flash flood watch

The whole area is under a Flash Flood Watch until tomorrow morning. Rain is approaching from the SW, and the heaviest rain will arrive after sunset into the early AM. Another 1-2" of rain can't be ruled out, with higher amounts in certain locations. After some places -- particularly in the northern suburbs -- saw 3" or more of rain last night the ground is already saturated and the flooding risk is elevated. 

The good news is that the rain should clear out tomorrow morning. The temps should climb into the 60s with a drier north wind and some sunshine. Sunday looks really nice with sun and temps near 70.

In other news, I've had more questions about El Niño -- or El Grande Niño as this one is being called -- and the effects on our weather. The answer remains that El Niño looks like to persist if not strengthen into the winter, and that usually correlates with a mild winter in Chicago. But the correlation is not perfect, and this year's El Niño is being affected by "The Blob" -- a massive layer of warm water in the North Pacific. See below if you want to read more. 

So, we're still favored for a much wilder winter this year than the prior two just based on reversion to the mean -- those were two pretty harsh winters. And the building El Niño gives us a further likelihood of a mild winter. But it's too early to write that in stone, and The Blob may well throw a monkey wrench into the system. 

http://www.nws.noaa.gov/com/weatherreadynation/elnino_article.html#.Vfx5r99VhBf

http://ww2.kqed.org/science/2015/08/09/possible-spoiler-for-el-nino-a-battle-of-the-blobs/

https://en.wikipedia.org/wiki/The_Blob_(Pacific_Ocean)

season recap and outlook

Summer 2015 in Chicago closed slightly on the cool side -- roughly the 35th percentile for warmth. June was certainly cool and wet but the rest the summer was unremarkable. We had a significant run of consecutive highs >80 but fewer than average highs >90. There has also been an abundance of tornadoes in the NWS Chicago region -- 29 confirmed so far -- which sets the all-time record. 

And now that summer is technically over, the first week of September goes down as the warmest of the year based on average temperature. 

Looking ahead, there is a likely resurgence of warmth next week. After temps peak in the 60s Friday and through the weekend we're likely to get in back to the 80s next week. 

And looking ahead to winter, there is a very strong El Nino in progress. The implications are significant, but it's also easy to over-extrapolate. For example, the North Pacific is also very warm, which could cause a "blocking pattern" similar to the one experienced at times in the prior two winters. That's not likely, but it's possible. So yes, the prior winters with a strong El Nino 1982-83 and 1997-98 -- were mild in Chicago, but that's not something to write in stone just yet. The odds are definitely in our favor to have a milder winter than the prior one (and certainly milder than 2013-14) but exactly how this plays out is TBD -- seasonal forecasts made a few months in advance are not especially good just yet. 

https://climateillinois.wordpress.com/2015/08/31/temperature-departures-in-illinois-during-the-1982-83-and-1997-98-el-nino/

https://climateillinois.wordpress.com/2015/08/26/last-two-big-el-nino-events-milder-winters-in-illinois/

Tornado warning extended

Radar showing rotation right on top of Oak Brook mall. Moving NE into Elmhurst soon. Storm in whatever form will hit north side of city and northern burbs soon.

Blinding downpours and flash food warning for most areas.

Tornado warning DuPage

New tornado warning for Dupage. Downers Grove, Lombard, Elmhurst. Over Downers right now moving NE at 30-40.

Tornado warning -- Will County

New tornado warning for Will County. Radar indicated for now. Anyone in Joliet, New Lenox, Lockport and Lockport should be very aware and get in a secure building.

Tornado watch extended

The tornado watch has been extended for all areas, now including Cook and Lake counties. Still through 10pm. And either way a line of severe or near-severe storms is approaching from the SW -- now near Joliet and impacting areas NE through the next few hours. Most or all locations will feel the effects tonight. High winds, downpours and frequent lightning are likely.

tornado watch (partial coverage)

A tornado watch has been issued for western areas of the Chicago metro, including DuPage, Kane, Will, McHenry, and Grundy counties. This extends a previous watch that was further west of us, and it is in effect until 10pm.

Severe/tornadic storms are moving out of Iowa into western and central Illinois. These are not hte most impressive storms but they have the potential to continue developing for several hours. The main threat lies to our west, as indicated by the location of the watch area, but certainly the threat cannot be ruled out in the Chicago area. 

Thunderstorms -- severe/tornadic or otherwise -- may well come into the area this afternoon and through the overnight hours. 

As a sidenote, I hope everyone has dried out after the deluge last night. Parts of the northern and southern burbs got little if any rain, but a corridor along the Ike and through the city got blasted with 2-3+ inches of heavy rain with significant street flooding. It was a fairly compact little storm that got somewhat stuck over one area, and that's a really hard situation to deal with -- even NWS was very late in issuing a Flash Flood warning. So I apologize that there wasn't more notice but there is not a lot that can be done in advance of those situations.