000
AXPZ20 KNHC 130936
TWDEP 

TROPICAL WEATHER DISCUSSION  
NWS NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC WED FEB 13 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0715 UTC.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
THE MONSOON TROUGH AXIS WAS ANALYZED FROM 02N79W TO 04N94W TO 
06N103W. ITCZ AXIS WAS ANALYZED FROM 06N103W TO 05N116W TO 
08N123W TO 05N140W. SCATTERED MODERATE CONVECTION WAS NOTED 
WITHIN 60 NM EITHER SIDE OF THE AXIS BETWEEN 122W AND 126W.

...DISCUSSION...
A POSITIVELY TILTED UPPER TROUGH THAT EXTENDS FROM THE CENTRAL 
U.S. PLAINS THROUGH BAJA CALIFORNIA NORTE INTO NE FORECAST 
WATERS WILL SHIFT E TODAY AND GRADUALLY BE REPLACED BY UPPER 
RIDGING. AT THE SURFACE...THE STRONG PRESSURE GRADIENT BETWEEN 
THE SUBTROPICAL RIDGE OVER NE WATERS AND TROUGHING OVER NORTHERN 
MAINLAND MEXICO DUE TO THE COLD FRONT ASSOCIATED WITH THIS 
TROUGH ALOFT IS FORCING FRESH TO STRONG N-NW WINDS DOWN THE 
LENGTH OF THE GULF OF CALIFORNIA. THE 0504 UTC ASCAT PASS 
CAPTURED THESE WINDS. THE LONG FETCH DOWN THE GULF HAS LIKELY 
ALLOWED SEAS TO BUILD TO 8 FT. THE 1037 MB SUBTROPICAL HIGH 
CURRENTLY NEAR 39N135W WILL REMAIN UNCHANGED UNTIL THU WHEN IT 
IS FORECAST TO WEAKEN AND SHIFT NORTHEASTWARD. WINDS AND SEAS 
WILL DIMINISH IN THE GULF OF CALIFORNIA BY THU AFTERNOON AS THE 
PRESSURE GRADIENT RELAXES. 

AN UPPER LOW LIES JUST W OF THE AREA NEAR 25N145W AND REFLECTS A 
1019 MB LOW AT THE SURFACE NEAR 26N146W WITH A TROUGH EXTENDING 
FROM THE LOW TO 28N145W TO 25N143W TO 18N151W. THE 0646 UTC 
ASCAT PASS SHOWS FRESH TO STRONG SE WINDS EXTEND E OF THE TROUGH 
INTO THE FORECAST AREA N OF 22N W OF 138W. THE SURFACE LOW IS 
FORECAST TO DISSIPATE TODAY AND THE TROUGH WILL SHIFT AWAY FROM 
THE AREA...DIMINISHING THE PRESSURE GRADIENT AND THE WINDS. SOME 
SCATTERED SHOWERS AND POSSIBLY AN ISOLATED THUNDERSTORM ARE 
CURRENTLY JUST W OF THE AREA AND E OF THE LOW N OF 24N. 

THE 0502 AND 0642 UTC ASCAT PASSES SHOW FRESH TO STRONG TRADE 
WINDS N OF THE ITCZ TO 20N BETWEEN 118W AND 136W. THIS AREA OF 
TRADES WILL GRADUALLY SHIFT W OF 124W OVER THE NEXT TWO DAYS AS 
THE SUBTROPICAL RIDGE AXIS SHIFTS SLIGHTLY WESTWARD. A WEAK MID 
LEVEL DISTURBANCE NEAR THE ITCZ AT 123W IS REFLECTING AN 
UNDULATION IN THE ITCZ. SCATTERED MODERATE CONVECTION WAS NOTED 
WITHIN 60 NM EITHER SIDE OF THE ITCZ BETWEEN 122W AND 126W AS A 
RESULT. THIS SYSTEM WILL SLOWLY MOVE W OVER THE NEXT FEW DAYS. 
THE PRESSURE GRADIENT BETWEEN THE WESTWARD MIGRATING SUBTROPICAL 
RIDGE AND THIS UNDULATION IN THE ITCZ WILL INTENSIFY ON WED AND 
ALLOW FOR WINDS TO BUILD TO 30 KT JUST N OF THE ITCZ. 

GAP WINDS...
GULF OF TEHUANTEPEC...NORTHERLY WINDS BEHIND A COLD FRONT MOVING 
THROUGH THE SW GULF OF MEXICO THU WILL SQUEEZE THROUGH CHIVELA 
PASS AND GENERATE FRESH TO STRONG N WINDS IN THE GULF OF 
TEHUANTEPEC BY EARLY FRI MORNING. 

$$
SCHAUER