Effects of Synoptic Surveillance on model forecasts for
18 September 2003 1200 UTC
Isabel.


Quicktime movie of GFS DLM wind model forecast
Quicktime movie of DLM wind data increment


TRACK AND INTENSITY PERFORMANCE

TRACK (km)
MODEL12 h24 h36 h48 h60 h72 h84 h96 h108 h120 h
AVNN 18 54162
AVNO 11126176
%IMP39%-133%-8%
GFNO 80293602
GFDL 89284681
%IMP-11% 3%-13%
INTENSITY (kt)
MODEL12 h24 h36 h48 h60 h72 h84 h96 h108 h120 h
AVNN-17-13 1
AVNO-13-15 -2
%IMP24%-15%-100%
GFNO -5 21 23
GFDL -7 18 23
%IMP-40%14% 0%
SHNO 15 39 42
SHIP 13 35 35
%IMP13%10%17%
DSNO-11 0 4
DSHP-12 0 4
%IMP-9% 0% 0%

Landfall forecasts

18/1700 UTC 34.9N 76.2W Drum Inlet, NC 5.0 h into the forecast
MODELLATLONTIMEERRORLOCATION
AVNN34.9476.21 4.5 4.5Little Port, NC
AVNO34.9876.04 4.0 17.1Ocracoke, NC
%IMP-100% -8%
GFNO34.9576.25 6.0 7.2Little Port, NC
GFDL34.9476.43 7.0 21.4Stacy, NC
%IMP-100% -19%

Figure 1. NCEP 850 - 200 hPa mean wind analysis for 18 September 2003 1200 UTC (Hurricane Isabel).

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 18 September 2003 1200 UTC.

Figure 3. Ensemble perturbation variance at the nominal sampling time 18 September 2003 1200 UTC from the previous day NCEP ensemble forecast. The 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 18 September 2003 1200 UTC. The 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 18 September 2003 1200 UTC.