Effects of Synoptic Surveillance on model forecasts for 09 September 1999 1800 UTC FLOYD.


QuickTime movie of DLM wind model forecasts
QuickTime movie of DLM wind data increments


TRACK AND INTENSITY PERFORMANCE

TRACK (km)
MODEL12 h24 h36 h48 h60 h72 h84 h96 h108 h120 h
AVNN87.190.282.281.241.215.214.193.150.122.
AVAL128.283.397.389.311.248.259.258.343.355.
%IMP-47%-49%-41%-38%-29%-11%-21%-34%-129%-191%
GFNO33.100.129.200.249.239.254.279.223.229.
GFAL39.68.76.82.121.120.129.100.82.180.
%IMP-18%32%39%59%51%50%49%54%63%21%
INTENSITY (kt)
MODEL12 h24 h36 h48 h60 h72 h84 h96 h108 h120 h
AVNN-21.-36.-59.-52.-54.-75.-95.-85.-64.-70.
AVAL-18.-31.-52.-52.-53.-72.-94.-86.-62.-64.
%IMP14%14%12%0%2%4%1%-1%3%9%
GFNO32.18.-1.17.14.-4.-17.-5.7.8.
GFAL31.27.15.13.7.-9.-15.-13.15.15.
%IMP3%-50%-1400%24%50%-125%12%-160%-114%-88%
SHNO10.7.-13.-3.-5.-22.-41.-30.-9.-14.
SHAL10.6.-17.-8.-12.-29.-49.-39.-19.-23.
%IMP0%14%-31%-167%-140%-32%-20%-30%-111%-64%
DSNO10.7.-13.-3.-5.-22.-41.-30.-9.-14.
DSAL10.6.-17.-8.-12.-29.-49.-39.-19.-23.
%IMP0%14%-31%-167%-140%-32%-20%-30%-111%-64%

Landfall forecasts

14/1200 UTC 25.4N 76.3W Near Alice Town, Eleuthera 114 h into the forecast
MODELLATLONTIMEERRORLOCATION
AVNN24.1274.48109.5232.2 San Salvador, Bahamas
AVAL21.8972.00107.0586.2 North Caicos, Turks and Caicos Islands
%IMP-56%-152%
GFNO27.4377.15116.0241.2 Near Abaco Island, Bahamas
GFAL25.5876.74111.548.4 Eleuthera Island, Bahamas
%IMP-25%80%
14/1900 UTC 26.3N 77.1W Near Cherokee Sound, Abaco 121 h into the forecast
MODELLATLONTIMEERRORLOCATION
AVNN24.2375.35118.0289.5 Cat Island, Bahamas
AVAL22.4976.46117.5428.2 Near Ragged Island, Bahamas
%IMP-17%-48%
GFNO27.4377.15116.0125.6 Near Abaco Island, Bahamas
GFAL25.7477.33114.066.3 Abaco Island, Bahamas
%IMP-40%47%
16/0630 UTC 33.8N 78.0W Near Cape Fear, NC 156.5 h into the forecast
MODELLATLONTIMEERRORLOCATION
AVNNNo landfall forecast
AVALNo landfall forecast
%IMP
GFNONo landfall forecast
GFALNo landfall forecast
%IMP

Figure 1. NCEP 850 - 200 hPa mean wind analysis for 09 September 1999 1800 UTC (Tropical Storm Floyd).

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 09 September 1999 1800 UTC. The best track is shown in black.

Figure 3. Initial condition differences in the 850 - 200 hPa mean wind between the no and all dropwindsonde cases for 09 September 1999 1800 UTC.

Figure 4. 12-h forecast differences in the 850 - 200 hPa mean wind between the no and all dropwindsonde cases for 09 September 1999 1800 UTC.