000 AXPZ20 KNHC 180943 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 1005 UTC TUE SEP 18 2012 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. ...SPECIAL FEATURES... HURRICANE LANE IS CENTERED AT 19.3N 127.8W AT 0900 UTC MOVING NNW OR 330 DEG AT 8 KT. MAXIMUM SUSTAINED WINDS ARE 65 KT WITH GUSTS TO 80 KT AND A MINIMUM PRESSURE OF 989 MB. CURRENTLY SCATTERED MODERATE ISOLATED STRONG CONVECTION IS OBSERVED WITHIN 120 NM OVER THE N QUADRANT...AND ELSEWHERE WITHIN 60 NM OF CENTER. LANE IS BEGINNING TO ENCOUNTER SOUTHERLY WIND SHEAR AND WILL TRACK OVER INCREASINGLY COOLER OCEAN WATERS. LANE IS EXPECTED TO WEAKEN TO A TROPICAL STORM LATER TODAY AND FURTHER WEAKEN TO A TROPICAL DEPRESSION ON WED...AND BECOME A REMNANT LOW PRES CENTER ON WED NIGHT. SEE THE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMEP2/WTPZ22 KNHC FOR ADDITIONAL DETAILS. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... THE MONSOON TROUGH IS FRAGMENTED WITH THE EASTERNMOST BRANCH HAVING AN AXIS EXTENDING WESTWARD ACROSS THE SW CARIBBEAN ALONG 10N FROM THE NW COAST OF COLOMBIA TO ACROSS NORTHERN COSTA RICA...THEN THE TROUGH AXIS TURNS NW ALONG THE PACIFIC COAST OF NICARAGUA AND EL SALVADOR TO NEAR 14N91W WHERE IT LOSES IDENTITY. LOW LEVEL WINDS INDICATE THAT A SECOND BRANCH OF THE MONSOON TROUGH RESUMES OVER THE PACIFIC AT 15N97W AND EXTENDS SW TO 09N107W...THEN TURNS WESTWARD TO NEAR 10N120W WHERE IT LOSES IDENTITY IN THE BROAD LOW LEVEL CIRCULATION ASSOCIATED WITH TROPICAL CYCLONE LANE. A THIRD BRANCH OF THE MONSOON TROUGH RESUMES SW OF TROPICAL CYCLONE LANE AT 16N128W...AND EXTENDS SW TO 12N137W WHERE LOW LEVEL CROSS EQUATORIAL SE WINDS INDICATE A TRANSITION TO AN ITCZ WHICH CONTINUES SW TO BEYOND 11N140W. SCATTERED MODERATE CONVECTION IS DISSIPATING ALONG THE COLOMBIAN COAST NEAR 04.5N77.5W. SCATTERED MODERATE ISOLATED STRONG CONVECTION ACCOMPANIED BY FREQUENT LIGHTNING IS INDICATED OVER AND WITHIN 60 NM OFFSHORE THE COAST OF CENTRAL AMERICA FROM 83W TO 89W WITH THE HEAVIEST ACTIVITY ALONG THE SE COAST OF EL SALVADOR. SIMILAR CONVECTION IS NOTED OVER AND WITHIN 90 NM OFFSHORE THE PACIFIC COAST OF MEXICO FROM 93W TO 105W. SCATTERED MODERATE CONVECTION IS DISSIPATING WITHIN 30 NM OF 06N89W AND WITHIN 90 NM EITHER SIDE OF A LINE FROM 12N96W TO 08N106W. ISOLATED MODERATE CONVECTION IS NOTED FROM 09N TO 16N BETWEEN 115W AND 121W. ISOLATED CLUSTERS OF MODERATE CONVECTION IS OBSERVED ALONG 14N BETWEEN 128W AND 134W. ...DISCUSSION... AN UPPER ANTICYCLONE IS CENTERED AT 24N116W...AND RIDGES N BEYOND 32N117W TO A CREST OVER NORTHERN CALIFORNIA. TROPICAL CYCLONE LANE HAS MOVED INTO THE SOUTHERN PERIPHERY OF THIS UPPER ANTICYCLONE RESULTING IN TWO UPPER RIDGES NOW EXTENDING SW FROM THE ANTICYCLONE. ONE RIDGE ENDS IN A SHARP CREST JUST TO SE OF TROPICAL CYCLONE LANE AT 12N126W WHILE THE SECOND RIDGE EXTENDS SW TO A CREST NW OF LANE AT 22N131W. THE DEBRIS MOISTURE FROM LANE IS NOW ADVECTED ONLY NE REACHING NEAR 27N120W WHERE IT CURRENTLY EVAPORATES. AN AN UPPER TROUGH AXIS IS JUST NW OF THE DISCUSSION AREA FROM 33N140W TO 29N144W. A SOUTHWESTERLY 50 KT JET IS INDUCED E OF THE TROUGH ALONG THE W PERIPHERY OF THE UPPER RIDGE...ROUGHLY WITHIN 90 NM OF LINE FROM 24N139W TO 32N133W. THIS UPPER MOISTURE IS NOTED WITHIN 180 NM OF 13N120W AND OVER THE CONVECTION ALONG THE WESTERN SEGMENT OF THE MONSOON TROUGH AND ITCZ ALREADY DESCRIBED. OTHERWISE...THE UPPER LEVELS REMAIN FAIRLY DRY N OF 13N W OF 108W AND S OF 13N W OF 116W. AN UPPER SHORTWAVE TROUGH DISSECTS CENTRAL N AMERICA AND CONTINUES SW ACROSS THE WESTERN GULF OF MEXICO AND ACROSS CENTRAL MEXICO AT 20N...THEN WEAKENS AS IT CONTINUES SW ACROSS THE UPPER LEVELS OF THE DEEP TROPICAL PACIFIC ALONG 14N110W TO A BASE NEAR 03N120W. THIS TROUGH DEFINES THE BOUNDARY OF DRY AIR ALOFT OVER THE WESTERN PORTION OF THE DISCUSSION AREA FROM A MOIST UPPER ATMOSPHERE OVER THE TROPICS E OF 105W. AN UPPER ANTICYCLONE IS QUASI STATIONARY OVER CENTRAL AMERICA NEAR 16N92W WITH ITS ANTICYCLONIC ENVELOPE COVERING THE UPPER LEVELS N OF 05N BETWEEN 83W AND 104W. THE ASSOCIATED UPPER DIFFLUENCE IS ENHANCING CONVECTION ALONG THE TWO EASTERN BRANCHES OF THE PACIFIC MONSOON TROUGH AS PREVIOUSLY DESCRIBED. THE RESULTANT UPPER DEBRIS MOISTURE IS ROTATING CLOCKWISE AROUND THIS UPPER RIDGE...WITH SOME OF MOISTURE CONCENTRATING INTO A TROPICAL PLUME THAT CONTINUES NE ACROSS THE CENTRAL GULF OF MEXICO AND FANS OUT OVER THE SE CONUS. VERY DRY UPPER AIR INDICATED TO THE S OF 03N BETWEEN 85W AND 110W EXTENDING NORTHWARD ACROSS THE EQUATOR FROM THE NE SOUTH PACIFIC. ELSEWHERE AT THE LOW LEVELS THE REMNANTS OF TROPICAL CYCLONE KRISTY ARE NEAR 26N120W AND ESTIMATED AT 1011 MB...AND ARE EXPECTED TO WEAKEN INTO AN OPEN TROUGH LATE TONIGHT. GAP WINDS...BUILDING HIGH PRESSURE IN THE WAKE OF A COLD FRONT OVER THE CENTRAL GULF OF MEXICO WILL SURGE AT 20 TO 25 KT THROUGH THE ISTHMUS OF TEHUANTEPEC LATE TONIGHT...AND INTO THE GULF OF TEHUANTEPEC AROUND SUNRISE ON WED. THESE DRAINAGE WINDS WILL INCREASE TO 20 TO 30 KT LATE WED...AND THEN PULSE THROUGH THE END OF THE WEEK WITH THE STRONGEST WINDS OCCURRING LATE AT NIGHT TILL A FEW HOURS AFTER SUNRISE EACH DAY. $$ NELSON