Tropical Storm Bonnie Forecast Verification
Written by Derek Ortt on May 29, 2005

Track forecasts for Tropical Storm Bonnie were below the long-term average through 72 hours. At 96 hours, the track errors were well below those of CLIPER, though above the long-term average. At 120 hours, the track forecasts completely lacked skill and were more than 300% greater than those of CLIPER. However, an important point needs to be stated. The track forecasts assumed that Bonnie would remain as a tropical cyclone and would turn to the north, then NE, across Hispaniola and the SE Bahamas. However, Bonnie weakened to a tropical wave and continued to the west. Bonnie then reformed, allowing verification of the 120 hour forecast point, though many intermediate times for forecasts 1 and 2 could not be verified as Bonnie was a tropical wave then.

Track forecasts for Bonnie improved once the storm moved into the Gulf of Mexico, except for some issues regarding the forward speed and heading after the storm made landfall, which resulted in a couple of forecasts having larger than normal errors.

Intensity forecasts were not very good at all. It was hard to get a handle on Bonnie due to its very small size and the changing atmospheric conditions, alternating between low and high shear. Many forecasts called for Bonnie to make landfall as a hurricane.

The Hurricane watches and warnings recommended by NWHHC did not verify. The tropical storm warning that eventually did replace the hurricane watches and warnings was recommended at the appropriate time. In retrospect, only the tropical storm warning should have been recommended and only for the area east of Destin.

For synoptic history, as well as official watches and warnings, please see the National Hurricane Center Tropical Cyclone Report for Tropical Storm Bonnie

Click Here for the forecast error statistics

Track and intensity forecast verification for Tropical Storm Bonnie

Table of Recommended Watches and Warnings

8/3 2100 UTC Tropical Storm Warning: St Lucia to Guadeloupe (Lesser Antilles)
8/4 1500 UTC Tropical Storm Warning Dropped: All
8/11 1615 UTC Hurricane Watch: Florida/Alabama Border to Cedar Key, FL
8/11 1800 UTC Hurricane WARNING: Ft Walton Beach, FL to Apalachicola, FL
8/12 0000 UTC Hurricane WARNING Extended: east to Cedar Key
8/12 0300 UTC Hurricane Watches and Warnings dropped: All 8/12 0300 UTC Tropical Storm Warning: FL/AL Border to Cedar Key
8/12 0900 UTC Tropical Storm Warning Dropped: West of Destin
8/12 1800 UTC Tropical Storm Warning dropped: All

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