Effects of Synoptic Surveillance on model forecasts for 13 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
AVNN23.23.56.56.89.249.291.65.204.167.
AVAL24.100.89.69.43.91.92.155.469.424.
%IMP-4%-335%-59%-23%52%63%68%-138%-130%-154%
GFNO45.104.106.158.203.255.381.403.
GFAL35.73.59.122.156.235.380.435.
%IMP22%30%44%23%23%8%0%-8%
INTENSITY (kt)
MODEL12 h24 h36 h48 h60 h72 h84 h96 h108 h120 h
AVNN-63.-63.-61.-46.-40.-13.-6.-9.6.1.
AVAL-27.-33.-38.-24.-27.-13.-7.-10.9.0.
%IMP57%48%38%48%33%0%-17%-11%-50%100%
GFNO8.2.7.12.-6.10.10.-3.
GFAL13.5.8.13.1.19.7.9.
%IMP-63%-150%-14%-8%83%-90%30%-200%
SHNO35.28.23.30.30.51.58.61.69.68.
SHAL35.27.21.27.27.48.54.58.66.65.
%IMP0%4%9%10%10%6%7%5%4%4%
DSNO35.28.23.30.30.51.58.61.69.68.
DSAL35.27.21.27.27.48.54.58.66.65.
%IMP0%4%9%10%10%6%7%5%4%4%

Landfall forecasts

14/1200 UTC 25.4N 76.3W Near Alice Town, Eleuthera 18 h into the forecast
MODELLATLONTIMEERRORLOCATION
AVNN25.1476.1316.033.6 Eleuthera Island, Bahamas
AVAL26.6676.8222.0149.3 Near Abaco Island, Bahamas
%IMP-100%-344%
GFNO26.3577.2321.0140.6 Abaco Island, Bahamas
GFAL26.7077.3024.0175.6 Abaco Island, Bahamas
%IMP-100%-25%
14/1900 UTC 26.3N 77.1W Near Cherokee Sound, Abaco 25 h into the forecast
MODELLATLONTIMEERRORLOCATION
AVNN26.7777.9130.096.0 Grand Bahama Island, Bahamas
AVAL26.6676.8222.048.7 Abaco Island, Bahamas
%IMP60%49%
GFNO26.8877.7724.592.6 Grand Bahama Island, Bahamas
GFAL26.7077.3029.548.7 Abaco Island, Bahamas
%IMP-800%47%
16/0630 UTC 33.8N 78.0W Near Cape Fear, NC 60.5 h into the forecast
MODELLATLONTIMEERRORLOCATION
AVNN34.9676.9271.0162.5 Emerald Isle, NC
AVAL34.6177.2662.5112.8 Duck Creek, NC
%IMP-44%-100%
GFNO33.2279.2052.5128.5 Caines, SC
GFAL33.8378.6656.061.0 North Myrtle Beach, SC
%IMP53%-38%

Figure 1. NCEP 850 - 200 hPa mean wind analysis for 13 September 1999 1800 UTC (Hurricane 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 13 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 13 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 13 September 1999 1800 UTC.