[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 251205 AAA
TWDAT

TROPICAL WEATHER DISCUSSION...UPDATED
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT THU SEP 25 2008

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

BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0945 UTC.

...SPECIAL FEATURES...
A WELL-DEFINED SURFACE LOW PRESSURE SYSTEM CENTERED ABOUT 170 NM
SE OF THE SOUTH CAROLINA-NORTH CAROLINA BORDER IS MOVING
SLOWLY WESTWARD. SHOWERS AND THUNDERSTORMS HAVE BECOME A LITTLE
BETTER ORGANIZED THIS MORNING AND THIS SYSTEM COULD DEVELOP INTO
A SUBTROPICAL OR TROPICAL CYCLONE LATER TODAY. REGARDLESS OF
WHETHER OR NOT THIS SYSTEM BECOMES A SUBTROPICAL OR TROPICAL
CYCLONE...STRONG WINDS...COASTAL FLOODING...HIGH SURF...AND
DANGEROUS RIP CURRENTS WILL CONTINUE ALONG PORTIONS OF THE U.S.
EAST COAST DURING THE NEXT COUPLE OF DAYS. OUTER RAINBANDS ARE
ALREADY SPREADING ONSHORE FROM SOUTH CAROLINA TO VIRGINIA.

A BROAD AREA OF LOW PRESSURE IS ANALYZED AS A 1005 MB LOW IS
JUST TO THE NE OF THE TURKS AND CAICOS NEAR 22N69W MOVING
NORTHWARD NEAR 10 KT. THIS SYSTEM IS NOT WELL ORGANIZED...WITH
THE LOW-LEVEL CIRCULATION CENTER DISPLACED TO THE WEST OF THE
SHOWER AND THUNDERSTORM ACTIVITY.  UPPER-LEVEL WINDS COULD
BRIEFLY BECOME MORE CONDUCIVE FOR DEVELOPMENT AND THIS SYSTEM
COULD BECOME A TROPICAL CYCLONE OVER THE NEXT DAY OR SO.
THIS SYSTEM IS BEING SHEARED BY THE DEEP LAYERED TROUGH TO THE W
WITH SCATTERED MODERATE/STRONG CONVECTION FROM 20N-24N BETWEEN
65W-68W AND SCATTERED SHOWERS/ISOLATED THUNDERSTORMS OVER THE SW
ATLC FROM 18N-26N BETWEEN 61W-70W INCLUDING ISLANDS THE VIRGIN
ISLANDS... PUERTO RICO AND HISPANIOLA.

...TROPICAL WAVES...
TROPICAL WAVE IS ALONG 42W/43W S OF 17N MOVING W 10-15 KT. BROAD
INVERTED-V CURVATURE IS OBSERVED ON SATELLITE IMAGERY WITH
SCATTERED MODERATE/ISOLATED STRONG CONVECTION E OF THE WAVE FROM
13N-16N BETWEEN 34W-40W.

TROPICAL WAVE IS ALONG 65W/66W S OF 16N MOVING W 10-15 KT. WAVE
POSITION IS BASED ON CONTINUITY AS IT IS HAS NO SATELLITE
SIGNATURE AND NO ASSOCIATED SHOWERS/CONVECTION.

TROPICAL WAVE IS ALONG 80W/81W S OF 16N MOVING W 10-15 KT. WAVE
IS EMBEDDED WITHIN SOMEWHAT DRY STABLE AIR LIMITING CLOUD
FORMATION AND SHOWERS.

TROPICAL WAVE IS ALONG 92W/93W S OF 20N MOVING W 10-15 KT. WAVE
IS IN THE BAY OF CAMPECHE ACROSS S MEXICO INTO THE E PACIFIC
REGION AND COMBINED WITH THE UPPER LEVEL RIDGE IS PRODUCING
SCATTERED MODERATE/STRONG CONVECTION INLAND AND WITHIN 90 NM
ALONG THE COAST OF THE YUCATAN AND S MEXICO BETWEEN 90W-95W.

...THE ITCZ...
ITCZ AXIS IS ANALYZED ALONG 12N13W 7N24W 10N40W 7N54W 7N60W.
CLUSTERS OF SCATTERED MODERATE/ISOLATED STRONG CONVECTION ARE
FROM 4N-11N BETWEEN 10W-21W AND TO THE COAST OF SW AFRICA.

...DISCUSSION...

GULF OF MEXICO...
A DEEP LAYERED TROUGH THAT COVERS THE SE US COAST AND THE W ATLC
IS NO LONGER IN THE GULF OF MEXICO. HOWEVER...THE SOMEWHAT DRY
STABLE UPPER AIR REMAINS OVER THE FLORIDA PENINSULA. A BROAD
UPPER RIDGE DOMINATES THE GULF ANCHORED OVER CENTRAL MEXICO
EXTENDING AN AXIS E TO W CUBA COVERING THE NW CARIBBEAN. UPPER
DIFFLUENCE COUPLED WITH THE TROPICAL WAVE IS GENERATING
SCATTERED SHOWERS/ISOLATED THUNDERSTORMS S OF 25N W OF 87W TO
INLAND OVER MEXICO AND THE YUCATAN PENINSULA AS WELL AS
ENHANCING THE ACTIVITY ASSOCIATED WITH THE TROPICAL WAVE ALONG
92W/93W LEAVING THE N GULF RATHER CLEAR THIS MORNING.

CARIBBEAN SEA...
THE UPPER RIDGE OVER THE GULF OF MEXICO COVERS THE NW CARIBBEAN
N OF 11N W OF 79W WITH THE DEEP LAYERED TROUGH OVER THE W ATLC
EXTENDING ACROSS E CUBA TO 16N BETWEEN 71W-79W. UPPER LEVEL
DIFFLUENCE CONTINUES TO GENERATING ISOLATED SHOWERS AND POSSIBLE
ISOLATED THUNDERSTORMS OVER THE GULF OF HONDURAS S OF 20N W OF
83W. AN UPPER RIDGE IS ANCHORED OVER THE E CARIBBEAN NEAR 16N65W
AND COVERS THE REMAINDER OF THE AREA AND DRAWING TROPICAL
MOISTURE N ACROSS THE CENTRAL CARIBBEAN. HOWEVER...THE CARIBBEAN
IS BEGINNING TO CLEAR THIS MORNING AS THE ACTIVITY ASSOCIATED
WITH THE LOW IN THE SPECIAL FEATURES ABOVE IS MOVING AWAY FROM
THE N CARIBBEAN ISLANDS.

ATLANTIC OCEAN...
TWO MAIN CONCERNS FOR THE W ATLC TONIGHT ARE THE ACTIVITY
DESCRIBED IN THE SPECIAL FEATURES ABOVE. THE DEEP LAYERED TROUGH
ASSOCIATED WITH THE FIRST SPECIAL FEATURE COVERS W ATLC W OF 70W
TO THE FLORIDA PENINSULA ACROSS CUBA INTO THE NW CARIBBEAN WITH
THE ASSOCIATED COLD FRONT ENTERING THE REGION NEAR 32N71W TO
28N73W WHERE IT PULLS UP STATIONARY TO OVER THE N BAHAMA ISLANDS
NEAR 24N79W GENERATING SCATTERED SHOWERS/ISOLATED THUNDERSTORMS
N OF 29N BETWEEN 68W AND THE FRONT. A SURFACE TROUGH EXTENDS
FROM THE STORM CENTER NEAR 32N76W ALONG 28N76W TO THE FLORIDA
COAST JUST N OF FORT LAUDERDALE. ISOLATED SHOWERS WITH POSSIBLE
ISOLATED THUNDERSTORMS ARE FROM 23N-27N W OF 76W TO OVER S
FLORIDA. STRONG WINDS ARE W OF THE SURFACE TROUGH ALONG THE N
PORTION OF THE AREA REACHING TO NEAR GALE FORCE. AN UPPER RIDGE
IS TO THE E OF THE SECOND LOW PRESSURE SYSTEM IN THE SPECIAL
FEATURES EXTENDING FROM THE CARIBBEAN ACROSS THE VIRGIN ISLANDS
TO 29N62W COVERING THE REMAINDER OF THE W ATLC. WEAKENING
CUT-OFF UPPER LOW REMAINS IN THE CENTRAL ATLC NEAR 27N50W BUT IS
STILL GENERATING ISOLATED SHOWERS FROM 23N-30N BETWEEN 46W-52W.
A DEEP LAYERED LOW IS IN THE E ATLC N OF 22N E OF 32W TO OVER NW
AFRICA WITH THE UPPER LOW NEAR 32N23W AND THE 1013 MB SURFACE
LOW NEAR 31N23W AND A SURFACE TROUGH EXTENDING SSW TO 24N28W
GENERATING ISOLATED SHOWERS FROM 29N-33N BETWEEN 19W-23W. THE
TYPICAL E/W UPPER RIDGE THAT EXTENDS FROM AFRICA TO NEAR 40W
ALONG 13N CONTINUES TO BE SUPPRESSED TO THE S DUE TO THE UPPER
TROUGH MENTIONED ABOVE. A WEAK SURFACE RIDGE REMAINS OVER THE
CENTRAL ATLC N OF 25N BETWEEN 30W-55W WITH A 1019 MB HIGH NEAR
31N38W.

$$
WALLACE/AC



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