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August 2012 General Discussion


Chicago WX

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PUBLIC INFORMATION STATEMENT

NATIONAL WEATHER SERVICE CHICAGO IL

855 PM CDT MON AUG 6 2012 /955 PM EDT MON AUG 6 2012/

..GUSTY THUNDERSTORMS HAVE BEEN FREQUENT DESPITE DROUGHT

WHILE THE SEVERE WEATHER SEASON WAS QUIET AT ITS NORMAL PEAK TIME

OF SPRING AND EARLY SUMMER ACROSS NORTHERN ILLINOIS AND NORTHWEST

INDIANA...IT HAS BECOME MORE ACTIVE SINCE THE TAIL END OF JUNE.

NEARLY 80 PERCENT OF THE PRELIMINARY SEVERE WEATHER REPORTS ACROSS

THE NWS CHICAGO COUNTY WARNING AREA THIS METEOROLOGICAL SUMMER

/JUNE-AUGUST/ HAVE BEEN CONVECTIVE WIND DAMAGE AND/OR OBSERVED

GUSTS. THERE HAVE BEEN APPROXIMATELY 225 PRELIMINARY REPORTS OF

EITHER WIND DAMAGE OR SEVERE CRITERIA WIND GUSTS /58 MPH OR

STRONGER/ RELAYED TO NWS CHICAGO SINCE JUNE 1ST.

SOME OF THE SEVERE WINDS HAVE BEEN EXTREMELY LOCALIZED IN THE FORM

OF MICROBURSTS...WHILE OTHERS HAVE BEEN WIDESPREAD WIND EVENTS

SUCH AS WHAT TRANSPIRED THIS PAST SATURDAY AUGUST 4TH. THUS IT IS

CHALLENGING TO TRY AND QUANTIFY THE NUMBER OF THESE GUSTY

THUNDERSTORMS VERSUS A NORMAL AND HAVE IT BE REPRESENTATIVE

EVERYWHERE. LOOKING AT PEAK CONVECTIVE GUSTS AT TWO INDIVIDUAL

AREA AIRPORTS CAN SHED SOME LIGHT HOWEVER.

CHICAGO...

SUMMER 2012* 1996-2011 SUMMER AVERAGE

DAYS WITH GUSTS >=40 MPH 8 4

DAYS WITH GUSTS >=58 MPH 3 <1

* = THROUGH AUGUST 6TH

THE THREE SEPARATE OCCASIONS WITH SEVERE WIND GUSTS THIS SUMMER IS

THE MOST OF ANY SUMMER AT CHICAGO OHARE AIRPORT DATING BACK TO AT

LEAST 1996. IT IS INTERESTING TO NOTE THAT THERE WERE SIX DAYS IN

JULY OF THIS YEAR ALONE WITH STORMS PRODUCING 40 MPH OR STRONGER

WINDS. THIS TIES WITH JUNE 2008 WITHIN ANY CALENDAR SUMMER MONTH

SINCE 1996 TO HAVE AS MANY SUCH DAYS AT OHARE.

ROCKFORD...

SUMMER 2012* 1996-2011 SUMMER AVERAGE

DAYS WITH GUSTS >=40 MPH 6 3

DAYS WITH GUSTS >=58 MPH 1 <1

* = THROUGH AUGUST 6TH

ROCKFORD HAD FOUR DAYS WITH 40 MPH CONVECTIVELY INDUCED GUSTS IN

JULY ALONE...TYING IT WITH JUNE 1998...JULY 2003...AND JUNE 2008

FOR THE MOST IN ANY ONE SUMMER MONTH.

THE MORE FREQUENT GUSTY STORMS CAN BE...AT LEAST IN

PART...ATTRIBUTED TO THE PERSISTENT HOT AND DRY CONDITIONS.

THE ONGOING VAST DROUGHT HAS LIKELY HELPED KEEP THE BOUNDARY

LAYER DRIER THAN NORMAL THROUGH SIGNIFICANTLY LESS

EVAPOTRANSPIRATION FROM WHAT WOULD TYPICALLY BE MOISTURE-LADEN

CROPS...WHICH IS WHY THE DEW POINTS HAVE NOT BEEN FREQUENTLY IN

THE 70S. DRIER NEAR-SURFACE AIR ALLOWS FOR DEEPER MIXING OF THE

LOWER ATMOSPHERE AND OVERALL HIGHER CLOUD BASES. THUNDERSTORMS

THAT ARE ABLE TO DEVELOP OR MOVE INTO SUCH AN ENVIRONMENT CAN HAVE

A HIGHER LIKELIHOOD OF PRODUCING STRONG WINDS AS THEIR DOWNDRAFTS

READILY ACCELERATE TO THE GROUND. IN ADDITION...THE PERSISTENT

UPPER LEVEL RIDGE AND ASSOCIATED STAGNANT HEAT ACROSS THE

MIDSECTION OF THE COUNTRY HAS ALLOWED FOR SCENARIOS IN WHICH THE

UPPER PARTS OF THE ATMOSPHERE ACROSS THE REGION REMAIN WELL-

MIXED...THROUGH WHAT METEOROLOGISTS CALL AN ELEVATED MIXED LAYER.

STORM GROWTH AND ASSOCIATED WIND STRENGTH CAN DEPEND HEAVILY ON

THIS. THE HEAT DOME HAS ALSO ALLOWED FOR THE OCCASIONAL RING-OF-

FIRE WEATHER PATTERN ON ITS PERIPHERY...WITH ORGANIZED STORM

COMPLEXES REGULARLY CAPABLE OF LONG-LASTING WIND EVENTS.

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Down to 64° at 10:40pm. If the EURO is right, Thursday may struggle to get to 70° in the area under clouds and rainfall.

The 12z GFS also indicated that. In fact, it somehow indicated 50s inland in Southern Wisconsin at 18z Thursday. That doesn't seem possible, but if it is consistent, it may need to be taken into account.

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In Chicago, only 3 of the past 61 days (June 7 - August 6) have been below normal. That is remarkable. And the departures on the 3 below normal days were only -5, -4, and -2.

Later this week, temperatures may actually drop below normal for a few days in a row.

If we move the goalposts a little, since June 1...7 days below normal at ORD through today.

The summer of 2010 had a total of 12 days below normal at ORD (June 1 through August 31). I'll take the over.

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After temps underachieved today, DVN wisely trimmed back max temps for tomorrow. NAM has consistently been showing us reaching well above 100 tomorrow, but it's likely 10+ degrees too warm yet again.

From the DVN AFD...

...HOWEVER...AFTER SEEING THE SLOW THERMAL RESPONSE TODAY...HAVE TRIMMED BACK HIGHS A BIT TO A RANGE OF UPPER 80S NORTH TO MID 90S IN THE FAR SOUTH.

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The NAM is definitely out of touch. Showing upper 90s in NE IL - that is :lmao: ~especially since it looks to get under 60° tonight.

Near 90° here sounds like a good prediction.

Yeah it's really gone off the reservation this year. The GFS is just as bad but in the other direction. The only model that comes close is the Euro, the others have their asinine biases.

If the NAM had verified this year Hawkeye and I would both have had 30+ 100 degree days by now. For whatever reason the warm bias of the NAM seems to lessen some further east.

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It's called climo. I believe you've had your fun for the spring and summer.

August climo says 90s are still possible. Just saying..

Climo also says that this has been such a hot year it is bound to flip or at least alleviate these positive departures at some point soon, that's what I was getting at.

lol...climo.

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Yeah it's really gone off the reservation this year. The GFS is just as bad but in the other direction. The only model that comes close is the Euro, the others have their asinine biases.

If the NAM had verified this year Hawkeye and I would both have had 30+ 100 degree days by now. For whatever reason the warm bias of the NAM seems to lessen some further east.

This might be a little simplistic but I think the longer you've been in drought, the better the NAM has verified.

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This might be a little simplistic but I think the longer you've been in drought, the better the NAM has verified.

That's a good point. The NAM was probably factoring in the dryness feedback of the ground, but a little bit too much in areas that had wetter ground.The 110s that it would show were extreme - east of the Mississippi especially!

Things are green here again, so I can't see a very hot day today. Low of 59° this morning.

...Thursday's high has been taken down to 72°.

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A nice 70.5F right now. I doubt we make it to our predicted high of 89F with all the clouds this morning, probably mid 80s.

Yeah cant really see us hitting 90 today. Mid 80's are probably a safe bet, maybe upper 80's depending how long it takes for a lake breeze to kick in.

Edit: Both LOT and MKX talking about lake effect thunder showers on Thursday.

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Yeah cant really see us hitting 90 today. Mid 80's are probably a safe bet, maybe upper 80's depending how long it takes for a lake breeze to kick in.

Edit: Both LOT and MKX talking about lake effect thunder showers on Thursday.

The delta T's should be good for lake effect that day.

Yeah I am thinking upper 80s.

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Looks like an awesome stretch starting Thurs... Looks warm today even with winds changing to the north.

Even though it's only August you can definitely notice that cold air outbreaks are increasing. We've lost 65-70 minutes of sunlight at our latitudes, polar regions even more.

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Yeah cant really see us hitting 90 today. Mid 80's are probably a safe bet, maybe upper 80's depending how long it takes for a lake breeze to kick in.

Edit: Both LOT and MKX talking about lake effect thunder showers on Thursday.

Waterspout threat too.

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