000
AXPZ20 KNHC 030905
TWDEP 

TROPICAL WEATHER DISCUSSION    
NWS NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC TUE APR 03 2012

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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0715 UTC.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...

THE ITCZ AXIS EXTENDS FROM 08N112W TO 05N127W TO 05N140W. 
SCATTERED MODERATE CONVECTION LIES WITHIN 90 NM N OF THE AXIS 
BETWEEN 114W AND 127W.

...DISCUSSION...

THE AMPLIFIED NORTHERN STREAM PATTERN ALOFT CURRENTLY IN PLACE 
WILL GRADUALLY BREAK DOWN OVER THE NEXT TWO DAYS. THE UPPER LOW 
OVER THE FOUR CORNERS STATES WILL MOVE EASTWARD QUITE SLOWLY 
TODAY...ALLOWING THE RIDGING TO ITS W TO ERODE AS THE NEXT 
TROUGH APPROACHES. THIS SECOND TROUGH IS CONSIDERABLY LESS 
AMPLIFIED THAN THE TROUGHING OVER MEXICO ASSOCIATED WITH THE 
AFOREMENTIONED UPPER LOW. THESE CHANGES TO THE PATTERN WILL 
ALLOW FOR THE FLOW TO BECOME RELATIVELY ZONAL ALOFT N OF 29N BY 
THIS EVENING. 

THE SUBTROPICAL HIGH LIES NEAR 29N132W. IT HAS WEAKENED OVER THE 
PAST 24 HOURS TO 1025 MB. THE PRES GRADIENT BETWEEN THE HIGH AND 
TROUGHING OVER MEXICO ASSOCIATED WITH THE UPPER LOW IS STILL 
STRONG ENOUGH TO SUPPORT A SMALL AREA OF STRONG N WINDS AND SEAS 
TO 16FT N OF 27N BETWEEN 120W AND 125W AS OBSERVED BY SHIPS DQXQ 
AND 3FQS8 AT 0600 UTC. THESE WINDS WILL DIMINISH EARLY TODAY AS 
THE SUBTROPICAL HIGH CONTINUES TO BE WEAKENED BY THE NEXT DEEP 
LAYER TROUGH APPROACHING FROM THE NW. THE COLD FRONT ASSOCIATED 
WITH THIS WESTERN TROUGH ALOFT WILL SLOWLY TO MOVE THROUGH NW 
WATERS BEGINNING LATE TUE AFTERNOON. THIS FRONT WILL ENTER THE 
FORECAST AREA WITH CONSIDERABLY LESS FANFARE THAN ITS 
PREDECESSOR...WITH FRESH NE WINDS BEHIND IT AND SEAS TO 9 FT. 
MEANWHILE...NW SWELL BEHIND THE PREVIOUS COLD FRONT CONTINUES TO 
MOVE SOUTHWARD THROUGH THE FORECAST AREA. 

FARTHER S...AN UPPER LOW IS EVIDENT ON WATER VAPOR IMAGERY NEAR 
17N129W. A SOUTHWESTERLY JET ON ITS SE SIDE IS DIRECTING A 
STREAM OF TROPICAL MOISTURE ALOFT NORTHEASTWARD FROM THE ITCZ ON 
THE WESTERN EDGE OF THE FORECAST AREA. A BAND OF MULTI-LAYERED 
CLOUDINESS CAN BE FOUND WITHIN ABOUT 210 NM EITHER SIDE OF A 
LINE FROM 18N117W TO 05N136W AS A RESULT. SCATTERED MODERATE 
CONVECTION CAN ALSO BE FOUND FROM 15N TO 18N BETWEEN 115W AND 
120W. THE REAR RIGHT QUADRANT OF THE SOUTHERN STREAM JET IS 
PROVIDING BROAD UPPER LEVEL DIFFLUENCE OVER THE ITCZ. THIS 
DIFFLUENCE ALOFT IS ENHANCING THE CONVECTION DESCRIBED IN THE 
ITCZ SECTION ABOVE. THE UPPER LOW WILL WEAKEN AS IT MOVES 
EASTWARD TO 115W THROUGH EARLY THU.

A SURFACE TROUGH CONTINUES TO LINGER OFFSHORE OF COSTA RICA FROM 
09N84W TO 05N91W TO 04N97W. WHILE THERE IS NO DEEP CONVECTION 
CURRENTLY NEAR THE TROUGH...PRECIPITABLE WATER VALUES NEAR AND S 
OF THE TROUGH ARE AS HIGH AS 2.25 INCHES AND INFRARED IMAGERY 
SHOWS INCREASING COVERAGE OF WARM TOPPED SHOWERS NEAR THE 
TROUGH. THE 40-50 KT WEST-SOUTHWESTERLY VERTICAL SHEAR OVER THE 
TROUGH SHOULD THAT IS INHIBITING CONVECTION SHOULD RELAX A BIT 
BY WED NIGHT.

GULF OF CALIFORNIA...THE PRES GRADIENT BETWEEN THE WEAKENING 
SUBTROPICAL HIGH AND TROUGHING OVER CENTRAL MEXICO CONTINUES TO 
SUPPORT FRESH NW TO N WINDS FROM 24N AND 29N. A PORTION OF THESE 
WINDS WERE CAPTURED BY THE 0402 UTC ASCAT PASS. WINDS SHOULD 
DIMINISH HERE LATER THIS MORNING.

$$
SCHAUER