[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 251803
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT THU OCT 25 2007

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHERN
SECTIONS OF SOUTH AMERICA...AND THE 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...TROPICAL WAVES...
TROPICAL TROPICAL WAVE IS ALONG 28W S OF 16N MOVING W 10-15 KT.
THE WAVE SHOWS UP WELL IN LOW LEVEL SATELLITE DERIVED WINDS AND
VORTICITY...AND THE UW-CIMSS TPW PRODUCTS. IN ADDITION...VIS
SATELLITE IMAGERY SHOWS A SWIRL OF LOW CLOUDS ALONG THE WAVE
AXIS NEAR 8N. SCATTERED SHOWERS AND ISOLATED TSTMS ARE RELATED
TO THE WAVE.

LOW AMPLITUDE TROPICAL WAVE IS NOW ALONG 43W S OF 13N MOVING W
10-15 KT. THIS WAVE ALSO SHOWS UP WELL ON THE MIMIC-TPW PRODUCT
AND 850 MB VORTICITY. VIS SAT IMAGERY SHOWS A WELL DEFINED
INVERTED-V PATTERN ASSOCIATED WITH THE WAVE. SCATTERED MODERATE
CONVECTION IS WITHIN 250 NM E OF THE AXIS...AND NORTH OF THE
ITCZ AXIS.

TROPICAL WAVE IS ALONG 72W S OF 17N MOVING W 10-15 KT. THE WAVE
IS GENERATING SOME SHOWER ACTIVITY OVER WESTERN VENEZUELA AND NE
COLOMBIA AS WELL AS OVER HISPANIOLA. A QUIKSCAT PASS FROM THIS
MORNING SHOWED SOME WIND SHIFT ASSOCIATED WITH THE WAVE.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 10N14W 10N26W 10N37W 7N50W 6N59W.
BESIDES FOR THE CONVECTION ASSOCIATED WITH THE TROPICAL WAVES...
SCATTERED MODERATE CONVECTION IS WITHIN 100 NM S OF AXIS EAST OF
18W TO THE COAST OF AFRICA. SIMILAR CONVECTION IS WITHIN 180 NM
N OF AXIS BETWEEN THE PREVIOUSLY MENTIONED TROPICAL WAVES.

DISCUSSION...

GULF OF MEXICO...
AN OCCLUDED SURFACE LOW IS CENTERED NEAR THE ALABAMA/MISSISSIPPI
BORDER WITH THE ATTENDANT STATIONARY FRONT EXTENDING S ACROSS SE
FLORIDA AND THE STRAITS OF FLORIDA TO W CUBA INTO THE NW
CARIBBEAN. A BAND OF MULTILAYERED CLOUDS WITH EMBEDDED SHOWERS
AND TSTMS IS ASSOCIATED WITH THE FRONTAL SYSTEM. SHOWER ACTIVITY
IS MORE CONCENTRATED OVER THE NW CARIBBEAN WHERE A SFC TROUGH IS
ALSO ANALYZED. WV IMAGERY SHOWS A CUT-OFF LOW OVER N MISSISSIPPI
WITH A DEEP LAYERED TROUGH EXTENDING SW INTO CENTRAL MEXICO. DRY
UPPER AIR ROTATING AROUND THE LOW COVERS THE WESTERN GULF AND
THE NE PORTION OF THE AREA WHILE ABUNDANT UPPER LEVEL MOISTURE
IS SEEN OVER THE SE GULF. BROKEN STRATOCUMULUS CLOUDS ARE OVER
MOST OF THE GULF EXCEPT WITH CLEAR SKIES OVER THE FAR W PORTION.
THE FRONT IS FORECAST TO SLOWLY DISSIPATE TONIGHT THROUGH FRI
NIGHT. WINDS OVER THE GULF WATERS ARE OUT OF THE N/NW AND HAVE
DIMINISHED OVER THE PAST 24 HRS WITH THE QUIKSCAT STILL SHOWING
20 KT OVER THE NW AND SW GULF. LOOKING AHEAD...STRONG HIGH PRES
WILL BUILD OVER THE SOUTHERN PLAINS ON SAT WITH INCREASING
NORTHERLY WINDS OVER THE WESTERN AND MIDDLE GULF DURING THE
UPCOMING WEEKEND.

CARIBBEAN SEA...
MAIN FEATURE IN THE CARIBBEAN SEA IS AN AREA OF LOW PRESSURE
LOCATED ABOUT 130 NM EAST-NORTHEAST OF SAN JUAN PUERTO RICO.
THIS 1008 MB SFC LOW IS PRODUCING A LARGE AREA OF CLOUDINESS AND
SHOWERS. ALTHOUGH THIS SYSTEM HAS BECOME A LITTLE BETTER
ORGANIZED SINCE YESTERDAY...UPPER-LEVEL WINDS ARE UNFAVORABLE
FOR ADDITIONAL DEVELOPMENT. HOWEVER...CONDITIONS COULD BECOME
MORE FAVORABLE OVER THE NEXT SEVERAL DAYS AS THIS SYSTEM MOVES
WESTWARD OR WEST-SOUTHWESTWARD INTO THE BASIN. SCATTERED
MODERATE TO STRONG CONVECTION IS MAINLY SE OF THE LOW CENTER
FROM 17N-19N BETWEEN 60W-63W. ACCORDING TO THE GFS MODEL...
MOISTURE FROM THIS LOW WILL GRADUALLY SPREAD OVER THE UK/US
VIRGIN ISLANDS AND PUERTO RICO TONIGHT THROUGH SATURDAY...
INCREASING THE CHANCES OF RAIN OVER THOSE AREAS. EASTERLY WINDS
HAVE INCREASED TO 20-25 KT N OF PUERTO RICO...THANKS TO A
TIGHTENING PRES GRADIENT BETWEEN THE AREA OF LOW PRES AND A SFC
HIGH LOCATED NE OF BERMUDAS. THIS GRADIENT IS EXPECTED TO
STRENGTHEN FURTHER AND EXPAND W THROUGH AT LEAST FRI NIGHT.
A FRONTAL BOUNDARY IS OVER WESTERN CUBA AND THE NW CARIBBEAN.
THE FRONT COMBINED WITH A BROAD AREA OF LOW PRES OVER THE
W-CENTRAL CARIBBEAN IS PRODUCING SCATTERED SHOWERS AND TSTMS
OVER THE AREA...PARTICULARLY WEST OF 80W. CLUSTERS OF MODERATE
TO ISOLATED STRONG CONVECTION ARE AFFECTING THE ABC ISLANDS AND
THE ISLANDS OFFSHORE OF VENEZUELA. SIMILAR CONVECTION IS FOUND
OVER THE CARIBBEAN COAST OF COLOMBIA E OF 76W. THIS ACTIVITY IS
PROBABLY ASSOCIATED WITH A SFC TROUGH AND A DIFFLUENT PATTERN
ALOFT RELATED TO A BROAD UPPER-LEVEL RIDGE THAT EXTENDS FROM N
SOUTH AMERICA NWWD THROUGH E CUBA...THE BAHAMAS AND THE W ATLC.
AN EARLIER QUIKSCAT PASS SHOWED VERY WELL THE WIND SHIFT
ASSOCIATED WITH THIS SFC TROUGH THAT EXTENDS ALONG 19N82W 15N81W
14N75W. THIS ACTIVITY IS MOVING EWD WITH THE MID LEVEL FLOW.

ATLANTIC OCEAN...

THE STATIONARY FRONT ASSOCIATED WITH THE UPPER TROUGH IN THE
GULF OF MEXICO EXTENDS INTO THE W ATLC OFF THE COAST OF SOUTH
CAROLINA THROUGH THE STRAITS OF FLORIDA AND WESTERN CUBA.
SCATTERED SHOWERS/THUNDERSTORMS ARE ALONG THE IMMEDIATE FRONTAL
BOUNDARY. BROAD UPPER LEVEL RIDGE FROM THE CARIBBEAN EXTENDS A
NARROW UPPER RIDGE E OF THE FRONT ACROSS CUBA...THE BAHAMAS AND
THE W ATLC BEYOND 31N75W. UPPER DIFFLUENCE ASSOCIATED WITH THIS
RIDGE IS HELPING TO INDUCE CONVECTIVE ACTIVITY ALONG THE FRONT.
BROAD UPPER HIGH OVER THE N/CENTRAL ATLC CONTINUES TO MOVE N OF
THE REGION WHILE A LARGE UPPER-LEVEL LOW CONTINUES TO SPIN OVER
THE E-CENTRAL ATLC. A SURFACE RIDGE ANCHORED BY A 1024 MB HIGH
LOCATED NE OF BERMUDAS IS BETWEEN THE STATIONARY FRONT AND A
1009 MB SFC LOW LOCATED NEAR 27N42W. A SFC TROUGH EXTENDS FROM
THE LOW TO NEAR 21N48W. A SURFACE RIDGE REMAINS OVER THE FAR E
ATLC WITH A 1017 MB SURFACE HIGH LOCATED W OF THE CANARY ISLANDS
NEAR 27N22W. THE TYPICAL E/W UPPER LEVEL RIDGE EXTENDS OVER THE
E TROPICAL ATLC ALONG 11N E OF 35W WITH A NARROW UPPER RIDGE
AXIS EXTENDING N ALONG 23W TO 34N COVERING THE REMAINDER OF THE
E ATLC.

$$
GR





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