Effects of Synoptic Surveillance on model forecasts for
17 September 2003 1800 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 9 35167342
AVNO 15 29 82248
%IMP-67%17%51%27%
GFNO 0 56209467
GFDL 15 73194415
%IMPund%-30% 7%11%
INTENSITY (kt)
MODEL12 h24 h36 h48 h60 h72 h84 h96 h108 h120 h
AVNN-37-31-17 -8
AVNO-17-15-11 -9
%IMP54%52%35%-13%
GFNO 2 14 -2 10
GFDL 5 5 -2 13
%IMP-150%64% 0%-30%
SHNO 0 5 35 45
SHIP -1 1 29 37
%IMPund%80%17%18%
DSNO 0 5 -6 2
DSHP -1-12 -8 1
%IMPund%-140%-33%50%

Landfall forecasts

18/1700 UTC 34.9N 76.2W Drum Inlet, NC 23.0 h into the forecast
MODELLATLONTIMEERRORLOCATION
AVNN34.9876.81 24.5 56.3Emerald Isle, NC
AVNO34.7776.50 23.0 30.9Cape Lookout, NC
%IMP 100% 45%
GFNO34.7176.78 23.5 57.0Morehead City, NC
GFDL34.7376.69 22.0 48.5Morehead City, NC
%IMP -100% 15%

Figure 1. NCEP 850 - 200 hPa mean wind analysis for 17 September 2003 1800 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 17 September 2003 1800 UTC.

Figure 3. Ensemble perturbation variance at the nominal sampling time 17 September 2003 1800 UTC from the previous day NCEP ensemble forecast. The circles represent the dropwindsonde locations.

Figure 4. Figure 4. Initial condition differences in the 850 - 200 hPa mean wind between the no and all dropwindsonde cases for 17 September 2003 1800 UTC. The circles represent the dropwindsonde locations.