STRONG WAVE WITH CLOSED CIRCULATION SOUTH OF JAMAICA BUT TIME MAY BE RUNNING OUT
Latest imagery shows that the strong wave in the Caribbean south of Jamaica does have a low level circulation,
but the convection associated with it has diminished -- more than the typical diurnal cycle would produce.
The intense convection of earlier today has weakened, but this is a typical diurnal variation.
statement earlier this evening:
TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT TUN SEP 27 2005
CENTRAL CARIBBEAN TROPICAL WAVE IS ALONG 77W S OF CUBA WITH A
1009 MB LOW ALONG THE WAVE NEAR 15N. VISIBLE SATELLITE PICTURES
SHOW BANDING FEATURES DEVELOPING ON THE N SIDE OF THE WAVE WITH
SYMMETRIC OUTFLOW. THIS AREA HAS THE POTENTIAL TO BECOME A
TROPICAL CYCLONE WITHIN THE NEXT 36 HOURS. A SLOW MOVEMENT TO
THE WNW IS LIKELY... PLACING THE SYSTEM IN THE W CARIBBEAN LATE
WED/EARLY THU. SCATTERED MODERATE TO ISOLATED STRONG CONVECTION
IS FROM 15N-19N BETWEEN 72W-76W...AND FROM 17N-20N BETWEEN 76W-80W.
they then just updated with:
CENTRAL CARIBBEAN TROPICAL WAVE IS ALONG 77W/78W S OF 20N WITH A
1009 MB LOW ALONG THE WAVE NEAR 16N MOVING WNW NEAR 12 KT.
FAIRLY WELL DEFINED LOW/MID LEVEL CIRCULATION WITH AN UPPER
LEVEL HIGH LOCATED JUST TO THE E NEAR 16N74W. THIS AREA HAS THE
POTENTIAL TO BECOME A TROPICAL CYCLONE WITHIN THE NEXT DAY OR
TWO AS THE UPPER LEVEL WINDS BECOME MORE FAVORABLE. ASSOCIATED
DEEP CONVECTION HAS DIED DOWN TONIGHT BUT IS EXPECTED TO
REGENERATE LATER THIS MORNING.
In addition, the NHC did run a few of the specialized tropical cyclone forecast models earlier
today and again this evening (see below).
BUT -- looking at the latest trends on water vapor imagery, there is dry air and very possibly some increased
westerly shears expected to reach into the northwest Caribbean over the next few days. The 00Z GFS no longer
really develops the system, instead opting for a broad area of lower pressure and 'wet weather'. I'm now of the
belief that unless the system develops into a Tropical Depression SOON -- and a Tropical
storm by Thursday -- it may not do either at all!
The reasoning for this is that tropical storms/hurricanes tend to develop a self -sustaining environment -- which
will only then, IMHO, be sufficient to fend off the overall weather pattern now being predicted by the global models.
So if the system doesn't manage to develop into a storm within 48 hours, the predicted synoptic scale pattern may very
well prevent it from doing so.
This kind of reminds me of the 'system' back in mid August that looked so promising to develop into a Hurricane just
northeast of Puerto Rico, and then just failed completely as shear from nearby upper level cyclones inhibited any
further development. Although, a week later it suddenly started to develop -- and ended up becoming a storm
named Katrina. (DO NOT mis-interpret what I just said -- this is NO Katrina -- I'm really just referring to how
so many systems' that 'look' on the verge of intensifying -- suddenly end up falling apart.)
Unless there is a major development, the next full update will be in the late afternoon
Wednesday on the WEATHER UNDERGROUND blog ONLY.
I will no longer be posting 'routine' updates on storms until they become a serious threat to the
U.S. -- or if I wish decide to post a 'general interest' type Diary entry.
(This includes financial, socio/economic and the always popular Polical view of the world commentary
So if you desire to see what's going on in the tropics of sifnificant interest, just visit my
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Water Vapor image shows a closed off upper level cyclone over Florida, and a deep layered TROF over the eastern Caribbean. Between the two, is an anticyclonic flow over the strong tropical wave along 78W with a closed low and mid level circulation near 16N/78W. However -- the deep convection associated with the tropical wave has really decreased tremendously, and, at the same time, the upper low over Florida is pulling down some very dry air into the Gulf of Mexico -- with some of it already nosing into the far northwest Caribbean near the Yucatan channel. So while there are a lot of good reasons for this system to develop into a tropical cyclone -- if it doesn't 'hurry up' -- the environment may not be all that conducive for it in another 48 hours. Outflow is very good in all quadrants -- but it is not at all certain it will last long if the upper low over Florida doesn't move out to the northeast. The GFS, in fact -- brings it eastward -- and this would impose a westerly shear in the north and northwest quadrants, and bring along dry westerly flow across the storm in a couple of days. The 00Z evening model runs track the (presumably) soon to be cyclone to the northern Yucatan by the end of the week. The Intensity forecast brings the system up to a tropical storm and possibly minimal hurricane -- thought the effects of crossing the Yucatan can be seen at 72-96 hours. +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
SEPT 27, 2005 / 10:00 AM CDT
STRONG WAVE LIKELY NEXT T.C. - HEADING FOR NW CARIBBEAN
The strong Tropical Wave in the Caribbean has slowed down from 15Kts to under 10Kts, and in so
doing, has become considerably more organized in it's overall structure and concentration of
convection -- which has now taken on a circular pattern to the southeast of Jamaica. The very broad
area of low pressure that dominated the central Caribbean yesterday, as confirmed by numerous
surface reports, appears to have become better defined and is a closed circulation.
Satellite imagery and surface reports indicate the most likely surface circulation center is near
14.5N/75.1W. The very latest Buoy report from at 15N/75W indicated winds went from
ENEat midnight, to N by 8AM CDT, & just in the past hour, have swung around now to WSW
indicating the passage of a closed low pressure center very close that location.
The models runs - for some 'unknown reason' have not been run since yesterday afternoon- but the
GFS model continues to develop this system into a cyclone in the NW Caribbean by Thursday. The
track shown by the GFS has it passing across the far northern end of the Yucatan now, and then
reaching the Gulf of Mexico on Monday. As is typical of newly forming systems, and the GFS
handling of them - each model run bounces back and forth on the track -- and without the aid of the
specialized tropical storm models -- it's rather difficult to determine which track is most likely. Since
the odds appear much higher today that the system will become a Depression -- once that happens,
the various specialized models WILL become available again. At the moment, NHC indicates it
may send a RECON out on WED to investigate the system. But I wouldn't be too surprised to see
that moved up in time depending on the next 6 hours of satellite and surface reports.
There are 2 other significant tropical waves over the central and western Tropical Atlantic -- neither
one of them pose any significant signs of development in the near term.
The next full update will be Wednesday morning -- unless conditions warrant an earlier update
NOTE for Dkos readers: Because I am only permitted 1 Diary entry per day -- and ONLY
if there really is an important reason to add or update to the latest information - if time
permits, I will try simply editing the existing Diary, and add the latest info at the
beginning. So you might want to check back in the afternoon or evening just to 'see'.
In any event - if you post questions, please check back late at night (I live in Chicago-
11PM?)since I will try and reply to any comments/questions at that time. I just can't
do it during the day. If there is a big storm going on, I most likely will not have any time
to reply at all. But if there is a big storm in progress, the cheapest (free) way to see what
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The surface chart from 1AM CDT indicated a low level circulation near 14.5N / 74.5W -- but pressures
are not especially low in the area. This has shown, however, great continuity from yesterday's estimated
position near 14N/73W.
By 12Z this morning, or 7AM CDT - the combined surface OBS and IR Image clearly implies a sharp wave,
if not closed low, approaching 75W. HOWEVER - with the report within the past hour from the very reliable
Buoy located at 15N/75W showing winds going form due N to WSW leaves no doubt that there is a closed
low at the surface, and, very well centered on the now circular shaped cloud formation. Based on the last
24 hours, the system's low level circulation is moving W-WNW (280°) at about less than 10Kts.
The latest HI-RES VISIBLE image shows deep convection in the eastern semi-circle, and not that far from the low level circulation center. There is also signs of cirrus outflow as well.
This highly enhanced water vapor image shows a strong concentration of deep moisture associated with
convection, taking on a circular shape surrounding the primary area if developing low and mid level circulation.
As luck would have it, the polar orbiter just missed getting a full
85Ghz scan of the system this AM - however, the very dark brown
areas - both north, and SE of where the the lower level circulation
has been identified -- indicates very strong convection has developed
this morning. in association with this system. Whether this is just
a 'diurnal cycle' burst of convection remains to be seen.
The outflow from the system is very good in all quadrants but the east -- being slightly enhanced by
the upper low now over Florida. The closed anticyclone over Puerto Rico yesterday, then over
Hispaniola last night, appears to have begun to weaken, or possibly has dissipated entirely.
Whether the very strong wave has managed to develop it's own anticyclonic flow above the center is
not immediately apparent, except.....
The Shear chart from this morning shows the system has now moved into an area of much lower
shears 5Kts-8kts, and there is a very significant chance this system could intensify into
a depression within 12 -24 hours. If it does NOT, then it is unlikely that it has managed to form it's
own anticyclone/high pressure system - atop it's lower level circulation center.
The steering layer flow forma developing system is generally in a WNW direction, though at a
significantly slower speed than yesterday. The slower forward motion is also somewhat more
conducive or indicative of a system that is more likely to be intensifying than simply remaining
as a tropical wave.