Tropical weather analysis - August 17, 2012

By: KoritheMan , 8:30 AM GMT on August 17, 2012

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Although operationally Tropical Storm Gordon is near hurricane strength as of the 11:00 PM NHC advisory, the new advisory is being written as I write, and the official ATCF estimate is down to 65 mph. Just extrapolate from the coordinates I list below:

Wind: 70 mph, with higher gusts
Location: 34.6°N 50.3°W
Movement: E at 17 mph
Pressure: 995 mb

There is no evidence of an eye on conventional satellite imagery at this time. Not even a warm spot. A TMI overpass taken near 0300 UTC indicated a rather ragged inner core structure. Gordon consists of some ragged central convection with numerous banding features to the north.

Figure 1. Latest infrared satellite image of Tropical Storm Gordon. Image credit: NOAA

Satellite images and UW-CIMSS upper air data suggest that Gordon has pretty much lost the anticyclone that was trailing it. Westerly shear is beginning to affect the tropical storm, and a little bit of dry air appears to have gotten entrained in the western semicircle. Conditions appear to have become unfavorable a little earlier than anticipated. There is still a chance Gordon recovers enough to restrengthen a bit, but it is no longer expected to become a hurricane. In about 24 hours, Gordon is forecast to cross the 26C isotherm, as well as encounter a sharp increase in westerly shear. The increase in shear will likely result in dry air being entrained into the cyclone circulation, which should hasten the extratropical transition process once the cyclone crosses the Azores. The global models remain in good agreement with this scenario. Given the seemingly deteriorating satellite appearance, I am not currently forecasting anything higher than 60 kt.

Gordon is well-embedded within mean westerly flow in advance of a deep-layer trough to the west and in the wake of a powerful extratropical low over the north Atlantic. The global models agree on a turn toward the east-northeast on Sunday morning as Gordon nears the Azores. After passing through that archipelago, there is some disagreement amongst the various models with regard to the forward speed of the cyclone, but all in all it appears that Gordon will move generally eastward subsequent to impacting the Azores.

Beyond day five, there is some indication within the models that Gordon could slow and move southward under the nose of the subtropical ridge.

Interests in the Azores should prepare for the possibility of hurricane force wind gusts, particularly in areas of higher terrain on the islands. Rainfall potential will be limited by Gordon's fast forward speed.

5-day intensity forecast

INITIAL 08/17 0600Z 55 KT 65 MPH
12 hour 08/17 1800Z 60 KT 70 MPH
24 hour 08/18 0600Z 60 KT 70 MPH
36 hour 08/18 1800Z 55 KT 65 MPH
48 hour 08/19 0600Z 50 KT 60 MPH
72 hour 08/20 0600Z 45 KT 50 MPH
96 hour 08/21 0600Z 40 KT 45 MPH...EXTRATROPICAL
120 hour 08/22 0600Z 35 KT 40 MPH...EXTRATROPICAL

5-day track forecast

Figure 2. My 5-day forecast track for Gordon.

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1. GeorgiaStormz
1:32 PM GMT on August 17, 2012
gordon going down

thanks man
Member Since: February 11, 2012 Posts: 0 Comments: 9769

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About KoritheMan

I'm just a 23 year old with an ardent passion for weather. I first became aware of this interest after Tropical Storm Isidore struck my area in 2002.

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