IRMA causing destruction the across the north-east Caribbean

Wednesday 6th September 2017

Cornered Disturbance Thirty Four which is held tightly in place by cool dry air to the north has developed overnight and become tropical storm KATIA. Currently 130 miles east of Tampico, this is weak and considering events to the east, negligible in comparison. With maximum winds between 40 and 55 knots and a hurricane severity rating of just 3 out of a possible 50 points (1 for size and 2 for intensity), this is expected to peak at around 8 (3 for size and 5 for intensity). This is milling around aimlessly but is expected to turn to the southwest eventually, to make a landfall somewhere between Tuxpan and Veracruz on Saturday. Having said that, there is a decent chance that this could strengthen to a hurricane before landfall. Nonetheless, the primary threat is from heavy rainfall that usually accompanies slow-moving storms but unlikely to extend as far north as HARVEY-soaked ground.

The eye of category 5 hurricane IRMA is currently centred around 35 miles east of the British Virgin Islands headed west-nor'west at 12 knots. Current wind speeds are a blistering 160 knots with gusts up to 195 knots. IRMA has a well-defined and robust eye of over 25 miles in diameter, has already trashed a number of the small northernmost Leeward Islands and doesn't look to be weakening in the short term. Shortly before landfall, an observing station site on the island of Barbuda measured sustained winds of 103 knots with a gust of 135 knots which broke their anemometer. All government buildings on the French-run side of the island of St Martin have been destroyed. This is a vicious storm. At a peak hurricane severity index rating of 39 (14 for size and 25 for intensity) with a tropical storm strength windfield of 220 miles, IRMA isn't taking any prisoners. This will cross the British Virgin Islands soon then strike the Turks and Caicos and southern Bahamas tomorrow, to be expected around the Florida straits on Sunday morning before executing a handbrake turn to the north. The low pressure system that has radiated fronts across the southern US, which is keeping KATIA at bay, has also pushed cool dry air into the Gulf of Mexico and is giving cause to believe IRMA will not enter the Gulf at all, but nudge a little east. As a consequence, the forward track consensus now seems to favour a pass along the Atlantic coast of Florida, some even suggesting missing landfall altogether (although close enough for it to be as good as a landfall in real terms), with a final run ashore in South Carolina on Monday evening. Interaction with land and the sharp turn north when it reaches the Florida strait may weaken IRMA a little, but this is still likely to be a category 3 or 4 at landfall, if indeed this proves to be its final track.

Three days astern of IRMA, tropical storm JOSE is now around three days east of the Leeward Islands and headed west-nor'west at 12 knots. This is happily deepening over warm water, unhindered by wind shear and is likely to hit hurricane strength tonight and perhaps an intense hurricane on Friday. This has a current hurricane severity index rating of 5 (2 for size and 3 for intensity) with a predicted maximum of 23 (11 for size and 12 for intensity). The predicted tracks JOSE close to the Leeward Islands over the coming weekend but likely to take a northerly turn earlier than IRMA.

Stand by for hurricane storm force conditions across the entire eastern Caribbean, Bahamas and Florida, southern Bay of Campeche and west-central Atlantic. 

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