As of the 8 PM advisory from the National Hurricane Center (NHC), Hurricane Irma was located 85 miles east of Antigua moving west at 15 mph. The storm hosted maximum sustained winds of 185 mph and a minimum central pressure of 916 mb.

This is an intensity considerably stronger than that previously projected or even expected as an outlier possibility for today. One that has heightened concern over an already powerful storm. A storm that is drawing extra energy from an atmosphere and ocean warmed by climate change.

#GOES16 IR loop of #Irma. Mesmerizing, jaw-dropping, and terrifying. It's also an amazing display of Mother Nature's raw power. pic.twitter.com/X4s5TrbkIy — Brian James (@BrianJamesNBC5) September 5, 2017

Though moving west at this time, Irma is expected to turn toward the west-northwest. On its present and predicted path, the NHC expects severe hurricane conditions including hurricane force winds, very tall and destructive breaking waves, and life-threatening 7-11 foot storm surges to start impacting the extreme northern Leeward Islands by late Tuesday afternoon and early evening.

A Worrisome Set of Forecasts

The storm is expected to continue on a west and then west-northwest track bringing it close to Puerto Rico and the Dominican Republic and over the Turks and Caicos and southeastern Bahamas by Thursday. After which time, the storm is expected to skirt the northern coast of Cuba before turning toward the Florida Keys on Saturday.

(National Hurricane Center’s official path brings Irma to the Florida Keys by Sunday. Image source: NHC.)

The current official National Hurricane Center forecast has the storm maintaining major hurricane status all along its projected path. Category 5 intensity is expected to be maintained for much of the next three days after which time the NHC projects Irma to weaken a bit — remaining in the very dangerous, strong category 4, range.

Meanwhile, various models, including GFS and SHIPS produce a very severe Category 5 storm featuring intensities from 895 to 910 mb in the vicinity of U.S. southeast by Saturday through Monday. This storm is, therefore, very dangerous and is likely to stay that way for some time — barring a close interaction with the mountains of Puerto Rico or Hispaniola or a prolonged landfall over Cuba.

Latest GFS model run shows insane 890mb CAT 5 Irma hitting the Carolinas by Mon Sep 11. WTH?? #climatechange #irma https://t.co/IYONAWUIqr pic.twitter.com/RxIJFyv6F6 — Robert Fanney (@robertscribbler) September 5, 2017

(The present GFS model run shows a nightmare scenario for the Carolinas with an 890 mb hurricane on approach by Monday. It’s worth noting that the official NHC projected track is more to the south with a weaker — but still very dangerous — category 4 storm in the region of Florida by late Saturday. Image source: Tropical Tidbits.)

Strongest Central Atlantic Storm on Record

The storm’s present intensity is now among the strongest storms ever to form in the Atlantic, Gulf or Caribbean. An earlier report from Weather Underground found that Irma, at 180 mph maximum sustained winds, was already the 5th strongest Atlantic storm as measured by wind speed. Irma has since strengthened to 185 mph — tying it with Wilma, Gilbert and the Labor Day Hurricane as second strongest Atlantic storm as measured by maximum winds. The strongest was Allen at 190 mph.

It’s worth noting that the Carribean and Gulf of Mexico are included in Atlantic hurricane listings. However, most of the top intensity storms have formed in these typically warmer seas. Irma, on the other hand, has reached such extreme strength over the typically cooler waters of the Central Tropical Atlantic. Though these waters, as with everything else that has been altered by human-caused climate change, are today warmer than they were in the past. As a result, the storm is now the strongest hurricane ever to form in that open water region.

NHC official forecast projections keep the storm quite strong as it moves into the warmer Carribean, though eventually weakening to CAT 4, as it moves west. Meanwhile, some models (GFS and SHIPS) show potential for an even more intense storm as Irma approaches Florida, the Gulf or the SE U.S. (strong CAT 5 that may dip into the 890 mb range).

Evacuation Orders Posted as Storm Defies Intensity Models

Officials appear to be very worried. Already evacuation orders and closings have been listed for Florida as interests across the Southeast take notice. This caution is wise. Irma has the potential to produce worse impacts than Harvey. So all interests should remain vigilant.

18z SHIPS file for #IRMA has Irma at its potential intensity and exceeding it in 6 hours, good time to review how this quantity calculated pic.twitter.com/rJHzcwNRgF — Kieran Bhatia (@KieranBhatia) September 5, 2017

Irma is presently exceeding both its predicted and its top predicted storm intensities — defying traditional storm prediction models like SHIPS. This is another concerning development for a powerful storm in a warming climate. That said, if the storm tracks further west (and some models show the storm tilting in this direction), interaction with large Caribbean islands will tend to reduce the storm’s intensity as it approaches the U.S.

This storm appears to be very efficiently tapping warmer than normal sea surfaces and a moister than normal atmosphere in order to spike its peak intensity. Two conditions set in play by human-caused climate change that are now helping to make storms like Irma both more intense and more dangerous. And it’s a condition that we need to take into account as we follow the track of Irma toward U.S. shores.

(UPDATED — UPDATES TO FOLLOW)

RELATED STATEMENTS AND INFORMATION:

7:15 PM – Whoa. Dropsonde in NE eyewall 196 knot winds just 19mb above the surface, 167 knot winds in lowest reported level. #Irma pic.twitter.com/rB31sZf61B — Alex Lamers (@AlexJLamers) September 5, 2017

In a year of hottest, driest, wettest records, #Irma is now strongest Atlantic storm ever measured. Hot new world https://t.co/7z7RHXdZ5h — Bill McKibben (@billmckibben) September 5, 2017

Table of all 17 Atlantic #hurricanes w/ max winds >=175 mph during their lifetime. #Irma pic.twitter.com/LtJz4otT7e — Philip Klotzbach (@philklotzbach) September 5, 2017

Links:

National Hurricane Center

Tropical Tidbits

Irma — 5th Strongest Atlantic Hurricane on Record

Hat tip to eleggua

Hat tip to wili