000 AXPZ20 KNHC 130949 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 1005 UTC WED MAR 12 2013 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0945 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS SW FROM THE COAST OF COSTA RICA AT 09N85W TO 01N90W THEN W TO 01N93W. SCATTEROMETER WINDS INDICATE AN ITCZ FORMS AT 03N113W AND EXTENDS WESTWARD TO BEYOND 04N140W. SCATTERED MODERATE CONVECTION IS OBSERVED WITHIN 120 NM OF 05N100W. BROKEN TO LOCALLY OVERCAST LOW AND MID LEVELS CLOUDS...WITH EMBEDDED ISOLATED MODERATE CONVECTION...ARE OBSERVED ELSEWHERE WITHIN 150 NM EITHER SIDE OF A LINE FROM 09N83W TO 03N92W TO 05N100W TO 01N108W. ...DISCUSSION... GULF OF TEHUANTEPEC...HIGH PRESSURE IN THE WAKE OF A COLD FRONT OVER THE EASTERN BAY OF CAMPECHE IS CURRENTLY SURGING THROUGH THE CHIVELA PASS INTO THE GULF OF TEHUANTEPEC AT MINIMAL GALE FORCE...WITH SEAS TO 12 FT. A REINFORCING NORTHERLY SURGE OVER THE GULF OF MEXICO WILL INCREASE THE GULF OF TEHUANTEPEC DRAINAGE FLOW TO 45 KT BY MIDNIGHT TONIGHT...AND FURTHER INCREASE TO MINIMAL STORM FORCE DURING MAXIMUM DRAINAGE JUST BEFORE SUNRISE ON THU. THE STORM CONDITIONS ARE EXPECTED TO PERSIST THROUGH MID MORNING THU WITH LATEST GUIDANCE SUGGESTING THE GRADIENT WILL QUICKLY RELAX THU NIGHT AND FRI WITH THE LAST SURGE... AND TO ONLY MINIMAL GALE FORCE...OCCURRING AT SUNRISE FRI...WHICH IS A FULL 24 HOURS EARLIER THAN GUIDANCE SUGGESTED YESTERDAY. GULFS OF PAPAGAYO AND FONSECA...NE WINDS CURRENTLY AT 15 TO 20 KT IN AND JUST DOWNSTREAM OF THE GULF OF PAPAGAYO WILL INCREASE TO 20 TO 25 KT BY SUNRISE THIS MORNING...AND SPREAD WSW TO NEAR 08N91W ON THU WITH SEAS THEN BUILDING TO 9 FT. THE GRADIENT WILL ALSO INCREASE FURTHER N REACHING THE GULF OF FONSECA AREA LATE THU. GUIDANCE SUGGESTS THE GRADIENT WILL RELAX SUPPORTING ONLY 15 KT IN THE GULF OF FONSECA ON FRI NIGHT. THE SAME GUIDANCE SUGGESTS NE WINDS WILL INCREASE TO 20 TO 30 KT IN THE GULF OF PAPAGAYO FRI NIGHT...WITH THIS EVENT PERSISITING THROUGH AT LEAST SUN NIGHT. GULF OF PANAMA...NORTHERLY WINDS AT 10 TO 15 KT WITH OCCASIONAL PULSES TO 15 TO 20 KT EXPECTED THROUGH THE WEEKEND. GULF OF CALIFORNIA...THE GRADIENT BETWEEN A PACIFIC RIDGE AND A TROUGH OVER MEANDERING ALONG THE SIERRA MADRE OCCIDENTAL OVER INTERIOR OLD MEXICO WILL SUPPORT NW WINDS AT 10 TO 15 KT ACROSS THE GULF OF CALIFORNIA THROUGH THU NIGHT. THE GRADIENT WILL RELAX ON FRI WITH LIGHT AND VARIABLE WINDS EXPECTED THROUGH MON. A REINFORCING SHORTWAVE TROUGH IS MOVING INTO AN ANCHORED LONGWAVE TROUGH OVER CENTRAL N AMERICA. THE UPPER TROUGH HAS ITS MEAN AXIS EXTENDING SW ACROSS NORTHERN OLD MEXICO AND THE SOUTHERN GULF OF CALIFORNIA...THROUGH 20N117W TO A BASE OVER THE DEEP TROPICAL PACIFIC AT 08N127W. AN UPPER RIDGE IS AMPLIFYING NNE ACROSS THE WESTERN PORTION OF THE DISCUSSION AREA...WITH THE RIDGE CREST NOW EXTENDING ACROSS THE W COAST OF THE NW CONUS. SOME UPPER MOISTURE CONTINUES TO SPILL E ACROSS THE RIDGE AXIS TO THE N OF 24N BETWEEN 130W AND 140W. OTHERWISE...VERY DRY UPPER AIR IS INDICATED W OF A LINE FROM 30N97W TO 08N130W. AN UPPER RIDGE EXTENDS NW ACROSS CENTRAL AMERICA FROM COLOMBIA TO A GENTLE CREST ALONG POINTS 15N112W...24N108W AND 30N95W. DEBRIS MOISTURE FROM THE SPORADIC MONSOON TROF AND ITCZ CONVECTION IS ADVECTED N BETWEEN 98W AND 110W TO ALONG 20N...THEN TURNS NE ALONG THE PERIPHERY OF THE UPPER RIDGE CONCENTRATING INTO A 480M NM WIDE TROPICAL PLUME THAT CROSSES CENTRAL OLD MEXICO...DISSECTS THE GULF OF MEXICO...CONTINUING ACROSS FLORIDA ALL AHEAD OF A VIGOROUS SHORTWAVE TROUGH. A SURFACE RIDGE EXTENDS FROM 32N132W TO 15N105W. THE ANCHORED RIDGE WILL BLOCK THE FORWARD ADVANCE OF AN APPROACHING COLD FRONT TO ONLY 142W ON TODAY. THE GRADIENT SW OF THE RIDGE IS SUPPORTING NE TRADES AT 15 TO 20 KT ACROSS THE TROPICS FROM 03N TO 20N BETWEEN 125W AND 140W...WITH SEAS 7 TO 9 FT IN NE SWELL. THE GRADIENT IS EXPECTED TO FURTHER RELAX TONIGHT WITH SEAS SUBSIDING BELOW 8 FT ON THU. $$ NELSON