[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 031757
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
105 PM EST THU FEB 03 2011

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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...THE ITCZ...
SATELLITE IMAGERY AND GFS ANALYSIS SUGGEST THE AXIS EXTENDS FROM
OFFSHORE OF W AFRICA NEAR 06N13W THEN MEANDERS W-SW TO 02N32W TO
NEAR THE EQUATOR ALONG 43W. VERY ACTIVE CNVTN WAS OCCURRING N OF
THIS ANALYZED ITCZ...WHERE SCATTERED TO NUMEROUS MODERATE TO
STRONG CNVTN WAS NOTED WITHIN 240 NM N OF THE AXIS...WHILE
SCATTERED MODERATE TO STRONG CNVTN WAS NOTED WITHIN 180 NM S OF
THE AXIS AND EXTENDED ACROSS THE EQUATOR INTO THE SRN HEMI
BETWEEN 24W AND 35W. SCATTERED CLUSTERS OF DEEP CNVTN WERE
OCCURRING ALONG COASTAL PORTIONS OF THE GULF OF GUINEA...S OF
THE MONSOON TROUGH.

...DISCUSSION...

THE GULF OF MEXICO...
A BROAD AND RELATIVELY FLAT MID TO UPPER RIDGE CONTINUED ACROSS
THE GULF OF MEXICO THIS MORNING EXTENDING E TO 70W. A MID TO
UPPER CYCLONE ACROSS THE SW U.S. WAS DIGGING SLOWLY S INTO NRN
MEXICO WHILE THE ASSOCIATED TROUGH AXIS OF THE CYCLONE WAS
ROTATING CYCLONICALLY. THIS DEEP LAYERED LOW IS FORECAST TO
SHIFT E-SE AND MOVE ACROSS NRN MEXICO AND THE W HALF OF TEXAS
NEXT 24 HOURS BEFORE SRN STREAM JET ENERGY SHEARS AND ELONGATES
THIS LOW NE TO SW BY FRI EVENING. THIS WILL SHIFT THE UPPER
RIDGE EWD AND AMPLIFY IT ACROSS THE WRN ATLC. THE COLD FRONT
ACROSS THE GULF HAS BECOME STATIONARY OVERNIGHT...WITH
MULTILAYERED CLOUDS MAKING IT DIFFICULT TO IDENTIFY PRECISELY.
GFS ANALYSIS AND OBSERVATIONS SUGGEST THE FRONT WAS LOCATED FROM
JUST S OF TAMPA BAY W TO NEAR 27N85.5W THEN ARCHING SW TO THE
BAY OF CAMPECHE NEAR 18N93W. MID LEVEL FLOW ACROSS THE S CENTRAL
AND SW GULF HAS BECOME S TO SW AND APPEARS TO BE SLOWLY NUDGING
THE FRONT BACK TOWARDS THE N AND NW. WIDESPREAD STRATIFORM
PRECIP IS LIKELY OCCURRING ACROSS THE SW AND CENTRAL PORTIONS OF
THE GULF NW OF THE FRONT AS AMPLE LOW AND MID LEVEL MOISTURE
OVERRUNS THE BOUNDARY. A FEW ISOLATED DEEP TSTMS WERE NOTED NEAR
THE BOUNDARY ACROSS THE NE GULF NEAR 27N. NLY FLOW 20-25 KT IS
ASSUMED TO BE OCCURRING ACROSS MUCH OF THE WRN GULF TO THE NW OF
THE FRONT...WITH THE POTENTIAL FOR WINDS TO 30 KT WITHIN 120 NM
OF THE MEXICAN COASTLINE. SCATTEROMETER PASSES LATER THIS
MORNING SHOULD PROVIDE INSIGHT INTO THE WIND FIELD AROUND THE
FRONT BUT MAY MISS THE FAR W GULF COAST.

THE FRONT IS FORECAST TO DRIFT NW AND W THROUGH 12Z FRI AND IS
EXPECTED TO ALLOW A FRONTAL WAVE TO DEVELOP ACROSS THE CENTRAL
OR S CENTRAL GULF AND SHIFT GRADUALLY NE ALONG THE BOUNDARY
THROUGH FRI NIGHT. GLOBAL MODEL GUIDANCE REMAINS SOMEWHAT IN
DISAGREEMENT ON THE LOCATION OF THIS LOW DEVELOPMENT. HOWEVER
GFS AND ECMWF ENSEMBLES SUGGEST THAT THIS LOW WILL EVENTUALLY
DEVELOP AND SHIFT TO NEAR 25N92W AROUND 12Z FRI. THIS WILL ALLOW
FOR A VERY TIGHT PRES GRADIENT AND DAMMING OF WINDS ALONG THE
MEXICAN COAST...AND NLY GALES ARE EXPECTED ACROSS PORTIONS OF
THE W GULF BY 12Z.

THE CARIBBEAN SEA...
SINKING AIR AND SUBSIDENCE GENERALLY DOMINATES THE ENTIRE CARIB
BASIN...ON THE S SIDE OF THE GULF OF MEXICO UPPER RIDGE. WATER
VAPOR IMAGERY REVEALS A MID LEVEL TROUGH AXIS MEANDERING FROM A
CENTRAL ATLC DEEP LAYERED LOW TO NEAR 10N60W THEN WWD TO A MID
LEVEL CYCLONE NEAR 12N75W. FAIR WEATHER AND MODERATE TO FRESH
E-NE TRADES THUS DOMINATE THE BASIN. RECENT SCATTEROMETER PASSES
SHOW NE TRADES 20-25 KT EXTENDING FROM THE WATERS S AND SW OF
PUERTO RICO TO THE SW CARIB ALONG 80W...WITH 25-30 KT WINDS
WITHIN 180 NM OF THE COLOMBIAN COASTLINE. THESE FRESH TRADES ARE
BLOWING ACROSS CENTRAL AMERICA AND PRODUCING GAP WIND EVENTS OF
20-25 KT IN THE TYPICAL EXIT REGIONS OF THE EPAC...INCLUDING NLY
WINDS IN THE GULF OF PANAMA. ENHANCED LLVL MOISTURE WILL MOVE
FROM THE TROPICAL N ATLC W-SW ACROSS THE S HALF OF THE WINDWARDS
DURING THE NEXT 24 HOURS TO PRODUCE SCATTERED SHOWERS AND
ISOLATED TSTMS.

THE ATLANTIC OCEAN...
STRONG UPPER RIDGING ACROSS THE GULF OF MEXICO EXTENDS E INTO
THE SW N ATLC TO 70W...WITH UPPER FLOW BECOMING CONFLUENT NEAR
70W...AND JET ENERGY CONTINUING E-NE ACROSS THE CENTRAL ATLC AND
A PORTION OF THE FLOW DIVERTING SE THEN S INTO THE BACKSIDE OF A
DEEP LAYERED CYCLONE NEAR 21N54W. CONVERGENCE ACROSS THE BROAD W
SEMICIRCLE OF THE LOW WAS YIELDING SUBSIDENCE FROM THE NE CARIB
NE AND E TO NEAR 55W. A MID TO UPPER HIGH WAS CENTERED JUST NE
OF THE SE BAHAMAS NEAR 23N70W. THE COLD FRONT ACROSS THE GULF OF
MEXICO WAS SOMEWHAT ILL DEFINED ACROSS THE FLORIDA PENINSULA BUT
WAS SOMEWHERE NEAR FORT PIERCE EXTENDING NE TO NEAR 30N77.5W. A
1024 MB HIGH NEAR 29N68W WAS THE SW LOBE OF THE ATLC RIDGE THAT
EXTENDED SW TO SRN FLORIDA. FAIR WEATHER AND LIGHT TO MODERATE
ANTICYCLONIC FLOW PREVAILED ACROSS THE SW N ATLC...THE BAHAMAS
AND INTO FAR SRN FLORIDA...W OF 67W. THE REMNANTS OF A SURFACE
LOW SPAWNED BY THE DEEP LAYERED CYCLONE WERE STILL EVIDENT NEAR
25.5N61W AND MOVING W...WHILE THE CURRENT LOCATION OF THE UPPER
CYCLONE ALONG 54W CONTINUED TO CARVE OUT A LLVL WEAKNESS AND
TROUGHING DOWN TO THE SURFACE S OF 21N ALONG 54/55W. LOW TO MID
LVL CONVERGENCE ACROSS THE SRN SEMICIRCLE OF THIS CYCLONE WAS
PRODUCING BANDS OF SCATTERED SHOWERS AND ISOLATED TSTMS...WITH
BEST CONVECTION OCCURRING ACROSS THE SE QUADRANT OF THE UPPER
CYCLONE WHERE A JET SEGMENT WAS ENHANCING UPPER SPEED
DIVERGENCE. STRONG HIGH PRES ACROSS THE NE ATLC WAS HELPING TO
PRODUCE A BROAD AREA OF FRESH NE TO E TRADES ACROSS THE
REMAINDER OF THE ATLC E OF 55W BETWEEN 25-30N ACROSS THE E ATLC
AND 08N IN THE DEEP TROPICS. VIS STLT IMAGES THIS MORNING SHOWED
GENERALLY FAIR WEATHER ACROSS THIS LARGE AREA WITH COLD AIR
STRATOCU. ELONGATED CONVERGENCE BANDS BETWEEN 40W AND 50W WERE
PRODUCING SCATTERED SHALLOW CONVECTION.

METEOSAT IMAGERY THIS MORNING SHOWS VERY STABLE NE LLVL FLOW
BLOWING OFF OF W AFRICA TURNING CYCLONICALLY INTO THE WEAK BUT
PERSISTENT MONSOONAL CIRCULATION ACROSS TROPICAL AFRICA. DRY
CLEAR AIR WAS MOVING W OFF THE W COAST AND HAD BEGUN TO REACH
THE CAPE VERDES...WITH TWO PLUMES OF AFRICA DUST BECOMING
EVIDENT BETWEEN 16N AND 22N. WARM WATERS ACROSS THE EQUATORIAL
ATLC AND GOOD LLVL CONVERGENCE DUE TO N TO NE FLOW ACROSS THE N
ATLC...CONTINUE TO PRODUCE SIGNIFICANT CNVTN ALONG THE ATLC ITCZ
E OF 45W...WHICH IS THEN ACTING TO MAINTAIN UPPER RIDGING ACROSS
THE TROPICAL ATLC.

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

$$
STRIPLING





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