000 AXPZ20 KNHC 191613 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 1605 UTC FRI MAR 18 2011 TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM THE EQUATOR TO 32N...EAST OF 140W. BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1545 UTC. ...ITCZ... THE INTERTROPICAL CONVERGENCE IS CENTERED ALONG 3N78W 3N90W TO EQUATOR AT 97W...THEN RESUMES NEAR 2N105W 3N116W 8N128W 4N140W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 60 NM N OF THE AXIS BETWEEN 134W-138W. SCATTERED MODERATE CONVECTION IS WITHIN 60 NM N OF THE AXIS BETWEEN 77W-79W. ...DISCUSSION... A LARGE UPPER LEVEL LOW OFF THE PACIFIC NW PORTION OF THE U.S. EXTENDS A BROAD UPPER THROUGH THE FORECAST DISCUSSION AREA NEAR 32N124W TO 24N130W TO W OF THE AREA AT 21N140W. A JET STREAM BRANCH ROUNDS THE BASE OF THE TROUGH WITH CORE WINDS OF 60-100 KT IN THE EXIT REGION OF THE JET. THESE WINDS ARE EJECTING UPPER LEVEL MOISTURE IN THE FORM OF SCATTERED TO BROKEN CIRRUS CLOUDS NORTHEASTWARD TO WELL INLAND THE INTERMOUNTAIN REGION OF THE U.S. TO THE SE OF THE TROUGH MODERATE TO STRONG SUBSIDENCE AS NOTED IN WATER VAPOR IMAGERY COVERS THE AREA FROM 12N TO 24N W OF 130W...AND ELSEWHERE SE OF THE TROUGH TO A LINE FROM 23N110W TO 12N130W. THIS IS MAINTAINING RATHER DRY AND STABLE CONDITIONS AT THE SURFACE WHERE BROKEN STRATOCUMULUS CLOUDS MOVING SW TO W ARE SEEN. A 150 NM WIDE PLUME OF UPPER LEVEL MOISTURE IS STREAMING ENE FROM AN UPPER LEVEL CYCLONE JUST E OF HAWAII EASTWARD INTO THE AREA AT 20N140W...AND EXTENDS NORTHEASTWARD TO 23N127W TO ACROSS CENTRAL BAJA CALIFORNIA BEFORE IT BECOMES DIFFUSE IN DRIER AIR OVER BAJA CALIFORNIA AND WESTERN MEXICO. A WEAK UPPER RIDGE AXIS EXTENDS FROM AN ANTICYCLONE LOCATED NEAR 14N105W TO 12N125W TO 9N140W. SPORADIC ITCZ CONVECTION DESCRIBED ABOVE CONTINUES UNDER THE RIDGE AXIS KEEPING RIDGE IN A RATHER PERMANENT STAGE. IN ADDITION...A SURFACE TROUGH MOVING W CLOSE TO 15 KT EXTENDS FROM 13N125W TO 5N131W. THIS TROUGH HAS A VERY GOOD TRACK HISTORY ON SATELLITE IMAGERY AS NOTED OVER THE PAST FEW DAYS...AND IS ENHANCING ITCZ CONVECTION SOME. THE BROAD UPPER TROUGH DOMINATING THE NORTHERN PORTION OF THE FORECAST AREA WILL BE RELOADED WITH NORTHERN STREAM ENERGY OVER THE NEXT FEW DAYS AS THE UPPER LOW WELL N OF THE AREA ENERGIZES THE TROUGH. AS A RESULT...THIS WILL ALLOW FOR THE ASSOCIATED SURFACE COLD FRONT TO QUICKLY SWEEP SE AS DEPICTED BY THE GLOBAL MODELS AND MOVE INTO THE THE NW PORTION BY EARLY SUN MORNING FROM 30N126W TO 28N140W WITH INCREASING SW-W WINDS AHEAD OF IT. THESE WINDS SHOULD BE IN THE RANGE OF 20-30 KT N OF 28N W OF 130W BY EARLY THIS EVENING...THEN INCREASE TO MINIMAL GALE FORCE BY EARLY SUN MORNING...WITH SEAS BUILDING UP TO 15 FT. WINDS BEHIND THE FRONT ARE FORECAST TO BE W-NW AT 20 TO 25 KT WITH SEAS TO 18 FT DUE TO A LARGE SET OF EXPECTED LONG PERIOD NW SWELLS. A 1028 MB HIGH CENTER ANALYZED WELL NW OF THE REGION NEAR 31N153W EXTENDS A RIDGE SE INTO THE FORECAST DISCUSSION AREA NEAR 28N140W ...AND TO 27N128W TO NEAR 22N111W. HIGH PRES GENERALLY COVERS THE AREA N OF 15N AND W OF 110W. FRESH TO STRONG TRADE WINDS LIE S OF THE RIDGE AXIS FROM 05N TO 21N W OF 130W. IN RESPONSE TO THE APPROACHING COLD FRONT...THE RIDGE WILL SHIFT SOUTHWARD TODAY AND WEAKEN CONSIDERABLY BY SUN. THIS ACTION WILL ALLOW FOR THE AREA OF TRADES TO SHIFT S AND DIMINISH A LITTLE THROUGH EARLY SUN...AT WHICH TIME THEY ARE FORECAST TO BE CONFINED FROM 7N-15N AND W OF 134W WITH SEAS 9-10 FT IN MIXED NE AND NW SWELL...AND FROM 6N-14N W OF 132W BY MON MORNING. BEFORE THE RIDGE BEGINS TO SHIFT SOUTHWARD...IT WILL CONTINUE TO MAINTAIN A TIGHT PRES GRADIENT IN THE FAR NE PORTION ALLOWING FOR NW WINDS OF 20 KT TO PERSIST N OF ABOUT 26N AND E OF 118W TO THE BAJA CALIFORNIA COAST...BUT THEN DIMINISH TO LESS THAN 20 KT IN 24 HOURS AS THE HIGH WEAKENS WHILE SHIFTING SOUTHWARD. A WEAK SURFACE TROUGH IS ALONG THE COAST OF COLOMBIA WITH SCATTERED MODERATE CONVECTION WITHIN 60 NM N OF THE ITCZ AXIS BETWEEN 77W-79W. THIS TROUGH IS EXPECTED TO MOVE LITTLE OVER THE NEXT 48 HOURS. GAP WINDS... GULF OF TEHUANTEPEC...N-NE WINDS OF 20-25 KT WITHIN 45 NM EITHER SIDE OF LINE FROM 16N95W TO 15N95W...INCLUDING THE GULF OF TEHUANTEPEC...WILL INCREASE TO 30 KT SUN MORNING AIDED BY THE DIURNAL MAXIMUM IN THE MORNING DRAINAGE FLOW THROUGH THE PASS. GULF OF PAPAGAYO...THE PRES GRADIENT WILL ALSO REMAIN STRONG THROUGH THE GULF OF PAPAGAYO...AND OVER THE AREA FROM 9N-11W AND W TO 89W WHERE LITTLE CHANGE IS EXPECTED IN THE STRONG NE TO E 20-25 KT WINDS FUNNELING FROM THE CARIBBEAN THROUGH CENTRAL AMERICA PASSES. GULF OF PANAMA...THE PRES GRADIENT BETWEEN THE COLOMBIAN LOW AND HIGH PRES OVER CENTRAL AMERICA IS ALLOWING FOR N WINDS OF 20-25 KT THROUGH THE GULF AND AS FAR S AS 5N BETWEEN 78W-81W. THESE WINDS ARE EXPECTED TO DIMINISH SLIGHTLY IN 24 HOURS...THEN INCREASE AGAIN TO 25 KT IN 48 HOURS. $$ AGUIRRE