000
AXPZ20 KNHC 250920
TWDEP 

TROPICAL WEATHER DISCUSSION   
NWS NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC WED MAY 25 2011

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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0745 UTC.
 
...ITCZ...
THE INTERTROPICAL CONVERGENCE ZONE WAS ANALYZED FROM 10N86W TO 
12N105W TO 07N116W TO 04N140W. ISOLATED MODERATE CONVECTION LIES 
WITHIN 150 NM S OF AXIS BETWEEN 87W AND 92W. ISOLATED MODERATE 
TO STRONG CONVECTION LIES WITHIN 150 NM NW OF AXIS BETWEEN 108W 
AND 116W. A SURFACE LOW IS EMBEDDED IN THE ITCZ NEAR 11N97W. 
SCATTERED MODERATE TO STRONG CONVECTION CAN BE FOUND WITHIN 450 
NM SW QUADRANT OF THE LOW. 

...DISCUSSION...
THE SUBTROPICAL RIDGE IS CURRENTLY BEING COMPROMISED BY A 
RAPIDLY WEAKENING COLD FRONT. HOWEVER...THE PRESSURE GRADIENT 
BETWEEN THE SUBTROPICAL RIDGE AND TROUGHING OVER THE 
SOUTHWESTERN UNITED STATES AND CENTRAL MEXICO IS STILL STRONG 
ENOUGH TO SUPPORT FRESH NW WITHIN 270 NM OF THE W COAST OF BAJA 
CALIFORNIA AS OBSERVED BY THE 0540 UTC ASCAT PASS. THE 
SUBTROPICAL HIGH WILL REORGANIZE W OF THE DISSIPATING PORTION OF 
THE AFOREMENTIONED COLD FRONT TODAY WHILE THE LEADING EDGE OF 
THE COLD FRONT MOVES INTO THE NORTHWESTERN UNITED STATES. THE 
AREA OF FRESH NW WINDS WILL EXPAND WESTWARD BY THU AS THE PRES 
GRADIENT BETWEEN THE RIDGE AND TROUGHING OVER THE INTERIOR 
WESTERN UNITED STATES BUILDS. WINDS ARE EXPECTED TO BECOME 
STRONG OFF THE BAJA CALIFORNIA NORTE COAST BY EARLY FRI MORNING. 

FRESH TRADE WINDS LIE OVER CENTRAL WATERS W OF 130W AS INDICATED 
BY THE 0536 UTC ASCAT PASS. THE AREA OF FRESH TRADES WILL EXPAND 
NORTHEASTWARD BEGINNING TONIGHT AS THE SUBTROPICAL HIGH W OF THE 
AFOREMENTIONED DISSIPATING COLD FRONT MOVES EASTWARD. THIS FRONT 
WILL BRING A BATCH OF NW SWELL WITH SEAS TO 9 FT INTO THE NW 
PORTION OF THE FORECAST AREA BEGINNING THU MORNING...BUT WINDS 
WILL REMAIN BELOW ADVISORY CRITERIA. CURRENTLY...A 40-50 KT 
SOUTHWESTERLY UPPER JET LIES OVER THE REGION OF TRADE WINDS AND 
IS TRANSPORTING UPPER MOSITURE MANIFESTED AS CIRRUS CLOUDS THAT 
OVERLAY THE DENSE STRATOCUMULUS THAT EXTENDS OVER MUCH OF THE 
AREA N OF 15N W OF 115W.

CONVECTION ALONG THE ITCZ IS STRONGEST SW OF THE 1011 MB 
EMBEDDED LOW PRES SYSTEM NEAR 11N97W. THIS CONVECTION IS 
DESCRIBED IN THE ITCZ SECTION. NORTHEASTERLY SHEAR ALOFT IS 
FORCING THE CONVECTION DOWNWIND OF THE LOW LEVEL CENTER. THE LOW 
IS EXPECTED TO DISSIPATE TO A TROUGH BY THU MORNING. THE 0354 
UTC ASCAT PASS SHOWS 20 KT SW TO W WINDS EXTEND WELL W OF THE 
LOW TO AT LEAST 107W S OF THE ITCZ. THESE WINDS ARE FORECAST TO 
GRADUALLY DIMINISH AS WELL. 

CROSS-EQUATORIAL S SWELL HAS BROUGHT SEAS TO 8 FT OVER S 
CENTRAL WATERS. THE MOST RECENT JASON2 AND ENVISAT PASSES 
CONFIRM THESE CONDITIONS. THIS SWELL WILL MAKE ITS WAY NORTHWARD 
INTO THU AS A NEW BATCH OF 14-16 SECOND PERIOD SW SWELL 
PROPAGATES N OF THE EQUATOR.

$$
SCHAUER