Wednesday, September 20, 2017

Hurricane Maria: September 20, Update A

Quick update on Maria with my morning cuppa tea…

Hurricane Maria
St. Croix managed to dodge a direct hit last night as her eye passed just south and west of the island. They did get hurricane force winds, but it looks like it was most likely around 100mph - in the cat 2 range (96-110mph).
At around 6.30am this morning she made landfall in southeast Puerto Rico (near Yabucoa) officially as a very strong cat 4 storm with winds of 155mph (cat 4 range: 130-155mph). She is currently crossing the island and the mountains really rapidly took her down a notch or two, as you can see with the rapid disappearance of the clear eye:
From the infrared imagery, the convection has diminished quite a lot and I would now place her as somewhere around a strong cat 2 storm. Officially though, the NHC she is still considers her to be a mid-sized cat 4 storm with winds of 145mph, central pressure of 928mb (once this is over, I'll list why its as bad to overestimate the intensity of a storm as it is to underestimate it!). My thinking is also backed up by weather from Aricebo, which is currently about 20 miles from her center. From the NHC:
A weather station near Arecibo, Puerto Rico, recently reported a
sustained wind of 78 mph (126 km/h) and a wind gust of 108 mph (174

It looks like the maximum wind gusts (in red) recorded at Aricebo reached the cat 3 range a short while ago and the sustained wind speed (blue) were in the cat 1 range: 
The wind values on the left are in knots, so the maximum gust recorded is just under 100knots = just under 115mph and the sustained winds reached ~70knots = 80mph.  

She is currently at 18.4N, 66.4W, heading NW at 13mph and the NHC forecast expects her to remain a cat 3 storm until Sunday, after she crosses the Turks and Caicos:
She still has a very good vorticity (circulation) signal throughout the troposphere, which means her structure is good so it is very possible that she will re-intensify once she clears Puerto Rico, but for now, she is considerably weaker thanks to the mountains of Puerto Rico!

More tomorrow,

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DISCLAIMER: These remarks are just what I think/see regarding tropical storms - not the opinion of any organization I represent. If you are making an evacuation decision, please heed your local emergency management and the National Hurricane Center's official forecast and the National Weather Service announcements. This is not an official forecast. If I "run away, run away" (Monty Python), I'll let you know. 


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