[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 281806
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT WED SEP 28 2005

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHEASTERN SECTIONS
OF SOUTH AMERICA...AND ATLANTIC OCEAN TO THE AFRICAN COAST FROM
THE EQUATOR TO 32N. THE FOLLOWING INFORMATION IS BASED ON
SATELLITE IMAGERY...WEATHER OBSERVATIONS...RADAR...AND
METEOROLOGICAL ANALYSIS.

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...SPECIAL FEATURE...

A WESTERN CARIBBEAN SEA TROPICAL WAVE IS MOVING WESTWARD
10 TO 15 KT. IT IS NOW ALONG 80W/81W SOUTH OF 20N.
A 1010 MB SURFACE LOW PRESSURE CENTER IS ALONG THE WAVE
NEAR 15N. THE DVORAK CLASSIFICATION POSITIONS HAVE JUMPED
AROUND A BIT THIS MORNING REGARDING THIS SURFACE LOW CENTER.
SCATTERED TO NUMEROUS STRONG SHOWERS AND THUNDERSTORMS ARE
FOUND FROM 14N TO 18N BETWEEN 73W NEAR HAITI AND 81W APPROACHING
THE COASTS OF EASTERN HONDURAS AND NORTHEASTERN NICARAGUA.
THIS PRECIPITATION IS OCCURRING UNDER THE RIDGE WHICH IS BETWEEN
THE CYCLONIC FLOW ASSOCIATED WITH THE EASTERN FLORIDA COASTAL
MIDDLE TO UPPER LEVEL LOW CENTER AND THE NEXT BIG ATLANTIC
OCEAN-TO-EASTERN CARIBBEAN SEA MIDDLE TO UPPER LEVEL TROUGH.
THIS SYSTEM STILL HAS THE POTENTIAL TO BECOME A TROPICAL
DEPRESSION LATER TODAY OR TOMORROW. THE RECONNAISSANCE FLIGHT
ORIGINALLY SCHEDULED TO INVESTIGATE THE SYSTEM THIS AFTERNOON
HAS BEEN CANCELED. ANOTHER AIR FORCE RESERVE UNIT RECONNAISSANCE
AIRCRAFT IS SCHEDULED TO INVESTIGATE THE SYSTEM TOMORROW MORNING
IF NECESSARY. RESIDENTS IN THE NORTHWESTERN CARIBBEAN SEA AND
ADJACENT LAND AREAS SHOULD MONITOR THE PROGRESS OF THIS SYSTEM
DURING THE NEXT FEW DAYS AS IT MOVES WEST-NORTHWESTWARD AT
10 TO 15 MPH.

...TROPICAL WAVES...

AN ATLANTIC OCEAN TROPICAL WAVE IS ALONG 34W/35W SOUTH OF 15N
MOVING WEST 10 TO 15 KT. ONLY ITCZ SHOWERS AND THUNDERSTORMS...
WHICH ARE FOUND FROM 10N TO 13N BETWEEN 31W AND 39W...ARE CLOSE
TO THIS WAVE.

AN ATLANTIC OCEAN 1012 MB SURFACE LOW PRESSURE CENTER IS NEAR
14N46W DRIFTING WESTWARD. THIS LOW IS UNDER THE WESTERN EDGE OF
AN UPPER LEVEL RIDGE. MOVING MORE EASTWARD...AT LEAST RIGHT
NOW...WOULD PUT IT UNDER MIDDLE TO UPPER LEVEL SOUTHWESTERLY
WIND FLOW WITH THE ATLANTIC OCEAN-TO-CARIBBEAN SEA TROUGH.
SCATTERED MODERATE TO ISOLATED STRONG ITCZ SHOWERS AND
THUNDERSTORMS ARE FOUND FROM 6N TO 11N BETWEEN 40W AND 50W.

A CENTRAL ATLANTIC OCEAN TROPICAL WAVE IS ALONG 52W/53W SOUTH
OF 21N MOVING WEST 10 TO 15 KT. LOW CLOUDS AND POSSIBLE
SHOWERS FROM 12N TO 20N BETWEEN 50W AND 57W.

A TROPICAL WAVE IS ALONG 97W/98W SOUTH OF 20N MOVING WEST 10 TO
15 KT. NO DEEP CONVECTIVE ACTIVITY IS OCCURRING IN THE ATLANTIC
BASIN.

...ITCZ...

ITCZ 12N16W 10N31W...11N37W 12N44W...12N54W 12N62W.
OTHER SHOWERS AND THUNDERSTORMS...ISOLATED TO WIDELY
SCATTERED MODERATE FROM 5N TO 10N BETWEEN AFRICA AND 30W.

...DISCUSSION...

THE GULF OF MEXICO...
THE GULF OF MEXICO 1010 MB SURFACE LOW PRESSURE CENTER NOW
NEAR 29N87W STARTED OUT AS A FEATURE THAT WAS SEPARATE FROM
THE MIDDLE TO UPPER LEVEL LOW CENTER...WHICH NOW IS ALONG
THE FLORIDA EAST COAST NEAR 27N80W. BROAD MIDDLE TO UPPER
LEVEL CYCLONIC FLOW COVERS THE ATLANTIC OCEAN...THE CARIBBEAN
SEA...AND THE GULF OF MEXICO FROM 20N TO 33N BETWEEN 75W AND
89W. MIDDLE TO UPPER LEVEL DRY AIR...IMPLYING SUBSIDENCE...
COVERS THE GULF WATERS...INCLUDING THE WESTERN SEMICIRCLE
OF THE CYCLONIC FLOW. MIDDLE TO UPPER LEVEL DRY AIR ALSO
COVERS MEXICO NORTH OF 22N. A UPPER LEVEL LOW AND HIGH COUPLET
ARE OVER INTERIOR MEXICO...NORTHEAST OF T.D. FIFTEEN-E...WITH
THEIR CIRCULATIONS COVERING THE AREA FROM 18N TO 25N BETWEEN
98W AND 106W. A SURFACE TROUGH EXTENDS FROM THE SURFACE LOW TO
THE CENTRAL GULF...MARKED IN VISIBLE IMAGERY BY A THIN LINE
OF LOW CLOUDS AND POSSIBLE SHOWERS.

THE CARIBBEAN SEA...
THE PATTERN HERE IS TROUGH...RIDGE...TROUGH. THE WESTERN TROUGH
IS ASSOCIATED WITH THE MIDDLE TO UPPER LEVEL LOW CENTER ALONG
THE EASTERN FLORIDA COAST. THIS TROUGH FINDS ITS BASE IN THE
NORTHWESTERN CORNER OF THE AREA. UPPER LEVEL ANTICYCLONIC FLOW
WITH THE FOLLOWING RIDGE COVERS THE AREA BETWEEN EASTERN CUBA
AND THE DOMINICAN REPUBLIC. MIDDLE TO UPPER LEVEL CYCLONIC FLOW
COVERS MOST OF THE REST OF THE AREA...WITH THE ATLANTIC OCEAN-
TO-EASTERN CARIBBEAN SEA TROUGH.

THE ATLANTIC OCEAN...
THE MIDDLE TO UPPER LEVEL LOW CENTER ALONG THE EASTERN FLORIDA
COAST IS THE MAIN FEATURE FOR THE UNITED STATES EAST COAST IN
THE TROPICS. ISOLATED MODERATE TO LOCALLY STRONG SHOWERS AND
THUNDERSTORMS ARE FOUND IN THE BAHAMAS FROM 21N TO 27N BETWEEN
73W AND 79W. A MIDDLE TO UPPER LEVEL TROUGH...WHICH EVENTUALLY
EXTENDS INTO THE EASTERN CARIBBEAN SEA...IS HELPING TO PRODUCE
ISOLATED MODERATE TO LOCALLY STRONG SHOWERS AND THUNDERSTORMS
FROM 18N TO 21N BETWEEN 58W AND 61W...AND WITHIN 40 NM ON EITHER
SIDE OF 28N56W 22N60W...AND FROM 30N TO 33N BETWEEN 48W AND 51W.
HIGH CLOUDS ARE BEING SPREAD NORTHEASTWARD...FROM 12N TO 33N
BETWEEN 37W AND 50W...WITH THE UPPER LEVEL RIDGE AS THE NEXT
FEATURE TO THE EAST. THIS IS THE SAME RIDGE WHICH IS ON TOP OF
THE 14N46W SURFACE LOW PRESSURE CENTER. A SURFACE TROUGH IS ALONG
24N59W BEYOND 32N52W. A SURFACE RIDGE IS ALONG 23N50W 30N42W
BEYOND 32N38W. MIDDLE TO UPPER LEVEL CYCLONIC FLOW COVERS THE
ATLANTIC WATERS FROM 5N TO 14N BETWEEN 33W AND 42W. MIDDLE TO
UPPER LEVEL CYCLONIC FLOW ALSO IS IN THE NORTHEASTERN ATLANTIC
WATERS FROM 18N TO 32N BETWEEN 22W AND 32W.

$$
MT

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