000 AXNT20 KNHC 201103 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 AM EDT MON OCT 19 2008 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1015 UTC. ...SPECIAL FEATURES... A 1011 MB SURFACE LOW IS CENTERED IN THE NW CARIBBEAN NEAR 17N87W...OR ABOUT 90 NM E OF THE COAST OF BELIZE. BROAD LOW LEVEL CONVERGENCE AROUND THE LOW...COUPLED WITH UPPER LEVEL DIVERGENCE OVER THE NW CARIBBEAN...IS SUPPORTING SCATTERED MODERATE/ISOLATED STRONG CONVECTION MAINLY TO THE E AND SE OF THE LOW...FROM 14N-20N BETWEEN 80W-87W. SOME SLOW DEVELOPMENT OF THIS SYSTEM IS POSSIBLE BEFORE IT MOVES INLAND OVER BELIZE OR THE YUCATAN PENINSULA IN A DAY OR TWO. REGARDLESS OF DEVELOPMENT...LOCALLY HEAVY RAINFALL IS EXPECTED OVER PORTIONS OF HONDURAS...GUATEMALA...BELIZE...AND THE YUCATAN PENINSULA OVER THE NEXT COUPLE OF DAYS. ...TROPICAL WAVES... TROPICAL WAVE IS ALONG 44W S OF 18N MOVING W 10-15 KT. SATELLITE IMAGERY DEPICTS INVERTED-V SIGNATURE IN CLOUD COVERAGE...ALONG WITH COUNTERCLOCKWISE MOTION OF CLOUD ELEMENTS IN THE VICINITY OF THE WAVE AXIS. CIMSS WAVETRAK PRODUCT CONFIRMS PRESENCE OF LOW LEVEL COUNTERCLOCKWISE CIRCULATION NEAR WAVE AXIS. THIS WAVE ALSO COINCIDES WITH A BROAD WESTWARD-MOVING DEEP LAYER MOISTURE SURGE BASED ON TOTAL PRECIPITABLE WATER PRODUCT FROM CIMSS. SCATTERED MODERATE CONVECTION IS FROM 14N-24N BETWEEN 36W-43W...WHICH IS BEING DRAWN NORTHWESTWARD ON THE NE PERIPHERY OF AN UPPER LOW CENTERED NEAR 20N49W. ALSO...SCATTERED MODERATE CONVECTION IS FROM 10N-14N BETWEEN 44W-52W. TROPICAL WAVE IS ALONG 66W S OF 14N MOVING W 10-15 KT. WAVE IS NOT PARTICULARLY WELL-DEFINED BASED ON SATELLITE IMAGERY... THOUGH WEAK COUNTERCLOCKWISE CURVATURE IS DEPICTED IN SURFACE WIND OBSERVATIONS NEAR WAVE AXIS. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 180 NM W OF WAVE AXIS N OF 10N...WHICH IS BEING ENHANCED BY LOW LEVEL CONVERGENCE NEAR THE ITCZ. ALSO...SCATTERED MODERATE CONVECTION IS FROM 5N-9N BETWEEN 63W-66W. ...THE ITCZ... ITCZ AXIS IS CENTERED ALONG 12N16W 7N29W 8N42W 10N50W 10N62W. CLUSTERS OF SCATTERED MODERATE/ISOLATED STRONG CONVECTION ARE NOW W OF THE W AFRICAN COAST FROM 7N-13N BETWEEN 16W-22W. ALSO...ISOLATED MODERATE CONVECTION IS FROM 2N-7N BETWEEN 22W-29W. ...DISCUSSION... GULF OF MEXICO... AN UPPER TROUGH AXIS EXTENDS FROM THE CENTRAL FLORIDA PENINSULA TO THE BAY OF CAMPECHE...WHICH IS SUPPORTING A COLD FRONT THAT EXTENDS FROM NW CUBA NEAR 23N80W TO 22N85W TO THE YUCATAN PENINSULA NEAR 21N88W. A STATIONARY FRONT THEN EXTENDS FROM 21N88W TO THE SE BAY OF CAMPECHE NEAR 19N91W. THE PORTION OF THIS COLD FRONT THAT WAS PREVIOUSLY STATIONARY IS SHOWING SIGNS OF SOUTHWARD PROGRESSION AS EVIDENT IN PROGRESSION OF THE LOW LEVEL THERMAL/MOISTURE GRADIENT AND CORRESPONDING CLOUD BANDS. WEAK ATMOSPHERIC LIFT IN RELATIVELY MOIST SOUTHWESTERLY FLOW ALOFT IS SUPPORTING ISOLATED SHOWERS WITHIN 60 NM EITHER SIDE OF THE COLD FRONT AND STATIONARY FRONT...IMPACTING PORTIONS OF THE SE GULF. FARTHER TO THE NW...AN UPPER RIDGE AXIS STRETCHES FROM S TEXAS TO THE S APPALACHIANS. SUBSIDENCE AND DRY AIR IN NW FLOW ALOFT BETWEEN THIS UPPER RIDGE AND THE AFOREMENTIONED UPPER TROUGH ARE RESULTING IN FAIR WEATHER ACROSS MUCH OF THE NW AND CENTRAL GULF...ESPECIALLY AS A SURFACE RIDGE EXTENDS INTO THE N GULF FROM THE SE CONUS. ADDITIONALLY...WITH A SURFACE RIDGE PRESENT OVER MEXICO...AND A 1011 MB SURFACE LOW OFF THE COAST OF W MEXICO NEAR 12N94W...STRONG WINDS CONTINUE TO BLOW THROUGH THE ISTHMUS OF TEHUANTEPEC RESULTING IN GALE FORCE WINDS IN THE NEARBY E PACIFIC REGION. CARIBBEAN SEA... MOIST SW FLOW ALOFT E OF THE UPPER TROUGH AXIS IN THE GULF OF MEXICO CONTINUES TO MOVE OVER THE NW CARIBBEAN...WHERE UPPER LEVEL DIVERGENCE CONTINUES TO SUPPORT CONVECTION. THIS CONVECTION IS BEING ENHANCED BY BROAD SURFACE CONVERGENCE AROUND A 1011 MB SURFACE LOW NEAR 17N87W. PLEASE SEE THE SPECIAL FEATURES SECTION ABOVE FOR MORE INFORMATION ON THIS SYSTEM. FARTHER TO THE E...SCATTERED MODERATE CONVECTION IS FROM 12N-20N BETWEEN 75W-80W...AFFECTING PORTIONS OF JAMAICA. THIS CONVECTION IS BEING ENHANCED BY UPPER LEVEL DIFFLUENCE NEAR AND N OF AN UPPER RIDGE. THIS RIDGE EXTENDS FROM AN UPPER HIGH NEAR 16N70W TO THE NW CARIBBEAN NEAR 16N82W. FARTHER TO THE E...CONVECTIVE COVERAGE IS LIMITED AS A RESULT OF SUBSIDENCE AND DRY AIR NEAR THE UPPER HIGH. HOWEVER...ISOLATED MODERATE CONVECTION IS OCCURRING ACROSS THE SE CARIBBEAN IN THE VICINITY OF THE TROPICAL WAVE ALONG 66W. ATLANTIC OCEAN... AN UPPER TROUGH IS OVER THE W ATLC...AND IS SUPPORTING A SURFACE COLD FRONT THAT EXTENDS FROM 32N65W TO 26N70W TO NW CUBA NEAR 23N80W. THE PORTION OF THE COLD FRONT THAT WAS PREVIOUSLY STATIONARY IS SHOWING SIGNS OF SOUTHEASTWARD PROGRESSION AS EVIDENT IN PROGRESSION OF THE LOW LEVEL THERMAL/MOISTURE GRADIENT AND CORRESPONDING CLOUD BANDS. ATMOSPHERIC LIFT IN MOIST SOUTHWESTERLY FLOW ALOFT IS SUPPORTING ISOLATED SHOWERS WITHIN 60 NM EITHER SIDE OF THE COLD FRONT...AS WELL AS SCATTERED MODERATE CONVECTION FROM 21N-24N BETWEEN 69W-74W. TO THE NW OF THE COLD FRONT...DEEP CONVECTION IS BEING SUPPRESSED BY SUBSIDENCE IN NW FLOW ALOFT UPSTREAM OF THE UPPER TROUGH AXIS. FARTHER TO THE E...A COMPACT UPPER LOW IS CENTERED NEAR 20N49W...AND AN UPPER HIGH IS CENTERED NEAR 22N37W. DEEP LAYER SOUTHEASTERLY FLOW BETWEEN THESE FEATURES IS DRAWING DEEP LAYER MOISTURE NORTHWESTWARD FROM THE TROPICAL WAVE ALONG 44W... RESULTING IN SCATTERED MODERATE CONVECTION FROM 14N-24N BETWEEN 36W-43W. FARTHER TO THE E...A 1025 MB SURFACE HIGH IS CENTERED NEAR 32N36W...AND A SURFACE RIDGE EXTENDS FROM THIS HIGH TO THE S NEAR 12N30W...WITH SUBSIDENCE AND STABLE CONDITIONS AROUND THE SURFACE HIGH AND SURFACE RIDGE PREDOMINATING OVER MUCH OF THE E ATLC. ALSO...AN UPPER TROUGH IS PRESENT OVER THE NE ATLC N OF 22N AND E OF 23W...WITH DEEP LAYER DRY AIR EMBEDDED WITHIN THE TROUGH PREVENTING DEEP CONVECTION NEAR THIS FEATURE. $$ COHEN