Tropical Storm Harvey: August 18, Update A

A public service announcement: If you like vanilla ice cream (or vanilla anything), you better stock up now. I say this not just because I am an ice-cream pusher (although I have been known to ‘encourage’ my friends to partake) but because the price of vanilla has gone up by ~500% because Madagascar, where 80% of the world’s vanilla is grown, was hit by a category 4 cyclone in March (Cyclone Enawo) resulting in a very poor vanilla harvest this year. A cyclone is a tropical storm so it is the same type of storm as a hurricane; it is called a cyclone because it is in the Indian Ocean, just as a tropical storm in the western Pacific Ocean is called a typhoon. 

As I eat my vanilla ice cream I think that today we’ll just pop in to see how Tropical Storm Harvey is progressing. We are ditching the Atlantic Blobette for now because it is not doing as well as it was yesterday; it has no circulation in the mid-troposphere anymore which is pretty much as expected.

Harvey is currently at 13.7N, 64.1W, heading W at 18mph. Central pressure is 1005mb and winds are still 40mph, which means he is officially barely a Tropical Storm (TS range: 39-73mph). He has crossed the Leeward Islands and is now in the Caribbean, but again as expected, he hasn’t really developed much so far because he was interacting with the islands and because of wind shear.

The convection has improved today, and we can see some very strong thundery weather (in the red and gray areas) in the infrared satellite imagery:

This increase in convection is because he is over some very warm ocean water. The sea surface is 28-29 deg C, and the upper 100-125m of the water is warmer than 26 deg C, which means that even though he is churning the surface, the water underneath is also warm.

But he is still experiencing some wind shear and although there is some good circulation over the entire lower half of the troposphere, you can really see the wind shear because the red splodge at the 850mb (lower troposphere) is definitely offset from the 500mb (mid-troposphere):

So, again, in this case we see a battle between the ocean and atmosphere, with the ocean pushing him to develop and the atmosphere really pulling him back. In my opinion, he will develop but it will be slow until he gets away from that wind shear (sometime tomorrow) and his structure has a chance to improve.

The NHC track takes him more or less westward for another day at least, and then a gradual shift to WNW and NW, and across the Yucatan.

That’s it for today. Time to get back to eating some more vanilla ice cream before it becomes an unaffordable luxury! 

Ciao until tomorrow!

J.

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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.