000 AXPZ20 KNHC 272149 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 2205 UTC SUN NOV 27 2011 TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM THE EQUATOR TO 32N...EAST OF 140W. THE FOLLOWING INFORMATION IS BASED ON SATELLITE IMAGERY...WEATHER OBSERVATIONS...RADAR...AND METEOROLOGICAL ANALYSIS. BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2145 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS SW FROM COSTA RICA AT 10N83W TO THE E PACIFIC AT 06N92W...THEN TURNS W-NW TO 09N116W WHERE LOW LEVEL WINDS INDICATE A TRANSITION TO AN ITCZ. THE ITCZ CONTINUES W THROUGH AN EMBEDDED 1009 MB SURFACE LOW PRESSURE AT 10N122W... THEN TURNS SW TO NEAR 08N132W...THEN W TO BEYOND 08N140W. ISOLATED MODERATE TO OCCASIONALLY STRONG CONVECTION...VERIFIED BY LIGHTNING DATA...IS FLARING ALONG THE MONSOON TROUGH NEAR 07N81W. SCATTERED MODERATE ISOLATED STRONG CONVECTION ASSOCIATED WITH THE ITCZ...IS NOTED WITHIN 30 NM OF EITHER SIDE OF A LINE FROM 08N114W TO 10N121W. ISOLATED MODERATE CONVECTION IS NOTED WITHIN 15 NM EITHER SIDE OF A LINE 05N128W TO 07N130W TO 08N133W. THE REMNANT TROUGH OF KENNETH IS ALONG 140W FROM 10N TO 16N... AND IS EXPECTED TO MOVE W OF 140W TONIGHT. A THUNDERSTORM CLUSTER RECENTLY FLARED WITHIN 15 NM OF 14.5N139W. LOW PRES AT 10N122W...NE TO E WINDS AT 20 TO 25 KT AND SEAS 8 TO 12 FT ARE NOTED WITHIN 300 NM NW SEMICIRCLE OF CENTER. THE LOW IS EXPECTED TO DRIFT W OVER THE NEXT 24 HOURS THEN OPEN INTO A NE TO SW ORIENTATED TROUGH FROM 13N120W TO 09N124W WITH THE PRESSURE GRADIENT SUPPORTING NE WINDS AT 15 TO 20 KT WITHIN 180 NM W OF THE TROUGH. ...DISCUSSION... A LONG WAVE UPPER TROUGH DISSECTS N AMERICA WITH ITS MEAN AXIS EXTENDING SW INTO THE DISCUSSION AREA OVER TEXAS AT 32N96W..SW ACROSS CENTRAL OLD MEXICO...THROUGH AN EMBEDDED UPPER CYCLONE OVER THE PACIFIC AT 20N111W...THEN CONTINUING S OVER THE PACIFIC TO A BASE AT 11N118W. THE ASSOCIATED SURFACE COLD FRONT DISSECTS THE GULF OF MEXICO WITH THE TAIL END DEPICTED BY A ROPE CLOUD MOVING THROUGH THE EASTERN BAY OF CAMPECHE. POST FRONTAL STRONG COLD AIR ADVECTION IS SURGING THROUGH THE ISTHMUS OF TEHUANTEPEC RESULTING IN THE STORM FORCE WINDS IN AND DOWNSTREAM OF THE GULF OF TEHUANTEPEC...FURTHER DISCUSSED BELOW. AN UPPER ANTICYCLONE IS QUASI STATIONARY OVER THE DEEP TROPICS AT 11N136W WITH A LONGWAVE RIDGE EXTENDING NE AND COLLAPSING EASTWARD ACROSS WESTERN N AMERICA. UPPER MOISTURE FROM ITCZ CONVECTION BETWEEN 139W AND 164W...AND FROM OTHER CONVECTION FURTHER W OVER THE CENTRAL TROPICAL PACIFIC...IS ALL ADVECTED NE ALONG THE NW PERIPHERY OF THIS LARGE RIDGE...SPILLING OVER THE RIDGE ACROSS CENTRAL N AMERICA INTO THE LONGWAVE TROUGH AXIS PREVIOUSLY MENTIONED. AS THE RIDGE COLLAPSES SE...A STRONG UPPER TROUGH...CURRENTLY ALONG 32N140W TO 23N147W...WILL CONTINUE E TO OVER THE NW PORTION OF CONUS WITH ITS SOUTHERN EXTENT JUST REACHING THE NW PORTION OF THE DISCUSSION AREA AND STALLING NEAR 32N140W. THE ASSOCIATED SURFACE FRONT IS ALREADY STALLING FROM 32N134W TO 26N141W...AND IS EXPECTED TO RETRACT W AS THE UPPER RIDGE AMPLIFIES N AGAIN CUTTING OFF AN UPPER CYCLONE NEAR 29N140W MON NIGHT INTO TUE. AN UPPER CYCLONE IS NOTED NEAR 04N113W. AN UPPER ANTICYCLONE IS NEAR 07N85W WITH A RIDGE EXTENDING SW TO A SHARP CREST JUST E OF THE CYCLONE...NEAR 05N108W. DEBRIS MOISTURE ASSOCIATED WITH THE ITCZ CONVECTION BETWEEN 114W AND 121W...FANS OUT BOTH N AND S OF THE ITCZ. SOME OF THE MOISTURE...IN THE FORM OF THIN BROKEN CIRRUS...CONTINUES NE TO OVER THE MEXICAN COAST AT 20N...BUT THEN SEEMS TO EVAPORATE. THE DEBRIS MOISTURE ASSOCIATED WITH THE MONSOON TROUGH CONVECTION JUST TO THE S OF PANAMA ALSO EVAPORATES AS THE UPPER LEVELS ARE VERY DRY S OF 22N E OF 130W. GULF OF CALIFORNIA...N TO NE WINDS AT 15 TO 20 KT WILL DIMINISH BELOW 20 KT ON MON. GULF OF TEHUANTEPEC...NORTHERLY WINDS AT STRONG GALE FORCE ARE REPORTED AT THE LAND STATIONS IN THE ISTHMUS OF TEHUANTEPEC AREA...AND OVER THE SW GULF OF MEXICO...AND ARE SURGING THROUGH THE CHIVELA PASS TO MINIMAL STORM FORCE. EXPECT STORM FORCE WINDS TO CONTINUE THROUGH MIDDAY TO MON...THEN DIMINISH TO STRONG GALE FORCE THROUGH TUE MORNING. BEST GUESS FOR NOW IS MINIMAL GALE CONDITIONS WILL CONTINUE THROUGH SUNRISE THU IN DRAINAGE FLOW...THEN QUICKLY DIMINISH AS LOW LEVEL WINDS FINALLY VEER TO THE SE IN THE BAY OF CAMPECHE. $$ NELSON