000
AXPZ20 KNHC 010326
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC FRI MAR 01 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0115 UTC.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
THE MONSOON TROUGH AXIS WAS ANALYZED FROM 05N77W TO 07N84W TO 
03N92W TO 04N98W TO 03N105W. THE ITCZ AXIS WAS ANALYZED FROM 
03N105W TO 02N112W TO 05N136W. SCATTERED MODERATE CONVECTION WAS 
WITHIN 120 NM N OF THE AXIS BETWEEN 81W AND 87W. ISOLATED 
MODERATE CONVECTION WAS FROM 02N TO 06N BETWEEN 88W AND 100W.

...DISCUSSION...

GULF OF TEHUANTEPEC...THE 1542 UTC ASCAT PASS SAW N WINDS TO 30 
KT IN THE GULF OF TEHUANTEPEC AND THE 1804 OSCAT PASS CONFIRMED 
THESE WINDS REACH AS FAR S AS 14N. GAP WINDS HERE 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 BUILD AS HIGH AS 24 FT 
OVERNIGHT SAT NIGHT. 

GULF OF CALIFORNIA...THE 1720 UTC ASCAT PASS CAPTURED STRONG NW 
WINDS S OF 25N IN THE GULF OF CALIFORNIA AS DID THE 1942 UTC 
OSCAT PASS. THE STRONGEST WINDS IN THE GULF SHOULD BE FARTHER N 
WHERE THE PASSES 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 19N142W ACCORDING TO 
WATER VAPOR IMAGERY. AN UPPER JET LIES E OF THE LOW...CENTERED 
ALONG 130W FROM 10N TO 28N BEFORE TAKING A SHARP TURN ALONG 28N 
EASTWARD INTO NW MEXICO. THIS JET IS DIRECTING MOISTURE FROM 
THE ITCZ OVER MUCH OF THE AREA N OF A LINE FROM 10N130 TO 
GUADALAJARA MEXICO. PRECIPITABLE WATER IMAGERY SHOWS MID- TO 
LOW-LEVEL MOISTURE IS ABUNDANT WITHIN THIS AREA S OF 23N W OF 
125W. 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 35N129W EXTENDS ITS PRIMARY 
RIDGE AXIS SOUTHWESTWARD THROUGH 31N140W WITH A SECONDARY AXIS 
FOUND FROM THE HIGH TO 20N115W. FRESH TO STRONG NE TRADE WINDS 
PREVAIL OVER MUCH OF THE REGION SW OF THE SECONDARY RIDGE AXIS N 
OF THE ITCZ. A SURFACE TROUGH...THE REFLECTION OF THE 
AFOREMENTIONED UPPER LOW JUST W OF THE AREA...LIES FROM 10N135W 
TO 03N139W. THE 1902 UTC ASCAT PASS SHOWED WINDS W OF THE TROUGH 
WERE 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 TO THE 
REGION NEAR THE TROUGH FRI AND SAT IN RESPONSE TO THESE CHANGES 
IN THE PATTERN.

$$
SCHAUER