[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 220521
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT TUE SEP 22 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0430 UTC.

...TROPICAL WAVES...

TROPICAL WAVE IS ALONG 35W/36W S OF 14N MOVING W NEAR 20 KT.
SATELLITE IMAGERY AND SATELLITE DERIVED WINDS INDICATE BROAD LOW
LEVEL CYCLONIC FLOW IN THE VICINITY OF THE WAVE AXIS. A LARGE
AREA OF SAHARAN DUST TRAILS THE WAVE MAINLY E OF 30W INHIBITING
MOST DEEP CONVECTION NEAR THE WAVE. HOWEVER...A FEW CLUSTERS OF
SHOWERS/POSSIBLE THUNDERSTORMS ARE N OF THE WAVE AXIS NEAR
16N35W...E OF THE WAVE AXIS NEAR 7N34W...AND W OF THE WAVE AXIS
FROM 8N-11N BETWEEN 37W-39W.

TROPICAL WAVE EXTENDS ALONG 23N43W TO 15N46W MOVING WNW NEAR 10
KT. THE WAVE IS APPROACHING A 1012 MB SURFACE LOW NEAR 14N48W.
SATELLITE IMAGERY INDICATES BROAD LOW-LEVEL CYCLONIC TURNING
AROUND THE WAVE AXIS EXTENDING TO THE LOW. A BROAD DEEP LAYER
MOISTURE MAXIMUM IS ALSO OBSERVED IN TOTAL PRECIPITABLE WATER
IMAGERY ALONG THE WAVE AND LOW. A LARGE CLUSTER OF NUMEROUS
STRONG CONVECTION IS E OF THE LOW AND ALONG THE S PORTION OF THE
WAVE FROM 13N-17N BETWEEN 46W-48W. SCATTERED MODERATE/ISOLATED
STRONG CONVECTION IS E OF THE WAVE AXIS FROM 17N-22N BETWEEN
41W-44W.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 13N15W 9N24W 10N35W 8N46W 8N61W.
ISOLATED MODERATE CONVECTION IS WITHIN 150 NM S OF THE AXIS
BETWEEN 21W-26W.

...DISCUSSION...

GULF OF MEXICO...
THE GULF OF MEXICO REMAINS FAIRLY CALM TONIGHT AS A WEAK SURFACE
RIDGE BUILDS FROM THE E ALONG 29N. AN UPPER LEVEL RIDGE COVERS
THE MAJORITY OF THE BASIN CENTERED OVER MEXICO NEAR 20N101W. A
FEW ISOLATED SHOWERS/POSSIBLE THUNDERSTORMS ARE NOTED NEAR SW
FLORIDA AND ACROSS THE YUCATAN CHANNEL DUE TO UPPER LEVEL
DIFFLUENT FLOW BETWEEN THE UPPER RIDGE AND A SHORTWAVE UPPER
TROUGH THAT DIGS ACROSS THE NW BAHAMAS TO THE STRAITS OF FLORIDA
CONTINUING TO THE NRN YUCATAN PENINSULA. MODERATE SURFACE WINDS
ARE ACROSS MUCH OF THE BASIN FLOWING ANTI-CYCLONICALLY AROUND
THE SURFACE RIDGE ACROSS THE N GULF. EXPECT THE RIDGE TO LIFT N
OF THE AREA AS A WEAK COLD FRONT MOVES OFF THE COAST OF TEXAS.

CARIBBEAN SEA...
AN UPPER LEVEL RIDGE COVERS THE W CARIBBEAN W OF 75W WHILE AN
UPPER LEVEL TROUGH COVERS THE REMAINDER OF THE BASIN EXTENDING
FROM THE ATLC. UPPER LEVEL DIFFLUENCE BETWEEN THE UPPER
RIDGE...THE UPPER TROUGH...AND THE AFOREMENTIONED SHORTWAVE UPPER
TROUGH EXTENDING FROM THE NE BAHAMAS ACROSS THE STRAITS OF
FLORIDA TO THE NRN YUCATAN PENINSULA IS SUPPORTING ISOLATED
SHOWERS/THUNDERSTORMS ACROSS THE NRN CARIBBEAN N OF 16N W OF
68W. SCATTERED SHOWERS/THUNDERSTORMS ARE ACROSS THE SW CARIBBEAN
S OF 10N W OF 77W DUE TO SURFACE CONVERGENCE NEAR THE E PACIFIC
ITCZ. A FEW ISOLATED SHOWERS ARE ALSO ACROSS THE LEEWARD ISLANDS
FROM 14N-15N E OF 63W. FRESH TRADE WINDS ARE ACROSS MUCH OF THE
S CENTRAL CARIBBEAN WITH STRONGER WINDS NEAR THE COAST OF
COLOMBIA AND ACROSS THE ERN CARIBBEAN.

ATLANTIC OCEAN...
A WEAKENING 1017 MB SURFACE LOW IS IN THE WRN ATLC NEAR 30N76W
SUPPORTING SCATTERED SHOWERS/THUNDERSTORMS FROM 28N-30N BETWEEN
72W-75W. THE SHOWER ACTIVITY IS ALSO ENHANCED BY DIFFLUENT FLOW
ALOFT BETWEEN A SHORTWAVE UPPER LEVEL TROUGH ACROSS THE NW
BAHAMAS AND AN UPPER LEVEL RIDGE CENTERED NEAR 29N72W. A SURFACE
TROUGH EXTENDS FROM 30N65W TO 25N67W. SURFACE CONVERGENCE NEAR
THE TROUGH IS SUPPORTING ISOLATED SHOWERS FROM 26N-28N BETWEEN
65W-68W. ANOTHER SURFACE TROUGH EXTENDS FROM 23N60W TO 17N60W.
THIS SURFACE TROUGH IS SUPPORTED BY AN UPPER LEVEL TROUGH WITH
AXIS ALONG 60W. ISOLATED SHOWERS/POSSIBLE THUNDERSTORMS ARE FROM
19N-22N BETWEEN 61W-65W...AND FROM 22N-27N BETWEEN 53W-60W. THIS
ACTIVITY IS PROBABLY ENHANCED MOSTLY BY UPPER LEVEL DIFFLUENT
FLOW ALONG THE E SIDE OF THE UPPER TROUGH VERSUS SURFACE
CONVERGENCE NEAR THE SURFACE TROUGH. THE REMAINDER OF THE ATLC
REMAINS FAIRLY CALM UNDER THE INFLUENCE OF A WEAK SURFACE RIDGE
ACROSS THE BASIN. IN THE UPPER LEVELS...AN UPPER LEVEL RIDGE
DOMINATES THE CENTRAL ATLC BETWEEN 30W-50W. AN UPPER LEVEL LOW
CENTERED NEAR 31N25W COVERS THE ERN ATLC SUPPORTING ISOLATED
SHOWERS N OF 26N BETWEEN 19W-25W. A BROAD UPPER LEVEL RIDGE
COVERS THE TROPICAL ATLC E OF 46W CENTERED NEAR 17N30W ENHANCING
CONVECTION NEAR THE TROPICAL WAVE AND SURFACE LOW CENTERED NEAR
14N48W.

$$
WALTON




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