000 AXPZ20 KNHC 132148 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 2205 UTC WED MAY 13 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2015 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... THE ITCZ AXIS WAS ANALYZED FROM 07N93W TO 07N114W TO 10N119W TO LOW PRES NEAR 09N131W 1009 MB. MONSOON TROUGH AXIS FROM LOW PRES TO 07N140W. SCATTERED MODERATE WITH ISOLATED STRONG CONVECTION WITHIN 330 NM S OF THE AXIS BETWEEN 97W-107W. SCATTERED MODERATE CONVECTION WITHIN 330 NM S OF THE AXIS BETWEEN 111W-118W. SCATTERED MODERATE CONVECTION WITHIN 120 NM OF LOW PRES. SCATTERED MODERATE TO STRONG CONVECTION FROM 10N-13N BETWEEN 110W-116W. ...DISCUSSION... A 1031 MB SUBTROPICAL HIGH CENTERED NW OF THE AREA NEAR 37N149W EXTENDS A RIDGE SE THROUGH 30N138W TO NEAR 26N114W. THE PRESSURE GRADIENT BETWEEN THIS RIDGE AND LOW PRES EMBEDDED IN THE ITCZ/MONSOON TROUGH NEAR 09N131W IS GENERATING MODERATE TO FRESH NE TRADE WINDS THIS AFTERNOON. THE SURFACE RIDGE IS EXPECTED TO SHIFT SW OVER THE NEXT TWO DAYS AS A COLD FRONT APPROACHES THE HIGH FROM THE NW AND A SERIES OF IMPULSES ON THE W SIDE OF THE UPPER TROUGH CENTERED ALONG 125W N OF 20N DIP INTO THE NE PORTION OF THE AREA. A TIGHTER PRESSURE GRADIENT WILL DEVELOP BETWEEN THE SUBTROPICAL RIDGE AND THE ITCZ/MONSOON TROUGH...ALLOWING TRADES TO PICK UP TO A FRESH TO STRONG BREEZE BY THU AFTERNOON. ONE OF THE IMPULSES IN THE AFOREMENTIONED UPPER TROUGH CENTERED NEAR 125W 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 WILL BUILD SEAS TO 8 FT N OF 29N BETWEEN 126W AND 134W BY THU EVENING. A STRONG COLD FRONT WILL MOVE INTO N WATERS FRI MORNING AND IS EXPECTED TO APPROACH THE COAST NEAR ENSENADA FRI AFTERNOON. WINDS WILL REACH A FRESH TO STRONG BREEZE ON THE LEADING EDGE OF THE SYSTEM FRI AND SEAS WILL BUILD AS HIGH AS 11 FT. A VAST ANTICYCLONE ALOFT IS CENTERED NEAR 09N118W AND EXTENDS RIDGE AXES W TO BEYOND 11N140W AND E TO THE COAST OF GUATEMALA. THE ITCZ IS PARTICULARLY CONVECTIVELY ACTIVE IN THE VICINITY OF THIS ANTICYCLONE WHERE UPPER LEVEL DIVERGENCE IS ENHANCING LIFT OF THE MOIST LOW-LEVELS AROUND THE ITCZ. THIS CONVECTION IS DESCRIBED IN THE SECTION ABOVE. THE ABUNDANT CONVECTION IN THIS AREA IS ASSOCIATED WITH A KELVIN WAVE PROPAGATING INTO THE REGION. FORECAST GUIDANCE SUGGESTS THAT THE ANTICYCLONE WILL SHIFT NW TO NEAR 11N127W THROUGH FRI AFTERNOON...CARRYING THE BULK OF THE CONVECTION W WITH IT. LONG PERIOD CROSS EQUATORIAL SOUTHERLY SWELL AT 18-20 SECONDS CONTINUES TO IMPACT THE MEXICAN AND CENTRAL AMERICAN COAST...EXCLUDING THE GULF OF CALIFORNIA. THIS LONG PERIOD SWELL IS PRODUCING HAZARDOUS SURF AND BEACH CONDITIONS ALONG THE MEXICAN AND CENTRAL AMERICAN COASTS. THESE CONDITONS SHOULD BEGIN TO IMPROVE OVERNIGHT. SEA HEIGHTS OF 8 FT OR GREATER IN SW SWELL ARE PRIMARILY IMPACTING THE AREA E OF A LINE FROM 16N98W TO 00N126W...EXCEPT IN THE LEE OF THE GALAPAGOS ISLANDS. SEAS OVER 8 FT DUE TO THIS SWELL WILL SUBSIDE N OF THE EQUATOR OVERNIGHT THU NIGHT. GULF OF CALIFORNIA...THE PRES GRADIENT BETWEEN THE SUBTROPICAL RIDGE AND TROUGHING OVER THE SW UNITED STATES WILL INCREASE THIS EVENING AS A NEW IMPULSE ALOFT MOVES INTO THE BASE OF THE MEAN UPPER TROUGH ALONG THE CALIFORNIA COAST...WITH FRESH TO STRONG S- SW WINDS EXPECTED IN THE GULF OF CALIFORNIA N OF 29.5N BY THE EARLY MORNING. THE WINDS ARE FORECAST TO INCREASE TO NEAR GALE FORCE HERE THU EVENING AS THIS IMPULSE TURNS THE UPPER TROUGH NEGATIVE TILT AND STRENGTHENS THE SURFACE TROUGHING. SEAS ARE EXPECTED TO REACH AS HIGH AS 8 FT. WINDS SHOULD DIMINISH AROUND SUNRISE FRI AS THE SURFACE SYSTEM MOVES EASTWARD. GULF OF PAPAGAYO...THE PRESSURE GRADIENT BETWEEN RIDGING OVER THE NW CARIBBEAN AND TROUGHING NEAR THE ITCZ CONTINUES TO BE TIGHT ENOUGH TO SUPPORT A FRESH TO STRONG BREEZE IN THE GULF OF PAPAGAYO THIS AFTERNOON. WHILE THE PRESSURE GRADIENT IS EXPECTED TO WEAKEN OVERNIGHT...WINDS WILL CONTINUE AT A FRESH TO STRONG BREEZE THROUGH THE MORNING HOURS THU WITH THE ASSISTANCE OF NOCTURNAL DRAINAGE FLOW. THESE WINDS WILL DIMINISH DURING THE DAY AND RETURN IN THE EARLY MORNING HOURS FRI BEFORE DIMINISHING YET AGAIN. SEAS ARE AS HIGH AS 11 FT RIGHT NOW IN MIXED NE AND SW SWELL...BUT THEY WILL GENERALLY SUBSIDE TO AS HIGH AS 9 FT BY FRI. GULF OF TEHUANTEPEC...A SURFACE TROUGH MOVING W OFF THE YUCATAN PENINSULA INTO THE BAY OF CAMPECHE WILL ABUT WITH RIDGING ALONG THE SW GULF COAST IN THE MORNING HOURS THU...ALLOWING FRESH TO STRONG N WINDS TO FUNNEL THROUGH CHIVELA PASS INTO THE GULF OF TEHUANTEPEC. THESE WINDS WILL DIMINISH TO LESS THAN 20 KT IN THE AFTERNOON. HIGH PRESSURE NE OF THE AREA WILL SHIFT FARTHER AWAY...DIMINISHING THE PRESSURE GRADIENT AND THE WINDS BY THU AFTERNOON. SEAS WILL REMAIN ABOVE 8 FT IN MIXED N-NE AND SW SWELL UNTIL EARLY FRI MORNING. $$ SCHAUER