000 AXPZ20 KNHC 130954 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 1005 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0900 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... THE ITCZ AXIS EXTENDS FROM 07N90W TO 03N103W TO 07N118W TO LOW PRES NEAR 09N130W TO 07N140W. SCATTERED MODERATE CONVECTION IS WITHIN 120 NM S OF A LINE FROM 09N85W TO 07N91W...WITHIN 120 NM S OF THE AXIS BETWEEN 91W AND 99W...FROM 02N TO 07N BETWEEN 105W AND 110W...FROM 01N TO 03N BETWEEN 111W AND 121W...WITHIN 210 NM N OF THE AXIS BETWEEN 108W AND 122W...AND FROM 01N TO 05N BETWEEN 121W AND 130W. SCATTERED MODERATE TO STRONG CONVECTION IS FROM 05N TO 10N BETWEEN 122W AND 127W. ALSO...SCATTERED MODERATE AND ISOLATED STRONG CONVECTION IS WITHIN 60 NM OF THE COAST OF COLOMBIA FROM 01N TO 05N. ...DISCUSSION... A 1033 MB SUBTROPICAL HIGH CENTERED NW OF THE AREA NEAR 38N151W EXTENDS A RIDGE SE TO NEAR 20N110W. THE PRESSURE GRADIENT BETWEEN THIS RIDGE AND TWO FEATURES EMBEDDED IN THE ITCZ...A TROUGH NEAR 120W...AND 1008 MB LOW PRES NEAR 09N130W...IS PRODUCING FRESH TRADES OVER THE WESTERN WATERS WITH SEAS OF 8 TO 9 FT ACROSS THE AREA FROM 08N TO 16N W OF 116W. THE SURFACE RIDGE IS EXPECTED TO WEAKEN AND SHIFT SW OVER THE NEXT 48 HOURS AS A SERIES OF IMPULSES ON THE W SIDE OF AN UPPER TROUGH POSITIONED ALONG N OF 20N ALONG 125W DIP INTO THE NE PORTION OF THE AREA. THE AREA OF FRESH TRADES WILL SHRINK IN RESPONSE...BUT NUMERICAL GUIDANCE SUGGESTS A NEW WEAK...QUASI-STATIONARY AREA OF LOW PRES DEVELOPING ALONG THE SURFACE TROUGH AT 10N122W BY 24 HOURS WHICH WILL CREATE A LOCALIZED TIGHT PRESSURE GRADIENT TO THE N OF THE LOW WHICH WILL ALLOW FOR THE RETURN OF FRESH TRADES. LONG PERIOD CROSS EQUATORIAL SOUTHERLY SWELL AT 19-22 SECONDS HAS REACHED THE MEXICAN AND CENTRAL AMERICAN COAST IN THE PAST FEW HOURS. THIS LONG PERIOD SWELL WILL LEAD TO HAZARDOUS SURF AND BEACH CONDITIONS ALONG THE MEXICAN AND CENTRAL AMERICAN COASTS THROUGH TODAY AND TONIGHT. SEA HEIGHTS OF 8 FT OR GREATER IN SW SWELL WILL PRIMARILY IMPACT THE AREAS S OF 12N E OF 127W...EXCEPT IN THE LEE OF THE GALAPAGOS ISLANDS...THROUGH TONIGHT...THEN GRADUALLY DECAYING TO S OF THE EQUATOR BY 48 HOURS. A COLD FRONT IS FORECAST TO DROP S OF 32N BY 24 HOURS WITH A REINFORCING COLD FRONT DROPPING IN BEHIND IT BY 48 HOURS. MODEL GUIDANCE INDICATES FRESH TO STRONG WINDS ASSOCIATED WITH THIS FRONT ALTHOUGH THEY WILL REMAIN N OF 30N AND WILL DIMINISH LATE THU AS THE FRONT WEAKENS WHILE MOVING SE-S. AN ASSOCIATED AREA OF 8-9 FT SEAS IN NW SWELL WILL REACH 28N BETWEEN 124W AND 134W BY 48 HOURS. GULF OF CALIFORNIA...THE PRES GRADIENT BETWEEN THE SUBTROPICAL RIDGE AND TROUGHING OVER THE SW UNITED STATES HAS TIGHTENED OVERNIGHT ALLOWING FOR THE DEVELOPMENT OF FRESH TO STRONG SOUTHERLY WINDS N OF 30.5N W OF 113.5W. THESE WINDS WILL DIMINISH SHORTLY AFTER SUNRISE TODAY...THEN WILL RETURN LATE TONIGHT INTO EARLY THU AS A NEW IMPULSE LOWERS THE SURFACE PRES ACROSS THE SW UNITED STATES. THIS IMPULSE WILL TURN THE UPPER TROUGH NEGATIVELY AND STRENGTHEN THE SURFACE TROUGHING. SW WINDS IN THE NORTHERN GULF OF CALIFORNIA ARE EXPECTED TO INCREASE TO NEAR GALE FORCE THU EVENING WITH MODEL GUIDANCE NOW INDICATING THE WINDS ACHIEVING MINIMAL GALE FORCE STRENGTH LATE FRI NIGHT THROUGH SUNRISE SAT WHEN A GALE WARNING MAY BE NEEDED. GULF OF TEHUANTEPEC...A BROAD SURFACE TROUGH MOVING W OFF THE YUCATAN PENINSULA INTO THE BAY OF CAMPECHE ABUTTING WITH RIDGING ALONG THE SW GULF OF MEXICO COAST IS SUPPORTING FRESH TO STRONG NORTHERLY WINDS FUNNELING THROUGH THE CHIVELA PASS TO JUST OFFSHORE IN THE GULF OF TEHUANTEPEC. THESE WINDS WILL APPROACH MINIMAL GALE FORCE BY SUNRISE THIS MORNING BEFORE DIMINISHING TO LESS THAN 20 KT OR LESS IN THE AFTERNOON. THE PRES GRADIENT SHOULD BE SLIGHTLY WEAKER THU MORNING...WITH A FRESH TO STRONG BREEZE EXPECTED DUE TO THE ASSISTANCE OF NOCTURNAL DRAINAGE FLOW JUST BEFORE SUNRISE BEFORE DIMINISHING YET AGAIN. GULF OF PAPAGAYO...THE PRES GRADIENT BETWEEN RIDGING OVER THE NW CARIBBEAN SEA AND TROUGHING SW OF THE AREA NEAR THE ITCZ IS TIGHT ENOUGH TO SUPPORT WINDS TO 30 KT IN THE GULF OF PAPAGAYO AS INDICATED BY RECENT ASCAT AND ASCAT-B SCATTEROMETER PASSES. THE PRES GRADIENT SHOULD SLACKEN SOME LATER THIS MORNING INTO THE AFTERNOON...WITH WINDS EXPECTED TO ONLY REACH A FRESH TO STRONG BREEZE LATE TONIGHT INTO THU MORNING BEFORE DIMINISHING AFTER SUNRISE THU...WITH ANOTHER BRIEF ROUND OF FRESH TO STRONG BREEZE LATE THU NIGHT INTO EARLY FRI EXPECTED. GULF OF PANAMA...A SMALL PLUME OF FRESH TO STRONG NORTHERLY WINDS IN THE GULF OF PANAMA WILL DIMINISH LATER THIS MORNING AS THE LOCAL PRES GRADIENT RELAXES SOMEWHAT. COMBINED SEAS OF 8-9 FT DUE TO THE WINDS AND LONG PERIOD SW SWELL WILL SUBSIDE TO LESS THAN 8 FT BY THE AFTERNOON. $$ LEWITSKY