[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 172348
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT THU SEP 17 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...TROPICAL WAVES...

TROPICAL WAVE IS ALONG 20W S OF 17N MOVING W NEAR 12 KT. THE
WAVE COINCIDES WITH A DEEP LAYER MOISTURE MAXIMUM ACROSS THE FAR
ERN TROPICAL ATLC AS NOTED ON TOTAL PRECIPITABLE WATER IMAGERY.
ALSO...CIMSS WAVETRAK MODEL GUIDANCE SHOWS AN AREA OF 850 MB
VORTICITY IN THE VICINITY OF THE WAVE AXIS FROM 9N-15N.
SCATTERED SHOWERS AND ISOLATED MODERATE CONVECTION IS FROM
7N-17N BETWEEN 17W-22W.

TROPICAL WAVE IS ALONG 84W S OF 22N MOVING W NEAR 15 KT. THE
WAVE IS FOUND WITHIN A BROAD AREA OF DEEP LAYER MOISTURE AS
NOTED ON TPW IMAGERY ACROSS THE WRN CARIBBEAN AND CENTRAL
AMERICA. THE LOW-LEVEL CLOUD FIELD SHOWS SOME CYCLONIC TURNING
IN THE VICINITY OF THE WAVE AXIS N OF 16N. SCATTERED MODERATE
CONVECTION IS WITHIN 150 NM EITHER SIDE OF THE WAVE AXIS.
SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS MOVING ACROSS
ERN HONDURAS AND CENTRAL NICARAGUA FROM 12N-16N BETWEEN 84W-86W.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 10N21W 11N32W 8N38W 7N44W 9N56W
10N62W. WIDELY SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS
FROM 6N-11N BETWEEN 24W-43W.

...DISCUSSION...

GULF OF MEXICO...
AS OF 2100 UTC...A COLD FRONT EXTENDS THROUGH ERN LOUISIANA AND
INTO THE N/CENTRAL GULF ALONG 29N90W SW TO 24N96W. SCATTERED
SHOWERS AND ISOLATED TSTMS ARE ACROSS THE WRN GULF FROM 24N-26N
BETWEEN 93W-98W. A PRE-FRONTAL SURFACE TROUGH IS ANALYZED FROM
THE FLORIDA BIG BEND REGION NEAR 29N85W TO 24N90W. SCATTERED
SHOWERS AND TSTMS ARE WITHIN 60 NM EITHER SIDE OF THE SURFACE
TROUGH WITH MOST OF THE ACTIVITY REMAINING N OF 26N OVER THE NE
GULF AND INLAND OVER THE NRN FLORIDA PENINSULA AND ERN FLORIDA
PANHANDLE. THESE BOUNDARIES ARE SUPPORTED ALOFT BY AN UPPER
LEVEL LOW CENTERED OVER NRN LOUISIANA WITH UPPER LEVEL TROUGHING
DIPPING ACROSS THE NW GULF TO 23N W OF 88W. WITH MOIST SWLY
UPPER LEVEL FLOW PRESENT ACROSS MUCH OF THE NE AND CENTRAL
GULF...THE CONVECTION ALONG THE SURFACE TROUGH AND OVER THE NE
GULF IS BEING ENHANCED BY UPPER LEVEL DIFFLUENCE BETWEEN THE
UPPER LEVEL TROUGHING OVER THE NW GULF AND AN UPPER LEVEL
ANTICYCLONIC CIRCULATION CENTERED OVER SRN FLORIDA NEAR 26N81W.

CARIBBEAN SEA...
WITH THE TROPICAL WAVE ALONG 84W AND AN UPPER LEVEL ANTICYCLONIC
CIRCULATION CENTERED OVER THE SRN FLORIDA PENINSULA THAT EXTENDS
UPPER LEVEL RIDGING ACROSS THE NW CARIBBEAN...SCATTERED SHOWERS
AND ISOLATED TSTMS ARE N OF 17N BETWEEN 80W-87W. AN UPPER LEVEL
LOW CONTINUES TO SPIN IN THE CENTRAL CARIBBEAN CENTERED NEAR
15N75W. ISOLATED SHOWERS AND POSSIBLE TSTMS ARE BETWEEN 75W-80W
ON THE WRN PERIPHERY OF THE UPPER LOW. MOIST TROPICAL AIR...
ATMOSPHERIC INSTABILITY...AND LIFT GENERATED FROM THE UPPER LOW
IS PRODUCING SCATTERED SHOWERS AND ISOLATED TSTMS ACROSS THE
REMAINDER OF THE CARIBBEAN FROM 62W-75W. ONE AREA OF MOST ACTIVE
CONVECTION IS N OF 16N BETWEEN 67W-72W...INCLUDING ERN PUERTO
RICO...THE MONA PASSAGE AND HISPANIOLA. ANOTHER AREA OF
SCATTERED SHOWERS AND ISOLATED TSTMS IS OBSERVED ON SATELLITE
IMAGERY S OF 14N BETWEEN 68W-75W. MODERATE TRADE WINDS REMAIN
ACROSS MUCH OF THE BASIN THIS EVENING.

ATLANTIC OCEAN...
AN UPPER LEVEL SHORTWAVE TROUGH IS ACROSS THE W ATLC NEAR 30N72W
AND SUPPORTS A SURFACE TROUGH THAT EXTENDS FROM NEAR 31N71W SW
TO THE CENTRAL BAHAMAS NEAR 25N75W. SCATTERED SHOWERS ARE WITHIN
120 NM E OF THE TROUGH AXIS AND EXTENDS ACROSS MUCH OF THE
CENTRAL AND NW BAHAMAS FROM 23N-26N BETWEEN 75W-78W. THIS
ACTIVITY IS SUPPORTED ALOFT BY UPPER LEVEL DIFFLUENCE AS AN
UPPER LEVEL ANTICYCLONIC CIRCULATION IS CENTERED OVER THE SRN
FLORIDA PENINSULA AND EXTENDS RIDGING TO ANOTHER UPPER HIGH
CENTERED NEAR 28N71W. FARTHER TO THE SE...A 1015 MB SURFACE LOW
...REMNANT OF FRED...IS CENTERED NEAR 25N62W AND EXTENDS A
SURFACE TROUGH FROM 22N62W THROUGH THE LOW TO 27N61W. SURFACE
CONVERGENCE NEAR THE LOW AND TROUGH ARE SUPPORTING ISOLATED
SHOWERS FROM 20N-26N BETWEEN 59W-65W. AN UPPER LEVEL LOW LOCATED
SE OF THE AFOREMENTIONED SURFACE LOW IS CENTERED NEAR 20N52W AND
CONTINUES TO GENERATE SCATTERED SHOWERS AND TSTMS FROM 19N-23N
BETWEEN 50W-55W. THE REMAINDER OF THE CENTRAL AND ERN ATLC IS
DOMINATED BY A BROAD SURFACE RIDGE ANCHORED BY A 1026 MB HIGH
NEAR 34N45W. NORTH OF THE ITCZ AXIS IN THE TROPICAL CENTRAL
ATLC...A 1008 MB LOW IS CENTERED NEAR 13N37W. SCATTERED SHOWERS
AND ISOLATED TSTMS ARE DISPLACED NORTH FROM THE ITCZ AXIS REGION
FROM 12N-16N BETWEEN 34W-38W. IN THE UPPER LEVELS ACROSS THE
TROPICAL ERN ATLC...AN UPPER LEVEL RIDGE EXTENDS FROM W AFRICA
ALONG 15N17W TO 8N40W AND CONTINUES TO SUPPORT THE CONVECTION IN
THE VICINITY OF THE ITCZ.

$$
HUFFMAN


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