[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 250549
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0315 UTC.

...SPECIAL FEATURES...
A WELL-DEFINED SURFACE LOW PRESSURE SYSTEM CENTERED ABOUT 200 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 THE SOUTHEASTERN COAST OF NORTH
CAROLINA...AND BUOY AND SHIP REPORTS INDICATE WINDS IN EXCESS OF
50 MPH ARE OCCURRING NORTH AND WEST OF THE CENTER.

A BROAD AREA OF LOW PRESSURE IS ANALYZED AS A 1005 MB LOW IS TO
THE E OF THE TURKS AND CAICOS NEAR 22N70W MOVING NORTHWARD AT
NEAR 10 KT. THIS SYSTEM HAS BECOME BETTER ORGANIZED DURING THE
PAST SEVERAL HOURS...AND UPPER-LEVEL WINDS ARE EXPECTED TO
GRADUALLY BECOME MORE FAVORABLE FOR A TROPICAL DEPRESSION TO
DEVELOP DURING THE NEXT DAY OR SO. SCATTERED MODERATE/ STRONG
CONVECTION IS FROM 19N-23N BETWEEN 66W-70W AND FROM 20N-23N
BETWEEN 63W-66W. SCATTERED SHOWERS/ISOLATED THUNDERSTORMS REMAIN
OVER THE NE CARIBBEAN AND THE SW ATLC FROM 16N-27N BETWEEN
62W-70W INCLUDING ISLANDS FROM THE LEEWARDS TO HISPANIOLA.

...TROPICAL WAVES...
TROPICAL WAVE IS ALONG 41W S OF 18N MOVING W 10-15 KT. BROAD
INVERTED-V CURVATURE IS OBSERVED ON SATELLITE IMAGERY WITH
SCATTERED MODERATE/STRONG CONVECTION FROM 12N-16N BETWEEN 34W
AND THE WAVE AXIS.

TROPICAL WAVE IS ALONG 65W/66W S OF 18N MOVING W 10-15 KT. WAVE
IS BENEATH AN UPPER RIDGE DRAWING TROPICAL MOISTURE N AS HIGH
CLOUDS MASKING ANY SATELLITE SIGNATURE WITH NO ASSOCIATED
SHOWERS/CONVECTION.

TROPICAL WAVE IS ALONG 79W/80W 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 S OF 20N MOVING W 10-15 KT. WAVE IS
ALONG THE W COAST OF THE YUCATAN PENINSULA AND COMBINED WITH THE
UPPER LEVEL RIDGE IS PRODUCING NUMEROUS STRONG CONVECTION INLAND
AND WITHIN 60 NM ALONG THE COAST OF S MEXICO IN THE BAY OF
CAMPECHE BETWEEN 92W-96W AS WELL AS SCATTERED MODERATE/STRONG
CONVECTION S OF 21N E OF 92W TO INLAND OVER THE YUCATAN.

...THE ITCZ...
ITCZ AXIS IS ANALYZED ALONG 12N16W 7N27W 10N40W 8N48W 10N62W.
NUMEROUS STRONG CONVECTION IS FROM 13N-15N E OF 18W TO INLAND
OVER SENEGAL AFRICA. SCATTERED MODERATE/STRONG CONVECTION IS
WITHIN 60/75 NM OF LINE FROM 10N16W TO INLAND OVER SIERRA LEONE
NEAR 9N13W.

...DISCUSSION...

GULF OF MEXICO...
A DEEP LAYERED TROUGH THAT COVERS THE SE US COAST AND THE W ATLC
REMAINS OVER THE FLORIDA PENINSULA BRINGING DRY STABLE AIR TO
THE FAE E GULF WATERS AND THE FLORIDA PENINSULA THROUGH THE
FLORIDA STRAITS. A BROAD UPPER RIDGE COVERS THE GULF ANCHORED
OVER CENTRAL MEXICO EXTENDING AN AXIS E TO THE FLORIDA STRAITS
NEAR 24N81W. UPPER DIFFLUENCE COUPLED WITH THE TROPICAL WAVE IS
GENERATING THE CONVECTION ASSOCIATED WITH THE TROPICAL WAVE
ALONG 92W AS WELL AS SCATTERED SHOWERS/ISOLATED THUNDERSTORMS S
OF 26NW OF 88W TO INLAND OVER MEXICO.

CARIBBEAN SEA...
THE UPPER RIDGE FROM THE GULF OF MEXICO COVERS THE W CARIBBEAN W
OF 81W WITH THE DEEP LAYERED TROUGH OVER THE W ATLC EXTENDING
ACROSS CUBA TO 20N. A SHEAR AXIS EXTENDS FROM NEAR 20N78W SSW TO
NEAR THE NICARAGUA/COSTA RICA BORDER. UPPER LEVEL DIFFLUENCE IS
GENERATING ISOLATED SHOWERS AND POSSIBLE ISOLATED THUNDERSTORMS
OVER THE GULF OF HONDURAS S OF 20N W OF 85W. AN UPPER RIDGE IS
ANCHORED OVER THE E CARIBBEAN NEAR 15N65W AND COVERS THE
REMAINDER OF THE AREA AND DRAWING TROPICAL MOISTURE N ACROSS THE
CENTRAL CARIBBEAN ENHANCING THE ACTIVITY ASSOCIATED WITH THE LOW
IN THE SPECIAL FEATURES ABOVE.

ATLANTIC OCEAN...
TOW 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
ACROSS CUBA INTO THE NW CARIBBEAN WITH THE ASSOCIATED COLD FRONT
ENTERING THE REGION NEAR 32N71W TO OVER THE N BAHAMA ISLANDS
NEAR 24N78W GENERATING SCATTERED SHOWERS/ISOLATED THUNDERSTORMS
N OF 30N BETWEEN 67W AND THE FRONT AND ISOLATED SHOWERS WITH
POSSIBLE ISOLATED THUNDERSTORMS FROM 23N-27N W OF 76W TO OVER S
FLORIDA. STRONG WINDS ARE W OF THE FRONT ALONG THE N PORTION OF
THE AREA REACH TO NEAR GALE FORCE WITH A RECENT SHIP REPORTING
50 KT JUST TO THE W OF THE STORM CENTER NEAR 32N75W. AN UPPER
RIDGE IS OVER THE SECOND LOW PRESSURE SYSTEM IN THE SPECIAL
FEATURES EXTENDING FROM THE CARIBBEAN ACROSS PUERTO RICO TO
27N62W COVERING THE REMAINDER OF THE W ATLC. WEAKENING CUT-OFF
UPPER LOW REMAINS IN THE CENTRAL ATLC NEAR 27N51W GENERATING
ISOLATED SHOWERS FROM 24N-30N BETWEEN 45W-52W. A DEEP LAYERED
LOW IS IN THE E ATLC N OF 18N E OF 33W TO OVER NW AFRICA WITH
THE UPPER LOW NEAR 32N22W AND THE 1013 MB SURFACE LOW NEAR
31N23W AND A SURFACE TROUGH EXTENDING SSW TO 21N29W GENERATING
SCATTERED SHOWERS/ISOLATED THUNDERSTORMS FROM 29N-34N BETWEEN
18W-22W. THE TYPICAL E/W UPPER RIDGE THAT EXTENDS FROM AFRICA TO
40W ALONG 12N CONTINUES TO BE SUPPRESSED TO THE S DUE TO THE
UPPER TROUGH MENTIONED ABOVE. THE SURFACE RIDGE CONTINUES TO
WEAKEN COVERING THE ATLC N OF 20N BETWEEN 30W-55W.

$$
WALLACE




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