000 AXNT20 KNHC 100548 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 105 AM EST MON DEC 10 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0515 UTC ...SPECIAL FEATURE... THE AREA OF DISTURBED WEATHER ASSOCIATED WITH A BROAD AREA OF LOW PRESSURE CENTERED ABOUT 370 NM EAST OF PUERTO RICO REMAINS FAIRLY WELL-ORGANIZED...BUT SATELLITE IMAGES AND SURFACE OBSERVATIONS SUGGEST THAT THIS SYSTEM HAS NOT DEVELOPED A CLOSED CIRCULATION YET. THIS FEATURE IS MOVING WESTWARD NEAR 15 KT AND IS PRODUCING HEAVY SQUALLS WITH GALE FORCE WINDS TO THE NORTH OF THE SHOWER ACTIVITY. ENVIRONMENTAL CONDITIONS APPEAR TO BE FAVORABLE FOR SOME DEVELOPMENT AND A TROPICAL OR SUBTROPICAL STORM COULD FORM DURING THE NEXT 24 HOURS. INTERESTS IN THE NORTHERN LEEWARD ISLANDS...THE VIRGIN ISLANDS...PUERTO RICO... HISPANIOLA...AND THE EASTERN BAHAMAS SHOULD MONITOR THE PROGRESS OF THIS SYSTEM. NUMEROUS MODERATE TO STRONG CONVECTION IS FROM 19N-21N BETWEEN 56W-61W. A GALE WARNING IS ALREADY IN EFFECT IN THIS AREA. THE GFS COMPUTER MODEL HAS MOISTURE FROM THIS SYSTEM SPREADING OVER THE NE CARIBBEAN TODAY. ...THE ITCZ... ITCZ AXIS IS CENTERED ALONG 7N12W 4N25W 5N35W 4N54W. CLUSTERS OF SCATTERED MODERATE/ISOLATED STRONG CONVECTION ARE WITHIN 140 NM SOUTH OF AXIS BETWEEN 19W-22W. SIMILAR CONVECTION IS FOUND WITHIN 100 NM EITHER SIDE OF AXIS BETWEEN 35W-42W. UPPER DIFFLUENCE IS ENHANCED THIS ACTIVITY. DISCUSSION... GULF OF MEXICO... HIGH PRES REMAINS IN CONTROL OF THE WEATHER PATTERN ACROSS THE GULF GIVING THE AREA LIGHT TO MODERATE E TO SE WINDS AND MOSTLY FAIR WEATHER. FRAGMENTS OF LOW LEVEL MOISTURE ARE OVER THE CENTRAL GULF MAINLY N OF 24N ASSOCIATED WITH A MOIST ONSHORE RETURN FLOW. BROAD UPPER-LEVEL RIDGE EXTENDS FROM THE CARIBBEAN THROUGH THE YUCATAN CHANNEL TO OVER THE SE U.S. COVERING THE ENTIRE GULF. MODERATE TO STRONG UPPER LEVEL SUBSIDENCE AND IMPLIED DRY/STABLE AIR MASS IS NOTED WITHIN THE RIDGE AXIS. . OTHERWISE SKIES ARE CLEAR TONIGHT. LOOKING AHEAD...A COLD FRONT WILL APPROACH E TEXAS WED...AND MOVE ACROSS THE NW CORNER OF THE GULF LATE WED AND THURSDAY. CARIBBEAN SEA... BROAD UPPER RIDGE COVERS CENTRAL AMERICA AND THE W CARIBBEAN W OF 80W ANCHORED BY AN UPPER HIGH LOCATED IN THE EPAC JUST SOUTH OF PANAMA. BROAD UPPER TROUGH COVERS THE REMAINDER OF THE CARIBBEAN WITH AN UPPER LOW SPINNING OVER PUERTO RICO AND THE SURROUNDING COASTAL WATERS. UPPER DIFFLUENCE BETWEEN THIS LOW AND AN UPPER RIDGE E OF THE WINDWARD ISLANDS IS ENHANCED CONVECTION ASSOCIATED WITH THE SPECIAL FEATURE. STRONG NE TO E SURFACE WINDS OF 20 TO 25 KT COVER THE CARIBBEAN DUE TO THE TIGHT PRESSURE GRADIENT INDUCED BY THE STRONG SURFACE RIDGE ACROSS THE ATLC. LOW LEVEL NELY FLOW AHEAD OF THE SPECIAL FEATURE COMBINED WITH THE UPPER LOW MENTIONED ABOVE IS GENERATING QUICK MOVING SHOWERS AND ISOLATED TSTMS OVER PUERTO RICO AND HISPANIOLA. TYPICAL PATCHES OF LOW LEVEL MOISTURE DOT THE REMAINDER OF THE BASIN. ISOLATED SHOWERS INLAND AND WITHIN 60 NM ALONG THE COAST OF PANAMA AND COSTA RICA DUE TO THE CLOSE PROXIMITY OF THE ITCZ AXIS IN THE E PACIFIC REGION. ATLANTIC OCEAN... THE MOST SIGNIFICANT FEATURE ACROSS THE FORECAST AREA IS THE BROAD AREA OF LOW PRESSURE CENTERED ABOUT 370 NM EAST OF PUERTO RICO WITH A SFC TROUGH EXTENDING SOUTH ALONG 58W/59W. SEE SPECIAL FEATURE ABOVE FOR MORE DETAILS. BROAD UPPER RIDGE COVERS THE REMAINDER OF THE ATLC WITH A WEAKNESS ALONG THE SURFACE TROUGH. IN THE UPPER LEVELS...BROAD UPPER RIDGE EXTENDING FROM THE CARIBBEAN OVER THE GULF OF MEXICO COVERS THE FAR W ATLC W OF 75W. A SHORT WAVE TROUGH IS OVER THE W ATLC ALONG 70W/71W N OF 24N. AN UPPER-LEVEL RIDGE DOMINATES MOST OF THE CENTRAL ATLC. A CUT-OFF UPPER LOW IS IN THE E ATLC NEAR 31N29W. AN UPPER HIGH IS IN THE TROPICAL ATLC NEAR 2N38W COVERING THE AREA S OF 19N BETWEEN THE WINDWARD ISLANDS AND THE AFRICAN COAST. A JET STREAM BRANCH IS RIDING ON THE N PERIPHERY OF THIS ANTICYCLONE DRAWING UPPER LEVEL MOISTURE FROM N SOUTH AMERICA NE AND E ACROSS THE OCEAN. $$ GR