000 AXPZ20 KNHC 162204 TWDEP TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 2205 UTC WED DEC 16 2009 TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM THE EQUATOR TO 32N...EAST OF 140W. BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1500 UTC. ...ITCZ... THE INTERTROPICAL CONVERGENCE ZONE LIES ALONG 05N77W TO 07N91W TO 05N101W TO 07N108W TO 06N140W. SCATTERED MODERATE CONVECTION CAN BE FOUND WITHIN 75 NM N OF THE ITCZ AXIS E OF 81W AS WELL AS WITHIN 75 NM EITHER SIDE OF AXIS BETWEEN 105W AND 110W. ISOLATED MODERATE CONVECTION CAN BE FOUND WITHIN 150 NM N AND 75 NM S OF THE ITCZ AXIS BETWEEN 120W AND 130W. ...DISCUSSION... AN AMPLIFIED NORTHERN STREAM PATTERN IS IN PLACE WITH A SHARP UPPER TROUGH FOUND FROM THE TEXAS BIG BEND TO THE MEXICAN COAST NEAR 20N105W AND 08N110W. AN UPPER JET LIES ON THE LEADING EDGE OF THIS TROUGH AND IS TRANSPORTING MID TO UPPER LEVEL TROPICAL MOISTURE NORTHEASTWARD THROUGH THE CENTRAL MEXICAN COAST TO THE EASTERN RIO GRANDE VALLEY. NEAR THE TAIL OF THE JET...THE 1732 UTC ASCAT PASS PLACES A LOW PRES SYSTEM NEAR 07N110W ALONG A SURFACE TROUGH FROM 12N109W TO 04N110W. THE CENTRAL PRES OF THE LOW IS ESTIMATED AT 1008 MB. SCATTERED MODERATE CONVECTION CAN BE FOUND FOCUSED ALONG THE ITCZ WITHIN 480 NM E QUADRANT AND 150 NM S QUADRANT OF THE LOW. TOTAL PRECIPITABLE WATER SATELLITE IMAGERY SHOWS THE LOW TO MID LEVEL MOISTURE POOLED NEAR THIS LOW AS WELL E OF A SECOND SURFACE TROUGH EMBEDDED IN THE ITCZ 10N133W TO 03N133W. AS MENTIONED IN THE ITCZ SECTION...ISOLATED MODERATE CONVECTION CAN BE FOUND WITHIN 150 NM N AND 75 NM S OF THE ITCZ AXIS BETWEEN 120W AND 130W IN ASSOCIATION WITH THIS SECOND TROUGH. THIS TROUGH LIES UNDER A DIFFLUENT REGION ASSOCIATED WITH AN UPPER ANTICYCLONE NEAR 07N130W. HOWEVER...THE SOUTHERN STREAM JET LIES JUST TO THE NORTH OF THIS ANTICYCLONE...WITH STRONG WESTERLY FLOW FOUND JUST TO ITS NORTH. SHEAR DUE TO THIS JET IS INHIBITING DEEP CONVECTION...BUT THE UPPER LEVEL MOISTURE TRANSPORTED BY THE JET IS GENERATING CIRRUS PRIMARILY BETWEEN 10N AND 15N W OF 120W. THE AMPLIFIED LONGWAVE PATTERN ALOFT SHOULD BE SLOW TO CHANGE. THE MEAN UPPER TROUGH OVER MEXICO WILL RELOAD THU AS IT PHASES WITH NORTHERN STREAM SYSTEM CURRENTLY OVER THE NW U.S. AS WELL AS SOUTHERN STREAM ENERGY WHICH HAD SUPPORTED THE COLD FRONT THAT DISSIPATED OVER NW WATERS LAST NIGHT BUT GENERATED THE NW SWELL CURRENTLY OVER MUCH OF THE AREA. THE DEEP LAYER RIDGE AXIS WILL SHIFT SLIGHTLY TO THE W AS THE TROUGHS TO ITS E AND W RELOAD WITH ENERGY MOVING INTO THEIR WESTERN EDGES. THE PRES GRADIENT BETWEEN THE SURFACE RIDGE STEMMING FROM 1026 MB HIGH PRES NEAR 31N125W EXTENDING SW TO 24N140W AND THE WESTERN SURFACE TROUGH HAS INDUCED 20 TO 25 KT TRADE WINDS IN MUCH OF THE REGION BETWEEN 10N AND 15N W OF 120W AS SEEN IN THE 1732 UTC ASCAT PASS. THE SLIGHT WESTWARD MIGRATION OF THE DEEP LAYER RIDGE WILL SHIFT THE TRADES SLIGHTLY WESTWARD AND PREVENT THE NEXT FRONTAL SYSTEM ASSOCIATED WITH THE LONGWAVE TROUGH IN THE CENTRAL PACIFIC FROM PUSHING INTO NW WATERS. HOWEVER...SW WINDS ARE EXPECTED TO REACH 20 KT THERE BY FRI AHEAD OF THE FRONT. CLOSER TO LAND...THE 1748 UTC ASCAT PASS SHOWS WINDS IN THE 20 TO 25 KT RANGE CONTINUE IN THE GULF OF CALIFORNIA. AS HIGH PRES MOVES EASTWARD BEHIND THE COLD FRONT CURRENTLY OVER THE NORTHERN GULF OF MEXICO...EXPECT THE PRES GRADIENT TO DECREASE ACROSS THE GULF OF CALIFORNIA AND WINDS WILL STEP DOWN A NOTCH TO 20 KT IN THE NORTHERN GULF OF CALIFORNIA. GAP WINDS...GAP WINDS PERSIST THROUGH THE GULFS OF PAPAGAYO AND TEHUANTEPEC. THE COMBINATION OF STRONG TRADE WINDS IN THE CARIBBEAN AND LOCAL DRAINAGE EFFECTS WILL ALLOW THE FRESH WINDS TO PERSIST IN PAPAGAYO THROUGH TONIGHT AND DIMINISH THROUGH THU INTO FRI MORNING. WINDS WILL INCREASE TO GALE FORCE THROUGH THE GULF OF TEHUANTEPEC TONIGHT AS THE COLD FRONT PUSHES INTO THE SW GULF OF MEXICO. WINDS ARE EXPECTED TO DIMINISH BELOW GALE FORCE BY FRI EVENING. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ SCHAUER