Effects of Synoptic Surveillance on model forecasts for
15 September 2004 1200 UTC
Ivan.


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
AVNN 10 29 52139247543672723809
AVNO 11 50 93175275529610655769
%IMP-10%-72%-79%-26%-11% 3% 9%10% 5%
GFNO 29 83146296385677951105211321473
GFDL 19 6612223832361086895610771397
%IMP34%20%16%20%16%10% 9% 9% 9% 5%
INTENSITY (kt)
MODEL12 h24 h36 h48 h60 h72 h84 h96 h108 h120 h
AVNN-34-11 -3 0 -2 3-20-24-27
AVNO-30 -5 -4 2 2 4-22-24-23
%IMP12%55%-33%und% 0%-33%-10% 0%15%
GFNO -3 24 21 16 16 26 10 5 -5 -8
GFDL -4 18 19 13 18 30 12 2 -9-12
%IMP-33%25%10%19%-13%-15%-20%60%-80%-50%

Landfall forecasts

16/0650 UTC 30.2N 87.9W Near Pine Beach, AL 19.0 h into the forecast
MODELLATLONTIMEERRORLOCATION
AVNN30.2388.10 19.0 19.4Dauphin Island, AL
AVNO30.2488.23 19.5 32.0Dauphin Island, AL
%IMP und% -65%
GFNO30.3688.59 20.0 68.5Pascagoula, MS
GFDL30.3688.48 19.0 58.4Pascagoula, MS
%IMP 100% 15%

Figure 1. NCEP 850 - 200 hPa mean wind analysis for 15 September 2004 1200 UTC (Hurricane Ivan).

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 15 September 2004 1200 UTC.

Figure 3. NCEP Global Ensemble Predction System track forecasts for all cyclones in the Atlantic basin initialized from 13 September 2004 1800 UTC to 15 September 2004 1200 UTC, showing the tracks of Hurricane Ivan.

Figure 4. Ensemble perturbation variance at the nominal sampling time 15 September 2004 1200 UTC from the previous day NCEP ensemble forecast. The green circles represent the dropwindsonde locations.

Figure 5. Variance explained within the verification region (large red circle) for observations taken at the sampling time 15 September 2004 1200 UTC from the Ensemble Transform Kalman Filter run from the previous day NCEP ensemble forecast. The green circles represent the dropwindsonde locations.

Figure 6. Initial condition differences in the 850 - 200 hPa mean wind between the no and all dropwindsonde cases for 15 September 2004 1200 UTC. The circles represent the dropwindsonde locations.

Figure 7. 24-h forecast differences in the 850 - 200 hPa mean wind between the no and all dropwindsonde cases for 15 September 2004 1200 UTC.