Effects of Synoptic Surveillance on model forecasts for 15 September 1999 0000 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
AVNN59.39.21.24.138.214.314.
AVAL56.0.38.67.169.529.741.
%IMP5%100%-81%-179%-22%-147%-136%
GFNO24.138.282.370.371.521.710.889.1220.
GFAL0.72.148.223.311.433.613.765.1097.
%IMP100%48%48%40%16%17%14%14%10%
INTENSITY (kt)
MODEL12 h24 h36 h48 h60 h72 h84 h96 h108 h120 h
AVNN-52.-43.-24.-3.-4.-4.3.
AVAL-29.-12.-9.0.-3.5.-2.
%IMP44%72%73%100%25%-25%50%
GFNO7.12.13.24.16.19.-2.-6.-8.
GFAL12.11.11.19.14.6.-4.-1.-6.
%IMP-71%8%15%21%13%44%-100%83%25%
SHNO11.12.25.36.38.43.49.53.49.
SHAL11.11.22.35.36.40.47.51.48.
%IMP0%8%12%3%5%7%4%4%2%
DSNO11.12.2.-9.-14.-12.-8.-8.-13.
DSAL11.11.1.-9.-14.-12.-8.-8.-13.
%IMP0%8%50%0%0%0%0%0%0%

Landfall forecasts

16/0630 UTC 33.8N 78.0W Near Cape Fear, NC 30.5 h into the forecast
MODELLATLONTIMEERRORLOCATION
AVNN34.2777.7231.558.2 Cape Fear, NC
AVAL33.8577.9731.06.2 Long Beach, NC
%IMP50%89%
GFNO33.8478.6136.556.5 Georgetown, SC
GFAL33.8678.5033.046.6 Near Georgetown, SC
%IMP58%18%

Figure 1. NCEP 850 - 200 hPa mean wind analysis for 15 September 1999 0000 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 15 September 1999 0000 UTC. The best track is shown in black.

Figure 3. Ensemble perturbation variance at the nominal sampling time 15 September 1999 0000 UTC from the previous day NCEP ensemble forecast. The green circles represent the dropwindsonde locations.

Figure 4. Initial condition differences in the 850 - 200 hPa mean wind between the no and all dropwindsonde cases for 15 September 1999 0000 UTC. The green circles represent the dropwindsonde locations.

Figure 5. 12-h forecast differences in the 850 - 200 hPa mean wind between the no and all dropwindsonde cases for 15 September 1999 0000 UTC.