000
AXPZ20 KNHC 071003
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1005 UTC THU AUG 07 2008

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM 
THE EQUATOR TO 32N...EAST OF 140W. 

BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0915 UTC.

...SPECIAL FEATURE...
TROPICAL STORM HERNAN AT 14.5N 114.0W OR ABOUT 585 NM...1080 KM 
S-SW OF SRN TIP OF BAJA CALIFORNIA AT 07/0900 UTC MOVING W-NW AT 
12 KT.  MAXIMUM SUSTAINED WIND 45 GUSTS TO 55 KT.  MINIMUM 
CENTRAL PRES 1000 MB.  SEE LATEST NHC FORECAST/ADVISORY UNDER 
AWIPS/WMO HEADER MIATCMEP4/WTPZ24 KNHC FOR MORE DETAILS.  DEEP 
CONVECTION HAS INCREASED AND BECOME CLOSER TO THE CENTER 
INDICATING A STRONGER BETTER ORGANIZED SYSTEM IN SPITE OF STILL 
STRONG NE WIND SHEAR.  HERNAN FORECAST TO STRENGTHEN TO 
HURRICANE STRENGTH WITHIN THE NEXT 48 HOURS.  NUMEROUS STRONG 
CONVECTION WITHIN 150 NM S SEMICIRCLE AND SCATTERED MODERATE TO 
STRONG WITHIN 60 NM N SEMICIRCLE.

...TROPICAL WAVES... 
TROPICAL WAVE ALONG 100W N OF 04N EXTENDING N INTO MEXICO MOVING 
W AT 10 KT.  SYSTEM ABLE TO DEVELOP PLENTY OF DEEP CONVECTION 
DESPITE MODERATE TO STRONG NE WIND SHEAR AND REMAINS WITH NO 
CYCLONIC ORGANIZATION AS OF YET.  AIR MASS STILL REMAINS WITH 
ABUNDANT MOISTURE BUT WITHOUT UPPER SUPPORT SYSTEM IS NOT 
EXPECTED TO BE ABLE TO GET ANYTHING GOING DURING NEXT 36-48 HRS.

TROPICAL WAVE ALONG 132W FROM 05N TO 18N MOVING W AT 10 KT. VERY 
HOSTILE UPPER LEVEL ENVIRONMENT HAS CURTAILED DEEP CONVECTION 
FROM WAVE...BUT THAT SCENARIO LIKELY TO CHANGE AS AN AREA OF 
DIFFLUENT FLOW LIES AHEAD OF N HALF OF AXIS.  ON THE OTHER HAND 
...VERY DRY AIRMASS LIES ON OTHER SIDE OF DIFFLUENT AREA WHICH 
COULD SHORTEN CONVECTION EXPECTANCY. 

...ITCZ...
ITCZ AXIS ALONG 08N81W TO 09N95W TO 13N108N TO 13N117W TO 
11N132W TO 09N140W.  SCATTERED MODERATE TO STRONG CONVECTION 
WITHIN 240 NM S OF AXIS E OF 103W.  SCATTERED MODERATE ISOLATED 
STRONG CONVECTION WITHIN 120 NM OF AXIS W OF 120W. 

...DISCUSSION...
MIDDLE/UPPER LEVEL TROUGH WITH AXIS FROM 32N130W TO CYCLONIC 
VORTEX AT 18N138W THEN 16N140W KEEPS VERY DRY AIR MASS WITHIN 
3-4 DEG FROM AXIS.  STATIONARY UPPER LEVEL ANTICYCLONE AT 
23N115W EXTENDS DRY SLOT N OF 20N EWD TO BAJA CALIFORNIA.  
MODERATE TO STRONG NE WINDS ALOFT SE OF ANTICYCLONE CONTINUE TO 
NEGATIVELY AFFECT TROPICAL STORM HERNAN.  EFFECT WILL DECREASE 
AS HERNAN MOVES FURTHER W AWAY FROM STATIONARY ANTICYCLONE.  
SECOND AND LESSER ANTICYCLONE ALOFT AT 20N101W SIMILARLY 
AFFECTING TROPICAL WAVE ALONG 100W WITH MODERATE NE FLOW 
PARTIALLY SHEARING CONVECTIVE DEVELOPMENT. 

ELSEWHERE AT THE SURFACE...REBUILDING HIGH PRES 1030 MB WELL NW 
OF AREA HAS RIDGE EXTEND TO 17N119W SUPPORTING WEAK TRADES FROM 
12N-17N W OF 132W THROUGH FORECAST PERIOD.  

WINDS ACROSS GULF OF PAPAGAYO CONTINUE ENHANCED BY TROPICAL WAVE 
OVER WRN CARIBBEAN MOVING OVER CENTRAL AMERICA WITHIN NEXT 36 
HRS.

$$
WALLY BARNES