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  • Tim McGill

Cool Today But More "Summer" Coming

Wind, Waves & Waterspouts! Oh My!


Waterspout Over Lake Michigan From A Kenilworth Beach (Courtesy Of Nina Brady)

We saw some interesting weather on Wednesday including everything from big waves to strong winds and even some waterspouts. There were at least 13 according to the International Centre for Waterspout Research (ICWR). The type of waterspouts that were seen from the shores of Lake Michigan yesterday typically develop and decay fairly quickly and usually aren't harmful except to boaters. The winds generally don't exceed 70 mph. Stronger waterspouts associated with supercell thunderstorms can produced damage equivalent to an EF2 tornado.


There is some potential for additional waterspouts mainly along Indiana's shoreline early today.


The arrival of the autumnal equinox yesterday coincided with the coolest day we have seen in nearly four months. O'Hare had a high of just 63° on Wednesday which was 10° below average. This morning's lows fell into the middle to upper 40s well west of the city. Hang in there all you warm weather fans. Another cool day today but there is some summer-like temperatures in my 7-day forecast.


The HRRR Model has our highs today again about 10° below average as we top out in the middle 60s.


The GFS Model suggests it will be cool and crisp tonight with lows in the outlying areas falling into the middle to upper 40s. Winds shift early Friday to the southwest to set us up for a warmer end to the week.


Some sunshine and gusty southwest winds will push Friday's highs well into the 70s. It's possible a few spots well west of the city could tag 80°.


Winds today will gust out of the northwest up to at least 30 mph and then diminish this evening. Winds make their shift early Friday and gust again near 30 mph tomorrow but out of the southwest.


A weak cold front will come through tomorrow evening and could produce some scattered showers and thunderstorms at that time. The best chance for rain is between 6 pm and midnight.



Strong winds will again whip up some big waves today but targeting northern Indiana more as the winds have shifted from a northerly to a northwesterly direction. A beach hazards statement continues until 7 pm tonight for Illinois' shoreline and until 4 am Friday for Indiana's shoreline. A lakeshore flood advisory is in effect for Cook County's shoreline until 10 AM today. Waves there will peak early around 8 to 11 feet. A lakeshore flood warning is in effect until 7 PM tonight for Lake and Porter Counties in Indiana where waves could build to 10-14 feet.



Comparing the wave height forest for 6 am today to the forecast for 7 pm tonight shows the waves diminishing. The yellows in the morning forecast which indicate waves potentially bigger than 10 feet are gone in the later forecast.



The swim risk remains high for nearly the entire shoreline of Lake Michigan and for other portions of the Great Lake's shores.





Squeezing Out More Summer

We are not done with the 80s. The National Blend Of Models has highs tomorrow and Sunday near 80°. Highs could hit 80° or even warmer Monday and Tuesday. Temperatures should be above average all of next week.



Next Tuesday may be the warmest day of the week. The temperature anomaly forecast has temperatures for most of the Midwest about 15° to 25° above average.


Our warm start to September may continue into the start of October. Most of the country is favored for a mild end to this month and start to the next. The 6-10 day outlook has Chicago favored for above average temperatures overall from September 28th through October 2nd. The longer range 8-14 day forecast also favors us for above average temperatures overall. It covers the period from September 30th through October 6th. Average highs for this period are in the upper 60s to lower 70s.





The even longer term 30 day forecast still suggests not only the Midwest but most of the country staying above average overall well into October. The Global Ensemble Forecast System (GEFS) is a weather forecast model made up of 21 separate forecasts, or ensemble members The model tries to give an idea of the amount of uncertainty in a forecast by running an ensemble of multiple forecasts which are each tweaked a bit with their initial conditions.


GEFS Temperature Anomaly Forecast From September 21st Through October 21st







A Mostly Dry Forecast


O'Hare picked up .40" of rain yesterday but is still 1.27" below average for September. Some showers and even a thunderstorm are possible Friday night but beyond that, the forecast for the next several days is dry. I'll have the new numbers from the US Drought Monitor report tomorrow.


Here is a recap of my post from Friday with the latest US Drought Monitor report:


The latest US Drought Monitor analysis is in and it is mostly good news for the Midwest but there is some bad news locally.


The US Drought Monitor analysis shows a slight increase in the area under a moderate drought ( 1 one out of 4 levels). The area grew to 10.11% from 9.81% last week. The area in a severe drought (level 2 out of 4 levels) did not change and remains at .79%. The area considered "abnormally dry" (the precursor to a moderate drought) nearly doubled and now stands at 32.94%.


For the Midwest the news was better. The areas in a moderate, severe and extreme drought all dropped slightly. The area in an exceptional drought (level 4 out of 4 levels) is unchanged at .99%. The most parched portion of the Midwest is northern Minnesota.


An analysis of the past two weeks of rainfall (ending on September 21st) shows just how dry it has been during the middle of this month. Most of the northern Illinois seen just 25% to 75% over average rainfall.


The GFS model's meteogram for O'Hare has some rain early today but I think this is overdone. Most of us will be dry. The best chance of rain will be in northern Indiana with maybe a spotty sprinkle or shower brushing ashore along the Illinois lakefront early. This meteogram does not show any additional rain until Monday. Most other models are suggesting some showers Friday night. All models keep us relatively dry for the next several days.




The GFS model total precipitation all the way through a week from Friday squeezes out nearly a third of an inch in north central Indiana and then tapers amounts off to just a few one hundredths of an inch or less in Illinois.



The long range precipitation outlooks don't offer much promise for some much needed rain. The latest 6-10 day forecast has the Chicago area favored for below average rainfall from September 28th through October 2nd. The longer range 8-14 day forecast has us outlooked for below average precipitation too from September 30th through October 6th. In both cases the Chicago area is in the highest probability contour for below average rainfall.





Here is my 7 day forecast:


Today: Partly to mostly cloudy (more sun west), showers near lake early, breezy High: 65


Friday: Mostly sunny (evening shower possible), breezy & warmer Low: 49 High: 78


Saturday: Partly to mostly sunny Low: 53 High: 71


Sunday: Mostly sunny Low: 52 High: 77 (cooler lakeside)


Monday: Mostly sunny Low: 57 High: 82 (cooler lakeside)


Tuesday: Mostly sunny Low: 61 High: 83 (cooler lakeside)


Wednesday: Mostly sunny Low: 63 High: 84 (cooler lakeside)

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