000
AXPZ20 KNHC 170344
TWDEP 

TROPICAL WEATHER DISCUSSION   
NWS NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC TUE MAY 17 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 ANALYZED FROM 10N84W 
TO 08N98W TO 05N112W TO 06N125W TO 04N140W. SCATTERED MODERATE 
AND ISOLATED STRONG CONVECTION WAS WITHIN 240 NM S OF THE AXIS 
BETWEEN 88W AND 92W. SCATTERED MODERATE TO STRONG CONVECTION WAS 
FROM 07N TO 10N BETWEEN 104W AND 110W.

...DISCUSSION...

AN UPPER LEVEL TROUGH DOMINATES THE WESTERN SEABOARD OF THE U.S. 
AND CANADA EXTENDING FROM NORTHERN CALIFORNIA NEAR 42N122W AND 
INTO THE AREA NEAR 32N123W TO A BASE NEAR 22N137W WHERE A NEW 
UPPER CYCLONE CIRCULATION HAS DEVELOPED AND PINCHED OFF FROM THE 
PARENT TROUGH. A NARROW BAND OF DRY AIR PRECEDES THE TROUGH 
WITHIN 90 NM SE OF THE AXIS FROM THE CALIFORNIA AND MEXICO 
BORDER TO THE BASE OF THE TROUGH. A SHORTWAVE UPPER TROUGH HAS 
DISCONNECTED FROM THIS PARENT FEATURE NOW EXTENDING TO THE S 
FROM THE UPPER CYCLONE TO NEAR 10N137W. MID TO UPPER LEVEL 
MOISTURE IS BEING ADVECTED FROM THE DEEP TROPICS NE AHEAD OF THE 
TROUGH TO ACROSS WESTERN MEXICO. 

UPPER RIDGING DOMINATES THE MAJORITY OF THE REMAINDER OF THE 
AREA ALOFT. A NORTH TO SOUTH ORIENTED RIDGE AXIS REACHES FROM 
THE U.S. CENTRAL PLAINS REGION TO ACROSS CENTRAL MEXICO. AN EAST 
TO WEST ORIENTED UPPER RIDGE IS TO THE S REACHING FROM A COL 
NEAR 06N80W TO 10N104W TO 09N120W TO ANOTHER COL NEAR 04N134W. 
ABUNDANT ACTIVE CONVECTION ENCOMPASSES THE ITCZ E OF 120W 
ALTHOUGH THE CONVECTION HAS BEEN DIMINISHING DURING THE PAST 6 
HOURS. THE UPPER RIDGE IS PROVIDING HEALTHY OUTFLOW ALOFT ALONG 
WITH UPPER LEVEL DIFFLUENCE S OF THE RIDGE AXIS. ADDITIONAL 
CONVECTION IS ASSOCIATED WITH A SURFACE TROUGH WHICH IS EMBEDDED 
IN THE ITCZ REACHING FROM 10N98W TO 07N100W TO 04N102W. 
SCATTERED MODERATE TO STRONG CONVECTION WAS OCCURRING WITHIN 120 
NM OF THE TROUGH.

ELSEWHERE AT THE SURFACE...1024 MB HIGH PRES IS POSITIONED JUST 
W OF THE DISCUSSION WATERS NEAR 28N145W EXTENDING E TO SE 
THROUGH 27N130W TO NEAR 10N110W. A TIGHT PRES GRADIENT REMAINS W 
OF THE BAJA CALIFORNIA PENINSULA SUPPORTING NORTHERLY 20 TO 25 
KT WINDS WITHIN 180 NM W OF THE BAJA CALIFORNIA PENINSULA ALONG 
WITH 8 TO 9 FT SEAS. THESE CONDITIONS WILL PERSIST THROUGH THE 
NEXT 48 HOURS. LINGERING NW SWELL TO 9 FT EXISTS N OF 24N W OF 
121W BEHIND A DISSIPATED COLD FRONT WHICH FELL APART OVER THE 
AREA YESTERDAY. THIS SWELL WILL DECAY THROUGH 48 HOURS GRADUALLY 
BECOMING OVERTAKEN BY THE SOUTHERLY SWELL MENTIONED BELOW.

VERY HIGH ENERGY CROSS EQUATORIAL SOUTHERLY SWELL WITH PEAK WAVE 
PERIODS OF 19 TO 21 SECONDS AND WAVE HEIGHTS OF 8 TO 10 FT HAS 
INVADED THE SW THIRD OF THE DISCUSSION AREA THIS EVENING. THIS 
SWELL WILL CONTINUE TO PROPAGATE NE BUILDING TO UP TO 11 FT AS 
IT ENCOMPASSES THE SW TWO THIRDS OF THE AREA IN 24 HOURS THEN 
ALMOST THE ENTIRE DISCUSSION AREA BY 48 HOURS. THE SWELL WILL 
ARRIVE AT THE MEXICO AND CENTRAL AMERICAN COASTLINES LATE TUE 
NIGHT INTO EARLY WED CREATING VERY HAZARDOUS CONDITIONS IN THE 
SURF ZONE INCLUDING AN ENHANCED RISK OF RIP CURRENTS. REFER TO 
YOUR LOCAL NATIONAL METEOROLOGICAL OFFICES FOR MORE INFORMATION.

$$
LEWITSKY