000
AXPZ20 KNHC 042147
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC THU OCT 04 2012

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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2145 UTC.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS W ACROSS THE SOUTHERN CARIBBEAN ALONG 
09N CROSSING THE PANAMA/COSTA RICA BORDER TO 09N84W...THEN DIPS 
SW TO 06N93W...THEN TURNS NW AND CRESTS AT 15N105W...THEN SW TO 
09N120W...W TO 10N128W...AND FINALLY SW TO 07N136W WHERE LOW 
LEVEL WINDS INDICATE A TRANSITION TO AN ITCZ WHICH CONTINUES SW 
TO BEYOND 06N140W. SCATTERED MODERATE ISOLATED STRONG CONVECTION 
IS OBSERVED WITHIN 180 NM EITHER SIDE OF A LINE FROM 06N78W TO 
07N83W...LINE 07N89W TO 10N93W...WITHIN 30 NM EITHER SIDE OF A 
OF LINE FROM 16N99W TO 14N102W TO 14.5N111W...WITHIN 60 NM 
EITHER SIDE OF A OF LINE FROM 07N108W TO 07N115W TO 
10N120W...AND WITHIN 60 NM OF 09.5N126W AND 09N131W.

...DISCUSSION...

A BROAD UPPER LEVEL CYCLONE IS CENTERED N OF THE DISCUSSION AREA 
NEAR 35N135W WHILE ANOTHER SMALL UPPER CYCLONE CUT OFF NEAR 
19N130W WITH A TROUGH S TO A THIRD CYCLONE AT 09N135W. AN UPPER 
LEVEL ANTICYCLONE IS POSITIONED NEAR 27N117W WITH AN UPPER RIDGE 
EXTENDING N BEYOND 32N115W...AND A SECOND UPPER LEVEL RIDGE 
EXTENDS W TO 20N127W. WEAK UPPER DIFFLUENCE IS NOTED OVER THE 
DEEP TROPICS ALONG THE SOUTHERN PERIPHERY OF THE ANTICYCLONE 
SUPPORTING THE CONVECTION ALONG THE MONSOON TROUGH AS IS 
DISCUSSED ABOVE. MOST OF THE DEBRIS MOISTURE EVAPORATES NEAR THE 
CONVECTIVE CLUSTERS BUTS SOME MOISTURE THAT WAS ADVECTED N ALONG 
THE W PERIPHERY OF THE UPPER RIDGE IS NOW STREAMING E ACROSS THE 
NORTHERN BAJA CALIFORNIA PENINSULA AND ACROSS SOUTHERN ARIZONA.
UPPER MOSITURE IS NOW SPREADING NE ACROSS THE DISCUSSION AREA N 
OF 17N W OF 135W.

AN UPPER TROUGH EXTENDS S ACROSS THE WESTERN GULF OF MEXICO AND 
OVER CENTRAL MEXICO TO A BASE AT 16N103W. A SECOND UPPER TROUGH 
EXTENDS SW ACROSS THE WESTERN CARIBBEAN TO ACROSS NORTHERN COSTA 
RICA. A BROAD UPPER RIDGE DOMINATES THE UPPER LEVELS OF THE DEEP 
TROPICS TO THE E OF 105W...BUT THERE ARE EMBEDDED SMALL UPPER 
CYCLONES OBSERVED WITHIN THE BROAD RIDGE. DENSE UPPER MOISTURE 
IS NOTED FROM 05N TO 10N E OF 93W. SOME OF THE DEBRIS MOISTURE 
FROM THE CONVECTION ALONG 16N BETWEEN 100W AND 111W CONTINUES TO 
STREAM NE ACROSS SE MEXICO AND THE EASTERN GULF OF MEXICO. 

ELSEWHERE AT THE LOW LEVELS...BROAD SURFACE RIDGING COVERS MUCH 
OF THE DISCUSSION AREA N OF 20N W OF 110W. SOUTHWESTERLY LOW 
LEVEL WINDS AT 15 TO 20 KT ALONG WITH CROSS EQUATORIAL S SWELL 
CONTINUES TO RESULT IN AN AREA OF SEAS TO 8 FT IN THE AREA 
BOUNDED BY 03N TO 06N BETWEEN 110W AND 117W. THIS AREA WILL 
SHIFT SLIGHTLY N ON FRI...THEN WINDS WILL DIMINISH TO 15 KT AND 
SEAS WILL SUBSIDE TO LESS THAN 8 FT. IN THE MEANTIME...NW WINDS 
NE OF THE SURFACE RIDGE WILL INCREASE TO 20 TO 25 KT JUST TO THE 
W OF THE NORTHERN BAJA CALIFORNIA PENINSULA.

THE INITIAL NORTHERLY SURGE THAT PASSED TROUGH THE TEHUANTEPEC 
AREA IS STILL PROPAGATING W AND IS CURRENTLY IN THE AREA FROM 
13N TO 16N BETWEEN 102W AND 112W...AND WILL MERGE WITH THE 
INCREASING WINDS OVER THE N SEMICIRCLE OF A SURFACE LOW EXPECTED 
TO DEVELOP WITHIN THE MONSOON TROUGH ON FRI NEAR 12N115W. THE 
LOW WILL MOVE W TO NEAR 12N122W ON SAT WITH THE GRADIENT 
BEGINNING TO RELAX BY THEN.
 
GAP WINDS...NORTHERLY WINDS AT 20 TO 25 KT ARE EXPECTED TO PULSE 
ACROSS THE GULF OF TEHUANTEPEC THROUGH FRI NIGHT...THEN DIMINISH 
ON SAT. NE TO E WINDS AT 20 TO 25 KT IN AND DOWNSTREAM OF THE 
GULF OF PAPAGAYO WILL DIMINISH LATE TONIGHT.
 
$$
NELSON