000 AXPZ20 KNHC 150908 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 1005 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0800 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS FROM 10N86W TO 06N95W TO 06.5N112W TO 11.5N123W TO LOW PRES NEAR 08N124W 1009 MB TO 07N140W. SCATTERED MODERATE TO STRONG CONVECTION NOTED N OF 04N E OF 82.5W...AND FROM 03.4S TO 04N E OF 86.5W. SCATTERED TO LOCALLY NUMEROUS MODERATE TO STRONG CONVECTION NOTED WITHIN 90 NM N AND S OF AXIS TO 01N BETWEEN 85W AND 114W. SCATTERED MODERATE ISOLATED STRONG CONVECTION NOTED WITHIN 240 NM N AND 360 NM S OF AXIS BETWEEN 115W AND 137W. SCATTERED LIGHT TO MODERATE CONVECTION ALOFT OCCURRING WITHIN 90 NM OF LINE FROM 18.5N114W TO 23N106W. ...DISCUSSION... A WEAKENING 1025 MB SUBTROPICAL HIGH CENTERED NW OF THE AREA NEAR 32N146W EXTENDS A RIDGE SE THROUGH 24N131W THEN E TO NEAR 23N110W. THE PRESSURE GRADIENT BETWEEN THIS RIDGE AND LOW PRES IN THE VICINITY OF THE MONSOON TROUGH IS GENERATING FRESH TO STRONG NE TRADE WINDS S OF THE RIDGE AS OBSERVED BY OVERNIGHT ASCAT PASSES. THE SURFACE RIDGE IS EXPECTED TO SHIFT SW TODAY AS A COLD FRONT MOVES SE INTO NE PORTIONS...AND CURRENTLY REACHES 30N ALONG 127W. THIS FRONT IS SUPPORTED BY A SERIES OF IMPULSES ON THE W SIDE OF THE UPPER TROUGH CENTERED OVER THE SW UNITED STATES DIPPING INTO THE NE PORTION OF THE AREA. THIS PATTERN 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 CURRENTLY ALONG 124W AND IS EXPECTED TO MOVE AND E REACH NEAR THE SOUTHERN CALIFORNIA COAST THIS MORNING. A 1009 MB SURFACE LOW HAS DEVELOPED BELOW THIS IMPULSE....AND WILL DRAG THE FRONT E AND SE TODAY. NW SWELL ASSOCIATED WITH THE SYSTEM HAS BUILT SEAS 8-10 FT N OF 28N BETWEEN 123W AND 136W OVERNIGHT. THE COLD FRONT WILL MOVE SE AND INTO THE N WATERS THROUGHOUT THE MORNING AND IS EXPECTED TO APPROACH THE COAST NEAR ENSENADA THIS 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 THIS MORNING WHILE SEAS BUILD AS HIGH AS 12 FT IN NW SWELL BEHIND THE FRONT TODAY. A BROAD AND PERSISTENT ANTICYCLONE ALOFT IS CENTERED NEAR 11.5N116W AND EXTENDS RIDGE AXES W TO BEYOND 140W AND NE ACROSS CENTRAL MEXICO. VERY ACTIVE CONVECTION CONTINUES UNDERNEATH THIS UPPER RIDGE BETWEEN 105W AND 137W IN THE VICINITY OF THE MONSOON TROUGH...BUT IS EXPECTED TO GRADUALLY DIMINISH DURING THE NEXT 24 HOURS...AND BEGIN TO PROPAGATE EASTWARD OF 120W AS A KELVIN WAVE PROPAGATES THROUGH THE REGION. 14-16 SECOND PERIOD CROSS-EQUATORIAL S-SW SWELL IS SLOWLY SUBSIDING ALONG THE MEXICAN AND CENTRAL AMERICAN COAST... EXCLUDING THE GULF OF CALIFORNIA. SURF CONDITIONS SHOULD BE IMPROVING IN THESE AREAS AS THIS SWELL SUBSIDES. SEAS TO 8 FT IN SW SWELL ARE NOW CONFINED TO THE SE WATERS PRIMARILY W THROUGH SW OF THE GULF OF PANAMA FROM 07N TO 13N BETWEEN 89W AND 97W...AND N OF 04N E OF 81.5W. THESE SEAS SHOULD SUBSIDE BELOW 8 FT BY THIS AFTERNOON. 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 THE MOUNTAIN PASSES LIKELY REACHING NEAR GALE FORCE THROUGH THE MOUNTAIN PASSES. 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 TONIGHT. 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 LOWER PRES NEAR THE MONSOON TROF IS SUPPORTING A FRESH TO STRONG BREEZE IN THE GULF OF PAPAGAYO... ENHANCED BY NOCTURNAL DRAINAGE FLOW. THESE WINDS WILL DIMINISH TO 15-20 KT BY AROUND NOON TODAY. THE PRESSURE GRADIENT WILL WEAKEN SLIGHTLY BY TONIGHT...AND AGAIN ALLOW FOR A SMALL ZONE OF FRESH TO STRONG GAP WINDS TONIGHT THROUGH SAT MORNING. $$ STRIPLING