684 
 WTPZ45 KNHC 260237
 TCDEP5
 HURRICANE DARBY DISCUSSION NUMBER  13
 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP052010
 800 PM PDT FRI JUN 25 2010
  
 EVEN THOUGH DARBY HAS MAINTAINED A SMALL CENTRAL DENSE OVERCAST
 DURING THE LAST SEVERAL HOURS...THE EYE TEMPERATURE HAS COOLED
 AS THE EYE HAS BECOME MORE RAGGED.  IN ADDITION...THE CLOUD
 PATTERN HAS BECOME LESS SYMMETRIC...WITH RECENT SATELLITE IMAGES
 INDICATING A SOMEWHAT ELONGATED APPEARANCE TO THE CONVECTIVE TOPS. 
 DVORAK SATELLITE CLASSIFICATIONS FROM TAFB AND SAB ARE 5.0/90KT AND
 5.5/102 KT...RESPECTIVELY...WHILE ADVANCED OBJECTIVE DVORAK
 ESTIMATES PEAKING EARLIER AROUND 5.5 HAVE BEGUN TO DECREASE.  ON
 THE BASIS OF RECENT TRENDS AND SLIGHTLY LOWER DVORAK INTENSITY
 ESTIMATES...THE INITIAL INTENSITY IS LOWERED TO 100 KT.  THE GLOBAL
 MODELS CONTINUE TO INDICATE AN ABRUPT INCREASE IN EASTERLY VERTICAL
 WIND SHEAR OVER DARBY WITHIN THE NEXT 6-12 HOURS...WITH THE SHEAR
 POSSIBLY BECOMING RATHER STRONG AFTER 48 HOURS.  THE OFFICIAL
 INTENSITY FORECAST IS ADJUSTED DOWNWARD FROM THE PREVIOUS
 ADVISORY...AND CLOSELY FOLLOWS THE SHIPS/LGEM INTENSITY GUIDANCE. 
 HOWEVER...DARBY COULD WEAKEN FASTER THAN FORECAST IF PERSISTENTLY
 STRONG EASTERLY SHEAR DEVELOPS AND THE CURRENT INTENSITY FORECAST
 IS OF LOW CONFIDENCE.
  
 CENTER FIXES ARE A BIT TO THE RIGHT OF PREVIOUS ONES AND YIELD AN
 INITIAL MOTION ESTIMATE OF 290/5. HOWEVER...RECENT SATELLITE
 IMAGERY INDICATES THAT THE FORECAST TURN TOWARD THE WEST MAY
 ALREADY BE OCCURRING. WATER VAPOR IMAGERY SHOWS DARBY ON THE
 WESTERN EDGE OF MID- TO UPPER-TROPOSPHERIC RIDGING EXTENDING FROM
 THE WESTERN CARIBBEAN THROUGH SOUTHERN MEXICO.  MODEL GUIDANCE
 INDICATES THAT THIS RIDGING WILL WEAKEN DURING THE NEXT 24 HOURS...
 LEAVING DARBY IN A REGION OF WEAK ENVIRONMENTAL STEERING. 
 THEREAFTER...MODEL SOLUTIONS DIVERGE CONSIDERABLY...WITH ONE CAMP
 OF MODELS NEARLY STALLING DARBY BEFORE MOVING IT ON A SLOW WESTWARD
 TO NORTHWESTWARD COURSE.  THE OTHER SET OF SOLUTIONS SHOWS THE
 SMALL CYCLONE BEING DRAWN EASTWARD BY THE LARGE CIRCULATION
 ASSOCIATED WITH TROPICAL DEPRESSION ONE  ENTERING THE SOUTHERN GULF
 OF MEXICO. THE NEW FORECAST TRACK IS ADJUSTED SLIGHTLY TO THE LEFT
 AFTER 72 HOURS TO ACCOUNT FOR A SLIGHT WESTWARD SHIFT IN THE
 GUIDANCE BUT NOT AS FAR WEST AS THE MULTI-MODEL CONSENSUS. GIVEN
 THE DISAGREEMENT IN THE TRACK GUIDANCE...CONFIDENCE IN THE THE
 OFFICIAL FORECAST IS LOW BEYOND ABOUT 48 HOURS.
  
 FORECAST POSITIONS AND MAX WINDS
  
 INITIAL      26/0300Z 13.8N 102.2W   100 KT
  12HR VT     26/1200Z 13.8N 103.0W    95 KT
  24HR VT     27/0000Z 13.6N 103.7W    90 KT
  36HR VT     27/1200Z 13.6N 104.2W    80 KT
  48HR VT     28/0000Z 13.9N 104.3W    75 KT
  72HR VT     29/0000Z 14.5N 103.0W    55 KT
  96HR VT     30/0000Z 14.8N 102.6W    45 KT
 120HR VT     01/0000Z 15.0N 102.5W    40 KT
  
 $$
 FORECASTER KIMBERLAIN