Severe local windstorm associated with the record-breaking 10 November 1998 mid-latitude cyclone

On 10 November 1998, a cyclone deepened rapidly as it passed through the Upper Midwest, bringing with it record-setting low pressures and damaging winds, including an 81-kt gust at the LaCrosse, Wisconsin NWS office. These winds caused eight deaths and more than $47.5 million in damages.

An examination of satellite imagery over the Upper Midwest during the height of the storm shows an area of dry air curving cyclonically behind the cold front. This dry intrusion forks into two distinct paths near the low pressure center, with the lowest tropopause heights (~ 600 mb) near the southern fork of the dry intrusion. Pilot reports indicated an area of significant clear air turbulence existed within this dry intrusion.

The main finding of this work is that the surface reports of damaging winds are very closely linked in time and space to the location of the southern fork of the dry intrusion. The possibility of improved nowcasting of extreme winds using satellite imagery is discussed. The satellite signatures of this storm are discussed in relation to other damaging windstorm events, such as the 1979 Fastnet yacht race cyclone and the 1975 cyclone which sank the Edmund Fitzgerald.