000 AXPZ20 KNHC 260327 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 0405 UTC FRI APR 26 2013 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 0130 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... MONSOON TROUGH AXIS EXTENDS FROM COLOMBIA NEAR 08N73W TO 03N80W TO 06.5N90W...WHERE IT TRANSITIONS TO ITCZ...CONTINUING ON TO 06N103W TO 10N112W TO 08.5N125W TO BEYOND 06N140W. SCATTERED MODERATE ISOLATED STRONG CONVECTION NOTED FROM 03N TO 06N BETWEEN 80W AND 85W. SCATTERED TO NUMEROUS MODERATE TO STRONG CONVECTION NOTED FROM 02N TO 08N BETWEEN 98W AND 106W. SCATTERED TO LOCALLY NUMEROUS MODERATE TO STRONG CONVECTION NOTED FROM 06.5N TO 13N BETWEEN 105W AND 126W. SCATTERED MODERATE ISOLATED STRONG CONVECTION NOTED WITHIN 120 NM N OF ITCZ BETWEEN 131W AND 137W. ...DISCUSSION... RELATIVELY QUIET MARINE CONDITIONS PREVAILING ACROSS THE DISCUSSION AREA THIS PAST FEW DAYS ARE SLOWLY CHANGING. HIGH PRES BUILDING ACROSS THE SE U.S. BEHIND A LATE SEASON GULF OF MEXICO COLD FRONT HAS INDUCED A LATE SEASON GULF OF TEHUANTEPEC GAP WIND EVENT. A 1624 UTC ASCAT PASS REVEALED NORTHERLY WINDS OF 20-25 KT HAS SPILLED THROUGH THE CHIVELA PASS AND THROUGH THE GULF...REACHING TO 15N. WINDS THERE WERE FORECAST BY GLOBAL MODELS TO INCREASE TO 20-30 KT THIS EVENING INTO FRI MORNING WITH SEAS BUILDING TO 10-11 FT. HOWEVER...WINDS MAY BRIEFLY REACH NEAR GALE FORCE WINDS EARLY FRI WITH THE ASSISTANCE OF THE NOCTURNAL DRAINAGE FLOW. SIMILARLY...THE NOCTURNAL DRAINAGE FLOW WILL AID FRESH WINDS ACROSS THE GULF OF PAPAGAYO OVER THE NEXT COUPLE OF DAYS...WITH GLOBAL MODEL GUIDANCE SUGGESTING INCREASING WINDS TO 20-25 KT ACROSS THE GULF OF PAPAGAYO EARLY FRI AND SAT MORNINGS. HIGH PRES REMAINS GENERALLY BLOCKED FROM BUILDING ACROSS THE LOCAL AREA...WHICH IS LIMITING THE STRENGTH OF THE LOCAL TRADE WINDS. AS A RESULT...A WEAK RIDGE DOMINATES THE N WATERS. THIS SUBTROPICAL RIDGE IS BEING DISRUPTED OR BLOCKED BY A DEEP LAYERED CUT OFF LOW THAT HAS MOVED INLAND ACROSS SOUTHERN CALIFORNIA TODAY. AN ASSOCIATED BROAD AND WEAK 1016 MB SURFACE LOW IS CURRENTLY LOCATED NEAR 35N126W...WITH VERY WEAK AND VARIABLE WIND FLOW EXTENDING S AND SE TO 20N AND 117W. DURING THE NEXT 36 HOURS...THE SURFACE LOW IS EXPECTED TO WEAKEN TO A TROUGH AS THE SUPPORTING CUT OFF LOW CONTINUES TO MOVE AWAY FROM THE DISCUSSION AREA WHILE WEAKENING. AS THIS OCCURS...THE SUBTROPICAL RIDGE WILL BUILD S AND SE ACROSS THE FORECAST REGION BY SAT...WITH AN INCREASE IN THE TRADE WIND FLOW. MARINE GUIDANCE ALREADY SHOWS A BELT OF FRESH TO STRONG TRADE WINDS WITH BUILDING SEAS TO AROUND 9 FT AFFECTING THE WEST-CENTRAL WATERS N OF THE ITCZ BY SAT EVENING. OTHERWISE...WINDS ARE EXPECTED TO REMAIN BELOW 25 KT OVER THE REMAINDER OF THE FORECAST WATERS THROUGH EARLY SAT. CONVECTION HAS INCREASED NEAR THE ITCZ BETWEEN 98W AND 112W TODAY...ON THE EAST SIDE OF A UPPER LEVEL TROUGH ALONG 115W S OF 17N. ABUNDANT TROPICAL MOISTURE CONTINUES TO CONVERGE E OF THIS TROUGH...WITH SEVERAL LOW TO MID LEVEL PERTURBATION NOTED ALONG THE ITCZ MOVING W...ONE ALONG 103W AND A SECOND ALONG 112W. SCATTERED TO NUMEROUS DEEP CONVECTION DESCRIBED ABOVE WAS OCCURRING NEAR BOTH OF THESE LOW LEVEL FEATURES...WITH CONVECTION BEING SUSTAINED UNDERNEATH AN UPPER LEVEL RIDGE. THESE LOW LEVEL WAVES ARE EXPECTED TO MOVE SLOWLY WWD OVER THE NEXT FEW DAYS...WHILE THE PERSISTENT UPPER RIDGING WILL MAINTAIN FAVORABLE CONDITIONS FOR ACTIVE CONVECTION TO CONTINUE ACROSS THIS ZONE. ALOFT...BROAD AND COMPLEX TROUGHING DOMINATES MOST OF THE AREA W OF 115W THIS EVENING...WITH AN UPPER RIDGE MENTIONED ABOVE... EXTENDING FROM AN ANTICYCLONE NEAR 08N102W NORTHWARD TO THE GULF OF TEHUANTEPEC AND THEN ACROSS CENTRAL AMERICA AND W GULF OF MEXICO. THIS RIDGE HAS AMPLIFIED IN THE PAST 24 HOURS IN PART DUE TO THE BURSTS OF PERSISTENT DEEP CONVECTION MENTIONED ABOVE. UPPER RIDGING ACROSS THE ITCZ IS FORECAST TO CONTINUE BETWEEN 95W AND 125W DURING THE NEXT FEW DAYS AND PROVIDE FAVORABLE VENTILATION FOR DEEP CONVECTION. $$ STRIPLING