000
AXPZ20 KNHC 122131
TWDEP 

TROPICAL WEATHER DISCUSSION                                    
NWS NATIONAL HURRICANE CENTER MIAMI FL                         
2205 UTC SUN APR 12 2015

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 
1915 UTC. 
 
...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...              

THE ITCZ AXIS WAS ANALYZED FROM 09N84W TO 02N108W TO 04N114W TO 
03N120W TO 05N124W...THEN CONTINUES FROM 06N127W TO 04N133W TO 
06N140W. SCATTERED MODERATE CONVECTION WAS WITHIN 180 NM S OF 
THE AXIS E OF 95W...WITHIN 150 NM S OF THE AXIS BETWEEN 129W-
133W AND WITHIN 150 NM S OF THE AXIS W OF 135W. A TROUGH LIES 
FROM 08N124W TO 04N126W. SCATTERED MODERATE WITH ISOLATED STRONG 
CONVECTION WAS WITHIN 120 NM EITHER SIDE OF THE TROUGH FROM 05N-
08N.

...DISCUSSION... 

A POTENT UPPER LOW OVER NW MEXICO WILL SLOWLY LIFT NE INTO 
EASTERN NEW MEXICO AND W TEXAS BY TUE AFTERNOON. THE LOW IS 
DRAGGING A MID LEVEL TROUGH THROUGH THE SOUTHERN GULF OF 
CALIFORNIA INTO MAINLAND MEXICO AT THE MOMENT. THIS IS ENHANCING 
THE SURFACE TROUGHING OVER THE SIERRA MADRE OCCIDENTAL RANGE 
JUST AS THE SUBTROPICAL RIDGE BUILDS OFF THE W COAST OF THE BAJA 
CALIFORNIA PENINSULA. NW TO N WINDS HAD BEEN AS STRONG AS 30 KT 
EARLIER TODAY IN THE GULF OF CALIFORNIA...BUT THE 1728 UTC ASCAT 
PASS NOW SHOWS A FRESH TO STRONG N BREEZE MAINLY IN THE MOUTH OF 
THE GULF FROM 21N-25N BETWEEN 107.5W AND 109.5W. SEAS TO 8 FT 
HAVE BEEN REPORTED IN THE VICINITY OVER THE PAST 3 HOURS. WINDS 
AND SEAS SHOULD DIMINISH THIS EVENING AS THE SYSTEM PULLS 
NE...BUT SHOWERS AND THUNDERSTORMS WILL CONTINUE OVER MAINLAND 
MEXICO SE OF THE UPPER LOW OVERNIGHT TONIGHT.

THE SUBTROPICAL RIDGE HAS BEEN WEAKENED ACROSS N WATERS...BUT IT 
SHOULD GRADUALLY STRENGTHEN THROUGH THE END OF THE FORECAST 
PERIOD TUE AFTERNOON AS HIGH PRES MOVES IN BEHIND A COLD FRONT 
EXPECTED TO PUSH INTO THE WESTERN U.S. MON NIGHT. TRADE WINDS 
SHOULD PICK UP TO A FRESH BREEZE OVER W WATERS TUE AS A RESULT. 
N WINDS ALONG THE CALIFORNIA COAST WILL ALSO INCREASE AS THE 
PRESSURE GRADIENT BUILDS BETWEEN THE FRONT OVER THE INTERIOR 
WESTERN U.S. AND THE 1035 MB SUBTROPICAL HIGH NEAR 37N137W TUE.
 
WATER VAPOR IMAGERY SHOWS A SHARP UPPER LEVEL TROUGH EXTENDING 
FROM CENTRAL CUBA ACROSS NE HONDURAS...NICARAGUA AND NW COSTA 
RICA THROUGH A LOW NEAR THE GALAPAGOS ISLANDS AND INTO THE 
SOUTHERN HEMISPHERE NEAR 10S92W. THIS RARE CROSS-EQUATORIAL TUTT 
IS BEING ENCROACHED UPON FROM THE E BY RIDGING EXTENDING ACROSS 
NORTHERN SOUTH AMERICA INTO THE PACIFIC ALONG 06N W OF 88W. 
BROAD DIVERGENCE ASSOCIATED WITH THE RIDGE AXIS IS ENHANCING 
CONVECTION ON THE E EDGE OF THE ITCZ. THE TUTT LOW IS EXPECTED 
TO LINGER NEAR THE GALAPAGOS AS IT CUTS OFF FROM THE REMAINDER 
OF THE TROUGH THROUGH TUE AFTERNOON. THE EASTERN EDGE OF THE 
ITCZ SHOULD CONTINUE TO SEE SOME ACTIVE CONVECTION AS A RESULT. 

$$
SCHAUER