Effects of Synoptic Surveillance on model forecasts for
16 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 23 40 95 24120312633
AVNO 31 49 57 39114251547
%IMP-35%-23%40%-63% 5%20%14%
GFNO 10 38 86135109133367
GFDL 11 35 82149129134404
%IMP-10% 8% 5%-10%-198-1%-10%
INTENSITY (kt)
MODEL12 h24 h36 h48 h60 h72 h84 h96 h108 h120 h
AVNN-40-36-31-26 -8 -1 -6
AVNO-11-16 -7 -8 -5 0 5
%IMP72%56%77%69%37%100%17%
GFNO 2 10 10 14 -5 20 31
GFDL 15 8 13 10 -3 18 30
%IMP-650%20%-30%29%40%10% 3%
SHNO -4 3 2 -3 16 36 35
SHIP -3 3 -1 -9 5 25 25
%IMP25% 0%50%-200%69%31%29%
DSNO -4 3 2 -3-11 1 5
DSHP -3 3 -1 -9-18 -2 4
%IMP25% 0%50%-200%-64%-100%20%

Landfall forecasts

18/1700 UTC 34.9N 76.2W Drum Inlet, NC 53.0 h into the forecast
MODELLATLONTIMEERRORLOCATION
AVNN34.8776.31 54.5 10.6Little Port, NC
AVNO35.0876.12 55.5 20.2Ocracoke, NC
%IMP -67% -91%
GFNO34.7576.64 49.5 43.5Beaufort, NC
GFDL34.7476.85 49.5 61.9Emerald isle, NC
%IMP 0% -42%

Figure 1. NCEP 850 - 200 hPa mean wind analysis for 16 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 16 September 2003 1200 UTC.

Figure 3. Ensemble perturbation variance at the nominal sampling time 16 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 16 September 2003 1200 UTC. The circles represent the dropwindsonde locations.

Figure 4. 12-h forecast differences in the 850 - 200 hPa mean wind between the no and all dropwindsonde cases for 16 September 2003 1200 UTC.