000
AXPZ20 KNHC 120317
TWDEP 

TROPICAL WEATHER DISCUSSION                                    
NWS NATIONAL HURRICANE CENTER MIAMI FL                          
0405 UTC FRI APR 12 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 
0315 UTC.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...              
A WEAK MONSOON TROUGH AXIS EXTENDS FROM NW COLOMBIA TO 08N79W  
TO 06N90W TO 07N110W TO 07N122W WHERE IT ENDS. THE ITCZ AXIS 
BEGINS AT 06N125W TO 06N140W. SCATTERED MODERATE CONVECTION 
EXISTS WITHIN 120 NM OF THE AXIS BETWEEN 90W-94W... AND BETWEEN 
110W AND 116W. SIMILAR ACTIVITY IS WITHIN 60 NM OF THE AXIS 
BETWEEN 85W-90W.

...DISCUSSION...                                                 

E OF 110W...                                                    
A MID/UPPER LEVEL TROUGH EXTENDS FROM NEAR 26N114W SE TO 20N107W 
TO 11N101W AND TO 03N98W. TO ITS E...AN UPPER LEVEL ANTICYCLONE 
SHIFTING EWD IS JUST SW OF THE GULF OF PANAMA WITH ITS 
ASSOCIATED ANTICYCLONIC ENVELOP COVERING THE AREA JUST E OF THE 
TROUGH AXIS. A SMALLER UPPER ANTICYCLONE MOVING SE IS JUST NE OF 
THE GALAPAGOS ISLANDS. DEBRIS BLOWOFF CLOUDINESS FROM VICINITY 
OF THE MONSOON TROUGH AXIS IS BEING CHANNELED N AND NE AROUND 
THE WESTERN PERIPHERY OF THE ANTICYCLONE OVER THE AREA N OF 05N 
AND BETWEEN 82W AND 95W. SOME OF THIS MOISTURE...IN THE FORM OF 
BROKEN TO SCATTERED CIRRUS CLOUDS IS EVIDENT ACROSS MOST OF 
CENTRAL AMERICA FROM HONDURAS TO COSTA RICA. UPPER NW FLOW 
BEHIND THE TROUGH IS ADVECTING HIGH LEVEL DEBRIS CLOUDINESS FROM 
ITCZ-RELATED CONVECTION AS DESCRIBED ABOVE SEWD TO NEAR 03N AND 
BETWEEN THE TROUGH AXIS AND 110W.

THE EASTERN EXTENSION OF A JET STREAM BRANCH EXTENDS FROM 
20N110W ENE TO ACROSS CENTRAL MEXICO. MODERATE SW TO W WINDS 
ALONG AND WITHIN 180 NM S OF THIS JET STREAM BRANCH ARE 
BRINGING SCATTERED TO BROKEN CIRRUS CLOUDS NEWD ACROSS CENTRAL 
MEXICO FROM ABOUT 18N TO 23N...AND NE FROM THERE TO ACROSS THE 
GULF OF MEXICO. WATER VAPOR IMAGERY GENERALLY SHOWS MODERATE 
SUBSIDENCE ELSEWHERE LEADING TO MOSTLY CLEAR SKIES...WITH THE 
EXCEPTION OF A POCKETS OF LOW LEVEL CLOUDS WITH POSSIBLE 
ISOLATED SHOWERS.
 
THE AFOREMENTIONED TROUGH WILL SHIFT E OF THE DISCUSSION 
AREA ON FRI ALLOWING FOR MORE A ZONAL UPPER PATTERN TO BECOME 
ESTABLISHED ACROSS THIS PORTION OF THE AREA.

W OF 110W...                                                
BROAD MID/UPPER LEVEL ANTICYCLONE FLOW IS PRESENT S OF 27N WITH  
THE PARENT ANTICYCLONE NEAR 08N117W. THE TAIL END OF AN UPPER 
TROUGH STRETCHES FROM THE FOUR CORNERS REGION OF THE U.S. SWWD 
ACROSS NRN BAJA CALIFORNIA AND TO 27N132W WHERE IT BECOMES A 
SHEAR AXIS WSW TO AN UPPER LEVEL LOW W OF THE AREA AT 22N147W. 
THE LOW IS CAUGHT IN BETWEEN THE AFOREMENTIONED MID/UPPER LEVEL 
ANTICYCLONE FLOW AND THE SE PERIPHERY OF HIGHLY AMPLIFIED BROAD 
SCALE RIDGING TO THE N OF THE SHEAR AXIS. THE ASSOCIATED 
ANTICYCLONE IS NW OF THE AREA AT 35N144W...AND IS MOVING EWD.    
A VERY PRONOUNCED JET STREAM BRANCH ENTERS THE DISCUSSION AREA 
THROUGH 20N140W...THEN ROUNDS THE CREST OF THE RIDGE THROUGH 
24N130W AND TURNS SE TO 23N120W AND TO ENE OF 20N110W AS 
DESCRIBED ABOVE UNDER E OF 110W. BOTH SATELLITE-DERIVED WINDS 
AND UPPER MODEL DATA INDICATE JET MAX WINDS OF 60-95 KT...       
...PRIMARILY WITHIN 100 NM EITHER SIDE OF THE LINE 15N140W 
19N134W. THESE WINDS ARE TRANSPORTING MOSTLY BROKEN CIRRUS 
CLOUDS FROM THE DEEP TROPICAL CENTRAL PACIFIC REGION NEWD TO 
WELL INTO THE CENTRAL AND WESTERN PORTIONS OF THE AREA FROM 
ABOUT 13N TO 25N.

AT THE SURFACE...A NEARLY STATIONARY 1033 MB HIGH CENTER IS
WELL N OF THE AREA AT 41N135W WITH A RIDGE EXTENDING FROM
IT SEWD THROUGH 32N133W TO NEAR 21N115W. HIGH PRES COVERS THE 
AREA N OF 14N AND W OF 115W. A WEAK LOW LEVEL TROUGH MOVING W 
ABOUT 16 KT EXTENDS FROM 09N122W TO 05.5N124W AS WAS HIGHLIGHTED 
BY THE 1946 OSCAT PASS. THE OSCAT PASS FROM 2122 UTC ALONG WITH 
PARTIAL ASCAT DATA FROM THU SUGGESTED THAT THE AREA OF NE 20-25 
KT TRADES FROM THE LAST FEW DAYS IS SLOWLY SHRINKING IN SIZE
...AND IS PRESENTLY NOTED WITHIN 150 NM EITHER SIDE OF LINE FROM 
27N129W TO 24N140W NE WINDS 20 TO 25 KT. SEAS THERE ARE IN THE 
RANGE OF 9-10 FT. WITH THE 1033 MB HIGH IS FORECAST TO DISSIPATE 
IN 24 HRS...AND WHILE A NEW 1030 MB HIGH FORMS FURTHER SW OF 
THIS INITIAL HIGH NEAR 35N140W ALSO IN 24 HRS EXPECT THE 20-25 KT 
NE WINDS TO DIMINISH TO 20 KT OR LESS. SEAS WILL SUBSIDE TO 9 FT 
IN MIXED NE AND NW SWELL FROM 19N TO 27N W OF 131W IN 24 HRS. BY 
48 HRS A NEW BATCH OF N SWELLS IS FORECAST TO HAVE ENTERED THE 
NRN PORTION OF THE AREA N OF ABOUT 28N BETWEEN 122W AND 130W 
WHERE WAVEWATCH GUIDANCE BUILDS SEAS TO 10 FT.

GLOBAL MODEL GUIDANCE INDICATES THE NEAR EQUATORIAL CONVERGENCE 
ZONE WILL WEAKEN SIGNIFICANTLY IN THE NORTHERN HEMISPHERE OVER 
THE NEXT FEW DAYS...WITH THE ITCZ AXIS SHIFTING SLIGHTLY S OF 
THE EQUATOR. THIS WILL MAIN
TAIN GENERALLY LIGHT WINDS THROUGHOUT 
...EXCEPT AS MENTIONED ABOVE WHERE THE NE 20-25 KT TRADES WEAKEN
TO 20 KT OR LESS.
  
LARGE LONG PERIOD S SWELLS CROSSING THE EQUATOR OVER THE SE 
PORTION AND NEAR THE GALAPAGOS ISLANDS ARE FORECAST TO BUILD 
SEAS TO 9 FT BETWEEN 92W AND 114W BY SAT.

$$
AGUIRRE