000
AXPZ20 KNHC 280342
TWDEP 

TROPICAL WEATHER DISCUSSION 
NWS NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC THU JUN 28 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0245 UTC.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
A MONSOON TROUGH EXTENDS ALONG THE COAST OF CENTRAL AMERICA FROM 
08N77W TO 13N86W. A SECOND MONSOON TROUGH AXIS EXTENDS 18N106W 
TO 10N120W WHERE LOW LEVEL WINDS INDICATE A TRANSITION TO AN 
ITCZ WHICH CONTINUES SW TO BEYOND 05N140W. ISOLATED MODERATE TO 
STRONG CONVECTION IS OBSERVED FROM 04N TO 15N BETWEEN 83W AND 
116W WITH THE HEAVIEST ACTIVITY CONFIRMED BY LIGHTNING DATA NEAR 
11N90W...BUT OVERALL THE ACTIVITY IS DECREASING IN BOTH AREAL 
COVERAGE AND INTENSITY. SCATTERED MODERATE ISOLATED STRONG 
CONVECTION IS OBSERVED ALONG THE ITCZ AXIS WITHIN 45 NM EITHER 
SIDE OF A LINE FROM 07N131W TO BEYOND 06N140W. 
 
...DISCUSSION...
A SMALL UPPER CYCLONE IS FILLING WITH TIME ALONG AN UPPER TROUGH 
AT 34N131W...WITH THE TROUGH CONTINUING SW ACROSS THE NW PORTION 
OF THE DISCUSSION AREA FROM 32N131W TO A BASE AT 26N140W. A 
COMPLEX UPPER ANTICYCLONE HAS ITS MEAN CENTER NEAR 25N118W WITH 
A RIDGE EXTENDING SW TO 16N131W. JUST TO THE SW OF THIS RIDGE AN 
UPPER CYCLONE IS OBSERVED OVER THE DEEP TROPICS AT 10N137W WITH 
AN INVERTED UPPER TROUGH EXTENDING N TO NEAR 15N137W... 
EFFECTIVELY SEPARATING THE JUST MENTIONED UPPER RIDGE FROM AN 
UPPER ANTICYCLONE NOW CUT OFF W OF THE AREA AT 15N147W. AN UPPER 
CYCLONE OVER SOUTHERN TEXAS HAS AN UPPER TROUGH EXTENDING SW 
ACROSS NORTHERN OLD MEXICO THROUGH A SECOND CYCLONE OVER THE E 
PACIFIC AT 22.5N109W...WITH THE UPPER TROUGH CONTINUING SW TO A 
BASE OVER THE E PACIFIC AT 17N111W. A THIN LINE OF UPPER DEBRIS 
MOISTURE IS EVAPORATING ALONG THE NW COAST OF OLD MEXICO AND 
CONTINUES N ALONG THE BORDER OF ARIZONA AND NEW MEXICO. 
OTHERWISE THESE UPPER FEATURES COMBINE TO SIGNIFICANTLY DRY OUT 
THE UPPER LEVELS OF THE DISCUSSION AREA TO THE N OF 16N W OF 
106W...AND ELSEWHERE N OF 10N W OF 125W. 

AN UPPER ANTICYCLONE OVER THE S CENTRAL GULF OF MEXICO HAS A 
RIDGE EXTENDING SW ACROSS CENTRAL AMERICA TO A GENTLE CREST OVER 
THE E PACIFIC ALONG POINTS 12N102W TO 17N106W TO 21N105W. A LOW 
LEVEL TROUGH EXTENDS ROUGHLY FROM 18N104W TO 15N103W. DEBRIS 
MOISTURE FROM CONVECTION OVER THE BAY OF CAMPECHE...OVER SE OLD 
MEXICO...ALL OF GUATEMALA...AND OVER THE E PACIFIC N OF 14N 
BETWEEN 90W AND 100W...IS ADVECTED ANTICYCLONICALLY NW AROUND 
THE UPPER RIDGE...BUT DRIES OUT OVER OLD MEXICO S OF 22N...AND 
IS ALSO DRYING OUT OVER THE GULF OF MEXICO ALONG 24N TO THE W OF 
86W. FURTHER TO THE S OF THIS ANTICYCLONE THE NE TO E UPPER FLOW 
IS INCREASING OVER THE DEEP TROPICAL PACIFIC...AND ACROSS THE 
CONVECTION NOTED BETWEEN THE MONSOON TROUGHS AS PREVIOUSLY 
DESCRIBED...WITH THE RESULTANT DEBRIS MOISTURE ADVECTED W TO 
ALONG ABOUT 120W WHERE IT EVAPORATES COMPLETELY. 

AT THE LOW LEVELS A WEAK COLD FRONT HAS PUSHED INTO THE NW 
PORTION WITH A SECONDARY N SURGE APPROACHING A LITTLE FURTHER 
ITS NW. A RIDGE AXIS HAS SHIFTED A LITTLE SOUTHWARD AND NOW 
EXTENDS FROM ROUGHLY 28N140W TO 17N118W. NW FLOW HAS DIMINISHED 
TO 15 TO 20 KT NE OF THE RIDGE AND W OF THE NORTHERN BAJA 
CALIFORNIA PENINSULA...AND SEAS HAVE SUBSIDED TO 7 FT IN THE 
CONTINUING NW SWELL. NE TRADES HAVE INCREASED TO 15 TO 20 KT SW 
OF THE RIDGE AXIS IN THE AREA FROM ABOUT 07N TO 12N BETWEEN 128W 
AND 140W. THIS AREA OF ENHANCED NE TRADES WILL DECREASE OVER THE 
NEXT 48 HOURS OR SO.
   
THE UPPER TROUGH OVER THE NW PORTION WILL BE REINFORCED FROM THE 
NW MAINLY TO N OF THE AREA...BUT CONTINUE TO EXTEND ACROSS THE 
NW PORTION. THE UPPER ANTICYCLONE OVER THE GULF OF MEXICO WILL 
STRENGTHEN WITH THE NE TO E UPPER LEVEL FLOW EXPECTED TO 
INCREASE ACROSS THE DEEP TROPICS OVER THE NEXT FEW DAYS. THE LOW 
LEVEL EASTERLY FLOW WILL LIKELY INCREASE OVER THE W CARIBBEAN AS 
THE POST TROPICAL LOW PRESSURE OF FORMER TS DEBBY LIFTS OUT TO 
THE NE. THIS SHOULD INCREASE THE E WINDS IN AND DOWNSTREAM OF 
THE GULF OF PAPAGAYO LATE IN THE WEEK WHILE LOW LEVEL SW MONSOON 
FLOW WILL CONTINUE JUST TO THE S OF PAPAGAYO AREA. THUS THERE 
LIKELY BE AN INCREASE IN LOW LEVEL CYCLONIC MOTION ALONG 09N 
BETWEEN 85W AND 95W. A TROPICAL WAVE CURRENTLY OVER THE 
CARIBBEAN ALONG 78W WILL MOVE ACROSS CENTRAL AMERICA THU AND THU 
NIGHT AND MOVE INTO THE MONSOONAL FLOW. MODEL GUIDANCE IS 
SUGGESTING A SURFACE LOW WILL DEVELOP ALONG THE MONSOON TROUGH 
AXIS ON FRI NEAR 09N87W...THUS A SURFACE LOW HAS BEEN INTRODUCED 
OUT INTO THE GRAPHICAL SUITE AND THE HIGH SEAS FORECAST.     

$$
NELSON