Effects of Synoptic Surveillance on model forecasts for
26 August 1999 1800 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
AVNN33.70.104.166.174.183.325.633.878.721.
AVAL51.81.164.249.300.289.352.532.663.537.
%IMP-55%-16%-58%-50%-72%-58%-8%16%24%26%
GFNO39.63.89.89.66.53.36.236.413.649.
GFAL11.33.46.56.33.33.138.350.562.821.
%IMP72%48%48%37%50%38%-283%-48%-36%-27%
INTENSITY (kt)
MODEL12 h24 h36 h48 h60 h72 h84 h96 h108 h120 h
AVNN-36.-37.-44.-57.-54.-52.-53.-53.-55.-49.
AVAL-24.-24.-37.-54.-51.-48.-47.-42.-47.-39.
%IMP33%35%16%5%6%8%11%21%15%20%
GFNO41.29.27.19.22.25.23.1.-10.-28.
GFAL39.31.28.8.23.26.14.-28.-21.-24.
%IMP5%-7%-4%58%-5%-4%39%-2700%-110%14%
SHNO9.13.4.-11.-11.-12.-12.-8.-4.5.
SHAL9.12.3.-12.-12.-14.-14.-9.-6.3.
%IMP0%8%25%-9%-9%-17%-17%-13%-50%67%
DSNO9.13.4.-11.-11.-12.-12.-8.-4.5.
DSAL9.12.3.-12.-12.-14.-14.-9.-6.3.
%IMP0%8%25%-9%-9%-17%-17%-13%-50%67%

Landfall forecasts

28/0700UTC 26.6N 76.8W Abaco Islands, Bahamas 37 h into forecast
MODELLATLONTIMEERRORLOCATION
AVNN25.3776.3427.0144.2 Alice Town, Eleuthera Island, Bahama Islands
AVAL25.8977.2328.089.8 Southwest Point, Abaco Island, Bahama Islands
%IMP10%38%
GFNO24.5574.212.5345.3 Near Cockburn Town, San Salvador, Bahama Islands
GFAL26.5476.9841.519.1 Hope Town, Abaco Island, Bahama Islands
%IMP87%94%
04/2100UTC 34.8N 76.5W Cape Lookout National Seashore, NC 219 h into forecast
MODELLATLONTIMEERRORLOCATION
AVNN31.9780.9384.5517.4 Wilmington Park, GA
AVAL32.5280.3593.5436.9 Edisto Beach, SC
%IMP7%16%
GFNO34.7177.3794.080.0 Jacksonville, NC
GFAL33.6778.8885.5252.1 Myrtle Beach, SC
%IMP-7%-215%

Figure 1. NCEP 850 - 200 hPa mean wind analysis for 26 August 1999 1800 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 26 August 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 26 August 1999 1800 UTC.

Figure 4. 12-h forecast differences in the 850 - 200 hPa mean wind between the no and all dropwindsonde cases for 26 August 1999 1800 UTC.