Thank you for 'setting the record straight' with regard to SST's.
Quote:
... temperatures of at least 27C (80F) are not always a necessary ingredient to cook up a warm core. Depending on the temperature of the atmosphere above, and other factors, tropical cyclogenesis can, and often does, occur, in regions where water temps are running considerably below the oft-cited 27C.
The most recent example of this was just last week, as TD-1 formed over water temps that were averaging about 25-26C.
Entirely correct. My discussion above was a bit too over-simplified, focusing solely on SST's, thunderstorm *intensity* and the vapor pressure temperatures necessary to impart the degree of energy (latent heat of condensation) requisite to cause substantial warming of the mid-levels and resultant pressure falls.
Usually, *all other factors being equal*, it takes SST's of about 26C to trigger this series of events. (Technically, it is the saturation vapor pressure of the ascending air parcels within the thunderstorms, and the *increasingly huge amount* of latent heat they carry upwards, once SST's attain that seemingly 'crucial degree' of warming and to a sufficient depth.)
Obviously, many factors come into play: Upper-level divergence, lack of appreciable shear, the lapse rate throughout the depth of the entire atmosphere, the measure of the 'convectively available potential energy' (CAPE), various stability indexes, the amount of 'precipitable water' in the area, and many other factors, can and do 'offset' the effects of the less-than-desirable SST's, especially when one includes the occurances of sub-tropical systems into the scope of consideration.
Clearly, I need to learn more (love to learn!) about the nature of neutral-core systems, especially the thermodynamics involved in subtropical development (transitioning).
In Hawaii, they are called "Kona Storms" and are assigned a Hawaiian name. I think one occurred sometime in the 70's in the month of April (ENSO year?). Will re-search that and post it under "Hurricane Ask/Tell" when I find it.
Finally, I've noticed, too, the large temperature 'anomalies' (2 to 3 degrees!) at high latitude, both in the atlantic and the pacific, over the past few years, and wondered how that might effect the frequency and location of tropical and (especially) subtropical systems in the years and decades to come. Interesting times.
Something is definitely afoot. Global Warming? Say it ain't so!
Edited by CoconutCandy (Fri Jun 05 2009 11:14 AM)
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What's in a Name? A Warm (or sometimes Neutral) Core!
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