000 AXPZ20 KNHC 200405 TWDEP TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 0405 UTC WED DEC 20 2006 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0345 UTC. ...ITCZ... THE ITCZ AXIS IS CENTERED ALONG 4N78W 6N95W 9N106W 7N120W 7N130W 6N140W. SCATTERED STRONG CONVECTION IS WITHIN 60 NM SOUTH OF THE AXIS BETWEEN 79W-80W. SCATTERED MODERATE CONVECTION IS WITHIN 90 NM EITHER SIDE OF THE AXIS BETWEEN 121.5W-126W. ...DISCUSSION... N OF 20N... A VERY PRONOUNCED FAST-MOVING SHORTWAVE TROUGH COVERS THE AREA EAST OF 116W WITH ITS AXIS EXTENDING FROM A LARGE MID TO UPPER LEVEL CYCLONIC CIRCULATION OVER THE SOUTHWEST UNITED STATES SOUTHWARD INTO NORTHERN MEXICO...AND CONTINUES SOUTH TO 23N105W. DIFFLUENT FLOW PATTERN EXISTS TO THE SOUTHEAST OF THE TROUGH TO OVER INLAND MEXICO. UPPER LEVEL DEBRIS MOISTURE IN THE FORM OF MOSTLY BROKEN MID AND HIGH LEVEL CLOUDINESS FROM THE DEEP TROPICS CONTINUES TO BE CHANNELED NORTHEASTWARD TOWARDS CENTRAL MEXICO AHEAD OF THE TROUGH. MOST RECENT SATELLITE WATER VAPOR IMAGERY SHOWS MODERATE TO STRONG SUBSIDENCE AND DRY AIR OVER THE AREA EAST OF 121W TO BAJA CALIFORNIA AND MEXICO. WEAK MID/UPPER LEVEL RIDGING WEST OF THE TROUGH IS ALONG 123W AND STRETCHES NORTH OF THE REGION TO A CREST NOW OVER CALIFORNIA. THIS RIDGE WILL FLATTEN OUT IN ADVANCE OF ANOTHER STRONG AND FAST MOVING SHORTWAVE TROUGH WHICH HAS ALREADY ENTERED THE NORTHWEST PORTION OF THE REGION FROM ABOUT 32N127W SOUTHWESTWARD THROUGH 26N133W TO 22N140W AND CONTINUES WELL SOUTHWEST OF THE REGION TO SOUTH OF THE HAWAIIAN ISLAND CHAIN NEAR 17N158W. THIS TROUGH IS FORECAST TO REACH CENTRAL AND SOUTHERN CALIFORNIA WED INTO THU. TO THE EAST OF THIS RIDGE...MID/UPPER LEVEL TROUGHING EAST OF THE AREA EXTENDS SOUTHWESTWARD FROM THE WESTERN CARIBBEAN TO WELL SOUTH OF 20N. S OF 20N... THE TROPICS CONTINUES TO BE DOMINATED BY MID TO UPPER LEVEL RIDGING ALONG 9N WEST OF 100W WITH A SMALL UPPER LEVEL ANTICYCLONIC CIRCULATION EVIDENT NEAR 9N117W. CONVECTION ALONG THE ITCZ IS ENHANCE UNDER THIS RIDGE MAINLY WEST OF 123W. BROAD ANTICYCLONIC FLOW COVERS JUST ABOUT THE ENTIRE AREA...EXCEPT FOR THE FAR EASTERN PORTION WHERE THE TROUGH MENTIONED ABOVE DIGS WELL SOUTHWARD INTO THE TROPICS FROM CENTRAL AMERICA TO NEAR 2N98W. A SMALL UPPER LEVEL ANTICYCLONIC CENTER MOVING WESTWARD AT 10 KT IS NEAR 2N91W. MOSTLY STRONG SUBSIDENCE AND ASSOCIATED DRY AIR COVERS THE EASTERN PART EAST OF 102W. ONLY SCATTERED TO LOCALLY BROKEN LOW CLOUDS WITH ISOLATED SHOWERS AND THUNDERSTORMS MOVING WESTWARD ABOUT 10-15 KT ARE NOTED SOUTH OF 8N NEAR THE ITCZ EAST OF 100W. LOW LEVELS FOR THE ENTIRE DISCUSSION REGION...HIGH PRESSURE OF 1026 MB IS ANALYZED NEAR 31N127W WITH A RIDGE EXTENDING SOUTHEASTWARD THROUGH 26N118W TO 22N112W. HIGH PRESSURE COVERS THE AREA NORTH OF 15N WEST OF 110W. THE TAIL END OF A SURFACE COLD FRONT ASSOCIATED WITH THE MID/UPPER LEVEL TOUCHES THE EXTREME NORTHWEST CORNER OF THE AREA AT 32N140W. FROM THERE IT CONTINUES SOUTHWESTWARD AS A DYING FRONT TO NEAR 27N151W. NWP MODELS TEND TO KEEP THIS FRONT JUST NORTH OF THE AREA THROUGH THU WHILE WEAKENING IT AS A STATIONARY FRONT. YET ANOTHER COLD FRONT IS FORECAST BY THE MODELS TO ENTER THE NORTHWEST PART THU AND FRI...WITH INDICATIONS RIGHT NOW THAT IT WILL ALSO WEAKEN JUST NORTH OF THE REGION LIKE THE FIRST FRONT. SCATTERED TO BROKEN COLD AIR STRATOCUMULUS CLOUDS WITH POSSIBLE ISOLATED SHOWERS ARE NOTED NORTH OF 20N AND WEST OF 119W. CLOUDS EAST OF 133W ARE MOVING SOUTH-SOUTHWEST AND THOSE WEST OF 133W ARE MOVING GENERALLY WESTWARD EXCEPT NORTHWEST NORTH OF 27N WEST OF 137W IN RESPONSE TO SOUTH-EASTERLY FLOW AHEAD OF THE APPROACHING COLD FRONT. GAP WINDS...N-NE WINDS TO 20 KT PRESENTLY IN GULF OF TEHUANTEPEC EXPECTED TO LAST FOR ABOUT 24 HOURS. NE WINDS TO 20 KT IN THE GULF OF PAPAGAYO ARE EXPECTED TO CONTINUE THROUGH THE NEXT 24 HOURS THEN DIMINISH IN 48 HOURS. NW WINDS TO 20 KT ACROSS THE SEA OF CORTEZ ARE EXPECTED TO INCREASE TO 20-25 KT IN 24 HOURS SOUTH OF 25N AND TO S OF 27N IN 48 HOURS. $$ AGUIRRE