'Extremely dangerous' cat 5 hurricane IRMA headed for north-east Caribbean & towards Florida

Tuesday 5th September 2017

Disturbance Thirty Four is still creeping slowly west across the far south of the Bay of Campeche, held against any northerly motion by frontal activity over the central southern states. Despite being pinned against the ropes, this has continued to become better organised overnight. Showers and thunderstorm activity have increased and aerial images show the disturbance has some shape to it now. This still has a slight chance of deepening into a tropical storm but would in any event be of limited scale and rainfall would not reach as far north as the HARVEY-soaked region. This should inch ashore in southern Mexico in two to three days' time.

A US Air Force fly-by of IRMA has just reported flight level winds of 175 knots, which will equate to around 155 knots at the surface. This is category five. IRMA is now described by US agencies as an ‘extremely dangerous hurricane' and is already the strongest hurricane in the Atlantic basin outside of the Caribbean and Gulf of Mexico in the NHC records. Some additional strengthening may still take place although some fluctuations in intensity are likely during the next couple of days due to eyewall replacement cycles. The well-defined eye of IRMA is now around 225 miles east of the Leeward Islands moving a tad north of west at 12 knots. Aside from the little erosion that will occur as IRMA passes islands, there is no environmental barrier to IRMA maintaining strength between now and closing in on Florida. The current hurricane severity index rating is now 38 out of a possible 50 points (13 for size and 25 for intensity) nearing an expected peak of 40 (15 for size and 25 for intensity). This will have a tropical storm strength wind field of 230 miles so the effect will be widespread. IRMA is expected to pass very close to, or make a direct hit on the northern Leeward and British Virgin Islands tomorrow evening as a category 5 hurricane and remain so before moving towards South Florida. IRMA is expected to grow significantly in size in the Bahamas and the eye is predicted to move over the southeastern Bahamas Thursday night into early Friday causing catastrophic damage. One or two modellers are still dithering between a track close to the east of Florida, and then threatening the Carolinas whilst a couple of others are predicting a slightly later turn into the far eastern Gulf of Mexico and then up the western coast of the Florida peninsula, however the general consensus would seem to be a tight turn somewhere close to the Florida Keys on Sunday and then a run north along the entire length of the peninsula. It's not good.

Disturbance Thirty Seven has developed rapidly in the last few hours and become Tropical Storm JOSE. Environmental conditions are ripe for this to develop into a hurricane towards Friday. Currently about 1450 miles east of the Windward Islands and moving west-nor'west at 12 knots, the forward track is uncertain but an approach towards the by-then soaked and windswept Leeward Islands cannot be ruled out.

Stand by for hurricane conditions across the islands of the north-east Caribbean.