A tale of two storms, the Great Lakes bombs of 98' and 40'

[Glenn Rivers]

I personally remember the Nov 10, 1998 964 mb superstorm mentioned by “rdeweyâ€, even though in S Ontario were I live, sustained hourly winds held to 35-40mph with 3 second gusts of 60 mph for typical airport exposures.

The superstorm on Nov 1998 storm had an uncanny resemblance to an even greater but almost identical bomb that occurred on Nov 11, 1940. In the former event, lowest SLP reached about 955mb over Central Lake Superior. Some of the differences were......

-The track of the 1940 event was perhaps 50-100 miles to the right (SE)
of the 98’ event.
-Also, the 40’ event had much colder air in its wake, and produced much more heavy snow to the NW of its track than the 98’ storm.

Many Great Lakes mariners consider the Nov 1940 storm more violent then even the Nov 1913 storm that took over 200 seamen on Lake Huron. Large freighters were driven ashore in the 40’ storm, with significant loss of life, especially after they made the mistake of hugging the E shore of Michigan to seek shelter from the prefrontal SE gales, only to be caught exposed to the murderous tempest that commenced from the SSW behind the cold-front.

After the cold front passed Lake Michigan, the wind settled into a remarkably steady blast from ~210° for several hours. These winds were directed only slightly askew from the length of Lake Michigan, creating conditions for waves with a long fetch. I recall reading that there was a ∆ storm setup of 6 feet near the Mackinaw straits compared to the S end of lake. It might be constructive to compare the setup from the 98’ storm to that of its 40’ counterpart, especially as the time sequence of wind directions was similar in both storms. This exercise might allow a reasonable reconstruction of the wind and wave fields during the 40’
storm.

An interesting counterpart of the Nov 1913 storm also occured in Nov 1950, but I will save this discusion for another time.

 

[mikegeukes]

Armistice Day Storm of Nov 11, 1940. I read somewhere waves were as high as 50 feet on Lake Michigan, pressure of the storm was 967 mb and winds gusted to 80 mph in Grand Rapids, Michigan.

http://www.carferries.com/armistice/
http://www.usatoday.com/weather/resources/...ary-history.htm

Mike

 

[Joel Wright]

Yeah that 1998 storm was a very interesting storm.

We had a slightly different perspective here in northern Illinois. I remember the night before as being rainy and cold, as the stratiform rain overspread the area. A little foggy also. We were under a high wind watch, as it was pretty obvious by this point the cyclone was going to be very intense. The LP was projected to pass about 300 miles northwest of us across NW IA into SW MN, which is a very favorable track to bring our area high winds with intense storms. The winds the night before were light easterly, barely noticable. I ended up going to bed pretty early, around 11. I was surprised when I was awakened by the wind around 5am. In a matter of six hours or so the winds had really kicked up and were gusting to over 40mph, now from the southeast. The clouds had broken a little, and the ceilings were much higher. I knew without even looking at the thermometer the warm front had passed. I turned on the weather channel and the cold front was very easy to pick out on radar. It was marked by a thin broken line of rain showers in an arc, at this time about 100 miles to my southwest. It was moving northeast at nearly 50mph so I figured the front would pass around 7am or so. Here's where it gets very interesting, I can't ever remember seeing anything like this before. I waited in anticipation at the line of showers approached. The clouds had really broken apart allowing the early sun to shine through. Of course the clouds were screaming to the north very rappidly. I waited for the dark bank of clouds to appear on the southwest horrizon, and when they finally did I was surprised at how I could see blue sky behind them. It looked as though it was mainly VIRGA! Sure enough as the cold front/thin bank of elevated nimbostratus approached the streaks of rain could clearly be seen evaporating beneath the bases. The dry air at the leading edge of the dry tounge must have been just punching in so fast it was starting to actually eat away at some of the frontal precipitation. I can't recall ever seeing this before or ever again. Anyway, as this line of clouds rappidly passed over the winds instantly veered from south-southeast to southwest and began to gust violently over 60mph. The combination of the cold front passing and the evaporating precip must have aided the downward momentum increasing the winds beyond what they normally would have been. A huge 3' diameter weeping willow tree across the road was uprooted, along with a large red oak at the top of the street. After a few minutes of this, the winds calmed down, and only gusted to about 30mph or so for an hour, before they really picked up again as the isoballic max approached. The sky had become totally clear. By late morning the winds were consistantly gusting over 60mph and then the stratocumulus field engulfed us as the wrap around swung in. By nightfall flurries were flying in the 60mph winds.

Definitely one fascinating day to be sure. Hopefully this will add a bit to the story of this incredible storm.

 

[Glenn Rivers]

98 in Illinois

I would like to thank Joel for his vivid description of the Nov 10, 1998 storm from his location in Illinois. I guess this is a good reminder to the unwary that even a very weak convective event e.g. a weak shower from a high base of Cumulonimbus or even Nimbostratus is not to be taken lightly when there is a lot of momentum aloft that might be draged down by evaporation of falling precip.

The description of the lull after the squall passage is also interesting. True the strongest surface pressure gradient had not yet arrived, but I wonder if the squall put down a cold pool that protected the ground from high winds untill the daytime heating mixed it out.