Effects of Synoptic Surveillance on model forecasts for 11 September 1999 0600 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
AVNN105.125.145.201.237.202.206.323.350.507.
AVAL56.157.196.235.316.311.351.379.473.557.
%IMP47%-26%-35%-17%-33%-54%-70%-17%-35%-10%
GFNO72.131.120.88.142.143.92.103.73.67.
GFAL47.61.22.30.73.118.134.202.242.431.
%IMP35%53%82%66%49%17%-46%-96%-232%-588%
INTENSITY (kt)
MODEL12 h24 h36 h48 h60 h72 h84 h96 h108 h120 h
AVNN-50.-56.-77.-96.-83.-59.-60.-54.-37.-36.
AVAL-26.-38.-58.-72.-69.-48.-47.-33.-13.-23.
%IMP48%32%25%25%17%19%22%39%65%36%
GFNO23.20.0.-20.-10.7.5.4.16.17.
GFAL27.20.2.-21.-7.16.11.14.21.19.
%IMP-17%0%und%-5%30%-129%-120%-250%-31%-12%
SHNO7.4.-13.-31.-22.-3.-10.-11.4.9.
SHAL6.2.-16.-35.-28.-9.-18.-20.-6.-2.
%IMP14%50%-23%-13%-27%-200%-80%-45%-50%78%
DSNO7.4.-13.-31.-22.-3.-10.-11.4.9.
DSAL6.2.-16.-35.-28.-9.-18.-20.-6.-2.
%IMP14%50%-23%-13%-27%-200%-80%-45%-50%78%

Landfall forecasts

14/1200 UTC 25.4N 76.3W Near Alice Town, Eleuthera 78 h into the forecast
MODELLATLONTIMEERRORLOCATION
AVNN23.7974.8476.0231.8 Rum Cay, Bahamas
AVAL22.7573.8474.0385.9 Acklins Island, Bahamas
%IMP-100%-66%
GFNO26.5976.9183.0145.6 Abaco Island, Bahamas
GFAL24.1075.4875.0166.4 Cat Island, Bahamas
%IMP60%14%
14/1900 UTC 26.3N 77.1W Near Cherokee Sound, Abaco 85 h into the forecast
MODELLATLONTIMEERRORLOCATION
AVNN24.9578.2093.0186.1 Andros Island, Bahamas
AVAL24.8078.2096.0199.8 Andros Island, Bahamas
%IMP-38%-7%
GFNO26.5976.9183.037.4 Abaco Island, Bahamas
GFAL26.6578.9997.5191.9 Grand Bahama Island, Bahamas
%IMP-525%-413%
16/0630 UTC 33.8N 78.0W Near Cape Fear, NC 120.5 h into the forecast
MODELLATLONTIMEERRORLOCATION
AVNN28.4580.51112.0640.5 Cape Canaveral, FL
AVAL26.6480.05109.5819.5 Lake Worth, FL
%IMP-29%-28%
GFNONo landfall forecast
GFAL28.5680.52112.5575.1 Merritt Island, FL
%IMP

Figure 1. NCEP 850 - 200 hPa mean wind analysis for 11 September 1999 0600 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 11 September 1999 0600 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 11 September 1999 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 1999 0600 UTC.