Jason M
(Weather Watcher)
Wed Aug 28 2002 12:24 AM
Possible Development

FORECAST POSTED: 8/27/02/ 8:10 PM EDT


Tropical Weather Outlook

The strongest tropical wave of the 2002 season has emerged off of the African continent. This wave is under an area that is favorable for slow tropical development. Tropical storm formation is possible over the next 2-3 days. Elsewhere, tropical storm formation over the next 72 hours will not occur.

Tropical Weather Discussion

Well after everyone giving up on the season, we're beginning to see some activity in the Atlantic basin. I am not saying that we aren't going to end up with a below average season. But I still believe that we will have an average to slightly above average season. The area of most interest, is the tropical wave south of the Cape Verde islands. Unlike the waves that have exited the coast earlier in the season, this wave is showing no signs of falling apart anytime soon. In fact, the wave has been becoming better organized over the last 12 hours. There appears to be a low to mid level circulation associated witht he wave. A circulation is very evident on QUICKSCAT imagery. This is the same wave that I mentioned about five days ago, when it was still over central Africa. The models aren't backing down neither. The UKMET (Which has been one of the better models this season) is the latest model now hinting on development. In addition, the NOGAPS model (Which is usually the last model to forecast development) is also hinting on tropical development.

Over the past week or two, I have been constantly posting on the site and at numerous weather forums, about conditions across the Mean Development Region (The area of the Atlantic between the Lesser Antilles and the coast of Africa). There is no doubt in my mind that conditions have been improving over the past few weeks. The Azores high is still rather strong. However, the high is now much farther north, allowing a few waves to make it all the way across the basin. The last one to make it across, is the wave just east of the Bahamas (I will get to this wave in just a second). In addition, the Inter Tropical Convergence Zone (ITCZ) is now located along the long term average latitude. The shear across the MDR has also weakened over the past two weeks and the sea surface temperatures have warmed as well. The slight increase in ssts is in response to the NAO turning negative, which was forecasted about a month ago. The NAO is now forecasted to go neutral, but not positive. So I don't see a dramatic decrease in ssts anytime soon. So all of these factors have made conditions across the MDR a little more condusive for development and it shows.

NRL should issue an INVEST later tonight or tomorrow, as soon as the National Hurricane Center begins doing model runs. The Satellite Analysis Branch should also be posting intensity numbers rather soon. As long as the wave stays on almost a due west track, slow development should occur over the next 72 hours. The majority of shear will be north of the wave, with a strong jet max developing just north of the system in 72 hours. Now if the wave begins to take a more west-northwesterly track, chances of development would significantly decrease. The forecast is for this wave to slowly develop within the next 48 hours, possibly into a tropical depression. A tropical storm would be likely in 72-96 hours, if the shear doesn't begin to increase. Even if the wave does develop into a depression, the system could still dissipate east of the Lesser Antilles. Currently, the eastern Caribbean and central Atlantic is experiencing moderate shear being caused by an upper level trough. However, an upper level ridge is forecasted to develop over the region, which could eventually weaken the shear before the wave makes that far west. So the intensity forecast is highly uncertain past 48 hours...but I do believe that this wave has a good shot at developing into a tropical depression. It is too early to say whether or not the islands will be affected.

We are also monitoring another wave just east of the Bahamas. This wave will continue on a westerly track, towards southern Florida. Conditions are forecasted to become a little more favorable for development so it does bear watching. The wave will eventually move into the eastern Gulf of Mexico. But with no organization and lack of convection, development at this time is unlikely.

the convection in the extreme southwest Caribbean is still persisting. The convection is associated with a slow moving tropical wave. The wave is expected to move over central America over the next few days. Therefore, development is unlikely.

The strongest part of the negative phase of the Madden Julian Oscillation still hasn't made it into the Atlantic basin. This concerns me because we're already seeing a decent increase in tropical activity across the basin. The peak of activity this season should come once the peak of the negative phase is over the central Atlantic. The Atlantic should see a nice burst of activity at least over the next four weeks.

FORECASTER: Jason Moreland, TWWFT



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DISCLAIMER: THIS IS NOT AN OFFICIAL FORECAST. PLEASE LISTEN TO YOUR LOCAL NEWS OR THE NATIONAL HURRICANE CENTER FOR THE LATEST INFORMATION.


Ed DunhamAdministrator
(Former Meteorologist & CFHC Forum Moderator (Ed Passed Away on May 14, 2017))
Wed Aug 28 2002 02:26 AM
Re: Possible Development/Invest 92L

It is certainly one of the better CV waves of this season - which probably isn't saying too much since there hasn't exactly been a rash of them. It faces some significant difficulties. The focus of circulation seems to be located at about 8N - and nothing much ever gets going at that low a latitude. Water temps are okay between 23W and 30W but they turn a bit cool again between 30W and 45W. Stiff westerly shear exists down to about 7.5N between 23W and 30-31W, but the shear relaxes between 30W and 40W and then it picks up again. So the area of least shear is also the area of marginal SSTs. In a couple of days, the wave should move more to the WNW which would be more favorable from the standpoint of circulation development, but the westerly shear gets stronger as you head north of west. If this one can hold together until it gets to 60W then it might have a chance, but right now the odds are against it.

Added: NRL has started Invest 92L - with a center at 7.2N
Cheers,
ED



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