[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 211756
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT MON SEP 21 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...TROPICAL WAVES...

TROPICAL WAVE IS ALONG 32W S OF 13N MOVING W NEAR 15 KT. VISIBLE
SATELLITE IMAGERY SHOWS CYCLONIC TURNING IN THE LOW-LEVEL CLOUD
FIELD IN THE VICINITY OF THE WAVE AXIS. AN EARLIER ASCAT PASS
AROUND 21/1200 UTC ALSO CONFIRMED THE PRESENCE OF THE LOW
AMPLITUDE WAVE. OF NOTE...A LARGE AREA OF SAHARAN DUST FOLLOWS
THE WAVE AND IS LOCATED MAINLY E OF 30W. ISOLATED SHOWERS ARE
FROM 10N-19N BETWEEN 31W-35W.

TROPICAL WAVE EXTENDS FROM 14N44W TO 21N41W MOVING WNW NEAR 15
KT. THE WAVE IS BEING GUIDED WNW AROUND A 1012 MB LOW THAT IS
CENTERED NEAR 15N48W. THE ENTIRE AREA SURROUNDING THE WAVE
COINCIDES WITH A MAXIMUM IN DEEP LAYER MOISTURE AS OBSERVED IN
TOTAL PRECIPITABLE WATER IMAGERY AND AN EARLIER QUIKSCAT PASS
AROUND 21/0900 UTC DEPICTED BROAD LOW-LEVEL CYCLONIC CURVATURE
EXTENDING FROM THE LOW TO THE NE NEAR THE WAVE AXIS. THIS
LOW-LEVEL CURVATURE AND SURFACE CONVERGENCE IS GENERATING
SCATTERED MODERATE/ISOLATED STRONG CONVECTION FROM 16N-23N
BETWEEN 39W-44W.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 10N15W 7N30W 8N34W 8N60W.
SCATTERED MODERATE CONVECTION IS WITHIN FROM 4N-8N BETWEEN
20W-27W.

...DISCUSSION...

GULF OF MEXICO...
UPPER LEVEL ANTICYCLONIC FLOW COVERS A MAJORITY OF THE GULF AS
AN UPPER LEVEL HIGH IS CENTERED OVER CENTRAL MEXICO NEAR
20N100W. AN UPPER LEVEL RIDGE EXTENDS FROM THE HIGH NE THROUGH
25N90W TO THE BIG BEND REGION OF FLORIDA. AT THE SURFACE...
GENERALLY LIGHT 10-15 KT SE WINDS ARE OBSERVED AS A SURFACE
RIDGE LIES FROM THE SE CONUS SW TO OVER E/CENTRAL MEXICO NEAR
VERACRUZ. A FEW ISOLATED SHOWERS AND TSTMS ARE OVER THE NE GULF
AND ARE FOUND N OF 26N BETWEEN 85W-91W DUE IN PART TO LOW-LEVEL
SURFACE WIND CONVERGENCE AND AIDED BY UPPER LEVEL DIFFLUENCE
FROM THE UPPER RIDGING ALOFT. THE SURFACE RIDGE IS EXPECTED TO
HOLD IN PLACE THROUGH WEDNESDAY ACROSS MUCH OF THE CENTRAL AND
ERN GULF...HOWEVER A COLD FRONT IS FORECAST TO ENTER THE NW GULF
WATERS LATE WEDNESDAY.

CARIBBEAN SEA...
THE NW CARIBBEAN IS INFLUENCE BY A MIDDLE TO UPPER LEVEL TROUGH
WITH AXIS ALONG 90W ACROSS THE YUCATAN PENINSULA...BELIZE AND
GUATEMALA. THIS TROUGHING IS GENERATING SCATTERED SHOWERS AND
ISOLATED TSTMS ACROSS THE NW CARIBBEAN N OF 16N W OF 80W...WITH
THE MOST CONCENTRATED ACTIVITY ON SATELLITE IMAGERY OVER BELIZE
AND THE ERN YUCATAN PENINSULA. AN UPPER LEVEL RIDGE IS LOCATED E
OF THE UPPER TROUGH ALONG 82W WITH THE ASSOCIATED UPPER LEVEL
DIFFLUENCE PRODUCING SCATTERED SHOWERS ALONG THE COASTAL WATERS
OF NICARAGUA...COSTA RICA AND PANAMA. THE CLOSE PROXIMITY OF THE
ITCZ AXIS ALONG 9N OVER PANAMA IS ALSO AIDING IN THE ACTIVITY
OVER SRN PORTIONS OF CENTRAL AMERICA. THE REMAINDER OF THE
CARIBBEAN E OF 78W IS COVERED BY AN UPPER LEVEL TROUGH AND
CYCLONIC CURVATURE ALOFT. MODERATE SUBSIDENCE IS EVIDENT ON
WATER VAPOR IMAGERY ACROSS THE ERN CARIBBEAN...HOWEVER ISOLATED
SHOWERS OVER THE N/CENTRAL CARIBBEAN N OF 15N BETWEEN 66W-75W.
MODERATE TO FRESH TRADE WINDS CONTINUE ACROSS MOST OF THE BASIN
AS DEPICTED BY AN EARLIER QUIKSCAT PASS AROUND 21/1100
UTC...WITH 20-25 KT WINDS NOTED ALONG THE COAST OF COLOMBIA S OF
14N BETWEEN 72W-77W.

ATLANTIC OCEAN...
THE UPPER LEVEL RIDGING LOCATED ACROSS THE GULF OF MEXICO
EXTENDS ACROSS NRN FLORIDA AND INTO THE FAR W ATLC W OF 75W.
UPPER LEVEL DIFFLUENCE IS CONTINUING TO GENERATE ISOLATED
SHOWERS AND TSTMS W OF 78W AND TO OVER THE ERN FLORIDA
PENINSULA. FARTHER EAST...AN UPPER LEVEL SHORTWAVE TROUGH...PART
OF A LARGER UPPER LEVEL TROUGH REGIME OVER THE CENTRAL ATLC...
SUPPORTS A SURFACE TROUGH THAT EXTENDS FROM 28N75W THROUGH A
1017 MB LOW CENTERED NEAR 30N73W TO 32N69W. SCATTERED SHOWERS
AND TSTMS ARE OCCURRING FROM 28N-32N BETWEEN 70W-75W. THIS
SURFACE TROUGH IS NEAR THE TAIL END OF A STATIONARY FRONT THAT
IS DRAPED ALONG 33N BETWEEN 55W-72W. LOW-LEVEL CONVERGENCE S OF
THE FRONT COUPLED WITH UPPER LEVEL DIFFLUENCE DUE TO LARGE SCALE
TROUGHING ACROSS THE NW ATLC IS GENERATING SCATTERED SHOWERS AND
TSTMS FROM 29N TO BEYOND 32N BETWEEN 58W-65W. ELSEWHERE...
SCATTERED SHOWERS ARE WITHIN 120 NM EITHER SIDE OF THE
STATIONARY FRONT. AN UPPER LEVEL LOW IS CENTERED NEAR 25N58W
WITH THE TROUGH AXIS EXTENDING S ALONG 60W AND NEAR THE LESSER
ANTILLES. UPPER LEVEL DIFFLUENCE LOCATED E OF THE TROUGH AXIS IS
GENERATING SCATTERED SHOWERS AND TSTMS FROM 17N-22N BETWEEN
54W-59W. ANOTHER EMBEDDED SHORTWAVE TROUGH IS LOCATED NEAR
20N50W AND IS ALSO PRODUCING AN AREA OF SCATTERED SHOWERS AND
TSTMS FROM 19N-22N BETWEEN 46W-51W. THE REMAINDER OF THE ATLC
REMAINS FAIRLY CALM UNDER THE INFLUENCE OF A BROAD SURFACE RIDGE
N OF 25N E OF 55W ANCHORED BY A 1025 MB HIGH CENTERED NEAR
34N42W. IN THE UPPER LEVELS...AN UPPER LEVEL RIDGE IS BETWEEN
35W-45W...E OF THE AFOREMENTIONED UPPER LOW N-NE OF THE LESSER
ANTILLES. ANOTHER UPPER LEVEL LOW DOMINATES THE NE PORTION OF
THE ATLC DISCUSSION AREA CENTERED NEAR 30N27W. IN THE TROPICAL
ATLC...AN UPPER LEVEL RIDGE DOMINATES E OF 40W ENHANCING THE
CONVECTION NEAR THE TROPICAL WAVE IN THE CENTRAL ATLC.

$$
HUFFMAN





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