[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 061831 AAA
TWDAT

TROPICAL WEATHER DISCUSSION...AMD
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT FRI SEP 06 2013

AMENDED IN ORDER TO INCLUDE UPDATED INFORMATION ABOUT THE
TROPICAL DEPRESSION IN THE GULF OF MEXICO

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...WEATHER OBSERVATIONS...RADAR...AND METEOROLOGICAL
ANALYSIS.

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

...SPECIAL FEATURES...

TROPICAL DEPRESSION EIGHT DEVELOPED IN THE GULF OF MEXICO ALONG
THE COAST OF MEXICO NEAR TAMPICO. THE CENTER OF TROPICAL
DEPRESSION EIGHT AT 06/1830 UTC IS NEAR 22.5N 97.3W. THE
DEPRESSION IS MOVING WEST-SOUTHWESTWARD 5 KNOTS. THE MINIMUM
CENTRAL PRESSURE IS 1009 MB. THE MAXIMUM SUSTAINED WIND SPEEDS
ARE 30 KNOTS WITH GUSTS TO 40 KNOTS. PLEASE READ THE NATIONAL
HURRICANE CENTER PUBLIC ADVISORIES ON GABRIELLE...THAT ARE
ISSUED UNDER WMO HEADER WTNT33 KNHC AND UNDER AWIPS HEADER
MIATCPAT3...AND THE FORECAST/ADVISORIES THAT ARE ISSUED UNDER
WMO HEADER WTNT23 KNHC AND UNDER AWIPS HEADER MIATCMAT3.
CONVECTIVE PRECIPITATION...NUMEROUS STRONG FROM 21N TO 25N
BETWEEN 94W AND 99W. SCATTERED MODERATE TO ISOLATED STRONG FROM
24N TO 26N BETWEEN 90W AND 93W. ISOLATED MODERATE ELSEWHERE TO
THE NORTH OF 26N TO THE WEST OF 90W...AND TO THE SOUTH AND
SOUTHEAST OF THE TROPICAL DEPRESSION.

...TROPICAL WAVES...

AN ATLANTIC OCEAN TROPICAL WAVE WAS ANALYZED ALONG 18W/19W TO
THE SOUTH OF 20N. FURTHER ANALYSIS OF THE SITUATION GIVES US THE
IDEA THAT THE WAVE REALLY STILL IS MORE INLAND IN AFRICA...AND
NOT IN THE ATLANTIC OCEAN YET. IT MAY TAKE ANOTHER DAY OR TWO
FOR THE WAVE TO EMERGE FROM AFRICA. CONVECTIVE PRECIPITATION...
NUMEROUS STRONG FROM 13N TO 15N BETWEEN 17W AND 18W...AND FROM
9N TO 10N BETWEEN 18W AND 20W.

AN ATLANTIC OCEAN TROPICAL WAVE IS ALONG 34W TO THE SOUTH OF
20N...MOVING WESTWARD 10 TO 15 KNOTS. A 1012 MB LOW PRESSURE
CENTER IS ALONG THE WAVE NEAR 14N. CONVECTIVE PRECIPITATION...
SCATTERED MODERATE TO ISOLATED STRONG FROM 12N TO 19N BETWEEN
28W AND 38W.

THE ATLANTIC OCEAN TROPICAL WAVE THAT WAS ALONG 19N59W 14N57W
10N54W FOR THE 06/0600 UTC MAP ANALYSIS HAS BEEN DROPPED FROM
THE MAP ANALYSIS FOR 06/1200 UTC. THE WAVE WAS BEING STRETCHED
AS IT WAS MOVING AROUND THE SOUTHWESTERN PERIPHERY OF AN
ANTICYCLONE. THERE WAS NO MORE EVIDENCE OF CYCLONIC TURNING.

A CARIBBEAN SEA TROPICAL WAVE IS ALONG 74W/75W TO THE SOUTH OF
15N MOVING WEST 10 TO 15 KNOTS. THIS WAVE HAS CONTINUED WESTWARD
AFTER GABRIELLE WAS FORMED. CONVECTIVE PRECIPITATION...SCATTERED
TO NUMEROUS IN COLOMBIA FROM 7N TO 8N BETWEEN 74W AND 75W.
SCATTERED TO NUMEROUS IN THE CARIBBEAN SEA FROM 14N TO 17N
BETWEEN 76W AND 81W.

A CARIBBEAN SEA TROPICAL WAVE IS ALONG 83W/84W TO THE SOUTH OF
19N. THE WAVE IS MOVING WESTWARD 10 TO 15 KNOTS DURING THE LAST
24 HOURS OR SO. THE WAVE IS MOVING THROUGH THE AREA OF AN
INVERTED TROUGH THAT RUNS FROM HONDURAS BEYOND NICARAGUA.

...THE ITCZ/THE MONSOON TROUGH...

THE MONSOON TROUGH PASSES THROUGH COASTAL GUINEA-BISSAU NEAR
12N16W TO 14N27W 14N34W...11N38W AND 10N43W. CONVECTIVE
PRECIPITATION...SCATTERED MODERATE FROM 5N TO 9N BETWEEN 22W AND
29W. ISOLATED MODERATE FROM 5N TO 10N BETWEEN 36W AND 53W.

...DISCUSSION...

FROM THE ATLANTIC OCEAN INTO THE GULF OF MEXICO...

A MIDDLE LEVEL TO UPPER LEVEL TROUGH PASSES THROUGH THE
SOUTHEASTERN UNITED STATES...ACROSS NORTHERN FLORIDA...INTO THE
NORTHEASTERN/EASTERN GULF OF MEXICO. A SURFACE TROUGH IS ALONG
31N80W...ACROSS NORTHERN FLORIDA...INTO THE GULF OF MEXICO NEAR
28N85W. CONVECTIVE PRECIPITATION...IN THE ATLANTIC OCEAN TO THE
NORTH OF THE LINE THAT PASSES THROUGH 32N64W 30N68W...TO THE
FLORIDA COAST NEAR 29N81W. CONVECTIVE PRECIPITATION IN THE GULF
OF MEXICO...SCATTERED MODERATE TO ISOLATED STRONG TO THE SOUTH
OF 27N TO THE EAST OF 90W.

THE REST OF THE GULF OF MEXICO...

THE SURFACE PRESSURE GRADIENT IS COMPARATIVELY WEAK IN THE GULF
OF MEXICO...EVERYWHERE ELSE AWAY FROM THE TROPICAL DEPRESSION
THAT IS ALONG THE MEXICO COAST NEAR TAMPICO.

FOR THE OFFSHORE OIL PLATFORM SITES THAT ARE TO THE NORTH OF 27N
TO THE WEST OF 88W...

A LOW CLOUD CEILING AT 5500 FEET IS REPORTED AT THE ICAO STATION
KBQX ALONG THE TEXAS GULF COAST. FAIR SKIES/CLEAR SKIES AT OR
LOWER THAN 12000 FEET ARE BEING REPORTED ELSEWHERE ACROSS THE
AREA.

SCATTERED TO BROKEN LOW CLOUDS AND LIGHT RAIN ARE IN THE DEEP
SOUTH OF TEXAS/ALONG THE BORDER WITH TEXAS. SCATTERED TO BROKEN
LOW CLOUDS COVER THE MIDDLE TEXAS GULF COASTAL PLAINS. BROKEN
MULTILAYERED CLOUD CEILINGS AND RAIN COVER THE COASTAL AREAS
FROM ANGLETON/LAKE JACKSON TO GALVESTON TO BEAUMONT-PORT ARTHUR.
SCATTERED TO BROKEN LOW CLOUDS ARE IN THE COASTAL SECTIONS OF
SOUTHWESTERN LOUISIANA. MULTILAYERED CLOUD CEILINGS AND
RAINSHOWERS WITH THUNDER ARE IN THE AREA THAT IS TO THE SOUTH OF
LAKE PONTCHARTAIN IN LOUISIANA. BROKEN HIGH CLOUDS COVER MOBILE
ALABAMA...AND IN THE FLORIDA PANHANDLE IN PENSACOLA AND
VALPARAISO. SCATTERED LOW CLOUDS AND BROKEN HIGH CLOUDS ARE AT
THE TAMPA INTERNATIONAL AIRPORT. MIDDLE LEVEL AND HIGH LEVEL
CLOUD CEILINGS ARE OBSERVED AT THE KEY WEST FLORIDA NAVAL AIR
STATION. FAIR SKIES/CLEAR SKIES AT OR LOWER THAN 12000 FEET ARE
BEING REPORTED ELSEWHERE IN THE COASTAL SECTIONS OF THE U.S.A.
GULF COAST STATES.

PLEASE READ THE HIGH SEAS FORECAST...MIAHSFAT2...AND THE
OFFSHORE FORECAST...MIAOFFNT4...FOR MORE DETAILS ABOUT TROPICAL
DEPRESSION EIGHT THAT IS ALONG THE MEXICO COAST NEAR TAMPICO.

FROM THE ATLANTIC OCEAN INTO THE CARIBBEAN SEA...

A MIDDLE LEVEL TO UPPER LEVEL TROUGH EXTENDS FROM A 31N57W
CYCLONIC CIRCULATION CENTER...TO 26N54W. MIDDLE LEVEL TO UPPER
LEVEL ANTICYCLONIC WIND FLOW COVERS THE ATLANTIC OCEAN FROM 10N
TO 26N TO BETWEEN 50W AND AND 60W. THE ANTICYCLONIC WIND FLOW
CONTINUES FROM THE ATLANTIC OCEAN INTO THE CARIBBEAN SEA...TO
THE EAST OF 84W. THE 1010 MB REMNANT LOW PRESSURE CENTER OF
GABRIELLE IS NEAR 20N68W. ONE TROUGH EXTENDS FROM THE LOW CENTER
NORTHEASTWARD TO 22N64W AND 25N62W. A SECOND TROUGH EXTENDS FROM
THE LOW CENTER ACROSS THE EASTERN DOMINICAN REPUBLIC TO 17N70W.
A SEPARATE SURFACE TROUGH IS ALONG 25N66W 29N64W. CONVECTIVE
PRECIPITATION...NUMEROUS STRONG IN THE MONA PASSAGE FROM 17N TO
21N BETWEEN 67W AND 69W. NUMEROUS STRONG FROM 25N TO 29N BETWEEN
61W AND 66W. WIDELY SCATTERED TO SCATTERED MODERATE TO ISOLATED
STRONG ELSEWHERE IN THE ATLANTIC OCEAN AND IN THE CARIBBEAN SEA
WITHIN 120 NM TO 180 NM ON EITHER SIDE OF 30N56W 25N58W 14N66W.
THE 24-HOUR RAINFALL TOTALS IN INCHES FOR THE PERIOD ENDING AT
06/1200 UTC...ACCORDING TO THE PAN AMERICAN TEMPERATURE AND
PRECIPITATION TABLES...MIATPTPAN...ARE 5.28 IN ST. THOMAS IN THE
VIRGIN ISLANDS...0.49 IN SAN JUAN PUERTO RICO...AND 1.35 IN
BERMUDA.

THE REST OF THE CARIBBEAN SEA...

MIDDLE LEVEL TO UPPER LEVEL NORTHERLY WIND FLOW COVERS THE REST
OF THE CARIBBEAN SEA THAT IS TO THE WEST OF 84W. THE WESTERN
CARIBBEAN SEA TROUGH THAT COVERED THIS AREA DURING THE LAST FEW
DAYS HAS WEAKENED AND DISSIPATED. AN INVERTED MIDDLE LEVEL TO
UPPER LEVEL TROUGH EXTENDS FROM EASTERN HONDURAS...THROUGH AND
BEYOND NICARAGUA SOUTHWESTWARD.

THE 24-HOUR RAINFALL TOTALS IN INCHES FOR THE PERIOD ENDING AT
06/1200 UTC...ACCORDING TO THE PAN AMERICAN TEMPERATURE AND
PRECIPITATION TABLES...MIATPTPAN...ARE 1.60 IN GUADELOUPE...AND
1.49 IN TRINIDAD.



THE MONSOON TROUGH IS ALONG 8N73W IN COLOMBIA...TO 8N81W IN
PANAMA...BEYOND COASTAL PANAMA/COASTAL COSTA RICA ALONG 83W...
INTO THE EASTERN PACIFIC OCEAN. CONVECTIVE PRECIPITATION...
NUMEROUS STRONG TO THE SOUTH OF 12N BETWEEN 77W AND 81W.

HISPANIOLA...

THE 1010 MB REMNANT LOW PRESSURE CENTER OF GABRIELLE IS NEAR
20N68W...ABOUT 90 NM TO THE NORTHEAST OF THE DOMINICAN REPUBLIC.
A SURFACE TROUGH EXTENDS FROM THE LOW CENTER ACROSS THE
EASTERNMOST PART OF THE DOMINICAN REPUBLIC TO 17N70W IN THE
CARIBBEAN SEA. CONVECTIVE PRECIPITATION...NUMEROUS STRONG IN THE
MONA PASSAGE FROM 17N TO 21N BETWEEN 67W AND 69W. MIDDLE LEVEL
TO UPPER LEVEL ANTICYCLONIC WIND FLOW COVERS HISPANIOLA.

THE GFS FORECAST FOR 700 MB SHOWS THAT AN INVERTED TROUGH WILL
COVER HISPANIOLA FOR THE FIRST 24 HOURS...FOLLOWED BY AN EAST-TO-
WEST RIDGE FOR THE REST OF THE FORECAST PERIOD. THE INVERTED
TROUGH WILL MOVE NORTHWESTWARD...OUT OF THE AREA. THE GFS
FORECAST FOR 500 MB SHOWS THAT AN INVERTED TROUGH/AREA OF
CYCLONIC WIND FLOW WILL COVER HISPANIOLA FOR THE ENTIRE 48 HOUR
PERIOD. THE GFS FORECAST FOR 250 MB SHOWS THAT HISPANIOLA WILL
BE ON THE NORTHERN EDGE OF AN EAST-TO-WEST ORIENTED RIDGE FOR
THE ENTIRE TIME.

THE REST OF THE ATLANTIC OCEAN...

A MIDDLE LEVEL TO UPPER LEVEL CYCLONIC CIRCULATION CENTER IS
NEAR 25N42W. A TROUGH PASSES THROUGH 32N43W...TO THE CYCLONIC
CENTER...TO 17N45W.

AN EASTERN ATLANTIC OCEAN MIDDLE LEVEL TO UPPER LEVEL TROUGH
PASSES THROUGH 32N15W TO 26N20W AND 22N22W. A DISSIPATING COLD
FRONT PASSES THROUGH 33N17W TO 32N26W.

A SURFACE RIDGE EXTENDS FROM A 1022 MB HIGH PRESSURE CENTER THAT
IS NEAR 33N46W TO 25N49W AND 14N49W.

PLEASE READ THE HIGH SEAS FORECAST...MIAHSFAT2...FOR MORE
DETAILS ABOUT 1010 MB LOW CENTER...REMNANTS OF T.D.
GABRIELLE...NEAR 20N68W...WITH A TROUGH EXTENDING TO 28N65W.
EXPECT 20 TO 25 KNOT WINDS AND SEA HEIGHTS LOWER THAN 8 FEET
WITHIN 120 NM IN NORTHEAST SEMICIRCLE AND WITHIN 90 NM IN
NORTHWESTERN QUADRANT OF THE LOW CENTER. EXPECT SOUTHEAST WINDS
20 TO 25 KNOTS AND SEA HEIGHTS FROM 8 TO 10 FEET FROM 19N TO 24N
TO THE EAST OF THE TROUGH TO 61W. EXPECT ALSO 20 KNOT WINDS OR
LESS AND SEA HEIGHTS TO 8 FEET FROM 24N TO 27N TO THE EAST OF
THE TROUGH TO 62W. A SECOND FEATURE IS A 1012 MB LOW PRESSURE
CENTER THAT IS NEAR 15N34W. EXPECT NORTHEAST 20 TO 25 KNOT WINDS
AND SEA HEIGHTS TO 9 FEET FROM 16N TO 21N TO THE EAST OF 37W.
EXPECT ALSO WINDS 20 KNOTS OR LESS AND SEA HEIGHTS TO 8 FEET
ELSEWHERE FROM 14N TO 20N TO THE EAST OF 40W.

FOR ADDITIONAL INFORMATION PLEASE VISIT
HTTP://WWW.HURRICANES.GOV/MARINE

$$
MT


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