[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 300003
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
705 PM EST SAT JAN 29 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...THE ITCZ...

THE ITCZ AXIS IS ANALYZED FROM SIERRA LEONE NEAR 7N12W ALONG
3N20W THEN S OF THE EQUATOR NEAR 33W TO THE SOUTH AMERICAN COAST
NEAR 2S46W. ISOLATED MODERATE TO STRONG CONVECTION IS FROM 2N-5N
BETWEEN 26W AND 34W...AND FROM 3N-5N BETWEEN 38W AND 42W.

...DISCUSSION...

GULF OF MEXICO...
A FLAT UPPER RIDGE WITH AXIS ALONG 90W APPEARS TO BE AMPLIFYING
SLIGHTLY OVER THE GULF OF MEXICO. STRONG SW FLOW ALONG THE
NORTHERN PERIPHERY OF THE RIDGE AT THE UPPER LEVELS IS ADVECTING
SOME MID AND HIGH LEVEL MOISTURE ACROSS THE NW HALF OF THE GULF.
AT THE SURFACE 1024 MB HIGH PRESSURE WAS CENTERED NEAR 27N88W.
INCREASING SOUTHERLY RETURN FLOW ON THE BACKSIDE OF THE HIGH WAS
RESULTING IN AN INCREASE IN LOW LEVEL MOISTURE AND OVERCAST
CONDITIONS ALONG THE CENTRAL AND UPPER TEXAS COAST. THE
INCREASED SOUTHERLY FLOW EXTENDS FURTHER SOUTH ALONG THE COAST
OF MEXICO AND HAS ERODED A SURFACE TROUGH WHICH WAS NOTED FROM
24N97W TO 19N95W EARLIER IN THE DAY. HIGH PRESSURE IS FORECAST
TO MOVE EAST OF THE GULF ON SUN WITH INCREASING SOUTHERLY WINDS
SPREADING ACROSS MOST OF THE GULF WITH SHOWERS DEVELOPING OVER
THE NW GULF.

CARIBBEAN SEA...
THE UPPER LEVELS OF THE CARIBBEAN ARE DOMINATED BY WESTERLY
ZONAL FLOW WITH MODERATE TO STRONG SUBSIDENCE OVER THE AREA WITH
THE EXCEPTION OF THE FAR NORTHWEST. AT THE SURFACE FRESH TRADE
WINDS CONTINUE ACROSS THE EAST AND CENTRAL CARIBBEAN WITH WINDS
OF A MORE NORTHERLY COMPONENT NORTHWEST OF A SHEAR AXIS WHICH
EXTENDS FROM NEAR JAMAICA OFF THE COAST OF NICARAGUA TO NEAR
11N83W. THE CONVERGENCE ALONG THE SHEAR LINE IS RESULTING IN AN
AREA OF SCATTERED MODERATE ISOLATED STRONG THUNDERSTORMS ALONG
THE COAST OF NICARAGUA FROM 12N-14N. ADDITIONAL AREAS OF
POSSIBLE ISOLATED SHOWERS ARE AFFECTING THE SOUTHEAST CARIBBEAN
FROM 10N-13N BETWEEN 62W AND 67W...AND SE CUBA FROM 19N-22N
BETWEEN 73W AND 77W AND OVER PORTIONS OF HAITI AND THE DOMINICAN
REPUBLIC. THE LATTER AREA OF SHOWERS WAS IN ASSOCIATION WITH
THE DISSIPATED TAIL-END OF A COLD FRONT IN THE SW ATLC. EXPECT
LITTLE CHANGE IN THE OVERALL TRADEWIND PATTERN THIS COMING WEEK.

ATLANTIC OCEAN...
A BROAD UPPER LEVEL LONGWAVE TROUGH MOVING OFF THE EASTERN
SEABOARD AND NOW OVER THE ATLC N OF 25N BETWEEN 60W AND 80W
SUPPORTS A SERIES OF SURFACE BOUNDARIES ANALYZED ACROSS THE
WESTERN ATLC. A COLD FRONT ENTERS THE AREA NEAR 32N62W EXTENDS
ALONG 28N65W TO 24N70W BECOMING DIFFUSE TO NEAR THE WINDWARD
PASSAGE. AHEAD OF THIS FRONT...A MORE ACTIVE PRE-FRONTAL TROUGH
ENTERS THE AREA NEAR 32N59W AND CONTINUES SW THROUGH 26N65W TO
JUST N OF THE COAST OF THE DOMINICAN REPUBLIC. SCATTERED SHOWERS
AND THUNDERSTORMS WERE OCCURRING WITHIN 45-90 NM E OF THE
PRE-FRONTAL TROUGH N OF 24N. THE COLD FRONT AND PRE-FRONTAL
TROUGH ARE FORECAST TO MOVE EASTWARD OVER THE NEXT 24 HOURS...
WITH THE COLD FRONT GRADUALLY OVERTAKING THE PRE-FRONTAL TROUGH.
A SURFACE TROUGH MARKING THE LEADING EDGE OF A REINFORCING SHOT
OF COLD AIR IS LOCATED NW OF THE COLD FRONT AND ENTERS THE AREA
NEAR 32N64W AND EXTENDS TO NEAR 28N73W.

TO THE E ACROSS THE CENTRAL ATLC...A SHARP NARROW UPPER LEVEL
RIDGE THROUGH 32N43W TO 19N55W IS NEARLY STATIONARY. A WELL
DEFINED UPPER LEVEL LOW NEAR 26N29W AND ASSOCIATED UPPER TROUGH
WAS UNDERCUTTING THE RIDGE TO THE SE. AT THE SURFACE...A
1031 MB HIGH WELL N OF THE AREA NEAR 39N33W RIDGED SW INTO THE
AREA S OF 32N AND W OF 35W. THE UNDERCUTTING UPPER LOW SUPPORTED
AN OCCLUDED 1011 MB LOW PRES NEAR 24N28W. THE OCCLUDED FRONT
EXTENDS NORTHWARD AROUND THE NRN SEMICIRCLE OF THE LOW TO A 1012
MB TRIPLE POINT LOW NEAR 27N20W WHERE A WARM FRONT AND COLD
FRONT MEET. THE WARM FRONT EXTENDS E TO THE COAST OF MAURITANIA
NEAR 26N AND THE COLD FRONT EXTENDS SW TO THE CAPE VERDE ISLANDS
NEAR 15N23W. THE CONVECTION SURROUNDING THIS SYSTEM IS FOCUSED
WITHIN 240 NM IN THE N SEMICIRCLE OF THE OCCLUDED LOW. THIS LOW
PRES SYSTEM WILL CONTINUE TO ROTATE TO THE SE WITH WEAK TO
MODERATE CONVECTION FLARING UP.

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

$$
COBB




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