Tuesday, August 30, 2016

Hurricane Gaston, Tropical Depressions 8 and 9: August 29, Update A

Another day with "So much time and so little to do. Wait a minute. Strike that. Reverse it. Thank you" - Willy Wonka, as most memorably said by Gene Wilder. Thank you for bringing the magical Mr. Wonka to life! 

Hurricane Gaston
Mr. Gaston is now a strong cat 2 storm with winds of 105 mph, central pressure of 968mb (cat 2 range: 96-110mph). He is currently at 31.6N, 54.6W and has finally started to move - he is heading NE at 6mph. His current forecast track takes him back to the northern Azores by the weekend.  

He has definitely weaker than he was yesterday and we can see this clearly in the satellite imagery:

The convection has weakened - there are no more areas of red, which would show areas of very strong thundery convection. He is still over water that is over 29 deg C in temperature, but now only the upper ~25m of the water column is warmer than 26.5 deg C, which means he is churning up cooler water. 

As he moves NW, he is heading slowly into slightly cooler waters (still warmer than 27 deg C) but because the wind shear will remain fairly weak for another couple of days he may weaken slightly, but will remain a hurricane until he runs into higher wind shear. This should happen before he gets near the northern Azores. I'm pretty much in agreement with the NHC on this one. 

Tropical Depression 8
This is the very disorganized blob that is heading to North Carolina. It is pretty difficult to see where the center of circulation is from both the infrared and visible satellite images:

He is officially centered somewhere around 33.8N, 74.1W, heading NW at 5mph. Winds are around 35mph, central pressure is 1012mb (Tropical Depression range: 17-39mph). Although the circulation in the lower troposphere is very strong, there is very little in the mid-troposphere, so he is definitely not a Tropical Storm yet. He still hasn't fully taken advantage of the Gulf Stream with it's delicious warm waters. It also looks like the wind shear will be weakening tomorrow so there is still a chance of intensification, but it seem unlikely that it will be much. 

The NHC forecast track shows that he will clip the outer banks of North Carolina tomorrow evening before heading NE and away from land. I would go with this track as it is in that 1-day zone and I think the NHC track is jolly darn tootin' good (that's proper scientific language for 'quite accurate' and feel free to quote me on that ;-)) in that time frame. 

If you want to have a look at data in that area (and off-shore), you can go to the SECOORA website at http://portal.secoora.org/. They have an interactive google map of buoy and other coastal station data. The winds are in knots so you'll have to convert them to mph (1 kt = 1.15 mph), but it looks like the winds off the cape are currently around 16 mph at the moment.

Tropical Depression 9
This blobette has finally almost broken free of Cuba and is mostly in the southern Gulf of Mexico, officially around 23.9N, 85.5W, heading W at 7mph. Her wind speed is around 35mph (same as TD 8), central pressure is 1003mb. 

She is not yet a Tropical Storm. I would agree with that for now because although she has a little circulation in the mid-troposphere, it is quite weak and it is also not in alignment with the circulation in the lower troposphere. However, her vorticity (circulation) is stronger than TD8 so she is actually slightly stronger than TD 8 and will probably get to Tropical Storm status quicker than TD8. You can see this in the mid-troposphere vorticity map: 
Despite the slightly stronger circulation, she is not really very well developed either and, like yesterday, it is difficult to see in the satellite images where her circulation actually is: 

She is on a more westward track than the NHC originally thought, so the track has been shifted southward, but their expectation is that she will reach 25N by tomorrow evening:

From the pressure fields, it looks like she now has some room to move NW, but I think she may continue a little more W than NW for a bit longer because I think her center may be south of the current official center. Part of the problem in forecasting the track of such a weak and poorly formed system is that her center is not very well defined so the models are basing their forecasts on where they think the center is. Regardless of what the track is, those of you in Florida should be ready with your bottles of wine and ice cream and other necessary hurricane season supplies! ;-) 

Until tomorrow!

Blogs archived at http://jyotikastorms.blogspot.com/
Twitter @JyovianStorm
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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