Atlantic basin has ever seen — with the storm seeing a 40 mb drop in pressure in approximately 6 hours and crossing the Category 4 threshold to Cat 5 intensity in even less time.

Maria is now a very dangerous hurricane — barreling into Dominica and the Leeward Islands before turning toward both the U.S. Virgin Islands and Puerto Rico over the next 36 hours. It is also the second Category 5 storm to threaten the region in just two weeks time.

As of this morning, Maria was a strong Category 2 Hurricane featuring 110 mph maximum sustained winds. Forecasters noted a potential for rapid intensification as the storm began to move over warmer than normal surface waters in the range of 29 degrees Celsius (84 to 85 degrees F) and as the atmospheric conditions became more favorable for storm development.

By late morning, the storm had strengthened into a major hurricane with 120 mph maximum sustained winds. But Maria still had a few surprises in store. The storm swiftly developed a small, pinhole, eye. Such small eye structures enable storms to more rapidly wrap winds around a compact center. It’s the kind of structure that can result in very fast intensification.

After the pinhole eye structure formed, Maria jumped to category 4 strength with 130 mph winds by late afternoon. Then, by the 9 PM advisory from the National Hurricane Center, the storm made the considerable leap to Category 5 status with 160 mph maximum sustained winds.

The storm, at this time is now zeroing in on Dominica — which is presently seeing very rapidly deteriorating conditions.

Maria presently has a smaller hurricane force wind field than Irma — with hurricane strength winds only stretching about 15-20 miles from the storm’s center. Those winds, however, are very intense and capable of inflicting catastrophic damage. All within the path of this terrible storm should seek shelter in the strongest structures possible immediately and heed any warnings or advice from local disaster authorities.

Conditions in Context

Like Irma and Harvey, Maria is tapping warmer than normal sea surface temperatures which is helping it to reach a higher peak intensity. This year, thunderstorms in the Inter-Tropical-Convergence-Zone (ITCZ) have been unusually intense. Strong thunderstorms in this region are basically the seeds that can grow into powerful tropical cyclones. So the larger, more energetic, more moisture-rich, and more numerous these storms, the higher potential that a strong hurricane will ultimately form once such systems enter the Tropical Atlantic. Warmer ocean surface temperatures are a direct upshot of human-caused climate change and there is some evidence that climate change is also increasing the intensity of the world’s most powerful thunderstorms — particularly over the Equatorial regions.

In addition to these climate change related factors, La Nina-like conditions in the Equatorial Pacific are helping to reduce wind shear over the Tropical Atlantic. Reduced shear helps to allow the larger than normal storms emerging from Africa to tap the warmer than normal surface waters across the Atlantic. So in total, this is a pretty vicious combination of both natural and climate change related factors. A set that is enabling one of the worst hurricane seasons on record for the Atlantic.

(UPDATED: UPDATES TO FOLLOW)

RELATED STATEMENTS AND INFORMATION:

Links:

The National Hurricane Center

Hat tip to Bostonblorp

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Irma’s Projected Path Shifts West; Storm Expected to Restrengthen to Category 5

As of the 5 PM advisory from the National Hurricane Center (NHC), dangerous Hurricane Irma was packing 155 mph maximum sustained winds and tracking just north of due west off the Cuba coast.

The new advisory provides a couple of surprises. One, Irma’s path has shifted more to the west. As a result, the West Coast of Florida and western South Florida is under more of a threat from Irma. That said, the NHC has not backed off its storm surge forecast of 5-10 feet for places like Miami. So, so far, that vulnerable city is not out of the woods — particularly for southern sections of the city.

(Official track shifts west for Irma as the Hurricane Center now predicts the storm will restrengthen to category 5 intensity over the Florida Straits after raking the coast of Cuba. Image source: The National Hurricane Center.)

This is likely due to the fact that Irma has a very large circulation with tropical storm force winds extending outward up to 160 miles from its center and hurricane force winds extending up to 60 miles from the storm’s center. So a west coast landfall in South Florida has the potential to still bring hurricane conditions to places like Miami. That said, if the track continues to shift west, Miami may dodge a bullet as our concerns shift to places like Fort Myers and possibly Tampa.

The NHC’s full statement on present storm surge potential is as follows:

SW Florida from Captiva to Cape Sable…8 to 12 ft
Cape Sable to Boca Raton including the Florida Key…5 to 10 ft
Venice to Captiva…5 to 8 ft
Anclote River to Venice including Tampa Bay…3 to 5 ft
Boca Raton to Flagler/Volusia County line…3 to 6 ft

So basically all of South Florida from Cape Coral to Boca Raton is looking at a 5-12 foot storm surge according to the present NHC forecast. That includes Miami, Ft Lauderdale, the Keys, and the Fort Myers area.

(The NHC’s 5 PM storm surge inundation map shows the potential for significant flooding from South Miami to the Cape Coral area and on out to the Florida Keys. For reference, blue regions are expected to see more than one foot of water above ground, yellow more than three feet, orange more than six feet, and red more than nine feet.)

The second surprise in the recent official forecast is that the NHC now briefly expects Irma to regain category 5 status as it crosses the Florida Straits. Projected 36 hour intensity from NHC is for a storm packing 160 mph winds at that time. This increase in strength now jibes with a number of model forecasts that show Irma tapping much warmer than normal Gulf Stream waters just prior to striking Florida.

It’s worth noting that intensity forecasts are sometimes tough to nail down and the NHC is quick to caution that fluctuations in storm strength are likely. In any case, this is a very dangerous storm that bears watching.

(UPDATES TO FOLLOW)

 

Models Show Irma Tracking Toward 88 Degree (F) Waters Before Setting Sights on Florida, Georgia and South Carolina

As of yesterday and today, Irma was the strongest storm ever to form in the Central Atlantic. Fueled by record atmospheric and ocean heat and related high atmospheric moisture content, the storm plowed into the Leeward Islands of Barbuda, St. Martin and Anguilla as a top-strength Category 5 monster hurricane.

(Alex Woolfall takes shelter in a concrete stairwell in St. Martin to avoid Irma’s catastrophic winds. It’s worth noting that hurricanes are heat engines. Tapping 87 F sea surface temperatures and producing 100 percent humidity would result in the very hot conditions Alex was experiencing 7 hours ago. We’re all pulling for Alex and those like him who were trapped in the belly of this massive beast. His last report was at 5:45 AM.)

As Irma’s eyewall began to pass over Barbuda, a reporting station recorded a wind gust of 155 mph before it was knocked out. That island of 1,800 people is now completely cut off from the outside world. Having just experienced winds in excess of those hosted by Andrew and Camille, it is likely that catastrophic damage was inflicted.

On St. Martin, which also passed through Irma’s eye and most intense wind bands, initial reports are also showing very considerable damage. Four of the strongest buildings on the island have been destroyed. And it is expected that most structures across this French/Dutch shared island which is home to 75,000 have seen moderate to catastrophic damage.

(Footage this morning, apparently taken from a camera near the airport at Simpson Bay in St. Martin shows debris, flooding, and very strong winds.)

Anguilla, which is north of St. Martin and is home to another 15,000 souls, passed through the northern eye wall. This is typically the most intense part of a hurricane. So far, reports from Anguila are spotty. But the damage there is likewise expected to be catastrophic.

As of the 5 PM advisory, according to the National Hurricane Center, Irma is still a devastatingly powerful Category 5 monster hurricane hosting maximum sustained winds of 185 mph. The storm had seen some weakening due to apparent eyewall replacement and mild wind sheer — which pushed pressures back up to 920 mb from a low of 914 mb last night earlier today. However, this weakening was not significant enough to impact Irma’s amazing wind intensity. Since that time, Irma’s central dense overcast has thickened while pressures have dropped back down to 914 mb as of the 5 PM advisory.

(Irma tracking just slightly north of the officially projected path from the NHC as of early afternoon on Wednesday. Image source: The National Hurricane Center.)

As the storm passes toward the Virgin Islands, roars by Puerto Rico, and howls into the Turks, Caicos and Bahamas, it is likely that some weakening will occur. Despite this fact, the storm is expected to maintain Category 5 intensity through at least the next 48 hours. After 72 hours, the official forecast calls for Irma to drop to strong Category 4 intensity and eventually a strong Category 3 by Monday. However, some models like the GFS show Irma again strengthening as it taps very warm waters off Florida.

(Very hot sea surface temperatures off Florida could provide fuel that allows Irma to strengthen a second time as predicted in forecast models like the GFS. Image source: Earth Nullschool.)

Most models are now starting to settle on a consensus that brings Irma toward Florida and along a course that may threaten Georgia and South Carolina. The GFS model shows Irma tapping extremely hot sea surface temperatures in the range of 88 degrees Fahrenheit (about 3.5 F hotter than average) and pumping up again into very strong Category 5 intensity with an 895 mb minimum central pressure off Florida by Sunday. This would be a stronger intensity than the 914 mb reached last night by measure of pressure alone.

(The GFS, ECMWF and other major models are starting to agree on a consensus track which has Irma raking the Florida coast before threatening Georgia and the Carolinas. Image source: The National Hurricane Center.)

GFS shows the storm raking most of the Florida coast as it bounces from one landfall or near landfall to another across the eastern seaboard before making a final landfall as a 924 mb monster along the Georgia-South Carolina border. Meanwhile, another major model — the Euro (ECMWF) — has the storm following approximately the same path at a lower intensity.

Though the GFS modeled intensity does not jibe with the official forecast — which calls for weakening of Irma to strong Cat 4 and then strong Cat 3 status — we should not completely rule out the GFS prediction due to those very warm ocean surfaces mentioned above. If predicted wind shear does not emerge, then it would allow Irma to more effectively tap those very warm waters off Florida and hit a second peak intensity. And if such a forecast were realized, it would produce a seriously catastrophic disaster for the U.S. East Coast.

(Models are starting to come into consensus on Irma’s track — which is zeroing in on it raking the Florida coast and then slamming into Georgia or South Carolina — but forecast intensity varies widely. GFS shows Irma off Florida at an intensity stronger than her present extreme strength by Sunday. Image source: Tropical Tidbits.)

Of course, the official forecast track and intensity — in which a strong Category 4 storm rakes coastal Florida and then tracks up into Georgia or South Carolina to make final landfall as a strong Cat 3 is bad enough. So in this case, we are looking a present forecast scenarios in which models are starting to come into consensus on track that range from bad (official Cat 4 and then Cat 3 intensity storm impacting Florida, Georgia and the Carolinas) to worse (GFS potential for a very strong cat 5 storm threatening the U.S. Southeast Coast).

(UPDATED — UPDATES TO FOLLOW)

STATEMENTS AND RELATED INFORMATION:

Links:

The National Hurricane Center

Earth Nullschool

Tropical Tidbits

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