[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 231052
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT SUN SEP 23 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1015 UTC.

...SPECIAL FEATURE...
SUBTROPICAL DEPRESSION ELEVEN WAS UPGRADED AT 23/0900 UTC AND IS
CENTERED NEAR 36.2N 46.1W OR ABOUT 920 NM W OF THE AZORES AT
23/0900 UTC AND IS NEAR STATIONARY. ESTIMATED MINIMUM CENTRAL
PRESSURE IS 1007 MB. MAXIMUM SUSTAINED WIND SPEED IS 30 KT WITH
GUSTS TO 40 KT. SEE LATEST NHC FORECAST ADVISORY UNDER AWIPS/WMO
HEADERS MIATCMAT1/WTNT21 FOR MORE DETAILS. T.D. ELEVEN CURRENTLY
DOES NOT SHOW ANY TROPICAL CHARACTERISTICS BUT WITH THE
CONVECTION BEGINNING TO WRAP AROUND IT COULD BECOME TROPICAL
CYCLONE LATER TODAY. T.D. ELEVEN HAS BEEN STATIONARY OVER THE
PAST SEVERAL HOURS WHILE TRAPPED BENEATH AN UPPER LEVEL LOW BUT
IS EXPECTED TO BEGIN TO MOVE N AND WILL BECOME ABSORBED WITHIN
AN EXTRATROPICAL SYSTEM CURRENTLY OVER THE CANADIAN MARITIMES.
CLUSTERS SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ARE REMOVED
FROM THE CENTER AND COVERING AN AREA FROM 34N-40N BETWEEN
40W-51W.

THE BROAD AREA OF LOW PRESSURE...ANALYZED AS A 1010 MB LOW IS
ABOUT 600 NM SSW OF THE CAPE VERDE ISLANDS NEAR 6N27W. THIS
SYSTEM CONTINUES TO BECOME BETTER ORGANIZED AND CONDITIONS
APPEAR FAVORABLE FOR THIS SYSTEM TO BECOME A TROPICAL DEPRESSION
DURING THE NEXT DAY OR TWO AS IT MOVES WESTWARD AT ABOUT 15 MPH.
CLUSTERS OF SCATTERED MODERATE/STRONG CONVECTION COVER A LARGE
AREA FROM 2N-13N BETWEEN 22W-31W.

A BROAD AREA OF LOWER PRESSURE ASSOCIATED WITH A TROPICAL WAVE
IS LOCATED ABOUT 500 NM EAST OF THE WINDWARD ISLANDS ALONG 52W.
SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 9N-13N
BETWEEN 51W-54W WITH CLUSTERS OF SIMILAR CONVECTION S OF 10N TO
THE COAST OF SOUTH AMERICA BETWEEN 52W-59W. THIS SYSTEM
CONTINUES TO BECOME BETTER ORGANIZED AND A TROPICAL DEPRESSION
COULD FORM DURING THE NEXT COUPLE OF DAYS AS IT APPROACHES THE
WINDWARD ISLANDS.

...TROPICAL WAVES...

TROPICAL WAVE IS ALONG 35W S OF 17N MOVING W 10-15 KT. THIS WAVE
HAS RAPIDLY BEGUN TO LOSE ITS IDENTITY OVERNIGHT AS THE TROPICAL
LOW TO THE E...SEE SPECIAL FEATURES ABOVE...HAS BECOME BETTER
ORGANIZED. NO ASSOCIATED SHOWER ACTIVITY/CONVECTION IS NOTED.

TROPICAL WAVE IS IN THE CARIBBEAN ALONG 80W S OF 20N MOVING W
10-15 KT. WAVE IS BENEATH AN AREA OF STRONG UPPER NORTHERLY
WINDS BETWEEN AN UPPER RIDGE TO THE W AND AN UPPER LOW TO THE E
THUS MASKING ANY SATELLITE SIGNATURE. NO ASSOCIATED SHOWER
ACTIVITY/CONVECTION.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 12N14W THROUGH THE 1010 MB LOW IN
THE SPECIAL FEATURES THEN ALONG 5N31W 12N53W 9N62W. IN ADDITION
TO ACTIVITY ASSOCIATED WITH THE TROPICAL WAVES AND 1010 MB LOW
IN THE E TROPICAL ATLC...CLUSTERS OF SCATTERED MODERATE/ISOLATED
STRONG CONVECTION ARE WITHIN 120 NM OF THE ITCZ AXIS FROM
44W-50W.

DISCUSSION...

GULF OF MEXICO...
BROAD UPPER LOW COVERS THE W GULF CENTERED OVER NE MEXICO SW OF
BROWNSVILLE TEXAS COVERING THE AREA W OF 93W. BROAD UPPER RIDGE
EXTENDS FROM THE NE YUCATAN PENINSULA OVER THE E GULF TO THE
FLORIDA PANHANDLE GENERATING DIFFLUENCE AND ADVECTING AN
ABUNDANCE OF TROPICAL MOISTURE TO PRODUCE SCATTERED
SHOWERS/ISOLATED THUNDERSTORMS FROM 85W-90W. THIS IS LEAVING THE
THE W GULF CLEAR THIS MORNING WITH ISOLATED SHOWERS E OF 85W TO
OVER THE FLORIDA PENINSULA.

CARIBBEAN SEA...
BROAD UPPER RIDGE COVERS THE W CARIBBEAN W OF 79W ANCHORED BY AN
UPPER HIGH IN THE GULF OF HONDURAS AND EXTENDING A RIDGE AXIS N
OVER THE E GULF OF MEXICO. A 1009 MB LOW IS OVER THE YUCATAN N
BELIZE WITH A WEAK SURFACE TROUGH EXTENDING JUST INTO THE S GULF
OF MEXICO. THIS LOW HAS THE POTENTIAL FOR SOME DEVELOPMENT AFTER
IT MOVES OVER OPEN WATER. THIS UPPER RIDGE IS ALSO GENERATING
DIFFLUENCE AND ADVECTING AN ABUNDANCE OF TROPICAL MOISTURE TO
PRODUCE CLUSTERS OF SCATTERED SHOWERS/ISOLATED THUNDERSTORMS W
OF 80W WITH THE STRONGEST ACTIVITY OVER NE NICARAGUA. AN UPPER
LOW IS OVER THE CENTRAL CARIBBEAN NEAR 14N74W COVERING THE AREA
FROM 10N-18N BETWEEN 70W-77W...THUS PRODUCING STRONG NORTHERLY
UPPER WINDS OVER THE TROPICAL WAVE ALONG 80W AND SCATTERED
SHOWERS/ISOLATED THUNDERSTORMS WITHIN 60 NM OF LINE FROM
COLOMBIA NEAR 10N75W TO 12N80W. UPPER RIDGE FROM THE TROPICAL
ATLC COVERS THE E CARIBBEAN WITH DRY SOMEWHAT STABLE AIR...THUS
CLEAR SKIES THIS MORNING.

ATLANTIC OCEAN...
BROAD UPPER RIDGE THAT EXTENDS FROM THE CARIBBEAN AND THE E GULF
OF MEXICO COVERS THE W ATLC W OF 67W GENERATING DIFFLUENCE AND
ADVECTING AN ABUNDANCE OF TROPICAL MOISTURE BUT IS ONLY
PRODUCING SCATTERED SHOWERS/ISOLATED THUNDERSTORMS WITHIN A 75
NM RADIUS OF 28N74W AND ISOLATED SHOWERS W OF 68W. A LONG DRAWN
OUT SURFACE TROUGH BISECTS THE CENTRAL ATLC EXTENDING FROM S OF
T.D. ELEVEN NEAR 32N46W ALONG 25N53W TO JUST E OF THE LEEWARD
ISLANDS NEAR 17N61W. SCATTERED SHOWERS/ISOLATED THUNDERSTORMS
ARE WITHIN 120 NM E OF THE SURFACE TROUGH FROM 19N-22N AND
WITHIN 120/150 NM OF A LINE FROM 24N53W TO BEYOND 32N39W. THIS
SURFACE TROUGH LIES ON THE BOUNDARY BETWEEN AN UPPER TROUGH TO
THE W AND A BROAD UPPER RIDGE COVERING THE TROPICAL ATLC
CENTERED NEAR 15N50W. A SECOND UPPER TROUGH IS OVER THE E ATLC
EXTENDING FROM AN UPPER LOW NEAR 32N21W W OF THE CAPE VERDE
ISLANDS TO NEAR 14N28W BUT IS NOT PRODUCING ANY SIGNIFICANT
ACTIVITY. WEAK SURFACE RIDGE COVERS THE W ATLC ANCHORED BY A
1020 MB HIGH N OF THE REGION NEAR 36N69W AND A SECOND SURFACE
RIDGE COVERS THE E ATLC ANCHORED BY A 1025 MB HIGH E OF THE
AZORES.

$$
WALLACE







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