000
AXPZ20 KNHC 232154
TWDEP 

TROPICAL WEATHER DISCUSSION   
NWS NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC SAT APR 23 2011

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

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2030 UTC.

...ITCZ...
AXIS ALONG AXIS FROM 04N77W TO 03N82W TO 08N96W TO 03N130W TO 
03N140W.  SCATTERED MODERATE TO STRONG CONVECTION WITHIN 120 NM 
S OF AXIS FROM 95W TO 99W AND WITHIN 180 NM OF AXIS FROM 106W TO 
113W.  ISOLATED MODERATE TO STRONG WITHIN 180 NM OF AXIS FROM 
113W TO 123W.

...DISCUSSION...
UPPER LEVEL LONGWAVE TROUGH CROSSES EPAC FROM 32N120W TO 18N140W 
WITH VERY DRY AIR MASS WITH 180 NM OF AXIS. ALTHOUGH PLENTY OF 
MOISTURE ALOFT AVAILABLE NW OF TROUGH AXIS...LARGE SURFACE RIDGE 
RESTRICT ANY SIGNIFICANT UPLIFTING OR CONVECTION.  ANTICYCLONE 
GYRE AT 13N107W ANCHORS UPPER LEVEL RIDGE WITH FLATTENED CREST 
ALONG 110W EFFECTIVELY BLOCKING TROUGH FROM FURTHER SOUTHWARD 
ENCROACHMENT.  ABUNDANT MOISTURE RUNS SW-NE PARALLEL TO TROUGH 
AXIS RIDING 90 KT JET CORE HEADING TOWARDS CENTRAL BAJA 
CALIFORNIA AND MEXICO.  MOISTURE REACHING AS FAR E AS CENTRAL 
TEXAS WHERE COLD FRONT IS EXPECTED TO CONVERT IT TO MUCH NEEDED 
RAIN. 

RIDGE MAINTAINS VERY DRY AREA BETWEEN MOIST JET STREAM AND ITCZ.

AT THE SURFACE...
WEAK TROUGH ALONG 98W HAS EMBEDDED 1010 MB LOW PRES AT 08N98W. 
SCATTERED CONVECTION WITHIN 150 NM IN LOW PRES E QUADRANT 
DRIFTING W THROUGH NEXT TWO DAYS.  FAVORABLE ENVIRONMENT ALOFT 
EXPECTED TO MAINTAIN TROUGH AND LOW PRES ACTIVE...BUT NO MODEL  
GUIDANCE MAKES ANYTHING OUT OF EITHER ONE.  

HIGH PRES CENTER 1023 MB OVER FAR NW PART OF AREA AT 27N143W HAS 
RIDGE EXTENDING E TO 11N96W.  PRES GRADIENT BETWEEN RIDGE AND 
WEAK TROUGH ALONG BAJA CALIFORNIA SUPPORTS FRESH NW BREEZE N OF 
23N E OF 118W TO W COAST OF BAJA CALIFORNIA.  PRES GRADIENT 
BETWEEN RIDGE AND LOWER PRES IN VICINITY OF ITCZ SUPPORTING 
MODERATE TO FRESH TRADES FROM 08N TO 20N W 0F 133W.  HIGH PRES 
CENTER SHIFT NW OF AREA IN NEXT 24 HOURS...BUT RIDGE HOLDS TO 
ITS POSITION THROUGH FORECAST PERIOD.  

MODERATE TRADES FLOW FROM CARIBBEAN SEA ACROSS CENTRAL AMERICA 
AND INTO PACIFIC THROUGH GULF OF PAPAGAYO EXPECTED TO WEAKEN 
SIGNIFICANTLY THROUGH NEXT 24 HRS.  

$$
WALLY BARNES