000 AXPZ20 KNHC 132213 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 2205 UTC TUE JAN 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 2115 UTC. ...SPECIAL FEATURES... GULF OF TEHUANTEPEC GALE WARNING...THE PRESSURE GRADIENT REMAINS STRONG BETWEEN RIDGING EXTENDING FROM THE GREAT PLAINS SOUTHWARD THROUGH NE MEXICO TOWARD THE ISTHMUS OF TEHUANTEPEC AND AN STALLED FRONTAL ZONE THROUGH THE CENTRAL BAY OF CAMPECHE. WINDS TO MINIMAL GALE FORCE WERE DEPICTED LATE THIS MORNING ACROSS THE GULF OF TEHUANTEPEC N OF 15.5N IN ASCAT DATA...AND ARE EXPECTED TO CONTINUE THROUGH THE END OF THE WEEK AND INTO THE UPCOMING WEEKEND. NOCTURNAL DRAINAGE FLOW OFF THE MOUNTAINS DURING THE LATE NIGHT AND EARLY MORNING HOURS IS EXPECTED TO ENHANCE THIS FLOW TO 30 TO 4O KT TONIGHT...WITH MAXIMUM SEAS BUILDING TO 14 FT. GAP WINDS ACROSS THE GULF AREA THEN EXPECTED TO REMAIN AT MINIMAL GALE FORCE THROUGH THE REST OF THE WEEK...WITH DOWNSTREAM SEAS IN THE 8-12 FT RANGE. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... THE MONSOON TROUGH PASSES THROUGH 09N78W TO 09N85W TO 07N90W...WHERE IT TRANSITIONS TO ITCZ...CONTINUING ON 05N95W TO 07N110W TO 09N120W TO 10N132W TO 08N140W. SCATTERED MODERATE ISOLATED STRONG CONVECTION WAS NOTED FROM 07N TO 08N BETWEEN 106W AND 108W. SCATTERED TO NUMEROUS MODERATE TO STRONG CONVECTION WAS NOTED WITHIN 450 NM E OF A TROUGH ALONG 121W/122W FROM 08N TO 14N. ...DISCUSSION... A SHARP UPPER LEVEL TROUGH CONTINUES ACROSS THE AREA THIS AFTERNOON...NOW ALONG 129W/130W....SHIFTING VERY SLOWLY EASTWARD. A SURFACE TROUGH IS ALONG 121W/122W FROM 08N TO 14N...WHERE SCATTERED TO NUMEROUS STRONG CONVECTION IS OCCURRING WITHIN 450 NM E OF THE TROUGH. PRECIPITABLE WATER IMAGERY SHOWS ABUNDANT TROPICAL MOISTURE MAXIMUMS CONVERGING ALONG THE ITCZ BETWEEN THE SURFACE TROUGH AND 103W. MOISTURE SHOULD CONTINUE TO BE PLENTIFUL ACROSS THIS AREA FOR THE NEXT FEW DAYS. THIS REGION SHOULD REMAIN CONVECTIVELY ACTIVE THROUGH THE FORECAST PERIOD AS THE UPPER TROUGH SHIFTS SLOWLY EASTWARD TO 120W...AIDED BY STRONG DYNAMICS ASSOCIATED WITH AN ACTIVE JETSTREAM MOVING THROUGH THE BASE OF THE TROUGH. A NARROW SUBTROPICAL RIDGE EXTENDS FROM WEAKENING 1025 MB HIGH PRESSURE NEAR 37N127W THROUGH 24N124W TO 18N110W. THE PRESSURE GRADIENT REMAINS SUFFICIENT BETWEEN THE RIDGE AND THE 121W/122W SURFACE TROUGH TO PRODUCE AND AREA OF STRONG NE TO E TRADEWINDS FROM 11N TO 14.5N BETWEEN 120W AND 130W...AND WERE DEPICTED BY LATE MORNING SCATTEROMETER DATA. THE RIDGE IS EXPECTED TO WEAKEN DURING THE NEXT TWO DAYS...SLOWLY DIMINISHING THE PRESSURE GRADIENT. HOWEVER FRESH TO STRONG TRADEWINDS FROM 11N TO 15N ARE EXPECTED TO SHIFT SLOWLY EASTWARD IN TANDEM WITH THE UPPER TROUGH...FUELING THE ACTIVE CONVECTION MENTIONED ABOVE. SEAS ACROSS THIS AREA WILL REAMAIN IN THE 8-9 FEET RANGE...WITH MIXED NW SWELL. A WEAK COLD FRONT IS EXPECTED TO MOVE INTO NW WATERS LATER TODAY AND DISSIPATE FROM 30N135W TO 28N136W WEDNESDAY MORNING...WITH A PRE FRONTAL TROUGH ALSO FROM 28N136W TO 14N136W. EXPECT A FRESH SOUTH BREEZE JUST AHEAD OF THE FRONT TODAY...WITH SEAS BUILDING TO 12 FT IN NW SWELL IN THE FAR NW WATERS AHEAD OF THE FRONT THIS AFTERNOON THROUGH THIS EVENING. THE NW SWELL WILL CONTINUE TO SEND SEAS OF 8 FT OR GREATER SOUTHEASTWARD INTO THE FORECAST AREA...SPANNING THE AREA W OF 126W N OF A LINE FROM 15N126W TO 9N140W BY EARLY THURSDAY MORNING. GAP WINDS... GULF OF PAPAGAYO...TRADE WINDS IN THE SW CARIBBEAN CONTINUE TO FUNNEL THROUGH NORTHERN COSTA RICA AND ACROSS THE GULF OF PAPAGAYO. FRESH TO STRONG E-NE WINDS IN PLACE THIS MORNING THROUGH MID AFTERNOON ARE EXPECTED TO DIMINISH TO 15-20 KT BOTH THIS EVENING AND WED EVENING...THEN INCREASE AGAIN TO 20-25 KT EACH NIGHT THROUGH MORNING...PEAKING DURING THE MAXIMUM NOCTURNAL DRAINAGE FLOW. GULF OF CALIFORNIA...AN UPPER LOW OVER THE U.S. GREAT BASIN WILL MAKE ITS WAY S TO THE ARIZONA/MEXICO BORDER WED BEFORE SHEARING EASTWARD THU. AT THE SURFACE...THE PRESSURE GRADIENT WILL BUILD BETWEEN LEE SIDE TROUGHING ALONG THE W SLOPES OF THE SIERRA MADRE OCCIDENTAL AND INCREASED RIDGING OVER THE GREAT BASIN IN THE WAKE OF THE SYSTEM WED AND THU. A FRESH N BREEZE IS EXPECTED OVER THE NORTHERN GULF OF CALIFORNIA WED...WITH AN OCCASIONAL STRONG BREEZE THROUGH FRI MORNING. $$ STRIPLING