[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 090017
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT MON OCT 08 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 2315 UTC.

...SPECIAL FEATURE...

A 1004 MB NORTHWESTERN CARIBBEAN SEA LOW PRESSURE CENTER IS NEAR
18N86W...ABOUT 120 NM EAST OF NORTHERN BELIZE. SURFACE PRESSURES
OVERALL REMAIN LOW IN THE AREA AND SATELLITE IMAGERY INDICATES
THAT THE LOW HAS BECOME A LITTLE BETTER DEFINED TODAY...WITH AN
INCREASE IN THUNDERSTORM ACTIVITY. ATMOSPHERIC CONDITIONS APPEAR
FAVORABLE FOR ADDITIONAL DEVELOPMENT OF THIS SYSTEM...AND IT MAY
BECOME A TROPICAL DEPRESSION DURING THE NEXT DAY OR TWO AS IT
MOVES SLOWLY WESTWARD OR NORTHWESTWARD. RESIDENTS IN THE
NORTHWESTERN CARIBBEAN SEA SHOULD MONITOR THE PROGRESS OF THIS
SYSTEM. AN AIR FORCE HURRICANE HUNTER AIRCRAFT IS SCHEDULED TO
INVESTIGATE THIS LOW PRESSURE AREA ON TUESDAY IF NECESSARY.
STRONG SHOWERS AND THUNDERSTORMS ARE IN THE EASTERN COASTAL
PLAINS OF THE YUCATAN PENINSULA FROM 18N TO 21N BETWEEN 88W
AND 89W. OTHER STRONG SHOWERS AND THUNDERSTORMS STRETCH FROM
NORTHERN GUATEMALA TO THE NORTHWESTERN CORNER OF THE YUCATAN
PENINSULA BETWEEN 89W AND 91W. SHOWERS AND THUNDERSTORMS IN THE
CARIBBEAN SEA ARE FROM 16N TO 18N BETWEEN 85W AND 88W...AND
FROM 19N TO 21N BETWEEN 86W AND THE YUCATAN PENINSULA COAST.
SCATTERED MODERATE SHOWERS TO ISOLATED STRONG THUNDERSTORMS
EAST OF 21N86W 15N83W TO 75W ARE IN AN AREA OF UPPER LEVEL
DIFFLUENT FLOW TO THE EAST OF THE SURFACE LOW PRESSURE CENTER.

...TROPICAL WAVES...

AN ATLANTIC OCEAN TROPICAL WAVE IS ALONG 42W SOUTH OF 14N MOVING
WEST 15 KT. ITCZ SHOWERS AND THUNDERSTORMS FROM 5N TO 11N
BETWEEN 40W AND 45W.

AN ATLANTIC OCEAN TROPICAL WAVE IS ALONG 57W/58W SOUTH OF 20N
MOVING WEST 10 KT. NO SHOWERS AND THUNDERSTORMS ACCOMPANY THIS
WAVE. A MIDDLE TO UPPER LEVEL TROUGH IS ALONG 11N60W 17N56W
20N54W SURROUNDED BY MIDDLE TO UPPER LEVEL DRY AIR/SUBSIDENCE.

...THE ITCZ...
11N16W 6N27W 8N41W 10N50W 10N56W. WIDELY SCATTERED TO SCATTERED
MODERATE SHOWERS/ISOLATED STRONG THUNDERSTORMS WITHIN 30 TO 60 NM
ON EITHER SIDE OF 4N19W 4N24W 3N28W 4N31W 4N37W 5N43W. ISOLATED
TO WIDELY SCATTERED MODERATE SHOWERS FROM 7N TO 10N BETWEEN 30W
AND 40W. STRONG SHOWERS AND THUNDERSTORMS FROM 9N TO 13N BETWEEN
47W AND 50W.

DISCUSSION...

THE GULF OF MEXICO...
THE SURFACE PRESSURE GRADIENT ACROSS MUCH OF THE AREA IS WEAK...
BECOMING COMPARATIVELY TIGHTER NORTH OF 28N EAST OF 90W.
A BROAD MIDDLE TO UPPER LEVEL CYCLONIC CIRCULATION CENTER IS
IN THE NORTHWESTERN CORNER OF THE AREA ENCOMPASSING MUCH OF
THE TEXAS COAST. AN UPPER LEVEL RIDGE IS ALONG 90W NORTH OF
23N. BROAD UPPER LEVEL ANTICYCLONIC FLOW IN MIDDLE TO UPPER
LEVEL DRY AIR/SUBSIDENCE PUSHES INTO THE AREA NORTH OF 25N
EAST OF 85W. ISOLATED MODERATE SHOWERS FROM NORTHEASTERN MEXICO
TO INLAND SOUTH TEXAS FROM 26N TO 29N BETWEEN 98W AND 99W.
DISSIPATING ISOLATED MODERATE SHOWERS FROM 26N TO 30N BETWEEN
89W AND 93W IN UPPER LEVEL DIFFLUENT FLOW. ISOLATED TO WIDELY
SCATTERED MODERATE SHOWERS ARE IN THE SOUTHWESTERN CORNER OF
THE AREA...SOUTH OF 22N BETWEEN 92W AND 97W...UNDER A MIDDLE
LEVEL TROUGH.

THE CARIBBEAN SEA...
THE MAIN WEATHER FEATURE FOR THIS BULLETIN IS THE SPECIAL
FEATURE 1004 MB LOW PRESSURE CENTER NEAR 18N86W...ABOUT 120 NM
EAST OF NORTHERN BELIZE. ATMOSPHERIC CONDITIONS APPEAR FAVORABLE
FOR ADDITIONAL DEVELOPMENT OF THIS SYSTEM...AND IT MAY BECOME
A TROPICAL DEPRESSION DURING THE NEXT DAY OR TWO AS IT MOVES
SLOWLY WESTWARD OR NORTHWESTWARD. RESIDENTS IN THE NORTHWESTERN
CARIBBEAN SEA SHOULD MONITOR THE PROGRESS OF THIS SYSTEM. AN AIR
FORCE HURRICANE HUNTER AIRCRAFT IS SCHEDULED TO INVESTIGATE THIS
LOW PRESSURE AREA ON TUESDAY IF NECESSARY. A MIDDLE TO UPPER
LEVEL TROUGH IS DIGGING FROM 25N70W IN THE ATLANTIC OCEAN TOWARD
THE MONA PASSAGE. ISOLATED MODERATE TO STRONG SHOWERS AND
THUNDERSTORMS FROM THE NORTHWESTERN DOMINICAN REPUBLIC TO THE
WATERS NORTH OF THE EASTERN DOMINICAN REPUBLIC...TO THE WATERS
AROUND PUERTO RICO...ARE BEING SHEARED BY SOME UPPER LEVEL
ANTICYCLONIC MOVING FROM EASTERN CUBA EASTWARD. SCATTERED
MODERATE SHOWERS TO ISOLATED STRONG THUNDERSTORMS EAST OF
21N86W 15N83W TO 75W ARE IN AN AREA OF UPPER LEVEL DIFFLUENT
FLOW TO THE EAST OF THE SURFACE LOW PRESSURE CENTER. BROAD
UPPER LEVEL ANTICYCLONIC FLOW COVERS THE AREA EAST OF 80W
AROUND THE 14N75W ANTICYCLONIC CENTER.

THE ATLANTIC OCEAN...
A WESTERN ATLANTIC OCEAN SURFACE TROUGH IS ALONG 28N58W TO
A 1008 MB LOW PRESSURE CENTER NEAR 24N70W...TO 21N80W CROSSING
THE BAHAMAS AND CUBA. A MIDDLE TO UPPER LEVEL CYCLONIC
CIRCULATION CENTER IS NEAR 27N72W. MIDDLE TO UPPER LEVEL
DRY AIR/SUBSIDENCE IS NORTH OF 28N BETWEEN 60W AND 68W...AND
NORTH OF 25N WEST OF 68W/69W UNTIL FLORIDA. THE ISOLATED
MODERATE TO STRONG SHOWERS AND THUNDERSTORMS IN INDIVIDUAL CELLS
ARE FROM 21N TO 27N BETWEEN 60W AND 68W. SHOWERS AND POSSIBLE
THUNDERSTORMS FROM 23N TO 25N BETWEEN 72W AND 79W HAVE BEEN
DIMINISHING DURING THE LAST 4 HOURS WITH WARMING CLOUD TOP
TEMPERATURES. ISOLATED MODERATE SHOWERS EXTEND FROM THE CENTRAL/
NORTHERN BAHAMAS TO THE STRAITS OF FLORIDA...AND FROM THE
SOUTHERN BAHAMAS TO CUBA. BROAD MIDDLE TO UPPER LEVEL CYCLONIC
FLOW ON WATER VAPOR IMAGERY IS NORTH OF 30N WEST OF 40W. THIS
CYCLONIC FLOW IS ASSOCIATED WITH A BROAD DEEP LAYER TROUGH THAT
SUPPORTS ONE COLD FRONT THAT PASSES THROUGH 32N44W TO 26N50W TO
23N53W. A SECOND COLD FRONT PASSES THROUGH 32N55W TO 31N61W TO
32N69W. A STATIONARY FRONT CONTINUES NORTHWESTWARD BEYOND
32N69W. STRONG SHOWERS AND THUNDERSTORMS FROM 23N TO 24N BETWEEN
48W AND 51W...AND ONE CLUSTER FROM 22N TO 23N BETWEEN 52W AND
53W. AN UPPER LEVEL RIDGE IS ALONG 22N50W 27N42W BEYOND 32N39W.
A MIDDLE TO UPPER LEVEL TROUGH PASSES OVER THE MADEIRAS
ARCHIPELAGO TO THE CANARY ISLANDS TOWARD THE CAPE VERDE ISLANDS.
THIS FEATURE IS ON TOP OF A SURFACE RIDGE THROUGH 32N26W TO
26N33W TO 22N42W.

$$
MT




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