Tuesday, September 24, 2019

Tropical Storms Jerry and Lorenzo, Tropical Depression Karen: September 23, Update A

Welcome to the first day of Autumn...
(self-portrait ;-))

Tropical Storm Jerry
Jerry is still a relatively strong Tropical Storm with winds of 65mph (TS range: 39-73mph), central pressure 991mb. The intensity continues to be impacted by strong wind shear plus some dry air at the moment. Here are the water vapor imagery for Jerry (top mass of clouds) and Karen (bottom mass of clouds):
He has got circulation in all levels of the troposphere, so if it wasn't for the wind shear, I think he would be a hurricane. The official forecast calls for his intensity continuing to decrease slowly over the next few days. I'd still be a little wary as he gets closer to Bermuda (tomorrow), as it looks like the wind shear may decrease (but just a little) - however, the dry air will continue. We can already see from the infrared that Bermuda has had a few raindrops... (cancel the golf!):

He is moving N at 7mph, and is currently at 29.2N, 68.3W. The forecast track has shifted to the south, which now takes him much closer to the island: 
He could go anywhere in that cone of course. How close he gets depends on when he makes that turn to the NE... that's what we are watching for tomorrow. The NHC are pretty good within a day, so I expect that turn will happen as they forecast. The best scenario is that he passes Bermuda to the north because that stronger convective weather is to the north of his center, so the worst of the weather will remain away from the island (and golfing can resume much sooner). 

Tropical Depression Karen
She has weakened since yesterday as she ran into some very dry air. However, as we can see from the water vapor satellite images above, that dry air is disappearing and the corresponding infrared imagery shows that her convection is returning. She is currently not quite a Tropical Storm, with winds of 35mph (TS range: 39-73mph), central pressure 1008mb. She is at 16.1N, 65.8W, heading NW at 10mph. 

She is heading towards Puerto Rico and the Virgin Islands and should really reach them tomorrow:
Luckily she's not very strong (in terms of wind speed), but she does have quite a lot of convection (rain and stuff (technical jargon for 'even more rain')), which means she'll bring that thing we jokingly like to call weather. And with the mountainous terrain, she may cause some flooding. I don't see the convection really decreasing between now and the islands because she is over waters that are 28 deg C, with the upper 100-125m being warmer than 26 deg C - plenty of warm water for her to feed on and then dump over the islands. 

We'll worry about her attempt to get to Bermuda later... (she's just trying to follow her bigger brother, who in turn was trying to follow his big sister and so the story goes...). For now, listen to your emergency managers, and don't forget - hide from the wind, run from the water. Which means that if you are in an area that is prone to flooding, move away! Water is the biggest cause of loss of life in a storm, not the wind. 

Tropical Storm Lorenzo
TD 13 has moved on... Tropical Storm Lorenzo is developing into something. He's currently at 11.6N, 26.7W, heading W at 15mph. He is a mid-size Tropical Storm with winds estimated to be 50mph, central pressure estimated to be 1002mb. I have to say, the Force is strong with this one. The NHC think he'll be a hurricane by tomorrow evening - I think he's already almost a hurricane; there is really good circulation in all levels of the troposphere. Plus, when we look at the infrared satellite imagery, we can already see that he is looking far more robust than Jerry: 

I would put his wind speed at closer to 75-80mph at the moment. The forecast track takes him into the Atlantic as a major hurricane in a few days: 
We'll have to keep an eye on him though - as that is a long-range forecast and the track forecast isn't that great that far out at the moment. 

That's all for ce soir. Good luck and stay safe to all my friends in Puerto Rico and the VIs - I hope it's all just a few drops in a rusty bucket somewhere. 

Ciao for now,

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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