000 AXNT20 KNHC 251754 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 105 PM EST TUE DEC 24 2007 TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHERN SECTIONS OF SOUTH AMERICA...AND THE 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... ITCZ AXIS IS CENTERED ALONG 6N10W 5N20W 4N32W 3N44W EQUATOR AT 52W. SCATTERED MODERATE CONVECTION IS WITHIN 180 NM N OF THE AXIS BETWEEN 31W-37W. ...DISCUSSION... THE GULF OF MEXICO... A WEAK RIDGE DOMINATES THE GULF THIS AFTERNOON GIVING THE AREA LIGHT TO MODERATE WINDS. THE RETURN FLOW WILL INCREASE TONIGHT OVER THE NW CORNER OF THE GULF AHEAD OF THE NEXT COLD FRONT THAT WILL MOVE OFF THE TEXAS COAST WEDNESDAY AFTERNOON. A CUT-OFF LOW OVER THE LOWER MISSISSIPPI VALLEY HAS A TROUGH OVER THE NORTH-CENTRAL GULF WATERS. THE UPPER-LEVEL LOW WILL MOVE TOWARDS THE CAROLINAS SUPPORTING THE DEVELOPMENT OF A SFC LOW ALONG A FRONTAL BOUNDARY LOCATED JUST EAST OF NORTH-CENTRAL FLORIDA. MOSAIC DOPPLER RADAR FROM THE SE U.S SHOWS BANDS OF SHOWERS WITH EMBEDDED TSTMS AHEAD OF THE CUT-OFF LOW/TROUGH AFFECTING PARTS OF GEORGIA AND ALABAMA AS WELL AS MISSISSIPPI AND THE FLORIDA PANHANDLE. SCATTERED SHOWERS AND ISOLATED TSTMS ARE ALSO SEEN ACROSS THE EAST COAST METRO AREAS OF FLORIDA AND THE ADJACENT COASTAL WATERS. THIS ACTIVITY IS ASSOCIATED WITH THE ABOVE MENTIONED FRONTAL BOUNDARY AND A WEAK INVERTED SURFACE TROUGH EXTENDING ALONG 80W FROM 22N TO 27N. ANOTHER SFC TROUGH IS ANALYZED ALONG 93W/94W SOUTH OF 23N. THIS TROUGH IS GENERATING ISOLATED SHOWERS AND TSTMS OVER THE SW PORTION OF THE GULF...INCLUDING THE BAY OF CAMPECHE. TROPICAL MOISTURE IS SEEN STREAMING NORTHEASTWARD BY A JETSTREAM BRANCH FROM THE E PACIFIC NE ACROSS THE CENTRAL GULF REACHING TO ACROSS THE SE UNITED STATES. SATELLITE-DERIVED WINDS INDICATE A CORE WINDS OF 70-110 KT ASSOCIATED WITH THIS JETSTREAM. THE CARIBBEAN SEA... AMPLIFIED MID TO UPPER LEVEL RIDGING IS PRESENT OVER THE NW AND CENTRAL SECTIONS OF THE SEA CREATING ABUNDANT MODERATE TO STRONG SUBSIDENCE IN THESE AREAS. THE TAIL END OF A MID/UPPER LEVEL TROUGH EXTENDS FROM THE E ATLC SW TO NEAR THE LEEWARD ISLANDS. PRETTY QUIET CONDITIONS ARE FOUND ACROSS THE BASIN UNDER THE INFLUENCE OF THIS STABLE ENVIRONMENT. TYPICAL PATCHES OF LOW LEVEL CLOUDS WITH LIGHT RAIN SHOWERS ARE ACROSS THE AREA PARTICULARLY OVER AND JUST SOUTH OF JAMAICA. LOW-LEVEL CONVERGENCE COUPLED WITH A DIFFLUENT PATTERN ALOFT IS PRODUCING A CLUSTER OF MODERATE TO ISOLATED STRONG CONVECTION OVER THE SW CARIBBEAN. THIS CONVECTIVE ACTIVITY IS AFFECTING THE CARIBBEAN PLAINS OF COSTA RICA AND PARTS OF PANAMA. A NARROW BAND OF TRANSVERSE HIGH CLOUDS ASSOCIATED WITH A TROPICAL JETSTREAM IS SEEN MOVING QUICKLY EASTWARD ACROSS THE SOUTHERN CARIBBEAN INTO THE N TROPICAL ATLC. MODERATE EASTERLY WINDS WILL PERSIST OVER THE AREA THIS AFTERNOON THROUGH SAT. THE ATLANTIC OCEAN... THIS REGION IS DOMINATED PRIMARILY BY TWO MAIN UPPER-LEVEL FEATURES. THE FIRST ONE IS A BROAD RIDGE COVERING W OF ABOUT 55W. MODERATE TO STRONG SUBSIDENCE AND IMPLIED DRY/STABLE AIRMASS IS FOUND WITHIN THE RIDGE AXIS. THE SECOND ONE IS A DEEP LAYERED TROUGH THAT ENTERS THE AREA NEAR 31N41W AND EXTENDS TO NEAR THE LEEWARD ISLANDS. AMPLE UPPER LEVEL MOISTURE IS EVIDENT WITHIN 500 NM SE OF THE TROUGH. A CUT-OFF LOW IS DEVELOPING ALONG THE TROUGH AXIS NEAR 29N42W. THE ATTENDANT FRONTAL SYSTEM ENTERS THE AREA...AS A STATIONARY FRONT NEAR 31N37W THEN CONTINUES TO 20N47W. THE SURFACE LOW PREVIOUSLY ANALYZED AS 1015 MB NEAR 23N51W BECAME DIFFUSED THIS MORNING...INSTEAD A SFC TROUGH WAS ANALYZED ON THE 1200 UTC MAP ALONG 51W FROM 14N-20N. A QUIKSCAT PASS FROM THIS MORNING ALSO CONFIRMED THAT THE LOW IS NO LONGER DISCERNIBLE...BUT COMPUTER MODELS SUGGEST THAT A NEW LOW MAY FORM ALONG THE FRONTAL BOUNDARY NEAR 28N40W. AN ASCAT PASS FROM AROUND 1300 UTC SHOWS SOME CYCLONIC CIRCULATION IN THIS AREA. TIGHT PRES GRADIENT BETWEEN THIS FRONT AND THE RIDGE TO THE W OF THE FRONT IS PRODUCING GALE FORCE WINDS FROM 23N TO 28N BETWEEN 40W AND 60W. AS A RESULT...A GALE WARNING HAS BEEN POSTED. POCKETS OF LOW LEVEL MOISTURE ARE SEEN ACROSS THE BAHAMAS AND THE STRAITS OF FLORIDA MOVING NW UNDER A PREVAILING SE WIND FLOW AROUND THE SOUTHERN PERIPHERY OF A SFC RIDGE EXTENDING INTO THE AREA BETWEEN THE PREVIOUSLY MENTIONED FRONTAL BOUNDARIES. RIDGING ALSO DOMINATES THE E ATLC ANCHORED ON A 1029 HIGH LOCATED JUST WEST OF THE MADEIRA ISLANDS. THE UPPER FLOW IS GENERALLY ZONAL OVER THE TROPICAL ATLC TO THE E AND SE OF THE FRONT/TROUGH. HIGH LEVEL MOISTURE STREAMING EASTWARD IS LOCATED S OF 18N...REACHING THE CAPE VERDE ISLANDS. $$ GR