000
AXPZ20 KNHC 130404
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC WED AUG 13 2008

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

BASED ON 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0315 UTC.

...SPECIAL FEATURE...
TROPICAL DEPRESSION HERNAN AT 18.2N 134.8W AT 0300 UTC MOVING 
W-SW OR 255 DEG AT 8 KT.  MAXIMUM SUSTAINED WIND 35 GUSTS TO 45 
KT.  ESTIMATED MINIMUM CENTRAL PRES 1006 MB.  SCATTERED MODERATE 
CONVECTION WITHIN 180 NM NE QUADRANT.  HERNAN RAPIDLY WEAKENING. 
IT HAS LOST A LOT OF ITS CONVECTION AS DRY COLD AND STABLE AIR 
WRAPS AROUND IT.  SEE LATEST NHC FORECAST/ADVISORY UNDER 
AWIPS/WMO HEADER MIATCMEP4/WTPZ24 KNHC FOR MORE DETAILS.

...TROPICAL LOWS...
LOW PRES AT 14N117W 1009 MB.  SCATTERED MODERATE ISOLATED STRONG 
CONVECTION WITHIN 210 NM NW QUADRANT.  LOW PRES UNDER MODERATE 
E-SE WIND SHEAR AND MOVING OVER COLDER SEA SURFACE TEMPERATURE 
SO ITS FUTURE APPEARS TO BE SEALED.  SYSTEM STILL MERITS 
MONITORING AS DEEP CONVECTION...WHILE DECREASING...IS STILL NOT 
COMPLETELY DECOUPLED FROM LOW LEVEL CIRCULATION. 

.LOW PRES AT 16N103W.  SCATTERED MODERATE CONVECTION HUGGING 
MEXICAN COAST APPEARS TO REMAIN ATTACHED TO LOW LEVEL 
CIRCULATION AND CAN PRODUCE HEAVY RAINFALL OVER COASTAL 
MOUNTAINS LEADING TO FLASH FLOODING.  SYSTEMS IS PULLING AWAY 
FROM LAND AND UNDER MODERATE NE SHEAR WHICH SHOULD DECREASE ITS 
THREAT TO LAND WITHIN NEXT 24-36 HRS. 

...TROPICAL WAVES... 
TROPICAL WAVE ALONG 90W MOVING W AT 15 KT.  SCATTERED MODERATE 
ISOLATED STRONG CONVECTION OVER HONDURAS AND GUATEMALA BOUND TO 
DECREASE AS DRY AIR MASS OVER YUCATAN AND BAY OF CAMPECHE 
COLLIDES WITH AXIS.  SYSTEM CONTINUES UNDER UNFAVORABLE UPPER 
CONDITIONS FOR ORGANIZATION...BUT COULD INTENSIFY AS SHEAR 
DIMINISHES.

...ITCZ...
ITCZ AXIS ALONG 10N85W TO 13N100W TO 09N114W TO 13N128W TO 
10N140W.  SCATTERED MODERATE CONVECTION WITHIN 240 NM OF AXIS 
FROM 100W-111W.

...DISCUSSION...
TROPICAL DEPRESSION HERNAN SHOULD BE OUT OF AREA WITHIN NEXT 48 
HRS AS IT CROSSES 140W WHILE CONTINUING TO WEAKEN.  AIR MASS W 
OF 125W REMAINS VERY DRY UNDER UPPER TROUGH APPROACHING NW 
WATERS.  TROUGH FORCES MID-UPPER LEVEL RIDGE CENTERED AT 27N121W 
FURTHER E WITHIN NEXT 48 HOURS WHILE INCREASING SW SHEAR OVER 
HERNAN.    

BROAD UPPER LEVEL ANTICYCLONE CENTERED OVER NW MEXICO SHOULD 
DRIFT E SHIFTING DECREASING NE SHEAR OVER LOW PRES CLOSE TO 
MEXICAN COAST MENTIONED ABOVE.  

HIGH PRES CENTER 1022 MB AT 33N138W HAS RIDGE EXTEND TO 20N110W 
EXTENDING DRY SLOT DUE TO SUBSIDENCE INTO BAJA CALIFORNIA COAST. 

$$
WALLY BARNES