Chicago not alone in July-level warmth—much of Midwest basked in temperatures well above typical late May norms 

Tuesday high temperatures —How much above normal?

SCATTERED T-STORMS ARE TO to “bubble up” in the more humid atmosphere predicted WEDNESDAY and THURSDAY—Radar has shown several low coverage northbound showers popped up late Tuesday in southern counties–and a number of you have submitted photos of towering cumulonimbus clouds in the area in Newton and Lake counties, Indiana and in small sections of Kankakee and Will county in Illinois.

Daytime heating will drive the precipitation development meaning the most widespread rains will occur in the warmer hours of the day from late morning in to afternoon. But areal coverage of the showers & t-storms appears likely to impact perhaps 20 to 30% of the metro area.

THE HOURLY SIMULATED PRECIP visualizes the manner in which the HREF model predicts showers and t-storms to develop Wednesday—then fade away with nighttime cooling heading into Wednesday night. 7 A.M. CDT WED. THROUGH 10 P.M. CDT WED.:

24 hour THUNDERSTORM PROBABILITY showing the chances for t-storms in the period from 7am CDT Wednesday through 7am CDT Thursday:

It’s DRY! VERY DRY! If there are widespread, soaking rains in our future, our models haven’t locked on to them yet. In fact the latest guidance we’re getting on potential rainfall over the coming 15 days suggests only 1/3 of normal rainfall may occur.

We had been doing so well late last year into the opening months of 2023. December, January, February and March had all produced ABOVE NORMAL PRECIPITATION. Then April arrived–and, with the exception of a generous multi-day rain April 3-5th (1.17″), nature has effectively turned the spigot off!

Early spring weather systems provide beneficial, widespread precip with well organized systems. Jet streams are strong in early spring which provides a key ingredient to precip-generating storm development. But as we move deeper into the spring season–and ultimately into the warm days of summer, jet streams weaken and so too does the organization of large scale system. Much of the rain is delivered to the Chicago area comes from by convective clouds–in other words, t-storms–and we all know how varied warm season convective rains can be. They can drench one area while bypassing others. This makes the job of overcoming moisture deficits–like the one we’re running this year— more difficult.

MAKE NO MISTAKE ABOUT IT:

Rains can fall—and the intensity of t-storm rains can be formidable and not only wipe away a moisture deficit but even produce flooding in the process. So to be sure, moisture deficits CAN BE ERADICATED–and at times quite dramatically. But how often have we seen dry swaths of terrain linger despite locally heavy downpours somewhere in the area. We had local 3″+ rains over some southern sections of the Greater Chicago area. But heavy as these rains were, the covered only a limited amount of terrain. Those rains bypassed much of the area.

HERE’S WHERE WE ARE NOW IN TERMS OF MOISTURE

May’s precip here in Chicago has been abysmal–just 10% normal. All of 0.42″ of rain has fallen—the normal precip to date is ten times higher at 4.22″. We are literally less than a day and a half to closing the books on the 2nd driest May in 153 years of record keeping here.

Rising humidities WILL introduce the chance of a few isolated t-storms in coming days–but barring a cloudburst of some sort over O’Hare–and should the 0.42″ tally hold—only 1992 will have provided a drier May with its paltry 0.30″ May, 1992 total. May 2023 will enter the books as Chicago’s second driest. The 3rd wettest May on the books would then be May 1994 with its 0.58″ tally.

WE WERE SETTING ALL-TIME MAY RAINFALL RECORDS ONLY THREE YEARS AGO

In fact, with the record wet Mays of 2018, 2019 and 2020 figured into the updated 30 year climate averages, May has emerged as Chicago’s wettest month of the year—with an average of 4.49″ of precip on the books. June follows at 4.10: then April at 3.75″ and July at 3.71″.

THINK BACK to that string of record wet Mays:

May 2018: 8.31″

May 2019: 8.25″

May 2020: 9.51″

What a difference 3 years makes!

HERE ARE SOME RAINFALL STATS SINCE APRIL 1:

The period April 21 through May 29 ranks 22nd driest of the past 153 years–placing it among the driest 14% of April/May periods.

THE GROWING SEASON IS GETTING UNDERWAY; LAWNS AREN’T YET BROWN–UNLESS RAINS START FALLING, THE EFFECTS OF THE DRY WEATHER WILL BEGIN TO SHOW IN VEGETATION

I’m already getting photos of cracked ground due to the dryness. And some gardeners have written to say they’d like to see rain.

National Weather Service and a number of model projections of meteorological summer precip still suggests the June, July, August period is favored to see ABOVE NORMAL PRECIP. One thing’s for sure, all eyes will be on future precip developments. And we’re not along in the Chicago area. Check out the graphics package I’m posting and the analyses of recent months’ precip trends across the Midwest. There is quite a swath of the Midwest in need of some soaking rains.

Hurricane Season Begins June 1

Despite a developing El Niño, and potentially a strong one, the upcoming 2023 Atlantic Hurricane Season—which begins this Thursday June 1—is predicted by NOAA to be an average season

NOAA forecasters note, in releasing the projection that the 2023 Atlantic Hurricane season is likely to produce hurricane numbers close to normal, that the usual El Niño impact of suppressing Atlantic basin hurricanes may not apply given other factors present this year–such as abnormally warm ocean temps.

READ MORE ON THE 2023 NOAA ATLANTIC HURRICANE SEASON FORECAST here: https://www.noaa.gov/…/2023-atlantic-hurricane-season…

A NEW, MORE ACCURATE NATIONAL WEATHER SERVICE HURRICANE FORECAST COMPUTER MODEL capable of predicting the movement and intensity of MULTIPLE TROPICAL CYCLONES–it’s called the “HAFS” model—IS TO BE USED OPERATIONALLY IN PREPARING HURRICANE FORECAST IN THE ATLANTIC 2023 HURRICANE SEASON WHICH BEGINS JUNE 1 (this Thursday)

It’s an interesting model and, run retrospectively on past storms, is showing a 10-15% increase in the accuracy of predicted tropical storm/hurricane track. And studies on the HAFS model’s performance when it’s handling more than one tropical storm and/or hurricane at a time, shows it seems to do even better when handling multiple storms.

The HAFS will be used by National Hurricane Center forecasters and other meteorologists in conjunction with other tropical cyclone forecast models and is TO BECOME THE OPERATIONAL HURRICANE MODEL in coming years.

READ MORE ON THE HAFS MODEL HERE: https://www.aoml.noaa.gov/hurricane-model-that-follows…/