[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 231100
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT FRI OCT 23 2009

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
1015 UTC.

...TROPICAL WAVES...

TROPICAL WAVE IS TILTED FROM 10N38W TO 20N35W AND DRIFTING NW.
THE WAVE IS EMBEDDED WITHIN A MAXIMUM AREA OF DEEP LAYER
MOISTURE AS DEPICTED BY TOTAL PRECIPITABLE WATER IMAGERY N OF
10N BETWEEN 27W-35W. CIMSS WAVETRAK MODEL GUIDANCE ALSO
INDICATES A NARROW AREA OF 850 MB RELATIVE VORTICITY IN THE
VICINITY OF THE WAVE AXIS N OF 10N BETWEEN 33W-39W. SCATTERED
MODERATE/ISOLATED STRONG CONVECTION IS OCCURRING FROM 12N-21N
BETWEEN 26W-37W PRIMARILY EAST OF THE WAVE AXIS. THIS ACTIVITY
IS BEING ENHANCED BY AN AREA OF UPPER LEVEL DIFFLUENCE LOCATED E
OF AN UPPER LEVEL SHORTWAVE TROUGH WITH AXIS DIPPING SOUTH TO
15N ALONG 35W.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 9N13W 7N23W 7N32W 6N57W.
CLUSTERS OF SCATTERED MODERATE CONVECTION ARE FROM 2N-10N
BETWEEN 20W-38W.

...DISCUSSION...

GULF OF MEXICO...
AS OF 0900 UTC...A COLD FRONT ENTERS THE GULF NEAR BILOXI
MISSISSIPPI AND EXTENDS SW ALONG 25N92W INTO EASTERN MEXICO NEAR
TAMPICO TURNING STATIONARY ALONG THE EASTERN SLOPES OF THE
SIERRA MADRE ORIENTAL MOUNTAINS. A PRE-FRONTAL SURFACE TROUGH
EXTENDS FROM 23N94W TO 20N96W. LOW-LEVEL CONVERGENCE NEAR BOTH
OF THESE SURFACE BOUNDARIES IS GENERATING SCATTERED SHOWERS AND
TSTMS WITHIN 120 NM OF A LINE FROM 22N95W TO INLAND OVER
SOUTHERN ALABAMA NEAR MOBILE BAY. THE FRONT IS SUPPORTED ALOFT
BY A BROAD UPPER LEVEL TROUGH ACROSS THE CENTRAL CONUS WITH THE
UPPER LOW CENTERED OVER WESTERN IOWA THIS MORNING. A DRY AND
STABLE AIRMASS FOLLOWS BEHIND THE FRONT WITH NW WINDS UP TO 25
KT. AN UPPER LEVEL RIDGE ANCHORED OVER THE EASTERN BAY OF
CAMPECHE NEAR 19N92W EXTENDS A RIDGE AXIS NE OVER THE NE GULF
AND FLORIDA PENINSULA THUS ENHANCING THE CONVECTION ASSOCIATED
WITH THE COLD FRONT.

CARIBBEAN SEA...
A 1007 MB LOW REMAINS QUASI-STATIONARY IN THE SW CARIBBEAN OFF
THE COAST OF NICARAGUA NEAR 13N83W. MOSTLY SCATTERED SHOWERS
ACCOMPANY THIS LOW ACROSS THE SW CARIBBEAN S OF 15N W OF 80W AS
MOST CONVECTION IS BEING INHIBITED BY HIGH SHEAR VALUES
ASSOCIATED WITH THE BASE OF A HIGHLY AMPLIFIED UPPER LEVEL
TROUGH THAT EXTENDS FROM THE SW NORTH ATLC TO AN UPPER LOW
CENTERED OVER EASTERN CUBA AND CONTINUES S-SW TO NICARAGUA. THE
TROUGH IS LOCATED BETWEEN A BROAD UPPER LEVEL RIDGE OVER THE
GULF OF MEXICO AND NW CARIBBEAN AND A SECOND UPPER LEVEL RIDGE
ANCHORED OVER VENEZUELA THAT EXTENDS A RIDGE AXIS ACROSS THE
EASTERN CARIBBEAN ALONG 68W. THIS UPPER LEVEL PATTERN IS
PROVIDING THE NW AND FAR EASTERN CARIBBEAN WITH STRONG
SUBSIDENCE AND A DRY AIRMASS IN PLACE WITH ONLY A FEW ISOLATED
SHOWERS OBSERVED ON SATELLITE IMAGERY MOVING ACROSS THE LEEWARD
ISLANDS AND PUERTO RICO. A SWATH OF MOISTURE IS ACROSS THE FAR
SW AND CENTRAL CARIBBEAN WITH SCATTERED SHOWERS FROM 10N-20N
BETWEEN 71W-77W. AN AREA OF SCATTERED STRONG TSTMS ARE OCCURRING
NORTH OF PANAMA FROM 10N-13N BETWEEN 78W-81W.

ATLANTIC OCEAN...
A NARROW AMPLIFIED UPPER LEVEL TROUGH AXIS EXTENDS SW FROM
30N70W THROUGH THE CENTRAL BAHAMAS TO AN UPPER LOW CENTERED OVER
EASTERN CUBA AND DIPPING S INTO THE WESTERN CARIBBEAN SEA. THIS
UPPER LEVEL TROUGH IS PROVIDING STRONG SUBSIDENCE AND DRY STABLE
AIR W OF 77W AND ALSO SUPPORTS A SURFACE TROUGH ANALYZED FROM
25N73W TO 20N75W. A 1009 MB SURFACE LOW HAS DEVELOPED OVER THE
PAST 6 HOURS AND IS LOCATED ALONG THE SURFACE TROUGH NEAR
22N75W. LOW-LEVEL CONVERGENCE NEAR THE SURFACE TROUGH COUPLED
WITH UPPER LEVEL DIFFLUENCE E OF THE UPPER LEVEL TROUGH AXIS IS
GENERATING SCATTERED SHOWERS FROM 20N-27N BETWEEN 65W-76W. A
BROAD UPPER LEVEL TROUGH IS OVER THE CENTRAL ATLC N OF 28N AND
SUPPORTS A COLD FRONT N OF THE REGION TO NEAR 31N39W. LINGERING
WEAK LOW-LEVEL CONVERGENCE TRAILS TO THE WEST ALONG 26N BETWEEN
50W-65W AND CONTINUES TO PRODUCE ISOLATED LOW-LEVEL SHOWERS FROM
24N-27N BETWEEN 52W-65W. EAST OF THE COLD FRONT ACROSS THE
CENTRAL ATLC...A PRE-FRONTAL SURFACE TROUGH IS ANALYZED FROM
23N47W TO BEYOND 32N34W WITH SCATTERED SHOWERS AND ISOLATED
TSTMS OCCURRING WITHIN 200 NM E OF THE SURFACE TROUGH. ACROSS
THE EASTERN ATLC...A SURFACE RIDGE IS PRESENT ANCHORED BY A 1021
MB HIGH CENTERED NW OF THE MADEIRA ISLANDS NEAR 34N14W. IN THE
TROPICAL ATLC...A 1010 MB LOW IS N OF THE ITCZ AXIS CENTERED
NEAR 14N44W WITH ISOLATED SHOWERS WITHIN A 200 NM RADIUS OF THE
LOW CENTER.

$$
HUFFMAN





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