Many locations across the U.P. have experienced very warm and dry conditions this summer. From June 23rd to August 31st, only 2.05 inches of rain fell at the National Weather Service office in Negaunee Township, resulting in the driest June 23rd to August 31st period on record. The second driest June 23rd to August 31st period is 3.10 inches recorded in 1976.
Continued dry weather through the first three weeks of September kept the NWS office on pace to have one of the driest July-September stretches on record. However, heavy rainfall at the end of the month resulted in 5.79" of precipitation over only 8 days. Here are the top 10 driest July-September periods. The normal rainfall for this period is 9.78 inches:
July 1st - September 30th total in 2011: 8.73"
July-September Total Precipitation (inches)
The Marquette NWS office also recorded the most consecutive calendar days with rainfall totals less than 0.25 inches for the time period ranging from May 1st through September 30th. This streak was finally broken on September 12th, 2011, when 0.38 inches of rain fell as a thunderstorm passed over the office.
|Rank||Year||Number of Days|
|1.||2011||81 (June 23rd to Sept 11th)|
The total of 81 consecutive days was 2nd for any time period on record. The longest stretch of consecutive calendar days with precipitation less than 0.25 inches occurred from November 5th,1967 to January 28th,1968 -- a total of 85 days. Additionally, this is not the only long stretch of dry weather this year. A 55 day streak of calendar days with rainfall less than 0.25 inches occurred from January 13th to March 8th this year, which is the 11th longest streak on record.
The image below shows that not all of the U.P. has been extremely dry. Many locations across Gogebic and Ontonagon Counties saw more than 5 inches of rain during July and August. However, even these numbers are ~20% below normal. Most of the larger rain amounts across the rest of the U.P. were randomly distributed because of heavy downpours from scattered thunderstorms. While one location may have observed more than 1" of rain from a given thunderstorm, nearby locations may not have received any precipitation. The second image below, produced by the Advanced Hydrologic Prediction Service (AHPS), represents the percent of normal rainfall that was observed over a 60 day period ending at 8AM EDT on September 2nd. Average precipitation across the U.P. for July-August ranges from around 6" north to 7.50" south. It is clear that much of the rain this summer has missed the U.P. and affected northwest Wisconsin. On multiple occasions since the beginning of July, there has been a cluster of thunderstorms that moved southeastward just south of the Michigan-Wisconsin state line.
Because of the lack of rainfall from not only the summer, but also most of the year, much of the U.P. has been placed in the D0 category in the Drought Monitor, which means conditions have been "abnormally dry". This designation was given around the end of July. The continued lack of precipitation into August resulted in the northern parts of Marquette and Baraga counties, as well the Keweenaw Peninsula, to be placed in the D1 category, or "moderate drought", in mid-August. By mid-September, more dry weather across much of the U.P. caused the drought to worsen and northern Marquette County was placed in the D2, "severe drought", category. Additionally, all but the extreme far east of the U.P. is offciailly in a drought. The image below shows the regions that are currently experiencing drought conditions. This chart is updated weekly and can be found at the website listed within the image.
The October through December precipitation outlook from the Climate Prediction Center (CPC) shows equal chances of experiencing above normal, normal, or below normal precipitation amounts across the Upper Peninsula this Fall. Because of this, it is expected that the current drought situation could persist well into the Winter months. However, September and October tend to be very active months in terms of weather across the U.P., so moderate to heavy rainfall is always possible with strong low pressure systems.
Here are a couple of other notable facts about the lack of precipitation this year:
* Weather records for the Marquette National Weather Service office located in Negaunee Township date back to 1961.