Effects of Synoptic Surveillance on model forecasts for
28 August 1999 0000 UTC
DENNIS.


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
AVNN35.45.35.93.96.153.78.361.434.642.
AVAL23.44.67.80.67.93.174.531.658.763.
%IMP34%2%-91%14%30%39%-123%-47%-52%-19%
GFNO30.30.15.35.102.133.218.433.467.469.
GFAL10.39.45.15.45.66.204.428.445.512.
%IMP67%-30%-200%57%56%50%6%1%5%-9%
INTENSITY (kt)
MODEL12 h24 h36 h48 h60 h72 h84 h96 h108 h120 h
AVNN-50.-56.-51.-53.-47.-31.-27.-7.-7.-15.
AVAL-38.-41.-39.-38.-33.-17.-19.-3.3.-2.
%IMP24%27%24%28%30%45%30%57%57%87%
GFNO18.17.19.19.19.21.24.35.35.23.
GFAL24.19.24.20.23.18.20.29.26.7.
%IMP-33%-12%-26%-5%-21%14%17%17%26%70%
SHNO-12.-12.-8.-8.0.3.10.26.37.36.
SHAL-12.-13.-9.-9.-2.1.8.24.35.34.
%IMP0%-8%-13%-13%und%67%20%8%5%6%
DSNO-12.-12.-8.-8.0.3.10.26.37.36.
DSAL-12.-13.-9.-9.-2.1.8.24.35.34.
%IMP0%-8%-13%-13%und%67%20%8%5%6%

Landfall forecasts

28/0700UTC 26.6N 76.8W Abaco Islands, Bahamas 7 h into forecast
MODELLATLONTIMEERRORLOCATION
AVNN26.7076.8010.511.1 Hope Town, Abaco Island, Bahama Islands
AVAL26.6876.868.010.7 Hope Town, Abaco Island, Bahama Islands
%IMP71%4%
GFNO26.7076.699.515.6 Hope Town, Abaco Island, Bahama Islands
GFAL26.6376.717.59.5 Hope Town, Abaco Island, Bahama Islands
%IMP80%39%
04/2100UTC 34.8N 76.5W Cape Lookout National Seashore, NC 189 h into forecast
MODELLATLONTIMEERRORLOCATION
AVNN No landfall forecast
AVAL No landfall forecast
%IMP
GFNO No landfall forecast
GFAL No landfall forecast
%IMP

Figure 1. NCEP 850 - 200 hPa mean wind analysis for 28 August 1999 0000 UTC (Hurricane Dennis).

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 28 August 1999 0000 UTC. The best track is shown in black.

Figure 3. Ensemble perturbation variance at the nominal sampling time 28 August 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 28 August 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 28 August 1999 0000 UTC.