000 AXPZ20 KNHC 150239 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 0405 UTC FRI MAY 15 2015 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 0115 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... THE MONSOON TROUGH AXIS WAS ANALYZED FROM 10N85W TO 06N94W TO 06N105W 11N118W TO LOW PRES NEAR 10N123W 1010 MB TO LOW PRES NEAR 08N134W 1010 MB TO 06N140W. SCATTERED MODERATE TO STRONG CONVECTION WAS S OF THE AXIS TO 03N BETWEEN 86W-90W. SCATTERED MODERATE CONVECTION WAS WITHIN 240 NM N OF THE AXIS BETWEEN 112W- 120W. SCATTERED MODERATE CONVECTION WAS WITHIN 180 NM W SEMICIRCLE OF THE LOW NEAR 10N123W. SCATTERED MODERATE CONVECTION WAS S OF THE AXIS TO 02N AND WITHIN 150 NM N OF THE AXIS BETWEEN 125W AND 137W. ...DISCUSSION... A 1025 MB SUBTROPICAL HIGH CENTERED NW OF THE AREA NEAR 32N147W EXTENDS A RIDGE SE THROUGH 25N135W TO NEAR 20N110W. THE PRESSURE GRADIENT BETWEEN THIS RIDGE AND LOW PRES SYSTEMS EMBEDDED IN THE ITCZ NEAR 10N123W AND 08N134W IS GENERATING FRESH TO STRONG NE TRADE WINDS AS OBSERVED BY THE 2112 UTC RAPIDSCAT PASS. THE SURFACE RIDGE IS EXPECTED TO SHIFT SW THROUGH FRI AS A COLD FRONT APPROACHES THE HIGH FROM THE NW AND A SERIES OF IMPULSES ON THE W SIDE OF THE UPPER TROUGH CENTERED OVER THE SW UNITED STATES DIP INTO THE NE PORTION OF THE AREA. THIS WILL KEEP THE PRESSURE GRADIENT STRONG ENOUGH TO SUPPORT FRESH TO STRONG TRADES DESPITE THE EXPECTED TRANSIENT NATURE OF THE LOW PRES SYSTEMS ALONG THE MONSOON TROUGH. THE SUBTROPICAL HIGH WILL SHIFT SOUTHWARD THROUGH FRI BEFORE MERGING INTO THE SE SIDE OF A NEW HIGH CENTERED N OF HAWAII SAT. TRADES ARE EXPECTED TO DIMINISH TO A FRESH BREEZE BY SAT AFTERNOON AS A RESULT. ONE OF THE IMPULSES IN THE AFOREMENTIONED UPPER TROUGH CENTERED OVER THE SE UNITED STATES IS EXPECTED TO LIE OFF THE SOUTHERN CALIFORNIA COAST BY FRI MORNING. A STRONG SURFACE REFLECTION IS EXPECTED WITH THIS IMPULSE. NW SWELL ASSOCIATED WITH THE SYSTEM HAS BUILT SEAS TO 8 FT N OF 29N BETWEEN 126W-135W THIS EVENING. A COLD FRONT WILL MOVE INTO N WATERS EARLY FRI MORNING AND IS EXPECTED TO APPROACH THE COAST NEAR ENSENADA FRI AFTERNOON BEFORE MOVING INTO THE NORTHERN GULF OF CALIFORNIA. WINDS IN THE PACIFIC WILL REACH A FRESH TO STRONG BREEZE ON THE LEADING EDGE OF THE SYSTEM OVERNIGHT TONIGHT AND SEAS WILL BUILD AS HIGH AS 12 FT IN NW SWELL FRI. A VAST ANTICYCLONE ALOFT IS CENTERED NEAR 10N120W AND EXTENDS RIDGE AXES SW TO BEYOND 03N140W AND NW TO BEYOND 14N140W. THE ITCZ IS PARTICULARLY CONVECTIVELY ACTIVE BETWEEN 110W AND 140W IN THE VICINITY OF THIS ANTICYCLONE AND THE AFOREMENTIONED RIDGE AXES WHERE UPPER LEVEL DIVERGENCE IS ENHANCING LIFT OF THE MOIST LOW-LEVELS AROUND THE MONSOON TROUGH. THIS CONVECTION IS DESCRIBED IN THE SECTION ABOVE. THE ABUNDANT CONVECTION IN THIS AREA IS ASSOCIATED WITH A KELVIN WAVE PROPAGATING THROUGH THE REGION. 16-18 SECOND PERIOD CROSS-EQUATORIAL S-SW SWELL IS SUBSIDING ALONG THE MEXICAN AND CENTRAL AMERICAN COAST...EXCLUDING THE GULF OF CALIFORNIA. SURF CONDITIONS SHOULD BE IMPROVING IN THESE AREAS. SEA HEIGHTS TO 8 FT IN SW SWELL ARE NOW CONFINED TO THE SE WATERS PRIMARILY S-SW FROM THE GULF OF PANAMA. SHIP A8PC6 REPORTED 9 FT SEAS NEAR 6.7N79.6W AT 1800 UTC AND A 2010 UTC ALTIMETER PASS SHOWED SEAS S OF 01N BETWEEN 84W AND 86W TO 8 FT. THESE SEAS SHOULD SUBSIDE OVERNIGHT TONIGHT. GAP WINDS... GULF OF CALIFORNIA...THE PRES GRADIENT BETWEEN THE SUBTROPICAL RIDGE AND TROUGHING OVER THE SW UNITED STATES SUPPORTS FRESH TO STRONG S-SW WINDS IN THE GULF OF CALIFORNIA N OF 29.5N...WITH WINDS FUNNELING THROUGH MOUNTAIN PASSES LIKELY REACHING NEAR GALE FORCE. SEAS ARE BELIEVED TO BE AS HIGH AS 8 FT. WINDS SHOULD DIMINISH AROUND SUNRISE FRI AS THE SURFACE SYSTEM MOVES EASTWARD...BUT WILL RESUME AHEAD OF THE COLD FRONT MOVING INTO THE NORTHERN GULF OF CALIFORNIA LATE FRI. THE COLD FRONT WILL WEAKEN QUICKLY...WITH WINDS AND SEAS EXPECTED TO DIMINISH AROUND SUNRISE SAT. GULF OF PAPAGAYO...THE PRESSURE GRADIENT BETWEEN RIDGING OVER THE NW CARIBBEAN AND TROUGHING NEAR THE ITCZ WILL SUPPORT A FRESH TO STRONG BREEZE IN THE GULF OF PAPAGAYO BY THE EARLY MORNING HOURS FRI WITH THE ASSISTANCE OF NOCTURNAL DRAINAGE FLOW. THESE WINDS WILL DIMINISH AFTER SUNRISE. THE PRESSURE GRADIENT WILL SLACKEN ENOUGH BY FRI EVENING TO PREVENT WINDS FROM EXCEEDING A FRESH BREEZE ON SAT. GULF OF TEHUANTEPEC...THE 1628 UTC ASCAT PASS SHOWED N WINDS IN THE GULF OF TEHUANTEPEC HAVE DIMINISHED BELOW A FRESH TO STRONG BREEZE. SEAS REMAIN AS HIGH AS 8 FT IN MIXED N-NE AND SW SWELL FROM THE COAST AS FAR S AS 14N. OVERNIGHT A SURFACE TROUGH MOVING W OFF THE YUCATAN PENINSULA INTO THE BAY OF CAMPECHE WILL ABUT WITH RIDGING ALONG THE SW GULF OF MEXICO COAST...ALLOWING FRESH N WINDS TO FUNNEL THROUGH CHIVELA PASS INTO THE GULF OF TEHUANTEPEC. THESE WINDS WILL KEEP SEAS TO 8 FT THROUGH SUNRISE BEFORE SUBSIDING. $$ SCHAUER