000
AXPZ20 KNHC 131615
TWDEP 

TROPICAL WEATHER DISCUSSION    
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC FRI APR 13 2007

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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1545 UTC.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 7N78W 8N92W 7N100W 4N124W 5N140W. 
SCATTERED MODERATE TO STRONG IS FROM 7N TO 11.5N BETWEEN 100W 
AND 110W. SCATTERED MODERATE IS WITHIN 75 NM EITHER SIDE OF THE 
AXIS BETWEEN 122W TO 124W.

...DISCUSSION...

THE UPPER LEVEL PATTERN REMAINS FAIRLY AMPLIFIED ACROSS THE 
DISCUSSION AREA WITH A VIGOROUS UPPER LOW OVER THE SWRN U.S. AND 
ASSOCIATED TROUGHING STRETCHING SW THROUGH BAJA CALIFORNIA. THE 
TAIL END OF THE TROUGH HAS NOW DEVELOPED INTO A CUT OFF UPPER 
LOW NEAR 17N130W. THIS CUT OFF LOW IS INTERRUPTING EXTENSIVE 
RIDGING THAT COVERS THE BULK OF THE AREA W OF THE TROUGH. THE 
NRN EXTENSION OF THE RIDGE IS ANCHORED BY AN UPPER HIGH CENTERED 
NEAR 25N129W. THE SRN BRANCH AXIS EXTENDS FROM THE EQ137W TO 
12N135W. UPPER LEVEL CONFLUENCE IS LEADING TO ABUNDANT DRY 
STABLE AIR ACROSS THE AREA N OF 20N. THE FLOW OVER THE FAR NW 
PORTION OF THE AREA HAS TURNED WLY IN RESPONSE TO THE 
APPROACHING LARGE TROUGH AND ASSOCIATED SURFACE COLD FRONT THAT 
IS EXPECTED TO PUSH INTO THE REGION TONIGHT.

THE MORE ACTIVE WEATHER IS OVER THE TROPICAL WATERS ESPECIALLY 
ALONG THE ITCZ ROUGHLY BETWEEN 100-115W S OF 12N. UPPER LEVEL 
DIFFLUENCE AND SWLY FLOW ALONG WITH LOW-LEVEL CONVERGENCE NEAR 
THE ITCZ AXIS ARE THE ELEMENTS PRODUCING THE SCATTERED SHOWERS 
AND TSTMS. A POSSIBLE WEAK SFC TROUGH EMBEDDED IN THE ITCZ MAY 
ALSO BE AIDING IN THIS ACTIVITY. UPPER LEVEL DEBRIS CLOUDINESS 
IS BEING ADVECTED N/NE FROM THIS CONVECTION TOWARDS SE MEXICO 
AND MUCH OF CENTRAL AMERICA. NWP MODELS INDICATE THAT THE UPPER 
LEVEL FLOW IS FORECAST TO REMAIN SWLY OVER THE WEEKEND WHICH 
SHOULD CONTINUE TO PROMOTE SOME CONVECTION AND UPPER MOISTURE 
ACROSS A SIMILAR REGION.  

AT THE SURFACE...HIGH PRESSURE RIDGE EXTENDS INTO THE DISCUSSION 
AREA THROUGH 32N129W 24N124W AND SE TO NEAR 20N110W. THE 
ASSOCIATED HIGH CENTER WAS ANALYZED AT 12 UTC JUST N OF THE AREA 
NEAR 32N130W AS 1027 MB. THE FAIRLY TIGHT PRES GRADIENT OVER THE 
FAR NE PART OF THE AREA IS USHERING STRONG NW FLOW AND LARGE NW 
SWELLS MAXING UP TO 14 FT. THESE SWELLS ARE FORECAST BY NWW3 
GUIDANCE TO SPREAD SE WHILE SLOWLY SUBSIDING OVER THE NEXT 48 
HRS. LATEST NWP MODELS SUGGEST THAT A WEAKENING COLD FRONT...
MENTIONED ABOVE...WILL MOVE INTO THE EXTREME NW CORNER LATER 
TODAY FOLLOWED BY A SURGE OF NW SWELL POSSIBLY MAXING OUT TO 
NEAR 9 FT. THESE SEAS WILL INCREASE FURTHER OVER THE WEEKEND AS 
STRONG HIGH PRES BUILDS E.

GAP WINDS...HAVE INTRODUCED AN INCREASE IN NLY WINDS...20 TO 30 
KT...IN 48-H ACROSS THE GULF OF TEHUANTEPEC. NWP GUIDANCE IS IN 
FAIR AGREEMENT IN THE TIMING AND MAGNITUDE OF THESE WINDS DUE TO 
THE TIGHTENING PRES GRADIENT BETWEEN A STRONG COLD FRONT IN THE 
GULF OF MEXICO AND HIGH PRES SURGING SWD BEHIND IT.

$$
CANGIALOSI/AGUIRRE