000
AXPZ20 KNHC 221606
TWDEP 

TROPICAL WEATHER DISCUSSION   
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC FRI APR 22 2011

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

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1515 UTC.

...ITCZ...

AXIS IS CENTERED ALONG 05N77W TO 05N82W TO LOW PRES NEAR 
08N95.5W 1008 MB TO 04N117W TO 04N131W TO 03N140W. SCATTERED 
MODERATE TO STRONG CONVECTION NOTED WITHIN 180 NM EITHER SIDE OF 
AXIS BETWEEN 100W AND 123W. 

...DISCUSSION...

AT UPPER LEVELS...RIDGING HAS INCREASED ALOFT DURING THE PAST 24 
HOURS E OF 135W...ANCHORED ON AN UPPER ANTICYCLONE NEAR 
14N110W...AND HAS EXPANDED N AND NE DURING THE PAST 24 HOURS AND 
NOW COVERS MOST OF THE AREA N OF THE ITCZ BETWEEN 105W AND 135W. 
THIS RIDGING HAS OCCURRED IN LARGE PART DUE TO A SHORTWAVE ALOFT 
SWEEPING EWD ACROSS NW PORTIONS OF THE AREA AND BROAD TROUGHING 
ACROSS THE WRN U.S. YESTERDAY SHIFTING E INTO TEXAS...ALLOWING 
THE RIDGE TO AMPLIFY NWD IN BETWEEN THESE TWO TROUGHS. THE 
SHORTWAVE MOVING ACROSS NW PORTIONS OF THE AREA HAS LINKED WITH 
AN ELONGATED MID TO UPPER LEVEL CYCLONE CENTERED NEAR 14N152W. S 
TO SW FLOW ALOFT THUS PREVAILS FROM 07N TO 25N BETWEEN 125W AND 
140W. S OF THE ITCZ...A PERSISTENT EQUATORIAL UPPER CYCLONE WAS 
NOTED NEAR 01N122W AND WAS BECOMING MORE ELONGATED W TO E. 
ACTIVE DEEP CONVECTION CONTINUES NEAR THE ITCZ BETWEEN THIS 
UPPER CYCLONE AND THE UPPER ANTICYCLONE...HELPING TO MAINTAIN 
DIFFLUENT FLOW ALOFT. 

AT LOWER LEVELS...HIGH PRES AND ANTICYCLONIC FLOW DOMINATES MUCH 
OF THE AREA N OF THE ITCZ AND W OF 106W...CENTERED ON A 1023 MB 
HIGH CENTERED NEAR 28N132W...WITH RIDGE EXTENDING SE TO NEAR 
15N106W. THE PRESSURE GRADIENT BETWEEN THE RIDGE AND A TROUGH OF 
LOW PRESSURE OVER MEXICO IS SUPPORTING FRESH 20 KT NW WINDS N OF 
24N E OF 118W TO THE W COAST OF BAJA CALIFORNIA. THESE WINDS 
WERE DEPICTED IN AN OVERNIGHT 0522 UTC ASCAT PASS. IN 
ADDITION...THE PRESSURE GRADIENT BETWEEN THE RIDGE AND LOWER 
PRESSURE IN THE VICINITY OF THE ITCZ IS SUPPORTING FRESH 20 KT 
NE TO E TRADEWINDS FROM 06N TO 14N W 0F 134W. THE HIGH PRESSURE 
AND RIDGE WILL SHIFT SLIGHTLY W AND REORGANIZE OVER THE NEXT 24 
HOURS AS A SHORTWAVE AND ASSOCIATED COLD FRONT SWEEP EWD AND 
OVER THE RIDGE. THIS WILL SHIFT THE FRESH TRADEWINDS SLIGHTLY 
WWD BEFORE REBUILDING SAT NIGHT AND SUN. FRESH NWLY WINDS OFF OF 
BAJA WILL ALSO DIMINISH SLIGHTLY AND SHRINK IN AREAL COVERAGE 
DURING THE NEXT 24 HOURS BEFORE EXPANDING SUN.

A PLUME OF ABUNDANT TROPICAL MOISTURE CONTINUES TO SPREAD FRO 
THE ITCZ NEAR 100W...NE INTO EXTREME SE MEXICO AND GUATEMALA 
THIS MORNING. ACTIVE DIURNAL CONVECTION SHOULD BE EXPECTED THIS 
AFTERNOON AND EVENING FROM CHIAPAS MEXICO E AND NE TO BELIZE AND 
HONDURAS. 

VERY LONG PERIOD CROSS-EQUATORIAL SW SWELL HAS REACHED THE 
PACIFIC COASTS FROM COLOMBIA TO SRN CALIFORNIA OVERNIGHT AND 
WILL BUILD TO 3 TO 6 FT DURING THE NEXT 24 TO 36 HOURS. THIS 
WILL PRODUCE HIGH SURF ALONG EXPOSED COASTLINES THROUGH 
SUN...AND GENERATE STRONG AND WIDESPREAD RIP CURRENTS THROUGHOUT 
THE SURF ZONE.

$$
STRIPLING