Thursday, October 03, 2013

Jerry the Blob and Tropical Storm Karen: October 3, Update B

Oh no! I made the mistake of reading a news piece about Tropical Storm Karen and am now sufficiently brainwashed and panicked that I have started to evacuate my freezer in preparation... (this ice cream is yummy by the way).

Jerry the Blob
I was about to write Jerry off as a post-tropical storm blob (sorry Jerry, I know you work out ;-))... but I just saw the infrared satellite images and it looks like he's having a last hurrah. The circulation is good in the very lowest levels of the troposphere, nothing in the middle. But the convection has increased in the last few hours. The NHC have issued their last advisory on this storm, but I'm going to wait until he's really a blob - i.e. less circulation or less convection.  

Tropical Storm Karen
She's currently centered at 23.8N, 88.9W heading NNW at 12mph. Officially winds are now 65mph, central pressure is 999mb. Hmm... not sure the winds are quite that strong, but more on that later.

She left the Yucatan Peninsula area this morning and as she moved away from that warm water in the Caribbean, she promptly fell apart. Here are a couple of satellite images from about 3 hours ago:

Doesn't look quite as composed as in the image I showed this morning, does she? This is because of wind shear, dry air, and because she's no longer over that very deep warm water in the Caribbean. The convection is slowly increasing- that little red splodge in the middle is getting a bit bigger as you can see in the latest infrared image:

but we're at a much weaker point than we were this time yesterday (as far as convection goes). Sea surface temperatures are around 29-30 degrees C, so definitely warm enough to sustain her and the upper 50-100m of the water are 26.5 deg C. This is enough to allow her to grow, but not as much as she would have if the warmer water had been deeper.

There is still dry air to her west and north:

And there is still some wind shear, which is why the convection is almost all east and north of the center of the circulation. The wind shear will continue, although it looks like it might get a tad weaker for tomorrow - this would allow her to intensify a bit more.

The circulation is still very strong in the lower half of the troposphere, but there is no signal at all in the upper troposphere, so she's not near hurricane strength yet. Winds are 65mph, which makes her a strong Tropical Storm (TS range: 39-73mph). This speed is from a hurricane hunter plane that flew in earlier today. I am usually a big big fan of the hurricane hunter planes because I'm all about the actual observed data, but I'm not sure about this wind speed. They didn't find a center yesterday, when clearly she had one, and now the speed seems a little too high given the circulation and convection.

I do wish we had a proper ocean observing system! I'd like a network of robust buoys across the Gulf that we could tap into to see what the wind speeds on the 'ground' actually were. Wouldn't that be awesome?! :-) As it is, the nearest buoy is about 120 miles north of the center (in the forecast path) and is showing winds of 22mph. And looking at satellite winds, it looks like the winds speed is somewhere around 50-60mph, which would mean she's a mid-strength storm.

The NHC's forecast has shifted a little to the west compared to yesterday/earlier today and landfall has moved forward to Saturday afternoon instead of later that night:

It's a bit tricky to assess landfall because she is skirting a high pressure and it is fluctuating - so she could move a little more to the west, or it is quite likely that she could shift back to the east and towards Florida. I'm not the only one having difficulty in pinpointing the track - the NHC and models are also having a difficult time, which is why that cone at landfall stretches from Florida to Louisiana!

The latest pressure field I've seen is showing that there's a possibility that she'll slow down from her 12mph movement (she may even become stationary) tomorrow. If she does, that will complicate things some more ( oh joy! we love complications in forecasting - it's too easy otherwise. ;-)). I'm going to have to rely on the NHC for the track for now as I don't see anything particularly wrong with it at the moment. But keep in mind that it's not just the center of the cone that we should watch and also keep in mind that the track may shift. I wouldn't even rule out the possibility that she'll skirt the northern Gulf coast yet! I'd say everyone from eastern Texas to central Florida should be watching Karen for now.

Water levels:
Water levels along the Florida coast are around 0.5ft above normal, and along Mississippi they are around 1.5ft above normal. The highest I've seen is in Louisiana - Shell Beach just showed 2ft above normal. You can find out water levels from Tides Online - if you can't recall how to do this, there's a refresher in this entry:

I'll be back tomorrow - I'll try to do two updates again (lucky you! ;-)). For now, time to go and evacuate a bit more from the freezer... ;-)

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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.

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