Hurricane Florence and Tropical Storms Isaac and Helene: September 9, Update A

Travel Day - 2 of 3 in a row. Here's the overall Atlantic view for today. First, the visible satellite imagery: 

And the infrared (cloud top temperatures) imagery, which shows the level of convection (rain and thunderstorms and whatnots (technical term ;-)) and really gives us an indication of how severe the storms are: 

Hurricane Florence

She's now just barely a cat 1 storm with winds of 75mph, central pressure 984mb (cat 1 range: 74-95mph). Earlier today it looked like she may have been trying to form an eye, but if she was, it isn't very clear:

Her structure isn't very well developed either, with most of the convection currently to the north. And although her structure is good in the lower half of the troposphere, there isn't a good signal in the upper troposphere yet, so I really think she's still a very strong Tropical Storm, but I'll go with the official estimate of barely a cat 1 storm with winds just 2 mph over the limit. They say she'll intensify into a cat 3 storm tomorrow (a major hurricane) - I think they are basing this on the fact that she'll be moving over warmer water tomorrow. That will cause a little intensification, but I don't know if she'll get to a cat 3 - but they may know something else that I don't know. I do see a little bit of wind shear in her path, so that might just result in a slower intensification. Guess we'll see what happens tomorrow on that front. 

 

She is currently at 24.4N, 56.3W, heading W at 6mph. The track is currently heading the the US east coast (as I'm sure you know!):

Getting to the coast in about 5 days. First, as it says on the cover of the Hitch-hikers Guide to the Galaxy, "Don't Panic". Get ready! Second, just a note that 5 days ago, the location and track she's on now was outside the cone:

 

So although you should all be ready, please keep in mind how much that cone can still shift. 

Tropical Storm Isaac

His circulation is good throughout the troposphere now, so he should be a hurricane. They have increased him to a strong TS with winds of 65mph, central pressure 999mb. That dry air is taking its toll though and the convection is quite weak, as you can see in the infrared satellite imagery. 

Tropical Storm Helene

Currently, I think Helene is the strongest of the three, although they have her as a TS with winds of 65mph, central pressure 997mb. Her convection is quite strong (also from the IR satellite imagery), but her structure throughout the troposphere is really good, which means she has some great circulation (vorticity). Here are the maps for 500mb (mid-troposphere) and 200mb (upper troposphere) - you can see the signals of all three storms quite clearly in the first map, but really only well for Isaac and Helene in the second:

Although Florence is under an upper-level low trough (that red line extending across the Atlantic that you can see in the last map above) - so I'm sure that is helping her a little. If that wasn't there, she'd be a weaker storm. 

I'll be back tomorrow. We'll see what mischief Florence has got up to then! Must run... another city, another plane...!

Ciao,

J.

Twitter: jyovianstorm

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DISCLAIMER:
These remarks are just what I think/see regarding tropical storms. If you are making an evacuation decision, please heed your local emergency management and the National Hurricane Center's official forecast. This is not an official forecast.
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