The National Weather Service in Grand Rapids conducted a survey of the July 11, 2009 storms that moved across portions of Allegan County. As a result of the survey, it was determined that straight-line winds of up to 60 mph produced widespread tree damage. The damage began between 5:57 am EDT and 6:05 am EDT. Strong to severe winds lasted up to 15 minutes at some locations, according to eyewitness reports. This is consistent with straight-line wind damage. Most of the damage was confined to the Sandy Pines Resort southeast of Burnips. Numerous tree limbs were scattered throughout this location. The hardest hit area was Phase III of Sandy Pines where a few uprooted trees and numerous broken tree limbs had fallen. A large tree fell on an unoccupied camping trailer, resulting in substantial damage to the trailer. No injuries were reported from these thunderstorm winds.
Here is a radar image from around the time the damage occurred (click on image to enlarge)
The image below is an estimation of wind speeds from the KGRR radar around the time of the damage. The radar estimated wind speeds of 30-40 knots (Click on image to enlarge)
A survey also was conducted in Wayland and Hastings based on preliminary reports of damage. However, findings indicated that numerous small limbs were downed on the east side of Wayland. Winds in these areas were estimated to have been around 50 mph. Radar data indicate the strongest winds occurred around 6:15 am EDT. Little or no tree damage was observed in the Hastings area.
Tree damage in Sandy Pines Resort
Willow tree damage west of Sandy Pines Resort
A damage survey map for Sandy Pines Resort and immediately surrounding areas is below.
Click on image to enlarge