Shelf clouds during rare October thunderstorms in Peoria, Ariz. Tuesday
afternoon. Thanks, Bill.
What were the weather conditions on Lake Superior during the storm that sank the Edmund Fitzgerald on Nov. 10, 1975? Have there been storms that strong since then?
---Joe Toepper, Manteno
The Edmund Fitzgerald storm had a barometric pressure of 28.95 inches when it crossed Lake Superior, the equivalent of a Category 1 hurricane. Its peak winds hit 80 mph and with gusts topping 90 mph the storm produced huge waves of 25 to 30 feet. The Fitzgerald's crew of 29 perished when the ship sank about 17 miles northwest of Whitefish Point, Mich., in the eastern part of the lake the evening of Nov. 10. The storm was on the high end of the severity scale, but stronger storms have hit the Great Lakes and every few years during the late fall or early winter storm season one will match or exceed its intensity.
From reader Dan Giampaolo: Frost on a soccer field in Bensenville. See more photos and send us yours.
By Tom Skilling
Frost has occurred in recent nights at a number of inland
locations--but NOT in the city at Midway Airport. Based the first
occurrences of frost at Midway Airport since 1996 from veteran observer
Frank Wachowski, October 14th has been the average first date for frost
at the South Side site. Since 1996, the earliest frost there occurred
Oct. 1, 2003, and the latest was Oct. 28, 2007.
Crank up the furnace
Another chilly--and in a number of areas--frosty morning. Lows
bottomed out at 29 in Wanatah, Ind., and Paxton, Ill. O'Hare dipped to
39 and Midway 40. Chicago's lakefront recorded 50. Colder area lows: 31
in Rochelle, Watseka and Sugar Grove; 32 at the Morton Arboretum (Lisle)
and Marengo; 33 in Mareseilles, Ill., Peru, Ill. and Rensselaer Ind.;
Elgin, Joliet, Dwight and West Chicago hit 34; 35 in Rockford; 36 in
DeKalb and Waukegan and 37 in Lansing and Valparaiso, Ind.
From reader Chuck Hagen: "Fall colors are starting to pop around the region as seen in this shot taken near Maple Lake."
See more photos and send us yours.
By Meteorologist Tom Skilling
The same air mass behind Chicago's coolest weather since May chilled a huge swath of real estate from the Midwest into portions of the Deep South Monday. The day opened with slew of new record lows across sections of seven states and ended with the issuance of overnight frost warnings in portions of a dozen states.
Chicago's 38-degree pre-dawn Monday low at O'Hare was the city's coldest in the nearly five months since May 9 and was followed by a third consecutive daytime high which failed to break above 60-degrees---a reading more typical of October's third week than to the month's fourth day.
An analysis of Midway Airport's 82-year observational record (dating back to 1928) reveals only one in four years have produced strings of three days with highs of 60-degrees or lower so early in the season. By Monday's close, the 52.4-degree average temperature over the young month's opening four days fell more than 7-degrees short of the 139-year Oct. 1-4 period---chilly enough to rank 22nd coolest since official records began in 1871.
Now begins a period of warming
Bright sunshine which filters at times through patches of high clouds Tuesday kicks off a period of slow warming likely to culminate in mid to upper 70s Sunday and low 80s by Monday next week. More than two-thirds of the years on record here have managed one or more 80-degree high temperatures beyond this date---and this year appears likely to become the latest.
Daytime highs are to stair-step from Tuesday's 68-degrees to Wednesday's 75-degrees--then top out in the 70s Thursday and Friday.
There are indications a back-door-type cool front---one which slips in from the north or northeast--is to settle southward across the area Friday night bringing easterly winds to the Chicago area Saturday. We've reduced our projected Saturday high temperature as a result. But, winds are to return from the south Sunday and from the southwest Monday allowing temps to rebound strongly. The expectation is that highs here could approach 80-degrees later Sunday and move into the low 80s Monday.
Cool weather indices hint at the potential for significant cooling again mid and late next week
Two indices which often flag significant cool spells in the medium range (from 7 to 16 days out)---the Arctic Oscillation Index (AO) which offers insight into the buildup of cool or cold air masses in the arctic and the North Atlantic Oscillation Index (NAO) index which forewarns of a buckling jet stream over the North Atlantic which can deliver that cool air to the central and eastern U.S.---both turn negative next week. Negative values signal the potential for cooler air in Chicago.
Country's eastward weather progression slows to snail's pace under "omega block"
The eastward progression of U.S. weather is being held hostage by what meteorologists refer to as a "blocking pattern" aloft. In the current situation, an "omega-type" block is at work. The block derives its name from the highly wavy orientation of jet stream which parallels the shape of the Greek alphabet letter "Omega". When winds blowing high above the U.S. orient themselves in this manner, weather systems slow. The current pattern is locking wet weather into the West and over the Mid Atlantic and sections of New England while leaving Chicago high and dry.
Los Angeles' all time 113-degree high just a week ago gives way to rain and 60s
Just a week ago, Los Angeles recorded its hottest daytime temperature on record---113-degrees. But, the current pattern slashed temperatures there 45-degrees Monday to the 60s and introduced rain. The new weather regime in the West is also behind the rash of big thunderstorms which prompted severe weather watches over western Arizona and southern sections of Nevada and Utah. Thunderstorm gusts topped 60 mph in areas near Phoenix and the storms, which towered above 50,000 feet at times, promised to bring an end to recent triple-digit heat there while threatening flooding downpours.
Sunday's Bank of America Chicago Marathon weather to kick-off with low 50s and end in upper 60s/low 70s
Runners participating in this Sunday's Bank of America Chicago Marathon might well prefer cooler weather than that which is being predicted. But, overall conditions do not appear bad from this distance. Light south to southwest winds are likely to average 4 to 12 mph and temperatures are forecast to start off in the low or mid 50s as the race opens and move into the low 70s by the race's conclusion. We'll continue updating this outlook in the week ahead.