000
AXPZ20 KNHC 290406
TWDEP 

TROPICAL WEATHER DISCUSSION                                    
NWS NATIONAL HURRICANE CENTER MIAMI FL                           
0405 UTC MON APR 29 2013

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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0300 UTC.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...           
THE MONSOON TROUGH EXTENDS FROM COLOMBIA NEAR 10N71W TO 04N80W 
TO 08N85W TO 08N100W...WHERE IT TRANSITIONS TO INTERTROPICAL 
CONVERGENCE ZONE AXIS...CONTINUING ON TO 08N112W TO 07N122W TO 
BEYOND 03N140W. SCATTERED MODERATE TO STRONG CONVECTION NOTED 
WITHIN 120 NM S OF MONSOON TROUGH BETWEEN 79W AND 93W. SCATTERED 
MODERATE TO STRONG CONVECTION NOTED WITHIN 150 NM EITHER SIDE 
OF ITCZ BETWEEN 111W AND 135W. 
 
...DISCUSSION...                                                
A STRONG UPPER LEVEL BLOCKING PATTERN PERSISTS ACROSS THE E 
CENTRAL PACIFIC THIS EVENING...AND IS HELPING TO MAINTAIN THE 
RELATIVELY QUITE MARINE WEATHER ACROSS THE DISCUSSION AREA. A 
HIGH AMPLITUDE OMEGA BLOCK IS CENTERED ALONG 149W-156W...FROM 
THE HAWAIIAN ISLANDS NNE INTO THE NE PACIFIC. A DOWNSTREAM CUT 
OFF UPPER CYCLONE WAS CENTERED NEAR 28N138W AND HAS BECOME 
STATIONARY TODAY...WITH A BROAD AND DEEP LAYERED CIRCULATION 
COVERING THE AREA FROM 15N TO 36N BETWEEN 130W AND 150W. 
ASSOCIATED SOUTHWESTERLY UPPER LEVEL FLOW PREVAILS SOUTH THROUGH 
SOUTHEAST OF THE UPPER CYCLONE AND DOMINATES MOST OF THE 
DISCUSSION AREA N OF THE ITCZ. A TROPICAL JET EXTENDS THROUGH 
THIS REGION...FROM NEAR 09N157W TO NEAR 21N120W WITH CORE WIND 
SPEEDS 80 TO 105 KT BETWEEN 140W AND 150W. TWO UPPER LEVEL 
RIDGED PREVAIL S OF THE SOUTHWESTERLY FLOW ALOFT...WITH WRN 
RIDGE A FLAT CROSS EQUATORIAL RIDGE S OF 07N W OF 130W...AND 
SECOND RIDGE ANCHORED ON AN UPPER ANTICYCLONE NEAR 11N98W. BROAD 
MIDDLE TO UPPER LEVEL TROUGHING SEPARATES THE RIDGES ALONG ABOUT 
120W...WITH SUFFICIENT CYCLONIC TURNING SUGGESTED BY SATELLITE 
IMAGERY TO INDUCE UNSTABLE CONDITIONS AND MUCH OF CONVECTION 
DESCRIBED ABOVE ALONG AND N OF THE ITCZ. GLOBAL MODEL FORECAST 
THE UPPER CYCLONE TO REMAIN GENERALLY STATIONARY THROUGH WED 
WITH SEVERAL SHORTWAVES ROTATING THROUGH THE BASE OF THE BROAD 
TROUGH...ACTING TO REINFORCE THE WEST TO SOUTHWESTERLY FLOW 
ALOFT AND SHIFT THE BASE OF THE TROUGH EASTWARD TO 135W.
 
AT THE SURFACE...A 1031 MB HIGH REMAINS CENTERED WELL NW OF THE 
AREA NEAR 40N137W AND EXTENDS A RIDGE SE TO NEAR 17N107W...AND S 
ACROSS SW PORTIONS OF THE AREA. RECENT SCATTEROMETER PASSES 
CONFIRM THAT THERE ARE THREE PERTURBATIONS MOVING W ALONG THE 
ITCZ TODAY...ONE ALONG 138W...A SECOND ALONG 126W...AND A THIRD 
WEAK TROUGH ALONG 112W. THE PRESSURE GRADIENT BETWEEN THE HIGH  
AND LOWER PRES ALONG THE ITCZ IS PRODUCING AN AREA OF FRESH TO 
STRONG TRADE WINDS...GENERALLY BETWEEN THE ITCZ AND 15N...AND 
FROM THE MIDDLE TROUGH ALONG 126W TO BEYOND 150W. SEAS IN THIS 
ZONE OF TRADES ARE RUNNING 8 TO 9 FT. THE TROUGHS WILL CONTINUE 
TO SHIFT W AND WEAKEN DURING THE NEXT FEW DAYS AS THE UPPER 
LEVEL WIND SHEAR INCREASES.

E OF 110W...RELATIVELY TRANQUIL CONDITIONS ARE NOTED IN 
OBSERVATIONAL DATA...RECENT SCATTEROMETER PASSES...AND LATEST 
GLOBAL MODEL DATA. OF NOTE...STRONG SW SWELL FROM A SOUTHERN 
HEMISPHERE LOW PRESSURE SYSTEM WILL CONTINUE SPREADING 
NORTHEASTWARD AND REACH THE MEXICAN AND CENTRAL AMERICAN COAST 
BY EARLY MONDAY WITH WAVE PERIODS IN THE RANGE OF 15 TO 17 
SECONDS.

$$
STRIPLING