Tuesday, August 25, 2020

Tropical Storm Laura and Tropical Depression Marco: August 24, Update A

One down (farewell, Marco), one to go! 

Seen in the Gulf...

But we all know this is 2020, so really... 

Hahaha. (thanks to Mark Z. for sharing that one). (Shadow Monster from Stranger Things)

Tropical Storm Laura

Laura is currently at 22.7N, 84W, heading WNW at pretty fast 20mph. She's just crossed Cuba, and is on track to hear towards the northern Gulf. 


She is officially a mid-to-strong Tropical Storm with winds of 65mph, central pressure of 996mb (TS range: 39-73mph). You can clearly see center of circulation because the heavy convection subsided as she crossed the northwestern tip of Cuba - partly because there is some wind shear which is pushing some of her clouds to the south:


She's officially remained at the mid-to-strong level all day - a result of the warm water to the south of Cuba, that is feeding her, and the interaction with the landmass of Cuba, which has kept her in check. There is some vorticity (circulation) in the upper troposphere, but it is offset from the middle and lower level circulation, so although close, her vertical structure is not quite there for a hurricane yet. Most of the really strong convection is to the south - over that very warm (30 deg C) and deep warm water (the upper 125m is warmer than 26 deg C) that you see here:


If you overlay her track on this map above, you'll see that she is going to continue over some deep warm water - at least until Tuesday (tomorrow) afternoon, after which she will be close to that blue area in the middle of the Gulf where the water is a lot cooler. So, until Tuesday afternoon at least, the ocean is going to help her convection grow.  

There also isn't any wind shear to speak of in the Gulf at the moment - Marco took that one for the team. This means that there isn't anything really holding her back from growing as she leaves Cuba. I agree with the NHC that she will be a hurricane tomorrow. They call for a cat 1, but she may even get closer to cat 2 by the time she gets to that cooler patch because her structure is almost in place already. 

From Tuesday to Wednesday, there are two things that may bring her down a notch. First, there is currently a bit of wind shear that is in the northern Gulf. And second, she may go over that cold water patch on Tuesday evening which may help calm her convection a little.

Tropical Depression Marco

He made landfall officially around 6pm CDT near the mouth of the Mississippi River as barely a Tropical Storm with winds of 40mph (TS range: 39-73mph). His convection is that patch you see in the satellite imagery above that is currently over Georgia (thank you, wind shear), however his 'center' is officially still near (offshore) Louisiana at 29N, 89.8W and is heading W at 9mph. 

His winds are at 35mph, making him a Tropical Depression. The circulation in the upper troposphere is non-existent, and it's not very well developed in the middle level of the troposphere now too, so I agree with the TD designation. Unless he somehow restrengthens, I think this is my last post on Marco.

More on Laura tomorrow!

Toodle pip,

J. 

Twitter: jyovianstorm

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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 local 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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