Daily Archives: Friday, May 27th, 2011

On the winds of change…Rain? Tropics?

We are now less than 100 hours away from Hurricane Season, and the numerical models continue to show a broad area of low pressure forming in the southern Caribbean Sea. This feature will be the dominate feature of interest over the next few days for those of you in the southeast unless you live in Florida. I’ll get to those Florida interests in just a moment, but first lets look at the tropics. Also, at the end of this entry we will find one more ingredient necessary for tropical cyclones to develop.

Below I have posted the National Hurricane Center 18Z (2pm ET) Surface Analysis. Notice to the east-southeast of Trinidad and Tobago the two tropical waves that will be moving into the Caribbean or northern South America over the next few days. Tropical waves generally travel along the easterlies in the lower tropics (roughly 2-12°N latitude) and can be the spark that ignite tropical cyclones in their beginning stages.

The first wave is forecast to move through the northern Caribbean, but the second wave looks like it may move a little bit more southern. I think that one of these wave may provide just enough of a kick to start the process of cyclogenesis. We’ll watch for another few days before we can make any further forecasts, but for now it is something to watch.



As for those of you in Florida, the weather will be quite active through your Memorial Day weekend. The big bubble of high pressure that has kept the severe weather away from Florida this past week has allowed for a stronger west coast sea breeze the last few days. As the ridge of high pressure re-anchors itself across the southeast, it will return to our north. Clockwise winds will push those storms back towards the west coast starting on Sunday. Saturday will be a transitional day where storms will meander about without much of a flow. If you get stuck under one of these storms, you could get a lot of rain. In just a few weeks you will be able to set your clocks by these sea breeze storms.


3. You probably didn’t realize that you have already learned the third of six ingredients needed for tropical growth. Yesterday we learned that warm sea surface temperatures and some instability are needed to sustain a cyclone for the duration of their lifespan, but they cannot just make themselves pop. They need some sort of kickstart, and this often comes in the form of a tropical wave. As discussed above, a pre-existing disturbance – a tropical wave, a surface front, outflow boundary, or pre-existing low pressure area – is required for the organization of tropical cyclones. This will be critical for the tropical forecast this weekend. Have a good night!

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