Hot September So Far, But Relief Is in Sight

Illinois and the Midwest have been running hot so far in September.  The statewide average temperature for September 1-19, 2018, in Illinois was 73.5 degrees and 4.7 degrees above normal.

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Days at or above 90 degrees have been quite common this September, especially in central and southern Illinois where we saw 8 to 12 days with temperatures at or above that threshold. Runs of hot weather like this in September are unusual but not necessarily record-breaking. For example, here in Champaign, we have reached the 90-degree threshold 10 times this month (including today).  That’s the 4th highest count for September since 1888.  The highest number of days was 15 set in 1897.

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But this is about to change on Friday as a cold front sweeps across the state.  Here is the forecast map for Friday morning with rain ahead of the front and cooler temperatures behind the front.  The NWS forecasts out to 14 days show that colder-than-normal temperatures will prevail with highs in the 60s and 70s and lows in the 40s and 50s across much of Illinois.

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From a harvest standpoint, the rains over the next five days may impact harvest with the heavier amounts expected in southern Illinois with potential amounts of 1 to 2 inches south of Interstate 70.  The expected amounts are much less in central and northern Illinois.  A look at the 6-10 and 8-14 day forecasts suggest that Illinois will continue to be in a wetter pattern with above-normal precipitation and below-normal temperatures.

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The NWS also released their latest outlooks today.  For October there is a “blob” of cooler-than-normal conditions centered over Iowa and Missouri and includes western Illinois.  Illinois has “equal chances” or EC on precipitation, meaning there is not an increased chance of either above or below normal precipitation.

For October-December, Illinois has an increased chance of above-normal temperatures. There is not an increased chance of either above or below-normal precipitation.  For the most part, the temperature pattern for October-December is based on climate trends (warming) and the odds favoring the arrival of El Niño this fall and winter.

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Wet Start to September Thanks to Gordon

Illinois experienced a wet start to September, thanks in part to Tropical Storm Gordon.  The statewide average rainfall through yesterday morning was 3.55 inches.  That is above the 3.24 normal rainfall for the entire month of September.  The highest month-to-date rainfall total was 10.15 inches and came from Clay City (east of St. Louis).

Here is another look at the rainfall totals (left) and the departures from normal (right) for September 1-9, 2018.  Areas in red received 5 to 8 inches of rain.  Areas in yellow received 2 to 5 inches.  Only a few spots near St. Louis and south of Chicago received less than 2 inches of rain.

What impact does this have on drought?  

The area in far western Illinois that was in serious drought conditions all summer received 4 to 8 inches of rain in the last week.  Areas in north-central and southeastern Illinois also received some relief, although not quite a dramatic as western Illinois.

Overall, the major impact of the recent rains on Illinois will be in slowing down the fall harvest. The good news is that no significant rain is expected in Illinois for the next 7 days, according to the National Weather Service.

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Both August and Summer Were Warmer, Wetter Than Normal for Illinois

August: the statewide average temperature for Illinois in August was 74.9 degrees, 1.3 degrees above normal.  The statewide average rainfall was 5.25  inches, 1.66 inches above normal and the 12th wettest August on record.

The warmest daily high temperature was 97 degrees reported at Chicago Botanical Gardens (8/5), Chicago O’Hare (8/4), Jerseyville (8/7), and Pittsfield (8/29).  The coolest reading was 42 degrees reported at Rochelle (8.22).

Rainfall for August was heaviest in the west and southern portions of the state with some areas up to 5 to 8 inches above normal (see maps).  Meanwhile, parts of east-central and northeast Illinois had below-normal rainfall. The largest monthly total was in Arlington Heights (IL-CK-163) with 10.22 inches.

 

Summer:  the statewide average temperature for the summer (June, July, and August) was 75.0 degrees, 1.4 degrees above normal.  The statewide average precipitation for the summer was 14.86 inches, 2.99 inches above normal and the 13th wettest summer on record. Continue reading

Battle of the Winter Forecasts

What the Almanacs Say

Recently, both the Farmer’s and Old Farmer’s Almanacs released their winter forecasts (below) and what they say for Illinois is quite different.  The Farmer’s Almanac predicts a “Biting Cold, Snowy” winter while the Old Farmer’s Almanac predicts a “Warm, wet” winter for Illinois.

The Farmer’s Almanac states that it “bases its amazingly-accurate long-range forecast on a mathematical and astronomical formula developed in 1818”.   We have learned quite a bit about the weather since then.  And the phrase of “biting cold, snowy” can describe a typical morning in January and February.

The Old Farmer’s Almanac states that their forecast for this winter is based on “a decrease in solar activity and the expected arrival of a weak El Niño, which will prevent cold air masses from lingering in the North.

El Niño

It turns out that the Old Farmer’s Almanac is at least partially correct in identifying a possible factor for this winter – El Niño.  Right now the NWS predicts a 70 percent chance that an El Niño will arrive by this winter.  The question remains regarding the strength of the El Niño.  The current forecasts suggest a weak to moderate event.  As a rule of thumb, stronger El Niño’s typically have stronger impacts on the weather over the US.  Speaking of which …

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25th Anniversary of the Great Flood of 1993

Introduction

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Source: https://water.usgs.gov/nwsum/WSP2425/flood.html

The Great Flood of 1993 resulted in $36.3 billion dollars in losses and 48 deaths.  It was considered the 8th worst natural disaster in US history in terms of dollars.  The top six were hurricanes, followed by the 1988 drought/heat wave.  Large regions of the Missouri and Upper Mississippi River basins were impacted by heavy rains from June through August of 1993. The rains were widespread with the largest totals concentrated in Iowa.

I will share some climatic factors of the event.  However, the most important thing to remember is that this was a large, slow-moving human disaster.  I had friends and family in the affected area and it was indeed tough times.  The St. Louis Post Dispatch recently did a story on the 25th Anniversary, showing the extent of the disaster.

In the end, I will try to answer the question – can it happen again?

Climate Factors

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July Slightly Cooler, Drier than Normal

Temperatures: Based on preliminary data, the statewide average temperature was 75.1 degrees, just 0.3 degrees below normal.  Temperatures reached into the upper 90s at several locations in the first half of the month.  One of the warmest readings was 99 degrees at Flora on July 5. A few stations dropped down into the upper 40s at night.  Four locations reported a low of 48 degrees: Mt. Carroll on July 7, Stockton on July 13, Shabbona on July 28, and Avon on July 31.

Here are the day to day temperature departures from normal for Champaign IL and reflect the changes experienced across much of the state.  The hot weather of May and June continued in the first week of July but quickly cooled by July 6.  This was followed by alternating periods of cooler and warmer weather until July 18 when temperatures remained at or below normal.

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Rainfall:  The statewide average rainfall was 3.41 inches, 0.67 inches below normal.  A few areas experienced above-normal rainfall, especially between Interstates 70 and 72. Much of the rest of the state was down by 1 to 2 inches.  The largest monthly total for July was 8.28 inches at Beecher IL (IL-WL-84).  Several stations reported less than an inch of rain for the month, including northern Cook and Lake counties.  The lowest monthly total for July with complete data was 0.59 inches at Park Ridge (IL-CK-180). Continue reading

The Outlook for August and Beyond

First of all, is it really July 19th already?  As a kid I remember summers lasting almost forever, now it seems to last about two weeks.  I feel cheated.

July: So far, the statewide average temperature for July is 77.4 degrees, 1.5 degrees above normal.  The statewide average precipitation is 1.94 inches, 93 percent of normal.  Strangely, the interior of the state is experiencing near to above-normal precipitation while the edges have experienced below-normal precipitation (map below).

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NWS Outlooks: The NWS has released their outlooks for August and beyond.  The big news is the possible return of El Niño. While conditions are currently neutral in the Pacific Ocean, the chance for El Niño increases to about 65 percent in the fall, and to about 70 percent during this winter. As a rule of thumb, warmer than normal temperatures are expected in winter during strong El Niño events. Continue reading