Monday, August 25, 2008

Introducing Tropical Storm Gustav

Tropical Storm Fay menaced Tampa on nearly all sides, but managed only to graze the area: the best possible outcome for the city from a rather bad situation.

So, Round Two. Tropical Storm Gustav, currently in the eastern Caribbean, is forecast to approach the Miami area on Sunday evening. It’s still way too early to make exact forecasts, however – the current westward movement of the storm is liable to bust this Sunday forecast way early.

And in the Pacific, Tropical Storm Julio has entered the Gulf of California and is inching its way to Arizona! Beware disintegrating tropical storms - they can bring lots of rain!

What do the friendly folks at the University of Arizona think?:
A major heavy rain event is shaping up for much of Arizona as tropical storm Julio is making it's way northward across central Baja and back into the Gulf of California. Satellite imagery indicates that cloud tops have warmed over the last few hours and the storm seems to be moving more northward than NNW. The upper outflow looks quite impressive. I'm no tropical expert so I'll leave it at that. As expected moisture has increased and much of Arizona is very wet. The low deserts are all in the low to mid 40mm range with Yuma at 47mm and even wetter to the southeast with Puerto Penasco and Hermosillo in the mid 50's. Significant clouds and showers are present over the state this morning which will act to reduce heating, but how much? 500 mb map has a broad high positioned somewhere around the 4 corners with a hint of a mid level trough southwest of El Paso with good mid level NE-E steering flow. 250 shows a trough along the SoCal coast with a SW 30 kt jet over southern AZ. Morning soundings from both Tucson and Phoenix are wet and potentially unstable with MLCAPE's above 1K J/Kg and have cooled in the mid layers as Phoenix has -7C at 500 mb. The major issue with tropical systems is as they spin down, they leave behind a mid level warm layer and combined with a very wet atmosphere, it stays cloudy, cool, and too stable to convect in the deserts. If the circulation can keep going over the northern gulf, as expected though, a big event is likely over the state especially with a upper trough to our west. SE AZ though, can get caught in the low level easterly downslope flow which will cause the atmosphere to further stabilize.

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