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I disagree with our weather forecasters on TV

Discussion pertaining to Detroit, Ann Arbor, Port Huron, and SW Ontario
jadednihilist
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Re: I disagree with our weather forecasters on TV

Post by jadednihilist » Tue Jul 27, 2021 11:02 pm

There's some severe weather popping up around La Crosse, WI right now. These can often leave a wake of subsidence and cloud debris that could limit the intensity of the storms tomorrow. I think it's kind of hard to make that case with the strength of the jet stream aloft. The fresh rainfall could just add to the mugginess for the instability tomorrow.


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MWmetalhead
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Re: I disagree with our weather forecasters on TV

Post by MWmetalhead » Wed Jul 28, 2021 6:58 am

Wisconsin upgraded to moderate risk west and northwest of Milwaukee and north of Madison back to the Minnesota border.

Bow echo and possible derecho formation likely by evening.

There is only a slim chance brunt of this activity will ever reach Metro Detroit. Some peripheral showers and storms are possible. Models are in good alignment on that question.

I think areas southwest of a Holland to Kalamazoo to Sturgis line have a much better chance of severe weather, with greatest risk being South Haven to Cassopolis westward. I would expect a risk upgrade for SW corner of the state by this evening. I suspect our area will remain marginal.

Chicago has a significantly greater chance of getting nasty weather from this system, especially its northern suburbs and NW Indiana, than we do.



jadednihilist
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Re: I disagree with our weather forecasters on TV

Post by jadednihilist » Wed Jul 28, 2021 2:03 pm

TL;DR: SPC has included Metro Detroit and most of SE MI in the Slight Risk and shifted the Moderate Risk a bit farther north as well. I agree with these adjustments. I think convective initiation will begin in the vicinity of the MN/WI border near Eau Claire and north of Wasau, quickly becoming supercellular and capable of producing tornadoes, large hail, damaging winds, and particularly intense downpours. These supercells will merge into a destructive line capable of producing hurricane force winds downstream across central/southern Wisconsin and northern Illinois. This line will move across Lake Michigan into SW/W Michigan tonight and it seems increasingly likely the line will track into southeastern Michigan tonight/overnight. The super quick propagation and high moisture content in the atmosphere will allow storms to remain above severe limits, albeit nowhere near as intense as WI and potentially SW MI. Locally, the big threat remains damaging winds (isolated tornadoes within the line may be possible given the strong directional shear) and localize flooding from the intense rains. I know I sound like an alarmist, but definitely stay weather aware today... especially in the west side of the state and in Wisconsin and Northern Illinois.

Analysis
I did some hand analysis of the surface, 850 mb, 700 mb, 500 mb, and 250 mb levels for 00 and 12 UTC which can give a draw a clearer picture of the atmosphere than automated models. You can see significant errors in model initializations, including the RAP which drives the SPC mesoanalysis.

At the surface, there's a ~1010 mb low in the Dakotas with an 1018 mb high in the Ozarks. This will aid southwesterly flow of deeply moist air into SE MN and WI. The frontal boundary at noon extends from the Twin Cities into the UP and across mid-Michigan with Metro Detroit near the front. I anticipate slight northward movements in this front through the day.

At 850 mb, the front is a bit farther south across northern Indiana, Wisconsin, central MN. With some warm air advection, I expect this front will also gradually progress a bit farther north. The advection would be aided by an 850 mb ridge centered over Missouri with a closed low over Wyoming, SE Montana, and the western Dakotas. Note that cooler 850 mb temps would support stronger low-level lapse rates and increase instability. The axis of greatest 850 mb moisture saturation is from the Twin Cities into MI (including the UP) and southern Ontario.

At 700 mb, the air is quite dry with dewpoint depressions across the Upper Midwest and Great Lakes generally greater than 10 to 20C. This dry air aloft suggests both the presence of an elevated mixed layer (near dry adiabatic lapse rates), so the lapse rates aloft should easily exceed 7ºC/km with 8ºC/km certainly not out of the question. The flow at 700 mb is more northwesterly, suggesting strong directional shear between the W/SWly flow near the surface and the NWly flow aloft.

At 500 mb, the weakly positively tilted upper level trough centered over Quebec and the NE US has deepened a bit since 00 UTC last night. With some limited height falls still in New England, I don't anticipate the 500 mb heights with the trough to deepen that much more today. This sets up a potent NWly flow with a broad region of >40 kt winds extending from the MI/OH/IN border northwest into Saskatchewan. There's a >50 kt jet streak peaking at 70 kts in SE Manitoba expected to move into northern Wisconsin and northern/mid-Michigan this afternoon and evening. Those are really impressive winds for this time of year, more than capable of supporting organized deep convection, increasing the risk of supercells soon after convective initiation. The 250 mb jet streak is still kicking at over 100 kt in the Manitoba/Saskatchewan border with the jet axis still oriented NW->SE from MN into MI.

Looking at the soundings, there seems to be a strong cap at around 900 mb in Minneapolis resulting in a surface-based convective initiation temp around 97C. If you follow the thermal profile up to 700 mb, it's around 10ºC. Meanwhile farther east in Green Bay and Gaylord, convective temps drop into the mid 80s to around 90F. 700 mb temps here are about 5-8C. Thus, I think the greatest potential for convective initiation will be where 700 mb temps are below 10ºC, which at 12 UTC extends from Duluth to Eau Claire, Madison, and Rockford IL.

Wet bulb freezing levels are pretty low in these areas <10kft, so in this particular air mass, this really amplifies the very large hail threat. I wouldn't be surprised to see hail exceed 3" in diameter in the supercells.

The deeply curved hodographs support 0-1km and 0-3 km storm relative helicity values in excess of 150 m^2/s^2 and 400 m^2/s^2, which is more than sufficient to support intensely rotating updrafts in Wisconsin. The tornado threat is nothing to sneeze at.

Precipitable water values should hover around 2", so with this kind of moisture and weakly capped atmosphere, the cold pools from the initial supercells should converge fairly quickly allowing for another QLCS-type line with bowing segments to develop later in the evening. This is when the tornado threat starts to decrease, and probably why the tornado threat is not hatched today (even though its at 10% across WI). This QLCS will race southeastward... and there's quite a bit of uncertainty at how fast these storms will move, so there's a significant window for when these storms will arrive in SE MI. The increased severe risk suggests from the SPC suggests an earlier hit across SE MI seems increasingly probable, even though the intensity of the storms should begin to be in the weakening phase by the time it gets here. The upper level flow and surface-based instability also supports a SE MI hit as well.


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jadednihilist
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Re: I disagree with our weather forecasters on TV

Post by jadednihilist » Wed Jul 28, 2021 2:25 pm

Here's this afternoon's discussion from NWS Grand Rapids:
UPDATE...
Issued at 1225 PM EDT Wed Jul 28 2021

Latest 12Z guidance is continuing the farther north trend of the
most severe convection later tonight, even hinting at the
possibility of a derecho impacting much or parts of wrn Lwr MI.
Since this is a potentially high impact severe weather event
while many folks will be sleeping, communication/messaging the
possibility of high/destructive winds this afternoon/evening will
be critical.

Timing looks to be similar, with potential for a large bow echo
sweeping across Lk MI toward or after midnight. Also some
potential for the warm advection wing ahead of the main line
becoming active a couple hours beforehand. If that does occur, we
could have some tornado potential with discrete cells since the
warm front will be draped over the area. HRRR has 0-1km SRH of
150-200 m2/s2 with LCLs below 1km. A QLCS-type tornado threat may
also develop/exist within the main line.

Also of note, in terms of the straight line wind potential, HRRR
shows 70 kts at 3 km, of potential descending rear inflow into
the back of that line. So some isolated pockets of destructive
80+ mph winds seem plausible later tonight.

As far as heavy rainfall/flooding concerns, some intense rainfall
rates are likely as the strong/svr convection is coming through
tonight, although the progressive nature of the MCS may limit
the overall flooding risk. That said, some urban flooding -
possibly worthy of areal flood advisories/warnings - may also be
needed.


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MWmetalhead
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Re: I disagree with our weather forecasters on TV

Post by MWmetalhead » Wed Jul 28, 2021 2:28 pm

We've seen these patterns before. Memorial Day weekend 1998 pounded southern Michigan very hard. Most other derecho events that originate in MN or WI seem to take a right turn and tend to stay south of a Holland to Jackson to Adrian line.

I still think the risk for Metro Detroit is low except for OH border counties and west of A2. Grand Rapids - risk is somewhat higher. Kalamazoo - risk is significantly higher.

Milwaukee, Fond du Lac, Wisconsin Dells area, Eau Claire, and even Wausau could see a very noteworthy severe event late today and tonight. Wisconsin could easily see 500,000+ power outages.

Parts of western MI could be placed under a rare PDS watch later!

Outstanding analysis, as usual, Jaded. Many, many thanks for sharing your thoughts! :)



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MWmetalhead
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Re: I disagree with our weather forecasters on TV

Post by MWmetalhead » Wed Jul 28, 2021 2:40 pm

Flash flood watch just issued. Probably the right call given recent events.



jadednihilist
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Re: I disagree with our weather forecasters on TV

Post by jadednihilist » Wed Jul 28, 2021 2:53 pm

Thank you -- definitely enjoying this thread! It's been quite an active summer up in the great lakes.


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MWmetalhead
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Re: I disagree with our weather forecasters on TV

Post by MWmetalhead » Wed Jul 28, 2021 3:06 pm

I think I may have understated the risk tonight for places like Muskegon and Grand Rapids and maybe even Ludington. You are right; storm initiation will probably be in northern WI. If that bow echo or derecho tracks mostly southeastward from, say, Wausau and Green Bay, a good swath of the western two tiers of counties in lower MI could be in play.

Directional tilt of the wind fields and warm front will be a major factor tonight.



jadednihilist
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Re: I disagree with our weather forecasters on TV

Post by jadednihilist » Wed Jul 28, 2021 3:40 pm

MWmetalhead wrote:
Wed Jul 28, 2021 3:06 pm
I think I may have understated the risk tonight for places like Muskegon and Grand Rapids and maybe even Ludington. You are right; storm initiation will probably be in northern WI. If that bow echo or derecho tracks mostly southeastward from, say, Wausau and Green Bay, a good swath of the western two tiers of counties in lower MI could be in play.

Directional tilt of the wind fields and warm front will be a major factor tonight.
Definitely watch the warm front for sure. Derechos love to ride those boundaries, although Lake Michigan may complicate the track a bit.

Of note, I looked at some of the sounding climatology to put the strength of upper level winds into context. That approaching 70 kt jet streak at 500 mb in Manitoba moving into MN/WI is near record territory for late July at both International Falls (INL) and Green Bay (GRB). The wind threat with this is quite real.

Image
Image


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Re: I disagree with our weather forecasters on TV

Post by Thunderstorm » Wed Jul 28, 2021 4:28 pm

Moderate risk now for parts of Michigan.



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MWmetalhead
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Re: I disagree with our weather forecasters on TV

Post by MWmetalhead » Wed Jul 28, 2021 4:44 pm

Not surprised part of lower MI was upgraded to MOD but definitely a bigger slice of West Michigan than I was thinking at this time yesterday.

Basically, the expectation for the worst weather has shifted 75 to 100 miles north and confidence has increased since this time yesterday.

The MOD zone almost reaches Ludington and includes Grand Rapids and Kalamazoo.



jadednihilist
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Re: I disagree with our weather forecasters on TV

Post by jadednihilist » Wed Jul 28, 2021 5:40 pm

Image

Theta-e gradient is setting up nicely right along the track of tonights storms.


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jadednihilist
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Re: I disagree with our weather forecasters on TV

Post by jadednihilist » Wed Jul 28, 2021 6:13 pm

And we now have convective initiation around Ashland, Wisconsin.
Mesoscale Discussion 1378
NWS Storm Prediction Center Norman OK
0509 PM CDT Wed Jul 28 2021

Areas affected...portions of east-central and northeast
MN...northern WI

Concerning...Severe potential...Tornado Watch likely

Valid 282209Z - 290015Z

Probability of Watch Issuance...95 percent

SUMMARY...Rapid development of supercell thunderstorms is
anticipated in the next few hours, with a risk for very large hail,
damaging winds, and potentially a few tornadoes. A Tornado Watch
will likely be issued prior to 00z.

DISCUSSION...A warm front extended south/southeast across
central/southern MN at 22z, and this front will continue to move
east through this evening as a weak surface low moves east across
central MN. Latest visible imagery reveals moderate/towering cumulus
over central MN north of the Twin Cities area, embedded within a
larger area of clouds over central/northern MN and northern WI.
Current expectations are for thunderstorms to develop in the next
few hours near the warm front and move southeast during the evening.
Northwesterly deep-layer shear of 45-55 kts in the vicinity of the
front will support intense supercells initially, and
locally-enhanced 0-3 km SRH will be favorable for low-level rotation
and potential for tornado development. Steep mid-level lapse rates
will also support a risk for very large hail, and damaging winds are
also expected. Current thinking is that the tornado threat will
warrant a Tornado Watch for the first few hours after initiation
given the near-storm environment, with eventual transition into a
fast-moving MCS with widespread damaging wind potential later this
evening/overnight.

A Tornado Watch will likely be coordinated with affected NWS Weather
Forecast Offices prior to 00z.
Image


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Robert Faygo
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Re: I disagree with our weather forecasters on TV

Post by Robert Faygo » Wed Jul 28, 2021 6:57 pm

This has been my favorite Buzzboard thread to read. I don't know squat about the weather other than what I'm told -- but feel like I'm learning just from reading what you guys take the time to post.

Kudos -- and your efforts are appreciated, at least by me.


Wellllll... la de frickin da

jadednihilist
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Re: I disagree with our weather forecasters on TV

Post by jadednihilist » Wed Jul 28, 2021 7:43 pm

Thank you so much for your kind words! I love teaching weather, so please don't hesitate to ask questions. This goes for anyone.


I'm here for a good, hearty debate, to agree and disagree respectfully, and commiserate on the current state of terrestrial radio.

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