By Jeff Masters
30 January 2013
[…] Today's severe weather outbreak was helped by record levels of January moisture, as a flow of unusually moist air rode northwards from the Gulf of Mexico, where water temperatures were about 0.5°F above average. Meteorologists use a term called "precipitable water" to discuss how much water vapor is in the atmosphere. Precipitable water is defined as how much rain would fall on the ground if one took a vertical slice of the atmosphere above a given location and condensed all the water vapor into rain. Precipitable water levels tend to be highest in the summer, since warm air holds more waver vapor, and can exceed two inches in the Midwest U.S. In winter, though, it is rare to see precipitable water values higher than one inch.
However, Tuesday night, precipitable water was well over an inch well into Canada, and two upper air stations--Detroit, MI and Lincoln IL--set all-time records for January moisture. From the 00Z and 12Z Wednesday January 30, upper air balloon soundings taken at the 73 radiosonde stations in the contiguous U.S., we observed these record or near-record precipitable water values for January:
- Detroit, MI: New Record: 1.21" Old record: 1.20" 1/11/75
- Lincoln, IL: New record: 1.46" Old Record: 1.35" 1/12/60
- Alpena, MI: 2nd place, 0.99". First place: 1.01", 1/5/97
- Buffalo, NY: 2nd place, 1.21". First place: 1.34", 1/15/95
- Wilmington, OH: 2nd place, 1.44" First place: 1.51", 1/12/2005
Green Bay (4th), Shreveport (6th), Little Rock (3rd), Nashville, TN (10th) and Maniwawi, Quebec (4th) all had top-ten January precipitable water values. Radiosonde data goes back to 1948.
The exceptional moisture led to record rains in many regions of the Midwest, with numerous locations setting daily precipitation records. Two airports recorded their wettest January day on record, including Madison, WI (1.84", previous record 1.80" on January 1, 1892) and Houghton Lake, MI (1.21", old record 1.08" on in 1938.) Top-five wettest January days in recorded history were also set at Muskegon, MI (2.48"), Marquette, MI (1.21"), and South Bend, IN (1.94".)
Here where I live, in Southeast Michigan, being outside yesterday was like walking through a surreal white soup. Rains like nothing I've ever seen in January fitfully poured from the sky throughout the day, ponding up on the frozen ground. Eerie white fog swirled over the sodden snow drifts as thunder rumbled overhead in temperatures 25°F above average. What planet was this? The heavy rains of 1.60" that fell in 26 hours at the nearby Flint airport made this month our wettest January in recorded history, with 3.66" of precipitation. [more]