[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 171707
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
105 PM EST THU JAN 17 2013

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 1645 UTC.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH PASSES THROUGH SOUTHERN COASTAL LIBERIA NEAR
5N9W TO 4N12W AND 5N17W. THE ITCZ CONTINUES FROM 5N17W TO 4N23W
2N30W 2N37W AND 1N43W. CONVECTIVE PRECIPITATION...SCATTERED
STRONG FROM 3N TO 4N BETWEEN 29W AND 30W...AND FROM 4N TO 8N
BETWEEN 33W AND 40W.

...DISCUSSION...

THE GULF OF MEXICO...

AN UPPER LEVEL TROUGH IS MOVING THROUGH MISSISSIPPI AND
ALABAMA...REACHING THE GULF WATERS THAT ARE JUST OFF THE
SOUTHEASTERN COAST OF LOUISIANA TO 28N93W. THE REST OF THE
MIDDLE LEVEL TO UPPER LEVEL WIND FLOW THAT IS IN THE GULF OF
MEXICO TO THE WEST OF 90W IS SOUTHWESTERLY. THE MIDDLE LEVEL
WIND FLOW THAT IS TO THE EAST OF 90W IS PRINCIPALLY
SOUTHWESTERLY WITH SOME SOUTHERLY WIND FLOW CLOSER TO THE
FLORIDA STRAITS. THE TROUGH SUPPORTS A COLD FRONT THAT PASSES
THROUGH FLORIDA ALONG 30N83W...TO 26N84W IN THE GULF OF
MEXICO...INTO THE NORTHWESTERN CARIBBEAN SEA...ABOUT 30 NM
OFF THE COAST OF THE YUCATAN PENINSULA...ACROSS NORTHERN
BELIZE...AND NORTHERN GUATEMALA AND WESTERN GUATEMALA ALONG
16N AT ITS BORDER WITH MEXICO. BROKEN TO OVERCAST LOW CLOUDS...
LIGHT RAIN...AND FOG...ARE BEING OBSERVED IN THE AREA FROM
SARASOTA FLORIDA TO THE TAMPA/ST.PETERSBURG AREA. SIMILAR
CONDITIONS ARE IN THE CLOUDINESS THAT ACCOMPANIES THE FRONT...
WITHIN 150 TO 210 NM TO THE WEST OF THE LINE THAT PASSES THROUGH
EXTREME NORTHEASTERN FLORIDA NEAR 31N81W 27N82W 24N84W...TO THE
NORTHEASTERN CORNER OF THE YUCATAN PENINSULA...INTO SOUTHEASTERN
GUATEMALA...AND IN THE SOUTHWESTERN CORNER OF THE GULF OF MEXICO
TO THE SOUTH OF 20N. BROKEN TO OVERCAST STRATIFORM CLOUDS ARE
SWEEPING ACROSS THE GULF OF MEXICO BEHIND THE COLD FRONT.
AREAS OF BROKEN LOW CLOUDS...LIGHT RAIN...AND FOG THAT COVERED
SOUTHEASTERN COASTAL FLORIDA FROM MARATHON KEY TO FORT PIERCE
DURING THE LATE NIGHT AND EARLY MORNING AND SUNRISE HOURS HAVE
GIVEN WAY TO SCATTERED TO BROKEN LOW CLOUDS AND SOME MIDDLE
LEVEL CEILINGS STUART FLORIDA SOUTHWARD.

A SURFACE RIDGE EXTENDS FROM A 1035 MB HIGH PRESSURE CENTER THAT
IS IN MEXICO NEAR 25N101W...TO 22N99W 20N97W...STRAIGHT TO THE
ISTHMUS OF TEHUANTEPEC AND THE GULF OF TEHUANTEPEC. STORM-FORCE
WINDS ARE BLOWING IN THE GULF OF TEHUANTEPEC OF MEXICO. PLEASE
READ THE HIGH SEAS FORECAST...MIAHSFEP2...AND THE EASTERN
PACIFIC OCEAN TROPICAL WEATHER DISCUSSION...MIATWDEP...
FOR MORE DETAILS.

PLEASE READ THE HIGH SEAS FORECAST...MIAHSFAT2...AND THE
OFFSHORE FORECAST...MIAOFFNT4...FOR DETAILS ABOUT THE GALE
WARNING WITH THE 30N83W 21N87W COLD FRONT...TO THE SOUTH OF 20N
TO THE EAST OF 94W...WITH 10 TO 14 FOOT SEA HEIGHTS. A SECOND
GALE WARNING COVERS THE AREA THAT IS TO THE NORTH OF 28N TO
THE EAST OF 87W...WITH 8 TO 11 FOOT SEA HEIGHTS. EXPECT
20 TO 25 KNOT WINDS AND 8 TO 10 FOOT SEA HEIGHTS TO THE
WEST OF THE FRONT TO 30N93W 22N98W.

THE CARIBBEAN SEA...

UPPER LEVEL SOUTHWESTERLY WIND FLOW STREAMS ACROSS CENTRAL
AMERICA FROM NICARAGUA TO EASTERN PANAMA TOWARD HISPANIOLA...
AND THEN IT CONTINUES NORTHWARD AS IT IS CAUGHT UP IN THE LARGE-
SCALE ANTICYCLONIC WIND FLOW THAT IS IN THE ATLANTIC OCEAN...
THAT IS MOVING AROUND THE 28N64W ANTICYCLONIC CENTER.

A MIDDLE LEVEL TO UPPER LEVEL RIDGE IS ALONG 67W FROM 8N IN
VENEZUELA BEYOND PUERTO RICO. SOME OF THE MIDDLE LEVEL WIND FLOW
THAT IS IN THE AREA OF 15N/16N ALONG 67W ALSO IS CAUGHT UP IN
THE ANTICYCLONIC WIND FLOW THAT IS RELATED TO THE 28N64W
ANTICYCLONIC CENTER. OTHER MIDDLE LEVEL WIND FLOW IS
NORTHEASTERLY AS IT MOVES TOWARD NORTHWESTERN VENEZUELA AND
COLOMBIA.

MIDDLE LEVEL TO UPPER LEVEL SOUTHERLY WIND FLOW COVERS THE REST
OF THE NORTHWESTERN PART OF THE AREA...AWAY FROM THE
SOUTHWESTERLY WIND FLOW THAT IS CROSSING CENTRAL AMERICA. THIS
WIND FLOW ALSO EVENTUALLY IS CAUGHT UP IN THE BROAD ATLANTIC
OCEAN ANTICYCLONIC WIND FLOW...AND THE SOUTHERLY WIND FLOW THAT
IS IN THE EASTERN GULF OF MEXICO WITH THE ADVANCING TROUGH AND
GULF OF MEXICO COLD FRONT.

COMPARATIVELY DRIER AIR IN SUBSIDENCE COVERS THE ENTIRE
CARIBBEAN SEA...IN WATER VAPOR IMAGERY.

RAINSHOWERS ARE POSSIBLE IN CLUSTERS OF BROKEN LOW LEVEL TO
MIDDLE LEVEL CLOUDS...TO THE EAST OF 70W...TO THE NORTH OF 12N
BETWEEN 70W AND 77W AND TO THE NORTH AND NORTHWEST OF 12N77W
11N80W 9N81W...AND ELSEWHERE TO THE WEST OF 80W.

THE MONSOON TROUGH IS ALONG 8N74W IN COLOMBIA...THROUGH EASTERN
PANAMA ALONG 78W...9N80W...THROUGH WESTERN PANAMA AND BEYOND
9N84W IN SOUTHERN COSTA RICA...INTO THE EASTERN PACIFIC OCEAN
BEYOND 7N90W. CONVECTIVE PRECIPITATION...WIDELY SCATTERED TO
SCATTERED MODERATE TO THE NORTH OF 6N BETWEEN 83W AND 90W...
SOME OF IT REACHING THE COASTAL AREAS OF WESTERN PANAMA AND
COSTA RICA.

PLEASE READ THE HIGH SEAS FORECAST...MIAHSFAT2...AND THE
OFFSHORE FORECAST...MIAOFFNT3...FOR MORE DETAILS ABOUT THE
20 TO 25 KNOT WINDS AND 9 FOOT SEA HEIGHTS FROM 11N TO 17N
BETWEEN 70W AND 78W. EXPECT A COLD FRONT TO REACH 23N83W 17N88W
IN ABOUT 12 HOURS. 20 TO 25 KNOT WINDS WILL BE TO THE WEST OF
THE COLD FRONT...AND SEA HEIGHTS WILL REACH 10 FEET IN THE
YUCATAN CHANNEL.

THE ATLANTIC OCEAN...

GALE FORCE WIND IS DEVELOPING DURING THE NEXT 12 HOURS IN THE
ATLANTIC OCEAN OFF THE COAST OF NORTHEASTERN FLORIDA. THIS WIND
IS IN ADVANCE OF THE COLD FRONT THAT CURRENTLY PASSES THROUGH
FLORIDA ALONG 30N83W...TO 26N84W IN THE GULF OF MEXICO...INTO
THE NORTHWESTERN CARIBBEAN SEA...ABOUT 30 NM OFF THE COAST OF
THE YUCATAN PENINSULA...ACROSS NORTHERN BELIZE...AND NORTHERN
GUATEMALA AND WESTERN GUATEMALA ALONG 16N AT ITS BORDER WITH
MEXICO.

A MIDDLE LEVEL TO UPPER LEVEL TROUGH IS ALONG 30N36W TO 25N38W
TO A 23N40W CYCLONIC CIRCULATION CENTER...TO 15N40W 9N45W 6N53W.
THE TROUGH SUPPORTS A 1013 MB LOW PRESSURE CENTER THAT IS NEAR
23N40W. A SURFACE TROUGH EXTENDS FROM THE LOW CENTER TO 22N38W
18N40W 13N45W. CONVECTIVE PRECIPITATION...SCATTERED STRONG FROM
21N TO 24N BETWEEN 34W AND 37W...SCATTERED MODERATE FROM 21N TO
23N BETWEEN 32W AND 35W...ISOLATED MODERATE ELSEWHERE FROM 17N
TO 28N BETWEEN 28W AND 42W.

A MIDDLE LEVEL TO UPPER LEVEL ANTICYCLONIC CIRCULATION CENTER
IS NEAR 28N64W. ANTICYCLONIC WIND FLOW COVERS THE ATLANTIC
OCEAN TO THE NORTH OF 18N BETWEEN 54W AND 80W.

AN EASTERN ATLANTIC OCEAN UPPER LEVEL RIDGE IS ALONG
5N18W 18N18W BEYOND 32N25W.

A WESTERN ATLANTIC OCEAN SURFACE RIDGE IS ALONG 19N57W 21N68W
30N76W...BEYOND A 1024 MB HIGH PRESSURE CENTER THAT IS NEAR
33N72W.

AN EASTERN ATLANTIC OCEAN SURFACE RIDGE EXTENDS FROM A 1028 MB
HIGH PRESSURE CENTER THAT IS NEAR 33N17W IN THE MADEIRA
ARCHIPELAGO...TO THE WESTERN CAPE VERDE ISLANDS. ANOTHER SURFACE
RIDGE EXTENDS FROM THE 33N17W HIGH PRESSURE CENTER WESTWARD TO
33N30W 34N47W...TO A 1026 MB HIGH PRESSURE CENTER THAT IS NEAR
32N58W...TO 32N65W NEAR BERMUDA...TO 27N74W TO THE FLORIDA
STRAITS.

PLEASE READ THE HIGH SEAS FORECAST...MIAHSFAT2...FOR MORE
DETAILS ABOUT...THE GALE WARNING...GALE-FORCE WINDS AND SEA
HEIGHTS RANGING FROM 8 TO 10 FEET...AT 12 HOURS INTO THE
FORECAST PERIOD...WITH THE COLD FRONT AT THAT TIME FROM 31N78W
TO 28N80W...25 TO 35 KNOT WINDS AND 8 TO 10 FOOT SEA HEIGHTS
TO THE NORTH OF 29N TO THE WEST OF 78W. A 1013 MB LOW PRESSURE
CENTER IS NEAR 23N40W. A SURFACE TROUGH EXTENDS FROM THE LOW
CENTER TO 22N38W AND 13N45W. EXPECT 20 TO 30 KNOT WINDS AND
8 TO 12 FOOT SEA HEIGHTS WITHIN 210 NM TO THE NORTH AND EAST
OF THE LOW CENTER AND TROUGH. EXPECT 20 KNOT WINDS OR LESS AND
8 TO 10 FOOT SEA HEIGHTS ELSEWHERE TO THE NORTH OF 18N TO THE
EAST OF THE LINE 18N59W 31N50W. EXPECT ADDITIONALLY...AT
12 HOURS INTO THE FORECAST PERIOD...20 TO 30 KNOT WINDS AND
SEA HEIGHTS LOWER THAN 8 FEET WITHIN 150 NM TO THE EAST OF THE
FRONT...AND 20 TO 25 KNOT WINDS AND SEA HEIGHTS LOWER THAN
8 FEET TO THE WEST OF THE FRONT.

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

$$
MT





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