Effects of Synoptic Surveillance on model forecasts for
11 September 2004 0600 UTC
Ivan.


Quicktime movie of AVN DLM wind model forecast
Quicktime movie of DLM wind data increment


TRACK AND INTENSITY PERFORMANCE

TRACK (km)
MODEL12 h24 h36 h48 h60 h72 h84 h96 h108 h120 h
AVNN 15 62 39 42 21 46108136 94 89
AVNO 15 76 78113157181266293402394
%IMP 0%-23%-100%-169%-648%-293%-146%-315%-328%-343%
GFNO 25 33 56146239313471546575492
GFDL 24 11 74135178193297344380267
%IMP 4%67%32% 8%26%38%37%37%34%46%
INTENSITY (kt)
MODEL12 h24 h36 h48 h60 h72 h84 h96 h108 h120 h
AVNN-95-75-60-69-61-57-35-50-45-44
AVNO-84-73-62-60-66-70-48-48-45-77
%IMP12% 3%-3%13%-8%-23%-37% 2% 0%-75%
GFNO-36-17 -2-14-24-28-15-32-62-73
GFDL-39-34-10-19-26-29-12-25-29-54
%IMP-8%-100%-400%-36%-8%-4%20%22%53%26%

Landfall forecasts

12/1415 UTC 18.9N 81.5W 22 n mi SSW of Georgetown, Grand Cayman Island 32.25 h into the forecast
MODELLATLONTIMEERRORLOCATION
AVNN 18.5781.91 32.0 56.6Offshore Georgetown, Grand Cayman Island
AVNO19.2281.41 28.5 36.8Georgetown, Grand Cayman Island
%IMP-1400% 35%
GFNO19.1381.53 31.5 25.7Georgetown, Grand Cayman island
GFDL19.2881.40 32.5 43.1Georgetown, Grand Cayman Island
%IMP 67% -68%
14/0100 UTC 21.7N 85.2W 15 n mi SW of Cabo San Antonio, Cuba 67.0 h into the forecast
MODELLATLONTIMEERRORLOCATION
AVNN 21.7185.31 65.5 11.4Offshore La Fe, Pinar del Rio, Cuba
AVNO21.8784.33 56.5 91.7La Fe, Pinar del Rio, Cuba
%IMP-600%-704%
GFNO22.1683.87 54.5146.3Galafre, Pinar del Rio, Cuba
GFDL21.9184.12 55.0113.8La Fe, Pinar del Rio, Cuba
%IMP 4% 22%
16/0650 UTC 30.2N 87.9W Near Pine Beach, AL 121.0 h into the forecast
MODELLATLONTIMEERRORLOCATION
AVNNNo landfall forecast
AVNO30.0884.24 99.0351.9St. Marks, FL
%IMP
GFNO29.8084.69 95.5312.0Carrabelle, FL
GFDL29.7585.27105.5173.8Port St. Joe, FL
%IMP 37% 44%

Figure 1. NCEP 850 - 200 hPa mean wind analysis for 11 September 2004 0600 UTC (Hurricane Ivan).

Figure 2. Track forecasts for the no dropwindsonde (NO or NN) and the all dropwindsonde (AL) runs for the AVN and GFDL models initialized on 11 September 2004 0600 UTC.

Figure 3. Initial condition differences in the 850 - 200 hPa mean wind between the no and all dropwindsonde cases for 11 September 2004 0600 UTC.

Figure 4. 12-h forecast differences in the 850 - 200 hPa mean wind between the no and all dropwindsonde cases for 11 September 2004 0600 UTC.