[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 181746
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT SAT OCT 18 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...SPECIAL FEATURES...
TROPICAL STORM OMAR IS CENTERED NEAR 33.4N 50.7W AT 18/1500 UTC.
ESTIMATED MINIMUM CENTRAL PRESSURE IS 1002 MB. MAXIMUM SUSTAINED
WIND SPEED IS 35 KT WITH GUSTS TO 45 KT. THIS IS THE LAST NHC
PUBLIC ADVISORY UNDER AWIPS/WMO HEADERS MIATCPAT5/WTNT35 KNHC
AND THE FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT5/
WTNT25 KNHC. THERE IS NO DEEP CONVECTION LEFT ASSOCIATED WITH
OMAR. LOW/MID CLOUDS WITH ISOLATED SHOWERS WITHIN 100 NM OF THE
LOW CENTER IN THE SE QUADRANT ARE ALL THAT REMAINS AS OMAR
BECOMES A REMNANT LOW.

...TROPICAL WAVES...
TROPICAL WAVE IS ALONG 35W S OF 15N MOVING W 10-15 KT. VERY
BROAD INVERTED-V CURVATURE IS OBSERVED ON SATELLITE IMAGERY.
SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 75 NM OF
LINE FROM 13N31W 16N33W TO 14N36W. CONVECTION IS BEING ENHANCED
BY A RAPIDLY AMPLIFYING UPPER RIDGE JUST TO THE E.

TROPICAL WAVE IS ALONG 54W S OF 15N MOVING W NEAR 10 KT. WEAK
INVERTED-V CURVATURE IS OBSERVED ON SATELLITE IMAGERY WITH A
LOW/MID LEVEL LOW ALONG THE WAVE NEAR 9N. ANY CONVECTION IN THE
VICINITY IS ASSOCIATED WITH THE ITCZ.

...THE ITCZ...
ITCZ AXIS IS ANALYZED ALONG 8N11W 9N34W 8N45W 10N55W 7N61W.
CLUSTERS OF SCATTERED MODERATE/ISOLATED STRONG TO SCATTERED
STRONG CONVECTION ARE FROM 3N-10N E OF 17W WITH CLUSTERS OF
SCATTERED TO NUMEROUS STRONG CONVECTION INLAND OVER W AFRICA
MOVING TOWARD THE E TROPICAL ATLC. CLUSTERS OF SCATTERED
MODERATE/ISOLATED STRONG CONVECTION ARE WITHIN 200 NM N OF THE
ITCZ AXIS W OF THE TROPICAL WAVE ALONG 54W TO INLAND OVER SOUTH
AMERICA. SCATTERED MODERATE WITH EMBEDDED CLUSTERS OF ISOLATED
STRONG CONVECTION ARE WITHIN 120/150 NM N AND 75 NM S OF THE
ITCZ AXIS FROM 43W-48W. CLUSTERS OF SCATTERED MODERATE
CONVECTION ARE FROM 3N-7N BETWEEN 20W-26W.

...DISCUSSION...

GULF OF MEXICO...
DOMINATING FEATURE TODAY OVER THE GULF IS THE COLD FRONT THAT
EXTENDS FROM THE W ATLC ACROSS FLORIDA FROM JACKSONVILLE THROUGH
CEDAR KEY ALONG 23N93W THEN S TO OVER MEXICO NEAR 18N95W. THE
STRONG SURFACE WINDS ARE BEGINNING TO ENTER THE ISTHMUS OF
TEHUANTEPEC FORMING GALE FORCE WINDS IN THE E PACIFIC REGION.
THE BROAD UPPER TROUGH ASSOCIATED WITH THIS FRONT COVERS THE E
HALF OF THE US EXTENDING INTO THE GULF N OF 24N. LOW/MID LEVEL
MOISTURE IS MAINTAINING A BAND OF LOW/MID LEVEL CLOUDS WITH
ISOLATED SHOWERS WITHIN 120 NM SE OF THE FRONT E OF 90W AND
WITHIN 150 NM NW OF THE FRONT W OF 90W. THE STRONG NORTHERLY
SURFACE FLOW COUPLED WITH THE SURFACE LOW IN THE NW CARIBBEAN IS
BRINGING SCATTERED SHOWERS AND POSSIBLE ISOLATED THUNDERSTORMS
OVER THE YUCATAN AND S MEXICO INTO THE BAY OF CAMPECHE WITHIN 60
NM ALONG THE COAST. ISOLATED SHOWERS ARE POSSIBLE IN THE SE GULF
S OF 26N E OF 84W. A SURFACE RIDGE IS BUILDING S OVER THE
CENTRAL US TO OVER THE NW GULF AND WITH DRY/STABLE AIR CLEARING
SKIES OVER THE N GULF BEHIND THE FRONT.

CARIBBEAN SEA...
THE W CARIBBEAN IS UNDER WEAK UPPER FEATURES AND EQUALLY WEAK
UPPER WINDS WHICH IS NOT PROVIDING STEERING CURRENTS FOR THE
1010 MB LOW ALONG THE COAST OF CENTRAL BELIZE. SCATTERED
MODERATE/ISOLATED STRONG CONVECTION IS NE OF THE LOW WITHIN 75
NM OF LINE FROM THE COAST OF HONDURAS NEAR 16N85W TO INLAND OVER
THE YUCATAN NEAR 19N88W. A STRONG UPPER RIDGE COVERS THE
REMAINDER OF THE CARIBBEAN ANCHORED IN THE CENTRAL ATLC. A 1011
MB LOW IS CENTERED NEAR 17N75W WITH A SURFACE TROUGH EXTENDING W
TO THE LOW ALONG THE COAST OF BELIZE. SCATTERED SHOWERS/ISOLATED
THUNDERSTORMS ARE MOSTLY NE OF THE SURFACE LOW FROM 17N-20N
BETWEEN 71W-76W. SIMILAR ACTIVITY IS OVER THE SW CARIBBEAN S OF
18N W OF 80W TO INLAND OVER CENTRAL AMERICA AND THE REMAINDER OF
THE YUCATAN. THE REMAINDER OF THE CARIBBEAN REMAINS RATHER
TRANQUIL TODAY.

ATLANTIC OCEAN...
A COLD FRONT CLIPS THE W ATLC ENTERING THE REGION THROUGH 32N79W
ACROSS FLORIDA NEAR JACKSONVILLE INTO THE GULF OF MEXICO. THE
ASSOCIATED UPPER TROUGH IS JUST BEGINNING TO MOVE INTO THE W
ATLC. HOWEVER...DRY/STABLE AIR THAT COVERS THE W ATLC IS
LIMITING CONVECTION OVER THE W ATLC TO ONLY ISOLATED SHOWERS
WITHIN 45 NM SE OF THE FRONT. AN UPPER LOW IS CENTERED NEAR
27N64W BUT IS ALSO EMBEDDED WITHIN THE DRY AIR THAT COVERS THE W
ATLC. IN THE CENTRAL ATLC IS AN UPPER HIGH NEAR 22N56W EXTENDING
A RIDGE AXIS SW TO OVER THE E CARIBBEAN ALSO COVERING THE W
TROPICAL ATLC. TO THE NNE OF THIS UPPER HIGH IS THE UPPER TROUGH
ASSOCIATED WITH REMNANTS OF TROPICAL STORM OMAR MAINLY N OF 27N
BETWEEN 45W-55W. SURFACE TROUGH EXTENDS FROM 30N53W TO 26N61W.
JUST TO THE E IS AN ELONGATED UPPER LOW CENTERED ALONG 26N38W TO
10N46W WHICH IS AMPLIFYING AN UPPER RIDGE OVER THE E TROPICAL
ATLC FROM THE CAPE VERDE ISLANDS NW TO 26N35W...ENHANCING THE
CONVECTION ASSOCIATED WITH THE TROPICAL WAVE ALONG 35W. ANOTHER
UPPER TROUGH IS DIGGING S OVER NW AFRICA N OF 22N E OF 20W
FURTHER AMPLIFYING THE UPPER RIDGE OVER THE E ATLC. BROAD
SURFACE RIDGE COVERS THE E ATLC N OF 15N E OF 48W ANCHORED BY A
1027 MB HIGH NEAR 32N31W. A WEAK AREA OF HIGH PRESSURE COVERS
THE W ATLC WITH A 1018 MB SSW OF BERMUDA NEAR 29N67W.

$$
WALLACE




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