000
AXPZ20 KNHC 151549
TWDEP 

TROPICAL WEATHER DISCUSSION                                      
NWS NATIONAL HURRICANE CENTER MIAMI FL                         
1605 UTC SAT AUG 15 2015

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 
1545 UTC.               
   
...SPECIAL FEATURE...

A BROAD AREA OF LOW PRESSURE IS ANALYZED AS A SURFACE LOW AT  
15.5N 111.5W WITH AN ESTIMATED CENTRAL PRESSURE OF 1006 MB. 
CONVECTION REMAINS DISORGANIZED AROUND MULTIPLE CYCLONIC SWIRLS. 
CURRENTLY SCATTERED MODERATE ISOLATED STRONG CONVECTION IS 
OBSERVED OVER SE SEMICIRCLE WITHIN 180 NM EITHER SIDE OF A LINE 
FROM 16N107W TO 08N117W...AND OVER THE NW SEMICIRCLE WITHIN 90 
NM EITHER SIDE OF A LINE FROM 21N112W TO 15N114W. OCEANIC AND 
ATMOSPHERIC CONDITIONS REMAIN FAVORABLE FOR TROPICAL CYCLONE 
FORMATION AS THE SYSTEM CONTINUES ON A WEST NORTHWARD TRACK AT 
ABOUT 10 KT. THE GRADIENT IS EXPECTED TO TIGHTEN OVER THE NEXT 
12 HOURS SUPPORTING MINIMAL GALE FORCE WINDS...INITIALLY N OF 
THE CENTER...AND LATER SURROUNDING THE CENTER WITH THE 
POSSIBILITY OF A TRANSITION TO A TROPICAL CYCLONE WARNING IF 
TROPICAL CHARACTERISTICS ARE ACQUIRED. THE 24 HOUR FORECAST 
POSITION IS NEAR 17.5N 115.5W AND THE 48 HOUR POSITION IS 
FORECAST NEAR 21N120W. PLEASE REFER TO THE HIGH SEAS FORECAST 
ISSUED UNDER AWIPS/WMO HEADERS MIAHSFEP2/FZPN03 KNHC FOR 
ADDITIONAL INFORMATION.   

...TROPICAL WAVE...

A TROPICAL WAVE IS ANALYZED N OF 09N ALONG 93W WITH SCATTERED 
MODERATE ISOLATED STRONG CONVECTION OBSERVED OVER WATERS WITHIN 
180 NM EITHER SIDE OF THE OF WAVE AXIS. 

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...            
THE MONSOON TROUGH EXTENDS SW OFF THE PACIFIC COAST OF COLOMBIA 
FROM 07.5N78W TO 07N80W...THEN TURNS NW TO 09N88W....THEN SW TO  
09N94W...THEN NW TO 12N101W WHERE IT LOSES IDENTITY IN THE BROAD 
CYCLONIC CIRCULATION ACCOMPANYING THE BROAD AREA OF LOW PRESSURE 
PREVIOUSLY DESCRIBED. SCATTEROMETER WINDS INDICATE A ITCZ AXIS 
DEVELOPS NEAR 09N120W AND EXTENDS W TO BEYOND 09N140W. 

SCATTERED MODERATE ISOLATED STRONG CONVECTION IS NOTED OVER AND 
TO THE S OF THE MONSOON TROUGH WITHIN 180 NM EITHER SIDE OF A 
LINE FROM 06N78W TO 08N101W. ISOLATED MODERATE TO STRONG 
CONVECTION IS OBSERVED ALONG THE ITCZ WITHIN 360 NM EITHER SIDE 
OF A LINE FROM 07N116W TO TO 07N130W TO 08N140W.

SCATTERED MODERATE ISOLATED STRONG CONVECTION IS NOTED WITHIN 90 
NM OF COAST OF MEXICO FROM 20N TO 24N. 

...DISCUSSION...

A BROAD SURFACE RIDGE DOMINATES THE AREA N OF THE ITCZ AND W OF 
THE BROAD AREA OF LOW PRESSURE PREVIOUSLY MENTIONED. NE 15-20  
TRADES ARE OBSERVED ACROSS THE TROPICS FROM 12-23N W OF 125W 
WITH SEAS OF 7-8 FT IN MIXING NE WIND WAVES AND CROSS EQUATORIAL 
SOUTHERLY SWELL. THE GRADIENT IS FORECAST TO GRADUALLY WEAKEN 
OVER THE NEXT DAY OR SO WITH THE COMBINED SEAS SUBSIDING TO LESS 
THAN 8 FT. 

GULF OF PAPAGAYO...REMNANT ENE SWELL FROM LAST NIGHTS DRAINAGE 
FLOW IS MIXING WITH CROSS EQUATORIAL SW SWELL WITH COMBINED SEAS 
OF 7-8 FT WITHIN 60 NM OF 11N88W THIS MORNING. THESE SEAS WILL 
SUBSIDE BELOW 8 FT THIS AFTERNOON. THE NOCTURNAL DRAINAGE FLOW IS 
EXPECTED TO MAX AT 20 KT FOR THE NEXT 3 NIGHTS WITH SEAS ONLY 
BUILDING TO 7 FT.
  
GULF OF TEHUANTEPEC...A BRIEF SURGE OF NORTHERLY 15-20 KT WINDS 
EARLY THIS MORNING WAS LIKELY ENHANCED BY A TROPICAL WAVE. 
EXPECT LIGHT NORTHERLY DRAINAGE FLOW THE NEXT FEW NIGHTS. 

$$
NELSON