000
AXPZ20 KNHC 121557
TWDEP 

TROPICAL WEATHER DISCUSSION  
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC TUE FEB 12 2013

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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1530 UTC.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
MONSOON TROUGH AXIS FROM 06N77W TO 06N90W TO 06N100W. ITCZ AXIS 
FROM 06N100W TO 04N111W TO 07N123W TO 03N140W. SCATTERED 
MODERATE WITHIN 60 NM OF 03N90W. 

...DISCUSSION...
A STRONG 130-140 KT WESTERLY SUBTROPICAL JET IN PLACE FROM 
20N140W TO NW MEXICO WILL WEAKEN TONIGHT AND WED AND SHIFT 
NORTHEASTWARD AS RIDGING BUILDS OVER THE NORTH CENTRAL PORTION 
OF THE FORECAST AREA. TO THE EAST...A STRONG AND ELONGATED 
SHORTWAVE TROUGH LIES IN THE SOUTHWESTERN SIDE OF A MEAN UPPER 
TROUGH CENTERED OVER THE INTERIOR WESTERN UNITED STATES. THIS 
ENERGY WILL SLOWLY MAKE ITS WAY INTO NW MEXICO TONIGHT AS A NEW 
SHORTWAVE SYSTEM ON THE BACKSIDE OF THE MEAN TROUGH APPROACHES 
NE FORECAST WATERS FROM THE N. BOTH SYSTEMS WILL MERGE WITH THE 
MEAN TROUGH BY THU. AS FIRST SHORTWAVE SYSTEM MOVES INLAND 
TONIGHT...WEAK SURFACE TROUGHING IN NE WATERS AND ALONG THE BAJA 
PENINSULA WILL STRENGTHEN AND MOVE INTO NW MAINLAND MEXICO AS 
THE SUBTROPICAL RIDGE BUILDS EASTWARD. THIS WILL INCREASE THE 
PRESSURE GRADIENT OVER THE GULF OF CALIFORNIA. FRESH TO STRONG 
N-NW WINDS ARE FORECAST TO OVERTAKE THE GULF TONIGHT THROUGH AT 
LEAST THU MORNING AS A RESULT. 

AN UPPER LOW LIES JUST W OF THE AREA NEAR 27N146W AND REFLECTS A 
1019 MB LOW AT THE SURFACE NEAR 26N144W WITH A TROUGH EXTENDING 
FROM 30N145W THROUGH THE LOW TO 21N147W. NW SWELL FROM THIS 
SYSTEM THAT MOVED INTO THE NW WATERS A FEW DAYS AGO IS MAKING 
ITS WAY SOUTHEASTWARD...WITH PERIODS ON THE LEADING EDGE OF THE 
SWELL TRAIN IN THE 19-21 SECOND RANGE. THE LEADING EDGE OF THE 
SWELL IS CURRENTLY NEAR MANZANILLO MEXICO AND WILL LIE ALONG 95W 
S OF 13N BY WED MORNING BEFORE MIXING WITH LONG PERIOD SW SWELL 
E OF 95W. THE SURFACE TROUGH WILL MOVE SW AND GRADUALLY 
DISSIPATE...BUT THE PRESSURE GRADIENT BETWEEN THE LINGERING 
TROUGHING AND THE SUBTROPICAL RIDGE WILL KEEP FRESH TO STRONG 
WINDS OVER THE NW CORNER OF THE FORECAST AREA INTO WED MORNING. 
SOME SCATTERED SHOWERS AND POSSIBLY AN ISOLATED THUNDERSTORM ARE 
CURRENTLY JUST W OF THE AREA AND E OF THE TROUGH N OF 27N. THESE 
CONDITIONS WILL HUG NW WATERS TODAY BEFORE SHIFTING SW AND 
DIMINISHING. 

A MUCH EARLIER 0730 UTC OSCAT PASS SHOWED FRESH TO LOCALLY 
STRONG TRADE WINDS OVER THE WATERS N OF THE ITCZ BETWEEN 117W 
AND 135W AS THE SUBTROPICAL RIDGE BUILT BETWEEN THE 
AFOREMENTIONED TROUGHING OVER THE BAJA PENINSULA AND TROUGHING 
OVER NW WATERS. LOOK FOR TRADES TO REMAIN UNCHANGED FOR THE NEXT 
24 HOURS AND THEN SHIFT WEST-SOUTHWESTWARD BY EARLY THU.

GAP WINDS...
GULF OF PAPAGAYO...THE PRESSURE GRADIENT BETWEEN THE MONSOON 
TROUGH TO THE S AND RIDGING OVER THE NW CARIBBEAN HAS GENERATED 
FRESH TO STRONG NE TRADE WIND FLOW THROUGH CENTRAL AMERICA AND 
INTO THE GULF OF PAPAGAYO. THESE WINDS ARE EXPECTED TO EXPAND 
WESTWARD TO 89W THIS MORNING. RIDGING IN THE CARIBBEAN WILL 
WEAKEN LATER TODAY...SLACKENING THE PRESSURE GRADIENT AND 
DIMINISHING WINDS IN THE GULF OF PAPAGAYO. 

$$
COBB