000 AXNT20 KNHC 291108 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 705 AM EST WED NOV 29 2006 TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHEASTERN 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...WEATHER OBSERVATIONS...RADAR... AND METEOROLOGICAL ANALYSIS. BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1100 UTC. ...THE ITCZ... ITCZ AXIS IS CENTERED ALONG 8N13W 6N26W 8N39W 5N50W 4N57W. THE AXIS IS MORE ACTIVE TODAY THAN THE PAST COUPLE DAYS. SCATTERED MODERATE CONVECTION IS WITHIN 120 NM N OF THE AXIS BETWEEN 20W-27W. A LARGE AREA OF SCATTERED MODERATE IS FROM 4N-11N BETWEEN 31W-45W. UPPER LEVEL DIFFLUENCE IS A PRIMARY FACTOR OF TRIGGERING THIS CONVECTION. HOWEVER BASED ON SFC OBS... SHORTWAVE IR IMAGERY AND LOW-LEVEL SATELLITE DERIVED WINDS THERE DOES APPEAR TO BE A SFC FEATURE ENHANCING THIS ACTIVITY. GIVEN THESE DATA...A SFC TROUGH WAS ADDED TO THE MAP ALONG 41W S OF 16N. THIS FEATURE MAY BE BETTER REPRESENTED AS A TROPICAL WAVE BUT DUE TO CLIMATOLOGY AND BECAUSE THIS FEATURE IS NOT EASILY TRACKABLE BACK TO AFRICA IT WAS ANALYZED AS A TROUGH INSTEAD. ...DISCUSSION... THE GULF OF MEXICO... MAINLY FAIR WEATHER CONTINUES ACROSS THE GULF AS SFC HIGH PRES REMAINS IN CONTROL. BREEZY 15 KT ELY WINDS ACROSS THE WRN ATLC IS ADVECTING PATCHES OF LOW-LEVEL CLOUDS AND EMBEDDED ISOLATED SHOWERS ACROSS CENTRAL AND SOUTH FLORIDA ON THE BREEZE. SOME OF THIS LOW-LEVEL MOISTURE IS BEING DRIVEN ACROSS THE GULF AND TOWARDS THE GULF COAST BY SELY RETURN FLOW AROUND THE 1028 MB SFC HIGH WHICH IS SLIDING E OFFSHORE OF THE MID-ATLANTIC STATES. IN THE UPPER LEVELS...A STRONG RIDGE HAS ALSO SHIFTED E OF THE AREA...NOW CENTERED OVER THE WRN BAHAMAS...IN RESPONSE TO A STRONG MID/UPPER LEVEL TROUGH OVER THE UPPER PLAINS/ROCKIES. WIDESPREAD STRONG SUBSIDENCE EXISTS EVERYWHERE ABOVE THE GULF. THIS STRONG CAP IS PREVENTING THE LOW-LAYER MOISTURE TO ACQUIRE MUCH DEPTH. GFS SHOWS THE SFC AND UPPER RIDGE CONTINUING ITS EASTWARD MOVEMENT AS THE UPPER TROUGH APPROACHES. TEMPS WILL REMAIN ABOVE NORMAL OVER THE NEXT DAY OR SO BEFORE A COLD FRONT ENTERS THE AREA ON THU. GALE FORCE WINDS WILL ADVECT A MUCH COLDER AIRMASS INTO THE WRN AND CNTRL GULF BEHIND THE FRONT. GFS STALLS THE FRONT ON FRI ACROSS N FLORIDA AND EVENTUALLY A SHORTWAVE GIVES IT A PUSH ALLOWING IT TO MOVE ACROSS CNTRL AND S FLORIDA ON SUN/MON. THE CARIBBEAN SEA... A WELL-DEFINED HIGHLY ELONGATED UPPER LEVEL TROUGH STRETCHES ACROSS THE VIRGIN ISLANDS SOUTHWESTWARD TOWARDS THE SOUTH AMERICAN COAST ALONG 16N69W 14N75W. THE ASSOCIATED COLD FRONT HAS PULLED E OF THE AREA. MULTILAYERED CLOUDINESS AND ISOLATED TO SCATTERED SHOWERS ARE LOCATED ON THE MOIST E SIDE OF THE UPPER TROUGH AXIS...WHICH INCLUDES THE LESSER ANTILLES. VERY DRY STABLE UPPER LEVEL AIR ALOFT EXISTS W OF THE TROUGH AXIS UNDER THE INFLUENCE OF A MID/UPPER LEVEL RIDGE CENTERED IN THE WRN BAHAMAS. THIS INCLUDES MOST OF THE AREA N OF 15N FROM PUERTO RICO WESTWARD. UNDERNEATH THE SUBSIDENCE INVERSION...LOW-LEVEL CLOUDS AND EMBEDDED ISOLATED SHOWERS ARE MOVING ACROSS PUERTO RICO...AS DEPICTED ON SAN JUAN'S 88-D...AND LIKELY HISPANIOLA/CUBA AS MODERATE NELY LOW-LEVEL FLOW ACROSS THE ATLC WATERS STIRS UP ENOUGH INSTABILITY TO PRODUCE SHALLOW SHOWER ACTIVITY. S-SWLY UPPER LEVEL FLOW IS DRAWING MOISTURE FROM THE ITCZ INTO THE SW CARIB AND UPPER DIFFLUENCE IS SPARKING SCATTERED SHOWERS AND TSTMS S OF 12N W OF 72W. TRADE WINDS HAVE INCREASED A LITTLE THIS MORNING BUT REMAIN MODERATE. THESE WINDS WILL CONTINUE TO STRENGTHEN AS THE FRONTAL BOUNDARY IN THE ATLC PULLS AWAY AND STRONG HIGH PRES BUILDS S TIGHTENING THE PRES GRAD. THE ATLANTIC OCEAN... MODERATE TO STRONG HIGH PRES BOTH AT THE SFC AND ALOFT COVERS THE WRN ATLC WITH THE MID/UPPER LEVEL HIGH CENTERED OVER THE WRN BAHAMAS. VERY DRY AIR ALOFT IS WIDESPREAD W OF 50W SUPPRESSING ANY DEEP CLOUDINESS. HOWEVER...BELOW THE SINKING INVERSION MODERATE NE-ELY FLOW IS GENERATING SMALL PATCHES OF LOW CLOUDS AND ISOLATED SHOWERS ACROSS THE SEA...SIMILAR TO THE CONDITIONS IN THE GULF AND NW CARIB. THE ONLY LOW PRES FEATURE IS IN THE CNTRL ATLC WHERE A COLD FRONT EXTENDS FROM AN OCCLUDED 991 MB LOW NEAR 39N32W ALONG 32N38W 24N46W 16N57W. A PRE-FRONTAL TROUGH IS ANALYZED 90 NM AHEAD OF THE FRONT S OF 20N. SWLY UPPER LEVEL FLOW...ON THE E SIDE OF A HIGHLY ELONGATED MID/UPPER LEVEL TROUGH...AND LOW-LEVEL LIFT NEAR THE SFC BOUNDARIES IS PRODUCING MULTILAYERED CLOUDS WITH EMBEDDED SCATTERED SHOWERS WITHIN 300 NM EITHER SIDE OF THE FRONT. MODELS SHOW THE SFC LOW QUICKLY RACING TO THE NE WHICH SHOULD HELP TO SLOWLY THIN THE MOISTURE PLUME IN THIS AREA OVER THE NEXT DAY OR TWO. AN ELONGATED RATHER HIGH AMPLITUDE MID/UPPER LEVEL RIDGE LIES E OF THE TROUGH AND COVERS THE AREA E OF 40W N OF 20N. SLIGHT UPPER LEVEL TROUGHING STILL EXISTS IN THE TROPICAL ATLC PROVIDING A FAVORABLE PATTERN FOR CONVECTION IN THE ITCZ. FOR DETAILS REFER TO THE ITCZ SECTION ABOVE. DEEP MOISTURE IS VERY LIMITED OUTSIDE OF THE ITCZ AND FRONTAL BOUNDARY/UPPER TROUGH IN THE CNTRL ATLC. PLENTY OF DRY STABLE AIR ALOFT IS LOCATED E OF 35W BETWEEN 13W-25N ENHANCED BY UPPER LEVEL CONFLUENT FLOW W OF AN UPPER TROUGH OVER AFRICA. AT THE SFC...MODERATE TO STRONG HIGH PRES RIDGING IS THE RULE ACROSS THE ERN AND WRN SUBTROPICAL ATLC SUPPORTED BY A 1032 MB HIGH IN NRN SPAIN AND A 1028 MB HIGH OFFSHORE OF THE MID-ATLANTIC U.S. A PRONOUNCED WEAKNESS IN THIS RIDGING LIES IN THE CNTRL ATLC DUE TO THE PRESENCE OF THE SFC LOW AND FRONTAL BOUNDARY MENTIONED. $$ CANGIALOSI