000
AXPZ20 KNHC 251525
TWDEP 

TROPICAL WEATHER DISCUSSION   
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1445 UTC.
 
...ITCZ...
THE INTERTROPICAL CONVERGENCE ZONE WAS ANALYZED FROM 07N77W TO 
11N96W TO 10N112W TO 07N122W TO 06N140W. SCATTERED STRONG 
CONVECTION FROM 09N TO 12N BETWEEN 107W AND 110W. SCATTERED 
MODERATE TO STRONG CONVECTION FROM 07N TO 12N BETWEEN 97W AND 
106W. SCATTERED MODERATE TO ISOLATED STRONG CONVECTION WITHIN 
150 NM S OF ITCZ E OF 80W TO COAST OF COLOMBIA...WITHIN 150 NM S 
OF ITCZ BETWEEN 82W AND 85W...AND WITHIN 150 NM N OF ITCZ 
BETWEEN 110W AND 114W. A 1010 MB LOW PRES EMBEDDED WITHIN ITCZ 
NEAR 11N97W AND 1011 MB LOW PRES NEAR 6N131W. SCATTERED MODERATE 
TO STRONG CONVECTION WITHIN 75 NM E AND S OF 1010 MB 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 1200 UTC SHIP OBSERVATIONS. THE SUBTROPICAL HIGH 
WILL REORGANIZE W OF THE DISSIPATING PORTION OF THE 
AFOREMENTIONED COLD FRONT LATER 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. 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 W OF THE 1010 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 
108W 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. 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 WITH 18 SEC REACHING THE MEXICAN COAST EARLY FRI.

$$
PAW