000
AXPZ20 KNHC 132046 RRA
TWDEP 

TROPICAL WEATHER DISCUSSION                                     
NWS NATIONAL HURRICANE CENTER MIAMI FL                         
1605 UTC TUE OCT 13 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.               

...TROPICAL WAVES...                                             

A TROPICAL WAVE IS BEING ANALYZED FROM 16N107W TO LOW PRES NEAR 
10N108W 1008 MB. THE WAVE HAS BEEN MOVING W AT 10-15 KT OVER THE 
LAST 24 HOURS. MODERATE ENE SHEAR CONTINUES ACROSS THE THIS 
REGION SE OF AN UPPER ANTICYCLONE CENTERED NEAR 19N109W. THIS 
SCENARIO IS KEEPING CONVECTION W OF THE WAVE AXIS AND LOW 
PRES...CURRENTLY ANALYZED AS SCATTERED MODERATE TO ISOLATED 
STRONG FROM 05N TO 12N BETWEEN 109W AND 115W. MODERATE WINDS 
PREVAIL IN THE NORTH SEMICIRCLE OF THE LOW...AND LIGHTER WINDS 
ELSEWHERE. SEAS ARE 7 FT OR LESS. THE UPPER ANTICYCLONE WILL 
SHIFT WEST KEEPING PACE WITH THE TROPICAL WAVE/LOW 
PRES...INHIBITING SIGNIFICANT DEVELOPMENT THROUGH THE NEXT 48 
HOURS. AFTERWARD THE LOW PRES WILL ENTER A MORE FAVORABLE AREA 
OF WEAKER SHEAR THAT IS MORE CONDUCIVE FOR DEVELOPMENT. PLEASE 
SEE THE LATEST NHC TROPICAL WEATHER OUTLOOK UNDER AWIPS/WMO 
HEADERS MIATWOEP/ABPZ20 KNHC FOR MORE DETAILS. 

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... 
           
THE MONSOON TROUGH AXIS EXTENDS FROM 08N78W TO 09N89W TO 09N100W 
TO LOW PRES NEAR 10N108W 1008 MB TO 11N127W TO 10N140W. 
SCATTERED MODERATE CONVECTION IS FROM 05N TO 08N BETWEEN 80W AND 
88W. SCATTERED MODERATE TO STRONG CONVECTION IS FROM 05N TO 10N 
W OF 131W. 

...DISCUSSION... 

N OF 15N E OF 120W...WEAK HIGH PRES IS BUILDING OVER BAJA 
CALIFORNIA SUR...ESTABLISHING A LIGHT WIND REGIME OVER THE 
REGION AS NOTED IN SEVERAL SHIP OBSERVATIONS. THE SURFACE HIGH 
WILL SHIFT WEST OF THE BAJA PENINSULA LATER TODAY...ALLOWING A 
RETURN TO NW WINDS ACROSS THE REGION. EXPECT MODERATE TO FRESH 
NW FLOW ALONG CENTRAL AND SOUTHERN PORTIONS OF THE GULF OF 
CALIFORNIA STARTING TONIGHT AS THE PRESSURE GRADIENT TIGHTENS 
BETWEEN A SURFACE TROUGH DEVELOPING OFF THE WESTERN MEXICO COAST 
AND HIGH PRESSURE OVER NORTHERN MEXICO. MODERATE TO FRESH NW 
FLOW OVER THE GULF OF CALIFORNIA WILL PERSIST THROUGH THU 
MORNING...THESE WINDS WILL START TO DIMINISH OFF THE WESTERN 
BAJA CALIFORNIA PENINSULA SAT MORNING.

GULF OF TEHUANTEPEC...WINDS AND SEAS HAVE TEMPORARILY DIMINISHED 
IN THE GULF OF TEHUANTEPEC. HOWEVER...THE PRESSURE GRADIENT WILL 
TIGHTEN AGAIN STARTING WED MORNING AS SURFACE RIDGING BUILDS 
ALONG MEXICO AND A TROPICAL WAVE CURRENTLY ALONG 90W MOVES S OF 
THE GULF. A TIGHTER PRESSURE GRADIENT WILL SUPPORT N TO NE WINDS 
OF 20 TO 30 KT WITH SEAS 8 FT BY THEN. EARLY THU MORNING...WINDS 
ARE FORECAST TO REACH GALE FORCE...PULSING THROUGH SAT. SEAS 
WILL GRADUALLY BUILD TO AS HIGH AS 13 FT DURING THIS 
TIME...MIXING WITH PERSISTENT LONG PERIOD SW SWELL. 
 
S OF 15N E OF 105W...SW WINDS SOUTH OF THE MONSOON TROUGH REMAIN 
GENTLE TO MODERATE. SEAS ARE STILL REACHING AS HIGH AS 7 FT IN 
SW SWELL. A REINFORCING ROUND OF SW SWELL WILL KEEP OVERALL WAVE 
HEIGHTS AROUND 5 TO 7 FT THROUGH WED MORNING. LOOKING 
AHEAD...GLOBAL MODELS CONTINUE TO SHOW LOW PRES FORMING ALONG 
THE MONSOON TROUGH OFF COSTA RICA LATE IN THE WEEK...ALTHOUGH 
THE STRENGTH AND EXACT LOCATION OF THE LOW PRES VARIES. 

N OF 15N W OF 120W...THE PERSISTENT UPPER LOW THAT HAS BEEN 
IMPACTING THE AREA OVER THE PAST COUPLE OF DAYS IS NOW CENTERED 
NEAR 28N123W. THIS FEATURE CONTINUES TO DRIFT NORTH AS IT DRIFTS 
NORTHWARD...AHEAD OF A DEEP LAYER TROUGH APPROACHING THE 
DISCUSSION AREA FROM THE N CENTRAL PACIFIC. AN ASSOCIATED 
SURFACE TROUGH IS DIRECTLY BENEATH THE UPPER LOW...EXTENDING 
FROM 30N122W TO 23N125W. THE MOST RECENT ALTIMETER PASS 
INDICATES SEAS ARE 7 TO 8 FT W OF THE TROUGH IN RESIDUAL NW 
SWELL. THIS WILL SUBSIDE BELOW 8 FT THIS EVENING. FOR WED AND 
BEYOND...A WEAK PRES PATTERN WILL SET UP ALLOWING LIGHT TO 
GENTLE WINDS AND SEAS 5 TO 7 FT PRIMARILY IN NW SWELL.

S OF 15N W OF 110W...THE CONVERGENCE OF A SURGE OF SOUTHERLY 
FLOW IS SUPPORTING SCATTERED MODERATE TO STRONG CONVECTION 
MAINLY SOUTH OF THE MONSOON TROUGH AXIS FROM 05N TO 10N W OF 
131W. LOOKING AHEAD...THE MAIN ISSUE LATER IN THE WEEK WILL BE 
THE DEVELOPMENT AND WESTWARD MOVEMENT OF THE LOW PRES AREA 
CURRENTLY NEAR 10N108W...WHICH HAS A HIGH CHANCE THROUGH LATE IN 
THE WEEK OF DEVELOPING INTO A TROPICAL CYCLONE.

$$
NR