000
AXPZ20 KNHC 281539
TWDEP 

TROPICAL WEATHER DISCUSSION                                   
NWS NATIONAL HURRICANE CENTER MIAMI FL                       
1605 UTC MON JUL 28 2014

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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1500 UTC.

...SPECIAL FEATURES...                                           
HERNAN WAS DOWNGRADED TO A TROPICAL STORM AT 28/0900 UTC. AT 
28/1500 UTC...IT IS CENTERED NEAR 20.5N 115.9W OR ABOUT 365 
NM...675 KM WSW OF THE SOUTHERN TIP OF BAJA CALIFORNIA MOVING NW 
OR 305 DEGREES AT 14 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 
996 MB. MAXIMUM SUSTAINED WIND SPEED IS 55 KT WITH GUSTS TO 65 
KT. SATELLITE IMAGERY SHOWS SCATTERED MODERATE ISOLATED STRONG 
CONVECTION WITHIN 75 NM SE QUADRANT AND 60 NM NW QUADRANT. A 
MODERATE SHEAR ENVIRONMENT ALONG WITH AN INCREASINGLY STABLE AIR 
MASS AND DECREASING SEA SURFACE TEMPERATURE SHOULD WEAKEN HERNAN 
INTO A POST TROPICAL CYCLONE IN ABOUT 48 HOURS. SEE LATEST NHC 
FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMEP3/WTPZ23 KNHC 
FOR MORE DETAILS.

...TROPICAL WAVES...                                            
A TROPICAL WAVE WITH AXIS ACROSS HONDURAS AND NICARAGUA EXTENDS 
INTO THE EPAC TO NEAR 08N86W. SCATTERED MODERATE CONVECTION IS 
NOTED WHERE THE WAVE MEETS THE MONSOON TROUGH...MAINLY FROM 05N 
TO 09N BETWEEN 84W AND 86W. THIS WAVE WILL CONTINUE TO MOVE 
WESTWARD REACHING NEAR 90W TUE MORNING AND 95W WED MORNING. 
 
A SECOND TROPICAL WAVE EXTENDS FROM 17N101W TO 08N102W. A 
CLUSTER OF MODERATE CONVECTION IS OBSERVED FROM 13N TO 15N 
BETWEEN 99W AND 102W. THIS WAVE IS EXPECTED TO PASS 110W EARLY 
TUE. A WEAK LOW PRES AREA IS FORECAST TO DEVELOP NEAR THE 
SOUTHERN END OF THE WAVE AXIS BY EARLY WED.  

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...           
THE MONSOON TROUGH EXTENDS FROM 08N78W TO 09N85W TO 07N100W TO 
09N98W. THE ITCZ AXIS CONTINUES FROM 09N98W TO 10N100W TO 
07N113W TO A 1011 MB LOW PRES NEAR 11N123W TO 09N130W TO A 
SECOND LOW PRES NEAR 15N135W TO 12N140W. SCATTERED MODERATE 
CONVECTION IS FROM 05N TO 09N BETWEEN 84W AND 86W. SIMILAR 
CONVECTION IS FROM 09N TO 11N BETWEEN 104W AND 106W...AND FROM 
09N TO 12N BETWEEN 123W AND 126W.

...DISCUSSION...                                                
AN UPPER LEVEL TROUGH IS NOTED ON WATER VAPOR IMAGERY WITH AXIS 
EXTENDING FROM 30N130W TO A BASE NEAR 15N127W. MOSTLY DRY AIR 
ACCOMPANIES THIS TROUGHING GENERALLY N OF 18N BETWEEN 125W AND 
135W. AN UPPER LEVEL RIDGE FOLLOWS THIS TROUGH WITH AXIS ALONG 
135W/136W. NWLY FLOW ALOFT ASSOCIATED WITH THIS RIDGE CONTINUES 
TO IMPACT THE LOW PRES LOCATED NEAR 15N135W. AN ANTICYCLONIC 
CIRCULATION IS NOTED OVER TEXAS NEAR 31N101W WITH A RIDGE 
EXTENDING SW ACROSS NW MEXICO AND SOUTHERN BAJA CALIFORNIA 
PENINSULA TO JUST NE OF HERNAN. ANOTHER ANTICYCLONE IS LOCATED 
NEAR 15N116W. AN UPPER-LEVEL LOW HAS DEVELOPED OVER SOUTH-
CENTRAL MEXICO AND IS CENTERED NEAR 19N98W. A TROUGH EXTENDS 
FROM THE LOW TO NEAR 13N98W. A DIFFLUENT PATTERN ALOFT W OF THE 
TROUGH AXIS IS HELPING TO INDUCE CONVECTION NEAR THE TROPICAL 
WAVE ALONG 101W/102W. 

WHILE NO SIGNIFICANT CONVECTION REMAINS NEAR A 1009 MB SURFACE 
LOW NEAR 15N135W...AN EARLIER ASCAT PASS INDICATED THAT FRESH TO 
STRONG WINDS PERSIST WITHIN 240 NM IN THE NORTHERN QUADRANT OF 
THE LOW...BETWEEN THE LOW PRES AND THE SUBTROPICAL RIDGE N OF 
THE AREA. A PAIR OF ALTIMETER PASSES ALSO INDICATED SEAS OF 8 TO 
11 FT IN THIS AREA OF ENHANCED TRADES. THE FORECAST CALLS FOR 
THE LOW TO WEAKEN AND THE WINDS TO DIMINISH THROUGH EARLY TUE AS 
THE LOW PRES CENTER MOVES W OF 140W...BUT WITH RESIDUAL SEAS 
OF 8-9 FT.

A WEAK 1011 MB LOW PRES IS WITHIN THE ITCZ AXIS NEAR 11N123W. A 
SMALL CLUSTER OF MODERATE CONVECTION IS OBSERVED WITHIN 120 NM 
NW QUADRANT OF LOW CENTER. THIS SYSTEM WILL MOVE GENERALLY W-NW 
WITH LITTLE CHANGE.

NORTHERLY WINDS OF 15-20 KT CONTINUE TO PULSE ACROSS THE GULF OF 
TEHUANTEPEC WITH SEAS OF 6-7 FT. WINDS ARE EXPECTED TO INCREASE 
BRIEFLY TO 20-25 KT BY TUE MORNING LIKELY ASSOCIATED WITH AN 
APPROACHING TROPICAL WAVE. SEAS ARE FORECAST TO BUILD TO AROUND 
9 FT. CONDITIONS ARE EXPECTED TO IMPROVE BY LATE TUE.  

WINDS ARE ALSO EXPECTED TO INCREASE TO 20-25 KT ACROSS THE GULF 
OF PAPAGAYO OVERNIGHT TONIGHT INTO TUE MORNING...THEN AGAIN TUE 
NIGHT INTO WED MORNING WITH SEAS TO 8 FT DURING EACH PULSE.
 
FINALLY...SE SWELL FROM THE SOUTHERN HEMISPHERE CONTINUES TO 
IMPACT THE SOUTH-CENTRAL WATERS...GENERALLY S OF 04N BETWEEN 
110W AND 120W. THIS SWELL EVENT WILL CONTINUE TO PROPAGATE 
FARTHER WEST ACROSS THE FORECAST REGION WHILE SUBSIDING.   

$$ 
GR