000
AXPZ20 KNHC 282148
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC THU FEB 28 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 
2045 UTC.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
THE MONSOON TROUGH AXIS WAS ANALYZED FROM 05N77W TO 06N86W TO 
03N93W TO 04N100W TO 03N105W. ITCZ AXIS WAS ANALYZED FROM 
03N105W TO 05N135W THEN CONTINUES FROM 04N138W TO 03N140W. 
SCATTERED MODERATE CONVECTION WAS WITHIN 150 NM N OF THE AXIS 
BETWEEN 80W AND 86W.

...DISCUSSION...

GULF OF TEHUANTEPEC...THE 1542 UTC ASCAT PASS SAW N WINDS TO 30 
KT IN THE GULF OF TEHUANTEPEC. THESE WINDS WILL BE REINFORCED 
TONIGHT BY A SECONDARY COLD FRONT CURRENTLY MOVING S THROUGH THE 
WESTERN GULF OF MEXICO. WINDS ARE EXPECTED TO REACH MINIMAL GALE 
FORCE AFTER MIDNIGHT TONIGHT. THE GRADIENT WILL CONTINUE TO 
TIGHTEN FRI INTO SAT...WITH MINIMAL STORM FORCE CONDITIONS 
EXPECTED BY SAT AFTERNOON AND CONTINUING THROUGH SUNRISE ON SUN. 
SEAS ARE FORECAST TO REACH 21 FT BY SAT AFTERNOON. 

GULF OF CALIFORNIA...THE 1720 UTC ASCAT PASS CAPTURED STRONG NW 
WINDS S OF 25N IN THE GULF OF CALIFORNIA. THE STRONGEST WINDS IN 
THE GULF SHOULD BE FARTHER N WHERE THE PASS MISSED. MAXIMUM 
SUSTAINED WINDS SHOULD BE AS HIGH AS 30 KT IN THE CENTRAL GULF 
OF CALIFORNIA WITH SEAS TO 11 FT ACROSS THE LONG FETCH AREAS IN 
THE CENTRAL GULF WATERS. WINDS WILL GRADUALLY DIMINISH TO 20 KT 
OR LESS AND SEAS SUBSIDE TO LESS THAN 8 FT BY SAT MORNING AS THE 
LOWER PRESSURE OVER WESTERN MEXICO ERODES AND WEAKENS THE 
PRESSURE GRADIENT OVER THE GULF OF CALIFORNIA.

AN UPPER LOW LIES JUST W OF THE AREA NEAR 19N141W ACCORDING TO 
WATER VAPOR IMAGERY. AN UPPER JET LIES E OF THE LOW...CENTERED 
ALONG 130W FROM 10N TO 27N BEFORE TAKING A SHARP TURN ALONG 27N 
EASTWARD INTO NW MEXICO. THIS JET IS DIRECTING MOISTURE FROM 
THE ITCZ OVER MUCH OF THE AREA N OF A LINE FROM 10N130 TO 
21N110W AND INTO THE GULF OF CALIFORNIA FROM 25N-30N. 
PRECIPITABLE WATER IMAGERY SHOWS MID- TO LOW-LEVEL MOISTURE IS 
ABUNDANT IN THIS AREA S OF 25N W OF 122W. SCATTERED SHOWERS AND 
ISOLATED THUNDERSTORMS ARE MOST LIKELY TO LIE IN THIS SW PORTION 
OF THE MOISTURE SWATH WITH MAINLY CIRRUS IS FOUND ELSEWHERE. THE 
UPPER LOW WILL MERGE WITH A NEW NORTHERN STREAM TROUGH 
APPROACHING FROM THE NW OVERNIGHT TONIGHT THAT WILL OPEN UP THE 
LOW AND TURN WHAT IS LEFT OF IT NEGATIVE TILT OVER WESTERN 
WATERS. THE NEW TROUGH WILL AMPLIFY W OF THE AREA. PRECIPITATION 
SHOULD GRADUALLY FOCUS WEST OF 130W THROUGH TONIGHT AND REMAIN 
THERE INTO SAT AS A RESULT.

THE 1034 MB SUBTROPICAL HIGH NEAR 36N127W EXTENDS ITS PRIMARY 
RIDGE AXIS SOUTHWESTWARD THROUGH 31N140W WITH A SECONDARY AXIS 
FOUND FROM THE HIGH TO 20N117W. FRESH TO STRONG NE TRADE WINDS 
PREVAIL OVER MUCH OF THE REGION W OF THE SECONDARY RIDGE AXIS. A 
SURFACE TROUGH...THE REFLECTION OF THE AFOREMENTIONED UPPER LOW 
JUST W OF THE AREA...LIES FROM 11N133W TO 03N138W. THE 1902 UTC 
ASCAT PASS SHOWS WINDS ARE AMPLIFIED W OF THE TROUGH WITH THE 
PASS REVEALING WINDS NEAR GALE FORCE. THE TROUGH WILL GRADUALLY 
WEAKEN AND MOVE NW AS THE UPPER SYSTEM EVOLVES. MEANWHILE...THE 
SUBTROPICAL HIGH WILL GRADUALLY WEAKEN THROUGH FRI AS A FRONT 
APPROACHES FROM THE W. THE HIGH WILL REORGANIZE BEHIND THE FRONT 
ON SAT. TRADEWINDS WILL DIMINISH TO A STRONG BREEZE AND SHRINK 
WESTWARD THROUGH SAT IN RESPONSE TO THESE CHANGES IN THE PATTERN.

$$
SCHAUER