Tuesday, September 11, 2018

Hurricanes Florence and Helene, Tropical Storms Isaac and Olivia: September 11, Update A

Jumping right in... (with an additional quite note on Hawaii... again)

Hurricane Florence
She certainly did intensify yesterday, just as the NHC said she would and faster than I expected she would. This is both great and also not great - one may say its very agathakalogical in fact! ;-)  

The bad side is obvious - she's now a 4 storm, and a very good looking one at that. Currently her wind speeds are holding at 140mph, which makes her a mid-level cat 4 (cat 4 range: 130-156mph). Central pressure was last measured to be 944mb. She's had a very solid eye, which is one obvious indication that she's a major storm:
(Ain't she boo-ti-ful?)  

Her structure is also really solid - great circulation (vorticity) in the lower half of the troposphere, and that line of vorticity we saw a day or so ago in the upper troposphere has changed so her upper level vorticity can be seen and is quite strong now too. 

So why is it great that she became a major storm as predicted? Yesterday was one of the few times since I started this, about 13 years ago, where the NHC intensity forecast surpassed mine so perfectly. As you may remember, about 3-4 years ago, their one-day track forecast overtook mine and now I defer to them on that. For intensity, they haven't been doing so well - not even a few days ago, earlier in the lifetime of Florence - so whatever happened over the last two days (the data and models they used) was a good move. Bravo! Now if they can replicate that for ALL storms ALL the time, then I can retire from this blog (and just post jokes and sci-fi geekiness instead :-)). :-) 

She is currently at 29.5N, 62.4W, heading WNW at a decent 13mph. Her track is also honing in on the mid-US east coast:
The troubling part is that there really isn't much to inhibit her from staying a strong storm. There isn't any wind shear, the water is warm - and on top of the warm water where she is, she still has to cross the Gulf Stream to get to the US east coast, which means that she'll have a nice deep-warm water supply. She's also clear of most of the dry dust (Saharan Air Layer): 
There's a small patch closer to the coast, but U think it's too far north to make much of an impact. So we are looking at a big beast as far as I can tell.

The other troubling thing is that she may slow down and stall as she gets closer to the coast because of a high pressure that they are forecasting to build up over the US. NOAA (which includes both the NHC and the NWS) are gathering extra data over land in order to get the most input for the models and monitor this situation more closely. 

So, if you are in the Outer Banks of NC, definitely get out now. If you are in another area that is subject to flooding and in the cone tomorrow (which not only includes the coast, but also river banks and places with poor drainage when it rains - even inland a bit), I would get ready to leave (or leave if it will take a couple of days). If you are in a place which is normally dry, then get ready to hunker down. Remember: Run from the Water, Hide from the Wind. Above all, pay attention to your emergency managers because they have the most up-to-date local information. 

Tropical Storm Isaac
Just a quick note that he's been downgraded from being a cat 1 yesterday. Winds are now 70mph, central pressure is 997mb. The dry air is the major factor in keeping him in check, and it looks like it extends all the way into the Caribbean. He is currently at 14.5N, 46.9W, heading W at a good 16mph:
He will be moving over warmer water as he approaches the Caribbean, so that will give him some energy, but the competing dry air should keep him relatively in check - perhaps a strong TS or cat 1. 

Hurricane Helene
She 'rapidly' jumped from a TS to a cat 2 storm yesterday - I think she was a hurricane a couple of days ago, so I'm not surprised at the official upgrade. She's now officially a borderline cat 2/cat 3 storm, with winds of 110mph (cat 2 range: 96-110mph), central pressure 968mb. I think she's a solid cat 3 - and therefore also a Major storm already. She also has a consistently solid eye, which we can see in the overall Atlantic satellite imagery: 
And her structure throughout the troposphere is as strong, if not stronger than Florence's structure. 

She's also combatting some dry and dusty air as she follows Isaac, but despite that, she is a big storm in size - which you can also see from the Saharan Air Layer image above. I think they have underestimated her intensity.

She is currently at 15.5N, 32.4W, heading WNW at 12mph. Fortunately, her track forecast keeps her out in the Atlantic at the moment:

Tropical Storm Olivia
And just briefly, for those of you with an interest in Hawaii, they are under yet another storm watch with TS Olivia currently at 21.9N, 149.7W, heading W at 10mph: 
Winds are 70mph, central pressure is 991mb, so she's a very strong Tropical Storm:
She has a fair amount of convection in her though, so get those raincoats out and throw the deck chairs into the swimming pool so they aren't flying around. Stay safe! 

Back tomorrow!

Twitter: jyovianstorm
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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