A Wet, Stormy, and Historic May 2004
All of Southeast Michigan experienced the very wet and stormy May. The month started out wet when on the first weekend over an inch of rain fell across most of the region. The storms started on May 6th with the first of many severe weather events. In many respects, May 2004 approached or eclipsed a number of records.
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Rainfall
Detroit Metroit Airport and Flint Bishop Airport both set rainfall records for the month of May. Saginaw Tri-Cities Airport placed second for May rainfall. Rainfall at all three sites was over 5 inches above the normal for the month. The following are the monthly rainfall amounts for May 2004 at the three observation sites in Southeast Michigan:
May 2004 Rainfall
monthly rainfall and departure from normalDetroit... 8.46" (5.41" above normal) Flint... 8.19" (5.45" above normal) Saginaw... 8.14" (5.25" above normal)
The following list the top five May rainfalls for the three sites. Observations from the current year are italic and highlighted in yellow.
Rainfall Records - Wettest May Rank Detroit Flint Saginaw 1. 8.46/2004 8.19/2004 9.95/1912 2. 8.05/1943 7.35/1945 8.14/2004 3. 7.84/1892 6.80/1956 7.93/1905 4. 6.97/1947 6.38/2000 7.59/1908 5. 6.20/1991 6.07/1943 6.98/1942
In addition to ranking 1st or 2nd for May rainfall, May 2004 also placed in the top 10 for wettest month on record at each of the sites. The following list the top 10 monthly rainfalls in the climate record. Observations from the current year are italic and highlighted in yellow.
Rainfall Records - Overall Wettest Month Rank Detroit Flint Saginaw 1. 8.76/July 1878 11.04/August 1975 16.16/September 1986 2. 8.46/May 2004 10.86/September 1986 9.95/May 1912 3. 8.33/August 1926 9.35/July 1992 9.01/August 1975 4. 8.31/June 1892 8.68/August 1956 8.15/September 1945 5. 8.05/May 1943 8.68/September 1950 8.14/May 2004 6. 7.84/May 1892 8.55/July 2000 7.93/May 1905 7. 7.83/August 1975 8.29/September 1985 7.78/October 1954 8. 7.80/October 1954 8.19/May 2004 7.59/May 1908 9. 7.55/July 1902 7.92/July 1957 7.49/September 1981 10. 7.52/September 1986 7.65/September 1981 7.33/August 1995
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Flooding
While Detroit and Flint set records for the amount of rainfall received during the entire month of May, a large portion of that rain fell during the second to last weekend in the month.
Using radar estimates and ground reports, generally 3 to 6 inches of rain fell across most of Southeast Lower Michigan between Thursday night 5/20 and Monday 5/24, with most places leaning toward the high side. Using an average of 5 inches of rain and some simple math, the following is approximately how many gallons of water fell on each county. Larger sized counties will have larger numbers since they have more surface area.
Estimated Amount of Rainfall County Amount of Water Genesee 51 billion gallons Macomb 37 billion gallons Oakland 70 billion gallons St. Clair 59 billion gallons Washtenaw 57 billion gallons Wayne 49 billion gallons
Some of this water soaked into the ground. However, with the soil being already moist from rains earlier in the month, a fair percentage of this water ran directly into creeks and rivers. This should give an idea of how much water our rivers had to drain and why flooding was experienced.
With the amount of rain that fell, a number of area rivers also
rose above flood stage. One of those rivers was the Huron River
at Hamburg in Livingston County. Minor flooding in the middle of
the month had only begun to recede when the billions of gallons of
water mentioned above started falling, leading to a renewed rise
in the river level and major flooding late in the month. More
information about the river flooding, including pictures, is available:
Tornadoes and Severe Storms
The thunderstorms not only brought heavy rainfall, but severe weather and tornadoes too.
Southeast Michigan had 14 tornadoes during the month of May. Most were brief touchdowns with little damage. The 14 tornadoes is a record for Southeast Michigan for the month of May. The previous record belonged to May 1956 when eight tornadoes were recorded (all on one day - May 12, 1956), most of which were significant tornadoes (F2 or greater).
The following is a listing of the May 2004 tornadoes:
May 2004 Tornadoes in Southeast Michigan Date Location Fujita Damage Scale Map Reference 5/13 West of Owosso F0 #1 5/14 West of Saginaw F1 #2 5/14 6 miles North of North Branch F0 #3 5/14 Near Brockway F0 #4 5/14 Near Croswell F0 #5 5/22 Near Arthur F0 #6 5/22 Near Burt and Birch Run F0 #7 5/22 Southwest of Owosso F0 #8 5/22 West of Fostoria F1 #9 5/22 Northeast of Deckerville F0 #10 5/23 South of Montrose F0 #11 5/23 Mt. Morris F0 #12 5/23 East of Yale F0 #13 5/31 Port Huron F1 #14
During the month of May, the National Weather Service in White Lake has issued 84 severe thunderstorm or tornado warnings (90 so far for the season). Looking back at the warning database, dating back to 1986, no other May (or spring season) has had more warnings. Statistics show that the May of 2000 previously had the most warnings issued with 53. The spring of 1998 (January 1 through May 31) previously had the most warnings issued with 62.
