000 AXNT20 KNHC 210559 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 AM EDT TUE OCT 21 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0515 UTC. ...TROPICAL WAVES... A TROPICAL WAVE IS ALONG 20W/21W S OF 14N MOVING W 10-15 KT. SATELLITE IMAGERY AND COMPUTER MODEL GUIDANCE DEPICT LOW LEVEL COUNTERCLOCKWISE CIRCULATION PRESENT ALONG WAVE AXIS. WESTWARD SURGE OF DEEP LAYER MOISTURE ALSO COINCIDES WITH WAVE AXIS BASED ON TOTAL PRECIPITABLE WATER PRODUCT FROM CIMSS. SCATTERED MODERATE CONVECTION IS WITHIN 210 NM E OF WAVE AXIS N OF 12N. A TROPICAL WAVE IS ALONG 46W S OF 20N MOVING W NEAR 10 KT. SATELLITE IMAGERY DEPICTS WELL-DEFINED INVERTED-V SIGNATURE IN CLOUD COVERAGE ALONG WAVE AXIS. DEEP LAYER MOISTURE IN THE VICINITY OF THE WAVE AXIS CONTINUES TO BE DRAWN NORTHWARD AROUND AN UPPER LOW CENTERED NW OF THE WAVE NEAR 22N51W. THIS IS RESULTING IN THE NORTH-TO-SOUTH ELONGATION OF THE DEEP LAYER MOISTURE FIELD AROUND THE WAVE AXIS. ISOLATED MODERATE CONVECTION IS FROM 9N-26N BETWEEN 35W-46W...AND SCATTERED MODERATE CONVECTION IS FROM 11N-14N BETWEEN 49W-58W. A LOW AMPLITUDE TROPICAL WAVE IS IN THE CENTRAL CARIBBEAN ALONG 72W S OF 16N MOVING W 10-15 KT. CIMSS WAVETRAK PRODUCT INDICATES LOW LEVEL COUNTERCLOCKWISE CIRCULATION MAXIMIZED ALONG WAVE AXIS. HOWEVER...DEEP LAYER DRY AIR AND SUBSIDENCE AROUND AN UPPER HIGH IN THE E CARIBBEAN NEAR 16N71W ARE LIMITING DEEP CONVECTION NEAR WAVE...WITH ISOLATED SHOWERS WITHIN 60 NM EITHER SIDE OF WAVE AXIS S OF 13N. ...THE ITCZ... ITCZ AXIS IS CENTERED ALONG 8N12W 8N23W 6N33W 10N49W 9N61W. IN ADDITION TO CONVECTION ASSOCIATED WITH TROPICAL WAVES... SCATTERED MODERATE CONVECTION IS FROM 4N-8N BETWEEN 13W-17W. ISOLATED MODERATE CONVECTION IS WITHIN 150 NM EITHER SIDE OF AXIS BETWEEN 24W-34W. ...DISCUSSION... GULF OF MEXICO... MUCH OF THE ENERGY WITH THE UPPER TROUGH PREVIOUSLY OVER THE GULF IS NOW OVER THE W ATLC...WITH A SECONDARY UPPER TROUGH TRAILING SOUTHWESTWARD FROM THE W ATLC ACROSS THE SE GULF INTO THE BAY OF CAMPECHE. TO THE NW OF THESE UPPER TROUGHS...A BROAD UPPER RIDGE IS PRESENT OVER THE SE CONUS. STABLE ATMOSPHERIC CONDITIONS AND WIDESPREAD SUBSIDENCE ARE RESULTING IN FAIR WEATHER CONDITIONS OVER MUCH OF THE GULF REGION...ESPECIALLY WITH A SURFACE RIDGE COVERING MUCH OF THE CENTRAL AND W GULF. INCREASED CLOUDINESS CAN BE FOUND OVER THE SE GULF...WHERE GREATER DEEP MOISTURE PERSISTS IN THE VICINITY OF A SURFACE COLD FRONT DRAPED ACROSS THE NW CARIBBEAN AND W ATLC. CARIBBEAN SEA... A 1010 MB SURFACE LOW REMAINS IS OVER THE GULF OF HONDURAS NEAR 16N87W. BROAD LOW LEVEL CONVERGENCE AROUND THIS LOW...COMBINED WITH UPPER LEVEL DIVERGENCE TO THE SE OF AN UPPER LEVEL WIND SPEED MAXIMUM IN MOIST SOUTHWESTERLY FLOW ALOFT...IS SUPPORTING SCATTERED MODERATE/ISOLATED STRONG CONVECTION FROM 15N-19N BETWEEN 83W-88W...INCLUDING PORTIONS OF THE NW CARIBBEAN SEA AND ADJACENT INLAND AREAS OF SE MEXICO AND CENTRAL AMERICA. SIGNIFICANT DEVELOPMENT OF THIS SYSTEM IS NOT EXPECTED DUE TO ITS PROXIMITY TO LAND. HOWEVER...LOCALLY HEAVY RAINS ARE POSSIBLE OVER PORTIONS OF HONDURAS...GUATEMALA...BELIZE...AND THE YUCATAN PENINSULA DURING THE NEXT COUPLE OF DAYS. FARTHER TO THE NE...A WEAKENING COLD FRONT EXTENDS FROM E CUBA NEAR 21N77W TO 21N83W TO THE N YUCATAN PENINSULA NEAR 21N87W. ATMOSPHERIC LIFT IN MOIST SOUTHWESTERLY FLOW ALOFT NEAR THIS FRONT IS SUPPORTING SCATTERED MODERATE CONVECTION WITHIN 60 NM EITHER SIDE OF THE FRONT BETWEEN 76W-82W. FARTHER TO THE E...CONVECTIVE COVERAGE IS LIMITED AS A RESULT OF SUBSIDENCE AND DRY AIR AROUND AN UPPER HIGH NEAR 16N71W. HOWEVER...ISOLATED MODERATE CONVECTION IS OCCURRING ACROSS THE SE CARIBBEAN IN THE VICINITY OF THE TROPICAL WAVE ALONG 72W. ALSO...SCATTERED MODERATE/ISOLATED STRONG CONVECTION OVER N VENEZUELA IS IMPACTING THE NEARBY S CARIBBEAN WATERS. THIS CONVECTION IS BEING ENHANCED BY GREATER INSTABILITY OVER HIGHER TERRAIN. ATLANTIC OCEAN... A DEEP LAYER TROUGH IS OVER THE W ATLC...AND IS SUPPORTING A SURFACE COLD FRONT THAT EXTENDS FROM 32N60W TO 25N67W TO E CUBA NEAR 21N77W. ATMOSPHERIC LIFT IN MOIST SOUTHWESTERLY FLOW ALOFT IS SUPPORTING ISOLATED SHOWERS WITHIN 120 NM EITHER SIDE OF THE COLD FRONT. TO THE NW...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 22N51W...AND AN UPPER RIDGE AXIS EXTENDS FROM 32N43W TO 13N39W. DEEP LAYER SOUTHERLY FLOW BETWEEN THESE FEATURES IS DRAWING DEEP LAYER MOISTURE NORTHWARD FROM THE TROPICAL WAVE ALONG 46W... RESULTING IN ISOLATED MODERATE CONVECTION FROM 9N-26N BETWEEN 35W-46W...AND SCATTERED MODERATE CONVECTION FROM 11N-14N BETWEEN 49W-58W. FARTHER TO THE E...A 1026 MB SURFACE HIGH IS CENTERED NEAR 33N38W...AND A SURFACE RIDGE EXTENDS FROM THIS HIGH TO THE S NEAR 16N31W...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 19N AND E OF 23W...WITH DEEP LAYER DRY AIR EMBEDDED WITHIN THE TROUGH PREVENTING DEEP CONVECTION NEAR THIS FEATURE. $$ COHEN