000
AXPZ20 KNHC 272133
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC WED FEB 27 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2030 UTC.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
THE MONSOON TROUGH AXIS WAS ANALYZED FROM 02N78W TO 05N85W TO 
03N93W TO 02N106W. ITCZ AXIS WAS ANALYZED FROM 02N106W TO 
03N118W TO 00N130W. SCATTERED MODERATE CONVECTION WAS NOTED 
WITHIN 90 NM EITHER SIDE OF THE AXIS BETWEEN 83W AND 87W. 
SCATTERED MODERATE CONVECTION WAS ALSO WITHIN 60 NM S AND 180 NM 
N OF THE AXIS BETWEEN 91W AND 96W.

...DISCUSSION...

STRONG HIGH PRES BUILDING SOUTHWARD BEHIND A COLD FRONT MOVING 
THROUGH THE GULF OF MEXICO WILL TIGHTEN THE PRES GRADIENT ACROSS 
SOUTHERN MEXICO. AS A RESULT...NORTHERLY WINDS WILL INCREASE TO 
20-25 KT IN THE GULF OF TEHUANTEPEC THU MORNING. THE GRADIENT 
WILL STRENGTHEN FURTHER THU...WITH MINIMAL GALE FORCE WINDS 
COMMENCING OVERNIGHT THU NIGHT. THE POTENTIAL EXISTS FOR STORM 
FORCE WINDS BY LATE SAT INTO SUN.  

THE PRESSURE GRADIENT BETWEEN HIGH PRESSURE OVER THE GREAT BASIN 
AND TROUGHING ACROSS WESTERN MEXICO HAS INDUCED FRESH TO STRONG 
NW WINDS ALONG THE LENGTH OF THE GULF OF CALIFORNIA. THE 1740 
UTC ASCAT PASS CAPTURED THESE CONDITIONS...WITH THE STRONGEST 
WINDS PRIMARILY HUGGING THE EAST COAST OF BAJA CALIFORNIA. 
WINDS HERE ARE EXPECTED TO INCREASE TO NEAR GALE FORCE THIS 
EVENING AS THE PRESSURE GRADIENT TIGHTENS FURTHER. SEAS WILL 
AGAIN BUILD TO 10-11 FT IN THE GULF OF CALIFORNIA BY THU...WITH 
N SWELL FROM THE GULF SPILLING SOUTH OF THE MOUTH OF THE GULF 
AND MIXING WITH LONG-PERIOD NW SWELL. 

A POSITIVELY TILTED UPPER TROUGH STRETCHED FROM 32N130W TO 
22N140W AND THEN W OF THE AREA HAS A 120 KT SOUTHWESTERLY UPPER 
JET AHEAD OF IT DIRECTING MOISTURE FROM THE ITCZ OVER WESTERN 
WATERS NORTHEASTWARD. PRECIPITABLE WATER IMAGERY SHOWS MID- TO 
LOW-LEVEL MOISTURE IS ABUNDANT S OF 20N. SCATTERED SHOWERS AND 
ISOLATED THUNDERSTORMS ARE MOST LIKELY TO LIE IN THIS SOUTHERN 
PORTION OF THE MOISTURE SWATH BETWEEN 135W-140W WITH MAINLY 
CIRRUS FOUND ACROSS MUCH OF THE AREA N OF 20N...INCLUDING OVER 
THE NORTHERN GULF OF CALIFORNIA. THE UPPER TROUGH WILL WEAKEN 
AND CUT OFF AN UPPER LOW NEAR 20N OVER W WATERS THU BEFORE 
MERGING WITH A NEW NORTHERN STREAM TROUGH APPROACHING FROM THE 
NW FRI THAT WILL OPEN UP THE LOW AND TURN WHAT IS LEFT OF IT 
NEGATIVE TILT OVER WESTERN WATERS. PRECIPITATION SHOULD MAINLY 
BE FOUND W OF 130W THU AND FRI.

THE 1031 MB SUBTROPICAL HIGH NEAR 34N135W EXTENDS ITS PRIMARY 
RIDGE AXIS NORTHEASTWARD TO NORTHERN CALIFORNIA AND 
SOUTHWESTWARD TO 32N140W. ANTICYCLONIC FLOW ASSOCIATED WITH THE 
RIDGE PREVAILS OVER MOST OF THE DISCUSSION AREA W OF 115W...WITH 
FRESH TO STRONG NE TRADE WINDS DOMINATING THE REGION N OF THE 
ITCZ TO 24N W OF 127W. THE SUBTROPICAL RIDGE WILL STRENGTHEN 
SLIGHTLY TOMORROW BEFORE SHIFTING NORTHEASTWARD AHEAD OF A COLD 
FRONT WELL N OF THE AREA. THE TRADE WINDS WILL SHRINK WESTWARD 
BY FRI AS A RESULT OF THE MIGRATION OF THE SUBTROPICAL HIGH. 

$$
SCHAUER