Effects of Synoptic Surveillance on model forecasts for
23 September 2002 0000 UTC
Isidore.


Quicktime movie of AVN 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
AVNN52.167.282.397.533.620.748.850.1506.
AVNO52.77.124.210.320.381.521.651.1212.
%IMP0%54%56%47%40%39%30%23%20%
GFNO33.84.169.219.284.355.515.748.1499.
GFAL33.76.156.248.284.402.521.723.1399.
%IMP0%10%8%-13%0%-13%-1%3%7%
AVNN-30.-3.-11.-4.-2.-10.-13.19.21.
AVNO-23.0.-9.-5.-3.-7.-4.32.20.
%IMP23%100%18%-25%-50%30%69%-68%5%
INTENSITY (kt)
MODEL12 h24 h36 h48 h60 h72 h84 h96 h108 h120 h
GFNO-2.17.11.23.53.56.55.69.42.
GFAL-8.14.13.23.45.34.33.57.34.
%IMP-300%18%-18%0%15%29%40%17%19%
SHNO45.78.71.75.79.74.72.102.94.
SHIP44.78.70.74.77.70.68.96.88.
%IMP2%0%1%1%3%5%6%6%6%
DSNO4.37.30.34.38.33.31.61.33.
DSHP4.38.29.34.37.30.27.56.30.
%IMP0%-3%3%0%3%9%13%8%9%

Landfall forecasts

26/0600 UTC 29.1N 90.3W Just west of Grand Isle, LA 78 h into the forecast
MODELLATLONTIMEERRORLOCATION
AVNN28.9395.36102.0492.0 Freeport, TX
AVAL29.7193.7899.5343.6 Johnsons Bayou, LA
%IMP10%30%
GFNO28.9095.3194.0487.3 Surfside, TX
GFAL29.1795.0597.0461.0 Bay Harbor, TX
%IMP-19%5%

Figure 1. NCEP 850 - 200 hPa mean wind analysis for 23 September 2002 0000 UTC (Hurricane Isidore).

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 23 September 2002 0000 UTC. The best track is shown in black.

Figure 3. Ensemble perturbation variance at the nominal sampling time 23 September 2002 0000 UTC from the previous day NCEP ensemble forecast. The triangles represent the dropwindsonde locations.

Figure 4. Initial condition differences in the 850 - 200 hPa mean wind between the no and all dropwindsonde cases for 23 September 2002 0000 UTC. The triangles 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 23 September 2002 0000 UTC.