Ed Dunham
Former Meteorologist & CFHC Forum Moderator (Ed Passed Away on May 14, 2017)
Reged:
Posts: 2565
Loc: Melbourne, FL
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Re: Invest 92L forms southeast of CVs. ATL entering an early Cape Verde mode?
Tue Jul 01 2008 10:37 PM
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Hmm - good to read such animated dialogue in defense of this system - you have all raised some good points to ponder. Especially good to see such support for the NHC - something usually quite rare on this site - please save some of that for later in the season. The use of the term 'fully' was not a good choice of words - I did not mean to imply agreement that the sole purpose of the Invest was for 'media hype' - far from it (for those of you who are familiar with my background at CPHC).
I had indeed checked the SSTs. The Atlantic, particularly the far eastern Atlantic, has warmed considerably in the past 6 weeks and these SSTs would easily support and maintain cyclonic development. Regarding the low center, it is not at all uncommon for easterly waves to exit the west coast of Africa with an open center of lower pressure - remember that on average only about one in ten become anything more than a tropical wave (and that is not to imply that 92L will not develop further - its just to educate the newer user on the site that may not be familiar with this statistic).
In support of the system, there is a narrow band of light shear below 18N latitude that extends westward to about 60W longitude. The GPS holds the system intact for about two weeks - the second of the two weeks can probably be ignored, i.e., its fodder for the Forecast Lounge long before that - but the first five or six days have some suggestion of support from an upper level high that will be in the vicinity of 50W longitude in a few days. At five days the GPS projects about 18N 44W (at 18Z), where westerly wind shear is anticipated to be around 30kts. However, below 18N the shear decreases rapidly (that narrow band that I mentioned), so if the system can stay at a lower latitude (and the upper high may keep 92L lower in latitude) then additional development is certainly possible.
"As for "Investigating" it, there are at least plenty of ships, a few planes, and certainly some buoys and several land stations in and around the CVs." There is sometimes a fine line between analysis and investigation, and these are indeed good data gathering methods (although unfortunately the buoys are limited and the ships are no longer plentiful because of the 'problems' in certain west African countries). The lack of frequent satellite data can often plague good investigation of tropical waves just off the west African coast, although NHC does get far more data from that region today.
My earlier concern, and still a valid one, is that even the southern limits of the guidance package places the system mighty close to the stronger wind shear zone - strictly a matter of timing on intensity and forward speed, i.e., before or after it reaches the influence of the upper level high? While the overall structure looks good, organization is still going to require a few more days.
"When is the last time you saw a wave drop off the coast of Africa with this kind of model support from so many runs?" Two hurricanes come to mind; Jeanne in 1998 and Cindy in 1999. I was going to comment on the new met term 'bingo-bango', but then I'd have to edit my own post! Certainly one of the better and on-topic discussions that the Storm Forum has seen in quite some time.
Cheers.
ED
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