000 AXPZ20 KNHC 311014 TWDEP TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 1005 UTC SUN DEC 31 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0945 UTC. ...ITCZ... ITCZ AXIS IS CENTERED ALONG 4N78W 6N84W 7N107W 7N120W 8N130W 6N140W. SCATTERED STRONG CONVECTION EXISTS FROM 7N-9N W OF 138W...AND IS ALSO SOUTH OF THE AXIS WITHIN 30 NM OF 3N79W. SCATTERED MODERATE CONVECTION IS WITHIN 120 NM S OF THE AXIS BETWEEN 120W-122.5W. ...DISCUSSION... EAST OF 110W... THE AREA CONTINUES TO BE DOMINATED BY BROAD MID TO UPPER LEVEL TROUGHING MAINLY NORTH OF 15N. THIS TROUGH EXTENDS SOUTHWESTWARD INTO THE AREA FROM A DEEP LAYERED LARGE CYCLONIC CIRCULATION CENTERED OVER THE LOWER GREAT PLAINS...AND HAS A MEAN AXIS RUNNING FROM WESTERN TEXAS THROUGH 27N107W TO 20N108.5W AND SOUTH/SOUTHEAST TO 15N107W. A MID-LEVEL VORTICITY MAXIMUM EMBEDDED WITHIN THE CYCLONIC FLOW AROUND THE TROUGH IS SWINGING SOUTH-SOUTHEAST OVER THE SOUTHERN PORTION OF THE GULF OF CALIFORNIA. A JET STREAM BRANCH ROUNDS THE BASE OF THE TROUGH FROM 15N110W NORTHEASTWARD THROUGH 16N105W TO INLAND THE MEXICAN COAST AT 17N99W. SATELLITE WATER VAPOR IMAGERY SHOWS AMPLE STRONG SUBSIDENCE AND ASSOCIATED DRY AIR COVERING JUST ABOUT THIS ENTIRE AREA EXCEPT WITHIN 270 NM SOUTHEAST OF THE JET STREAM WHERE UPPER LEVEL MOISTURE IN THE FORM OF MOSTLY CIRRUS CLOUDINESS ARE STREAMING EAST-NORTHEAST TOWARDS SOUTHEASTERN MEXICO. WEAK MID/UPPER LEVEL RIDGING WILL FOLLOW IN BEHIND THE TROUGH THROUGH MONDAY BEFORE A SHORTWAVE TROUGH BEGINS TO DROP SOUTHEASTWARD THROUGH THE NORTHEAST LATE MON INTO TUE THEN NUDGE FURTHER SOUTHEAST DURING THE MIDDLE TO LATTER PART OF THE UPCOMING WEEK. AT THE SURFACE...A WEAK TROUGH MOVING WEST ABOUT 10-15 KT IS ALONG 108W FROM 5N-10N. ONLY ISOLATED THUNDERSTORMS ARE NOTED IN ASSOCIATION WITH THE TROUGH WITHIN 30 NM OF 8N108W. HIGH PRESSURE COVERS THE AREA NORTH OF 17N. NW FLOW HAS INCREASED SOME OVER THE GULF OF CALIFORNIA S OF 26N AND FROM 18N-22N E OF 110W...AND IS FORECAST TO EXPAND ACROSS THE GULF OF CALIFORNIA THROUGH THE NEXT 48 HOURS AS THE SHORTWAVE TROUGH MOVES OVER THE AREA. A COLD FRONT PRESENTLY ACROSS THE CENTRAL AND WESTERN GULF OF MEXICO WILL BE FOLLOWED BY HIGH PRESSURE BUILDING SOUTHWARD INTO SOUTHEASTERN MEXICO BEGINNING LATER THIS MORNING. GFS WIND FIELDS ARE IMPLYING THAT NLY WINDS WILL INCREASE OVER THE GULF OF TEHUANTEPEC THROUGH LATE TONIGHT AND SHOULD CONTINUE THROUGH WED AFTERNOON. THESE WINDS ARE FORECAST TO REMAIN AT JUST BELOW GALE FORCE WITH MAXIMUM PEAK WINDS REACHING 30 KT LATE MON NIGHT AND LAST THROUGH WED MORNING BEFORE DIMINISHING SOME. WEST OF 110W... BROAD MID AND UPPER RIDGING COVERS THIS PORTION OF THE REGION WITH A MID/UPPER LEVEL ANTICYCLONIC CIRCULATION LOCATED OVER THE ITCZ NEAR 7N121W. SURFACE HIGH PRESSURE IS PRESENT NORTH OF 16N ASSOCIATED WITH A HIGH CENTER OF 1027 MB ANALYZED NEAR 32N135W. SHARP MID/UPPER LEVEL TROUGH IS WEST OF THE REGION ALONG 146W. NWP MODELS SUGGEST THAT THIS TROUGH WILL ENTER THE NORTHWEST PART LATER THIS MORNING. ON MON AND TUE...THE TROUGH SPLITS WITH THE SOUTHERN TIER BECOMING A CUT-OFF UPPER LEVEL LOW WEST OF THE REGION NEAR 15N144W...WHILE THE REMAINDER OF THE TROUGH BEGINS TO TRANSLATE MORE INTO A SHEAR AXIS NORTHEAST TO SOUTHWEST ACROSS THE AREA INTO WED OF NEXT WEEK. THE CUT-OFF LOW BEGINS TO LIFT NORTHEASTWARD TOWARDS THE END OF THE WEEK AS IT GETS A BOOST FROM A LARGE MID/UPPER LEVEL TROUGH TO THE NORTHWEST OF THE REGION. NWP MODELS FORECAST THE SHEAR AXIS BEING REPLACED BY HIGH PRESSURE ALSO TOWARDS THE END OF THE UPCOMING WEEK. EXPECT MODERATE NORTHEAST TRADES CURRENTLY FOUND FROM 7N-25N TO WEAKEN BEGINNING TUE NIGHT AND INTO WED AS THE SURFACE HIGH PRESSURE WEAKENS IN RESPONSE TO AN APPROACHING WEAK FRONT ASSOCIATED WITH THE TROUGH STATED ABOVE. MAIN PROBLEM...HOWEVER...WILL BE LARGE PREDOMINATELY NW SWELLS THAT WILL PLAGUE THE NORTHWEST SECTOR BEGINNING ON WED AND CONTINUE INTO FRI BY WHICH TIME STRONG NORTHEAST WINDS WILL ALSO HAVE OVERTAKEN MUCH OF THE AREA IN RESPONSE TO A FORECAST HIGH OF 1045 MB NORTH OF THE REGION AS SUGGESTED BY THE LATEST GFS MODEL RUN AND OF 1041 MB AS SEEN IN THE EUROPEAN HIGH RESOLUTION BOUNDARY LAYER WIND FIELD FOR FRI. $$ AGUIRRE