Sunday, June 24, 2012

Tropical Storm Debby: June 24, Update A

It was a dark and stormy night. Then I woke up and it was a not-quite-so-dark-but-not-very-bright and stormy morning. I have had a lovely morning cup of tea, and for breakfast I will have ice cream. As I told my husband when I did this yesterday, it is the only logical thing to do to prepare for a storm... what if the power goes out? ;-)

Tropical Storm Debby is behaving pretty much as I expected. She is currently at 27.5N, 87W, which means she has slowly been moving northeastward because yesterday she was at 87.5W. The NHC have extended their tropical storm warnings east and into the Florida panhandle. They have also shifted their cone to the north, so although the center is still heading to Texas for landfall on Friday, it is now northern Texas. Currently they say she is moving northward at 3mph. It’s difficult to tell if she’s moving northward at that speed from the satellite images. I don’t think we’ll see her move too far from her current location today though because there is still high pressure to her north. There is a small window and so I think if anything, she’ll scoot a little more to the northeast (towards the FL panhandle) but I’m not sure she’ll actually make landfall, so those of us in Florida and along the northeastern Gulf can expect at least another day of this sort of weather.

The NHC have also increased her wind speed to 60mph, which makes her a mid-to-strong Tropical Storm (TS range: 39-73mph). This seems reasonable to me. I expect the winds to get stronger today. The circulation in the lower half of the troposphere continues to be very strong. There is still some wind shear impacting her, so the circulation in the upper reaches of the troposphere is not quite strong enough for her to be a hurricane yet. (If you are just joining and want to know about the troposphere, scroll down to the <Science Alert> in this post:

Even though wind shear will decrease, I am not sure she will get to hurricane strength actually, and if she does, she will be a weak hurricane. There are a couple of reasons for this. First, although the water temperatures are warm at the surface at 28-29 deg C, she has moved away from the Loop Current, which at the moment extends to the same approximate latitude as Tampa Bay. The Loop Current is the region of very warm water in the upper 125m of the Gulf. At 27.5 deg N, it looks like the upper 50m of the water are warmer than 26.5 deg C. The other thing working against her now is that she is interacting with land.

Her convection is really strong, but still mostly on the east and north sides of the center. Here is an Infrared satellite image of Debby:

I like to look at the IR image because I can get an idea not only of where the convection is, but how strong it is. <Science Alert> In the troposphere the air gets colder the higher up you go. What the infrared satellite image shows is the temperature of the tops of the clouds, with red being the coldest, and blue and white being the warmest. The higher the cloud tops, the colder they will be. But also, high clouds tops are those big deep clouds that you see with very strong thunderstorms. Generally, red areas indicate very severe thunderstorms, with possible tornadoes etc. (the IR image shows dark gray sometimes in the middle of the red, which indicates even more severe weather). Orange areas indicate some thunderstorms and heavy rain. Yellow areas indicate rain. Blue are thick clouds, white are wispier clouds. To look at the IR image for yourself, go here: for the video and here for a still image like the one I attached. <End of Science Alert>

Storm surge: In St. Pete the observations are now showing about 2 ft above normal tides. Apalachicola, FL, in the Panhandle is about 2.5 ft. Elsewhere across the northern Gulf the surge is still between 1-2 feet.

As I said, it’s been raining and windy here in St. Pete all night and it looks like we are about to get some stronger weather. If you want to send me weather reports or pics from wherever you are, please do. I’ll include them in the next update.

More later! Time for ice cream... I mean breakfast. ;-)

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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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