Sunday, August 19, 2007

Hurricane Dean reaches Jamaica - Maybe a near miss. Computer models tracks updated


3 PM, 19 Aug 2007, Hurricane Dean has reached the eastern tip of Jamaica with the eye directly south of Morant Bay. The cyclone is tracking south of the island at the moment. A couple of wobbles shifted the track slightly south although Dean is continuing to track a West-Northwesterly direction at about 16 knots.

Kingston may avoid the absolute worst Dean has to offer. That is probably the best that can be hoped at this point as Jamaica is now experiencing high winds and heavy rains. The problem now is that Dean has two eye walls: the inner eye wall has a radius of about 7 miles and the outer eye wall has a radius of about 19 miles. In order for Kingston and other southern areas of Jamaica to avoid the most extreme and dangerous winds of Dean, the hurricane will have to pass at least 25 to 30 miles south of the island. In relative terms the north coast of Jamaica will probably fare better than the windward south coast. I say relative because Montengo Bay, Discovery Bay, Clark,s Town, Ocho Rios, Port Maria and Port Antonio are all going to, (if they're not already), experience extremely high winds and rain from the spiral bands that extend out from the eye.

The wind field and moisture have developed into a relatively wide area and the south coast of Cuba now has a Tropical Storm Warning issued. That includes Guantanamo.

Weather observations out of Jamaica are somewhat thready. According to one report I picked up, the power in several areas was going to be shut off as a safety measure. The last pressure reading from Kingston was 998 millibars and falling rapidly.

The next few hours will tell us if those occasional wobbles saved Jamaica from a direct hit, but at the moment, a very near miss is the best they can hope for. The same may be true for the Caymans.

Computer model tracks have not changed significantly in the past several hours. Click on images to enlarge.

Update: Dr. Jeff Masters has an analysis and update on Hurricane Dean and its close pass on Jamaica.
It could have been much worse, but it is very bad for Jamaica. Hurricane Dean's northern eyewall is just offshore the southern tip of Jamaica, bringing sustained Category 2 hurricane winds to southern Jamaica. A recent wind analysis prepared by NOAA's Hurricane Research Division (Figure 1) at 3:30pm EDT today shows winds of Category 1 strength (>65 knots, or 74 mph) already affecting the east end of the island. By extrapolating this wind field over the island to the west-northwest, in anticipation of Dean's track, it is apparent that perhaps 90% of the island will experience sustained winds of 74 mph or greater. At 4pm EDT, Kingston, on the southern side of the island, recorded sustained winds of 81 mph before the instrument failed. We can expect that the southern 1/3 of the island, including Kingston, will receive sustained winds of Category 2 strength--96 to 114 mph. Category 3 and higher winds will be confined to the southernmost 5% of the island, and it appears that the Category 4 winds will stay offshore. The portion of the island affected by the Category 3 winds is very sparsely populated.
Jeff is estimating that the winds in Kingston will, when analyzed, have reached in the range of 106 mph/171 kmh/92 knots.

NEW INFORMATION HERE. Dean leaves Jamaica.

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