Top U.P. Weather Events of 2011
While the U.S. as a whole saw many unprecedented weather disasters in 2011, the weather across the U.P. was fortunately much more tranquil. Below is the top 5 list, in no particular order, of the most significant weather events that affected the U.P. in 2011.
2011 Very dry year for the Western U.P. :
2011 will go into the record books as being a very dry year across the western half of Upper Michigan. It started out very dry with below normal snowfall and one of the driest January to March stretches on record. After a slightly cooler and wetter than normal Spring, warm and dry weather returned for the Summer with the driest July through August period on record for some locations across the west half of the U.P. After a wetter than normal September, precipitation deficits returned for the remaining months of 2011. Precipitation deficits for the year mainly west of a Marquette to Escanaba line have been on the order of 5 to 10 inches or about 70-80% of normal.
Temperature wise, 2011 wasn’t as warm as the record warm year of 2010, but it will still go in the record books as being an above normal year due to a warm start to the year and a warm summer and fall.
Figure 1. December 13, 2011 US. Drought Monitor Page showing
parts of Western Upper Michigan in a moderate drought.
While seiches are not that uncommon on the Great Lakes, typically the water level changes are so minor they go unnoticed. Seiches occur in enclosed basins when strong winds cause water to pile up on one side of the lake. Once the strong winds die down, the water sloshes back to the other side of the lake. This 'sloshing' motion can last for days at at time, sometimes causing water level fluctuations of several feet.
Figure 2. Diagram of the sloshing motion caused by a seiche, indicated by the rise above the still water level.
During the Spring of 2011, several clusters of thunderstorms moved across Lake Superior, producing strong, short duration winds that resulted in very noticeable seiches. One localized seiche occurred in Whitefish Bay on May 11th, causing the water to fluctuate several feet on both sides of the Bay. The most significant seiche that occurred during this period was during the day on May 30th after a complex of thunderstorms moved across the eastern half of Lake Superior. Witnesses reported water levels dropping 3 to 5 feet from Marquette to the eastern shore of the Keweenaw Peninsula, then returning to several feet above normal. This sloshing of the water back and forth continued for the next day or two, slowly diminishing with time. Fortunately, there was no damage or injuries caused by the seiches.
Figure 3. Graphs from The Marquette Coast Guard showing the rising and falling water levels throughout the 4 day period (left) and the quick changes in wind speed and direction.
July 1st Thunderstorm wind damage in the Keweenaw:
While the number of severe weather reports associated with thunderstorms was below normal in 2011, there were still some bouts of thunderstorms that produced damage in Upper Michigan.
A cold front moving through a warm and unstable airmass triggered a line of severe thunderstorms which affected portions of the Keweenaw Peninsula on the evening of July 1st. As this decaying line of thunderstorms crossed the Keweenaw Peninsula, strong outflow winds produced localized wind damage around Calumet and Copper Harbor.
Winds gusting in excess of 70 mph produced a damage path that stretched from Mine Street through the intersection of US-41 and Church Street in North Calumet. The damage path was oriented from southwest to northeast and estimated to be one-quarter mile wide. A metal building housing a travel trailer destroyed. Several trees estimated to be between 18 to 24 inches in diameter were uprooted. A drill shop roof near the elementary school sustained significant damage. Several houses sustained minor roof and window damage. The Calumet Golf Club also sustained tree damage.
Localized strong winds up to 70mph also affected an area just west of Copper Harbor in Keweenaw County. A 150-yard stretch of approximately 40 trees were uprooted or snapped. The trees ranged from 6 to 18 inches in diameter and fell in the same general direction. Several of the trees fell across Highway M-26 closing the highway.
Figure 4. Pictures from the Damage survey in Calumet, MI. Left shows the largest tree downed, and the Right shows the carport that was thrown into the church building by the strong winds. Photos taken by NWS Marquette.
August 19th Ontonagon tornado:
Michigan’s Upper Peninsula averages around one tornado per year. Since waterspouts over inland lakes are officially classified as tornadoes, there was a suprising total of four tornadoes that touched down in the U.P. in 2011.
On May 23rd, weak low pressure and cold air aloft helped spin up a weak tornado/waterspout in the Helmer Bay portion of Manistique Lake in Luce County during the early evening hours. The tornado/waterspout was not associated with a thunderstorm. The waterspout never moved onshore and did not produce any damage.
A similar weather situation later in the summer resulted in a weak tornado/waterspout over the Dead River storage basin. This weak tornado/ waterspout was observed for 15 to 20 seconds on the afternoon of the August 11th. Once again there was no damage associated with it.
The most significant tornado of the year to touchdown in the U.P. occurred during the early morning on August 19th in Ontonagon. A line of thunderstorms moving through the area produced a strong EF0 tornado with winds estimated around 85 mph that touched down at the River Pines RV Park and Campground in Ontonagon. It then skipped northeastward across the village, lifting on the east side of the Ontonagon Golf Course. Most of the damage was confined to snapped and uprooted trees, snapped power poles, a small flipped boat, minor roof damage, and some structural damage to a garage. There were no injuries.
Late in the afternoon on this same day, August 19th, a severe thunderstorm produced an EF1 tornado in Marinette County, Wisconsin, near Wausaukee. The twister flattened a mobile home, killing the occupant. Hundreds of trees were snapped or uprooted along the nearly eight mile long storm path. (This was the first death from a tornado in northern Wisconsin since August 29, 1992.) This tornado did briefly cross the Menominee River into Upper Michigan where about a dozen trees were uprooted and numerous branches broken in the Escanaba River State Forest. It then crossed back across the Menominee River into Wisconsin.
Figure 5. The Yellow line on the map (left, courtesy of Googlemaps, 2011) depicts the path of the Ontonagon Tornado. On the right is a photo (taken by NWS Marquette) of some of the damage.
September 29-30th Windstorm:
The Upper Peninsula is not immune to wind storms, especially in the Fall. A rapidly deepening low pressure system moving through the Upper Great Lakes on September 29th and 30th caused heavy rain and damaging north winds across the U.P. and the Lake Superior shoreline. Winds gusting up to 70mph resulted in thousands of trees being snapped and uprooted. The falling trees knocked out power to thousands, and in some cases, the power outages lasted up to five days!
Figure 6. Satellite image overlaid with isobars (lines of constant pressure) on the left. Right: trees damaged from the storm.