000
AXPZ20 KNHC 150341
TWDEP 

TROPICAL WEATHER DISCUSSION   
NWS NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC SUN MAY 15 2011

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM 
THE EQUATOR TO 32N...EAST OF 140W.

BASED ON 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0230 UTC.

...ITCZ...

THE INTERTROPICAL CONVERGENCE ZONE AXIS WAS ALONG 05N TO 06N W 
OF 115W. SCATTERED MODERATE AND ISOLATED STRONG CONVECTION WAS 
WITHIN 75 NM N OF THE AXIS BETWEEN 117W AND 120W AND ALSO WITHIN 
120 NM N OF THE AXIS BETWEEN 125W AND 129W. SCATTERED MODERATE 
CONVECTION WAS WITHIN 120 NM N OF THE AXIS BETWEEN 132W AND 135W.

...DISCUSSION...

ALOFT...A DEEP LAYERED TROUGH DOMINATES THE FAR NE PACIFIC THIS 
EVENING CENTERED ON AN UPPER CYCLONE DIVING SE TOWARD NORTHERN 
CALIFORNIA NEAR 41N130W EXTENDING SE THROUGH S FROM THE LOW TO 
NEAR 22N130W. MID TO UPPER LEVEL MOISTURE WAS ROTATING THROUGH 
THIS TROUGH N OF A LINE FROM 23N140W TO 25N125W TO THE NORTHERN 
BAJA CALIFORNIA PENINSULA. A LARGE BAND OF DRY AIR AND 
SUBSIDENCE WAS APPARENT ON WATER VAPOR IMAGERY WITHIN 120 TO 300 
NM SE THROUGH S OF THIS SAME LINE...INDICATING MID TO UPPER 
CONVERGENCE WITHIN A 50-75 KT JET SEGMENT.

A SMALL UPPER CYCLONE HAS CUT OFF OVER THE DEEP TROPICAL PACIFIC 
NEAR 03N120W...WITH ITCZ RELATED CONVECTION FLARING WITHIN 300 
NM OVER THE N SEMICIRCLE. A LARGE UPPER RIDGE DOMINATED THE AREA 
E OF 115W...WITH THE MEAN RIDGE AXIS EXTENDING FROM OVER THE 
SOUTHERN TIP OF THE BAJA CALIFORNIA PENINSULA SE TO A PARENT 
ANTICYCLONE NEAR 10N93W SW OF THE COASTS OF GUATEMALA AND EL 
SALVADOR.

AT THE SURFACE...ANTICYCLONIC FLOW DOMINATES THE AREA W OF 
105W...CENTERED ON A 1032 MB HIGH WELL NW OF THE AREA NEAR 
36N150W. AN ASSOCIATED SURFACE RIDGE EXTENDS SE FROM THE HIGH TO 
NEAR 16N111W. THE PRESSURE GRADIENT HAS TIGHTENED ENOUGH E OF 
THE RIDGE TO PRODUCE FRESH NWLY WINDS WITHIN 180 NM W OF THE 
BAJA CALIFORNIA PENINSULA. EXPECT THIS SCENARIO TO PREVAIL 
TONIGHT EXPANDING TO ENCOMPASS THE AREA N OF 21N BETWEEN THE 
PENINSULA AND 117W BY LATE MON. A COLD FRONT IS CLIPPING THE 
AREA N OF 28N. A BRIEF SURGE OF 20 KT NORTHERLY WINDS WILL OCCUR 
BEHIND THE FRONT TONIGHT ALONG WITH NW SWELLS TO 9 FT. THE SWELL 
WILL PROPAGATE SE REACHING 24N BY 48 HOURS.

LONG PERIOD CROSS EQUATORIAL SOUTHERLY SWELL WITH PEAK WAVE 
PERIODS OF 20 SECONDS WILL MOVE INTO THE FAR SW WATERS SUN NIGHT 
WITH 8 FT OR GREATER SEAS REACHING ACROSS THE SW HALF OF THE 
AREA BY TUE.

E OF 105W...WEAK 10 TO 15 KT SW FLOW PREVAILS S OF A TROUGH AXIS 
EXTENDING FROM NEAR THE PANAMA AND COSTA RICA BORDER TO 06N89W 
TO 08N98W. ACTIVE CONVECTION WAS NOTED IN THE CONVERGENT SWLY 
FLOW S OF THE TROUGH. SCATTERED MODERATE TO STRONG CONVECTION 
WAS FROM 02N TO 07N BETWEEN 81W AND 94W AND ALSO WITHIN 60 NM OF 
06N97W. MODERATE NORTHERLY LOW LEVEL FLOW ACROSS CENTRAL AMERICA 
WILL CONTINUE TO PROVOKE ACTIVE CONVECTION ACROSS THIS AREA E OF 
95W DURING THE NEXT 24 HOURS. WINDS MAY INCREASE TO 20 KT S OF 
THIS TROUGH SUN MORNING CONTINUING THROUGH 48 HOURS.

MAY 15 MARKS THE BEGINNING OF THE 2011 EASTERN PACIFIC HURRICANE 
SEASON.

$$
LEWITSKY