000 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