610 
 WTPZ45 KNHC 191432
 TCDEP5
 HURRICANE RICK DISCUSSION NUMBER  17
 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP202009
 800 AM PDT MON OCT 19 2009
 
 SOUTHWESTERLY SHEAR...ANALYZED AT 15 TO 20 KNOTS BY THE SHIPS MODEL
 AND UW-CIMSS...APPEARS TO BE TAKING A TOLL ON RICK. THE CLOUD
 PATTERN HAS CONTINUED TO DETERIORATE...WITH AN EROSION OF THE COLD
 CLOUD TOPS IN THE WESTERN SEMICIRCLE AND THE DISAPPEARANCE OF THE
 EYE IN GEOSTATIONARY IMAGERY. AN AMSR-E PASS FROM 0913 UTC SHOWED
 THAT THE SOUTHWESTERN EYEWALL HAS ERODED AND ALSO SUGGESTS THAT THE
 CIRCULATION MAY BE BECOMING VERTICALLY TILTED. SATELLITE INTENSITY
 ESTIMATES HAVE DECREASED...AND THE INITIAL INTENSITY OF 100 KT IS
 BASED ON A BLEND OF DVORAK DATA-T NUMBERS AND CI-NUMBERS FROM
 TAFB...SAB...AND THE UW-CIMSS ADT. AN AIR FORCE RESERVE
 RECONNAISSANCE AIRCRAFT IS CURRENTLY EN ROUTE TO INVESTIGATE RICK
 AND WILL PROVIDE VALUABLE DATA TO HELP DETERMINE THE INTENSITY AND
 STRUCTURE OF THE HURRICANE LATER TODAY.
  
 THE SHIPS MODEL SUGGESTS THAT RICK WILL BE EXPERIENCING VERTICAL
 SHEAR OF 15 TO 20 KNOTS FOR MOST OF THE FORECAST PERIOD...EXCEPT
 FOR A BRIEF REDUCTION BETWEEN 12 AND 24 HOURS. GIVEN THIS...ALONG
 WITH CURRENT SATELLITE TRENDS...THE INTENSITY FORECAST HAS BEEN
 ADJUSTED DOWNWARD...BUT REMAINS ABOVE THE ICON INTENSITY CONSENSUS
 THROUGH 24 HOURS OUT OF RESPECT FOR CONTINUITY. BEYOND 24 HOURS THE
 OFFICIAL FORECAST IS CLOSE TO ICON AND SHOWS RICK WEAKENING TO A
 TROPICAL STORM IN 72 HOURS AFTER MAKING LANDFALL IN MAINLAND
 MEXICO.
  
 THE INITIAL MOTION ESTIMATE IS 305/08...A LITTLE TO THE LEFT OF THE
 PREVIOUS PACKAGE BASED ON GEOSTATIONARY AND MICROWAVE IMAGERY. RICK
 SEEMS TO BE SLOWING DOWN AS THE SUBTROPICAL RIDGE NORTH OF THE
 HURRICANE WEAKENS DUE TO A PAIR OF SHORTWAVE TROUGHS DIGGING INTO
 THE SOUTHWESTERN UNITED STATES OVER THE NEXT COUPLE OF DAYS. MOST
 OF THE TRACK GUIDANCE REMAINS TIGHTLY CLUSTERED AROUND A SCENARIO
 THAT SHOWS RICK ACCELERATING TOWARD THE NORTH AND NORTHEAST AS IT
 INTERACTS WITH THE AFOREMENTIONED TROUGHS. AN ALTERNATIVE SCENARIO
 ...WHERE THE CIRCULATION OF RICK BECOMES VERTICALLY DECOUPLED
 LEAVING THE LOW-LEVEL CENTER BEHIND...IS REPRESENTED BY THE UKMET
 MODEL AND THE SHALLOW BAM. THE OFFICIAL FORECAST FOLLOWS THE FIRST
 SCENARIO...AND IS ADJUSTED SLIGHTLY TO THE RIGHT OF THE PREVIOUS
 FORECAST BEYOND 12 HOURS TOWARD THE MODEL CONSENSUS. IN THE FIRST
 12 HOURS...THE FORECAST IS SLIGHTLY LEFT OF THE PREVIOUS PACKAGE
 DUE TO THE INITIAL POSITION AND MOTION.
  
 THE INITIAL WIND RADII WERE ADJUSTED BASED ON INFORMATION FROM AN
 ASCAT PASS AT AROUND 0500 UTC.
 
 FORECAST POSITIONS AND MAX WINDS
  
 INITIAL      19/1500Z 17.8N 111.6W   100 KT
  12HR VT     20/0000Z 18.6N 112.2W    90 KT
  24HR VT     20/1200Z 19.7N 111.9W    80 KT
  36HR VT     21/0000Z 21.1N 111.0W    75 KT
  48HR VT     21/1200Z 22.8N 109.6W    70 KT
  72HR VT     22/1200Z 25.5N 106.5W    35 KT...INLAND
  96HR VT     23/1200Z...DISSIPATED
  
 $$
 FORECASTER BRENNAN
  
 

This page was last modified on: Thu, Jul 23 2020 - 2003 UTC
Send comments to: Ryan Lyman