[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 271706
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT TUN SEP 27 2005

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHEASTERN SECTIONS
OF SOUTH AMERICA...AND ATLANTIC OCEAN TO THE AFRICAN COAST FROM
THE EQUATOR TO 32N. THE FOLLOWING INFORMATION IS BASED ON
SATELLITE IMAGERY...WEATHER OBSERVATIONS...RADAR...AND
METEOROLOGICAL ANALYSIS.

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1645 UTC.

...SPECIAL FEATURE...

CENTRAL CARIBBEAN TROPICAL WAVE IS ALONG 75W/76W S OF CUBA WITH
A 1010 MB LOW ALONG THE WAVE NEAR 14N.  OBSERVATIONS FROM BUOY
42058 SUGGEST THERE IS A WEAK LOW ASSOCIATED WITH THE WAVE WITH
WLY WINDS RECENTLY REPORTED...THOUGH THOSE WINDS ARE LIKELY
ENHANCED BY DOWNDRAFTS AND OUTFLOW BOUNDARIES.   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 CONVECTION IS FROM 13.5N-17.5N BETWEEN 74W-78W.  HEAVY
RAIN IS POSSIBLE FOR JAMAICA LATER TODAY AND OVERNIGHT.

...TROPICAL WAVES...

E-CENTRAL ATLC TROPICAL WAVE IS ALONG 30W/31W S OF 14N MOVING W
15 KT.  THERE COULD BE A WEAK LOW ELONGATED E-W ALONG THE WAVE
NEAR 10.5N AS INDICATED BY VISIBLE SATELLITE AND QUIKSCAT.
SCATTERED MODERATE CONVECTION IS FROM 10N-12N BETWEEN 30W-34W
WITH DRY AIR IN THE MID/UPPER LEVELS PREVENTING ANY TSTMS AT THE
NORTHERN END OF THE WAVE.

CENTRAL ATLC TROPICAL WAVE IS ALONG 44W/45W S OF 21N WITH A 1012
MB LOW ALONG THE WAVE NEAR 14N MOVING W 15 KT.  SLY SHEAR
CONTINUES OVER THE WAVE... KEEPING THE SCATTERED TSTMS LIMITED
TO THE NRN END FROM 16N-20N BETWEEN 45W-48W.  TSTMS ARE ALSO IN
THE "TAIL" OF THE WAVE CONNECTING IT TO THE ITCZ WITHIN 45 NM OF
LINE 11.5N39.5W 14N42W.  SOME COMPUTER MODELS TRY TO DEVELOP THE
NRN END OF THE WAVE AS IT INTERACTS WITH A COLD LOW TO THE NW..
BUT IF THIS OCCURS ANY DEVELOPMENT WOULD TAKE DAYS.

CENTRAL CARIBBEAN WAVE IS NOW A SPECIAL FEATURE.

CENTRAL AMERICAN TROPICAL WAVE IS ALONG 90W S OF 20N MOVING W 15
KT.  THERE IS NOT A WELL-DEFINED WAVE AXIS AND IT COULD BE
ANYWHERE FROM 88W-90W.  THE PSN IS BASED ON LOW-LEVEL TURNING
SEEN IN THE EPAC.  WAVE WILL LIKELY ENHANCE CONVECTION OVER
CENTRAL AMERICA AND MEXICO S OF 19N TODAY.

...ITCZ...

ITCZ IS CENTERED ALONG 11N16W 11N28W 9N35W 14N41W AND IS
ILL-DEFINED TO THE WEST.  WIDELY SCATTERED MODERATE WITHIN 60 NM
OF 7N32W 9N45W.  ISOLATED MODERATE FROM 7N-14N E OF 20W.

...DISCUSSION...

GULF OF MEXICO...
A BROAD UPPER HIGH IS ANCHORED OVER S TEXAS NEAR 30N99W COVERING
THE WESTERN GULF.  RATHER DRY AIR IN THE MID/UPPER LEVELS IS
KEEPING SHOWERS TO A MINIMUM EXCEPT ALONG A SURFACE TROUGH.
THIS TROUGH WITH A 1010 MB LOW NEAR 28.5N86.5W EXTENDS FROM THE
LOW TO 25N90W WITH ISOLATED TSTMS WITHIN 60 NM OF THE TROUGH.
MID/UPPER LOW IS OVER S FLORIDA MOVING SLOWLY NORTHWARD.  THIS
LOW SHOULD SLIGHTLY ENHANCE DAYTIME SHOWERS/TSTMS OVER FLORIDA S
OF LAKE OKEECHOBEE.  OTHERWISE A FEW SHOWERS ARE IN THE BAY OF
CAMPECHE S OF 22N W OF 94W.  A WEAKENING STATIONARY FRONT IS
OVER THE NRN GULF FROM DESTIN TO ERN LOUISIANA BRINGING A LITTLE
DRIER AIR INTO THE REGION.  GENERALLY INCREASING RAIN CHANCES
ARE LIKELY FOR FLORIDA DURING THE WEEK WITH THE UPPER LOW
PROVIDING INSTABILITY AND SLOWLY INCREASING LOW-LEVEL MOISTURE
FROM THE SOUTH.

CARIBBEAN...
TWO TROUGHS AND A HIGH IN BETWEEN ARE THE MID/UPPER FEATURES OF
NOTE TODAY.  THE TROUGHS ARE IN THE NW AND EXTREME NE
CARIBBEAN...FROM NW CUBA TO HONDURAS AND IN THE LEEWARD ISLANDS
SW TO 16N64W.  ENHANCED SHOWERS/TSTMS ARE N OF 20N BETWEEN
80W-85W AND IN THE BAY OF CAMPECHE... WITH WIDELY SCATTERED
SHOWERS/TSTMS NEAR THE LEEWARDS DUE TO WSW TO E HONDURAS AND SE
TO 12N65W.  LIGHT SE SHEAR IS OVER THE TROPICAL WAVE IN THE
CENTRAL CARIBBEAN WITH COMPUTER MODELS SUGGESTING NO SIGNIFICANT
SHEAR FOR AT LEAST THE NEXT COUPLE DAYS.  OTHERWISE DRY AIR IN
THE MID/UPPER LEVELS DOMINATES THE E CARIBBEAN SAVE THE LEEWARD
ISLANDS WITH LESS OF A TSTM CHANCE THAN AVERAGE.  THE WESTERN
CARIBBEAN SHOULD STAY ON THE WET SIDE THIS WEEK WITH THE WAVE
MOVING IN AS WELL AS THE LEEWARD ISLANDS DUE TO THE UPPER
TROUGH.  DRY WEATHER SHOULD DOMINATE THE WINDWARD ISLANDS.

ATLANTIC...
THE UPPER LOW OVER FLORIDA COULD ASSIST A FEW DAYTIME TSTMS OVER
THE NW BAHAMAS.  OTHERWISE MID/UPPER RIDGE LIES FROM HAITI TO
31N71W WITH GENERALLY DRY WEATHER BENEATH THE HIGH SAVE A FEW
SHOWERS NEAR THE TURKS/CAICOS.  DEEP TROUGH EXTENDS FROM AN
UPPER LOW NEAR 31N58W SSW TO 21N60W THEN SW INTO THE LEEWARD
ISLANDS.  THE ASSOCIATED COLD FRONT CONTINUES TO WEAKEN... ALONG
31N51W TO 25N56W WITH A TROUGH WESTWARD TO 24N64W.  WIDELY
SCATTERED TSTMS ARE FROM 22N-25N BETWEEN 54W-60W NEAR THE FRONT
WITH UPPER DIFFLUENCE FROM THE UPPER TROUGH PRODUCING A SIMILAR
COVERAGE OF TSTMS FROM 18N-21N BETWEEN 55W-63W.  IN THE CENTRAL
ATLC... UPPER HIGH IS NEAR 23N35W RIDGING NW TO 31N40W KEEPING
BENIGN CONDITIONS IN THE AREA.  TO THE E...AN UPPER LOW HAS
DROPPED INTO THE REGION NEAR 27N24W WITH INCREASING HIGH CLOUDS
N OF 22N BETWEEN AFRICA AND THE UPPER LOW.  THE TROPICAL ATLC
HAS A THIN UPPER RIDGE FROM SENEGAL TO 17N38W... NOW PART OF THE
LARGER HIGH IN THE CENTRAL ATLC.. THEN RIDGING SW TO 9N48W.
NARROW MID/UPPER TROUGHS PERSISTS NEAR 12N51W TO 22N51W....
CAUSING STRONG SLY SHEAR OVER A NEARBY TROPICAL WAVE.  DIFFLUENT
UPPER PATTERN IS OVER THE ITCZ ... CAUSING A FEW MORE TSTMS THAN
YESTERDAY.   AT THE SURFACE...THE SUBTROPICAL RIDGE IS BROKEN BY
THE COLD FRONT NEAR 51W... WITH THE RIDGE AXIS FROM 31N39W TO
22N55W.  HIGH PRESSURE IS AS STRONG AS IT HAS BEEN FOR QUITE
SOME TIME WITH A FAIRLY LARGE AREA OF 20-25 KT WINDS NEAR THE
COAST OF NW AFRICA.

$$
BLAKE

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