NAM4KM is beginning to see Sunday, predicting very ugly *potentially tornadic* conditions

The model I trust the most in predicting severe weather is beginning to indicate that a high end event is likely to occur this Sunday evening across central/possibly even northern lower Michigan.

Supercell composite is beginning to go purple.

0-1km EHI measures both instability and "spin" that the wind has in the first 1000 meters above ground.  No other factor is more important in the development of significant tornadoes - if this index is high, watch out.

Simulated radar is beginning to look very, very scary.  This is going to be a very active weekend.

This is still early, as we're just on the horizon of the model being able to see the day, but what I'm seeing does not look good.  Initial supercells would likely congeal into a squall line which would plow south east, leading to a potentially high-end damaging wind event across those areas and a potentially tornadic event where storms initially form.

Strongly disagree with SPC's day 3 outlook - Possible repeat of June 22nd this Sunday

Two things have become apparent to me over the past 24 hours regarding this weekend's weather: a) the series of "shortwave troughs" which were expected to affect Michigan this weekend have merged into one massive trough, per the southward movement of the monster low pressure system currently spinning over the Hudson Bay, b) much stronger flow is going to be present over our area than what was originally expected, and this potentially explosive weather - along with the trigger - are going to arrive this Sunday evening in one fell swoop, rather than spaced out into Monday as the thinking was last week.

As I stated in an earlier post, when such patterns are spread out over several days, it usually lessens the chances of widespread severe weather over a given area, mainly because you have multiple straws sucking up the energy.  This is definitely not always the case, as you can get strong enough shortwaves combined with high moisture jets which can drive multi-day severe weather events (as what happened in April of 2011), but it's the exception.  With that in mind, what was originally looking like a decent if somewhat tempered chance of severe thunderstorms across Michigan is now looking like it could very well be an event similar to what occurred on June 22nd of this year.

Simulated radar, 2am NAM run 07/31/15

Looking at the simulated radar from the latest NAM run, we can immediately see that a line of thunderstorms are expected to move through Michigan in the morning to mid-afternoon hours.  Should these storms appear where they're forecast to occur, they may strengthen as they move across the state, as conditions for severe weather - instability/moisture content and strong flow aloft - are expected to improve throughout the day.  These conditions will remain in place into the late afternoon and evening hours, and that's when a second round of thunderstorms should erupt as the cold front plows through.

Supercell composite, 2am NAM run 07/31/15

Significant tornado potential, 2am NAM run 07/31/15

This second round of thunderstorms is what I'm most concerned about.  Wind profiles are quickly arranging in such a way that supercells should be the initial storm mode when they develop, and even after they coagulate into a squall line, they should have adequate power at their disposal to produce significant damaging wind gusts.  With all of this in mind, I've issued a "widespread severe possible" outlook for mid-to southern-lower Michigan for this Sunday evening.

So far, the Storm Prediction Center does not agree with me:

Storm Prediction Center's day 3 severe weather outlook

There are likely a couple of reasons for this, chief among them that the NAM tends to overestimate moisture content in its forecasts on a regular basis: 

The NAM is forecasting dewpoints in the 70s despite forecasting temperatures only reaching 75° in some places.

This leads to much more instability being forecast than what will actually occur.  The second reason is that, as was the case before, the morning storm complex could significantly temper the atmosphere to the point where instability is marginal. 

With that in mind, I still strongly disagree with this day 3 outlook, and believe widespread severe weather is possible.

Despite potential issues with the NAM, the GFS is also forecasting strong severe potential throughout Michigan, as well as late afternoon/evening convective precipitation matching this severe potential.  Wind profiles are forecast to be even stronger by the GFS than the NAM.

My number one reason for this is the wind profile being forecast across the spectrum of models.  Winds aloft are expected to be significantly stronger than what was originally expected for this weekend, as the monster Canadian storm system dips to the south.  Under the influence of this system, wind speeds in the mixed layer may increase to 60 knots in some areas of Michigan (as forecast by the much more conservative GFS), and even the low-level jet may also reach this point.  Winds higher up in the atmosphere at the tops of the thunderstorms will be coming from the northwest, and they may reach 65-70kts (again, according to the GFS).  Both models suggest storm initiation in the late afternoon/evening hours across lower Michigan, and I believe that regardless of how unstable the atmosphere is, the storms should have enough horsepower to pose a significant danger to life and property.

I will be continuing to monitor this situation throughout the day today and tomorrow, too.  The SPC could still be spot on, and we could wind up seeing very little severe weather in our state this weekend.  But my gut won't allow me to believe this based on what these models are saying and what very recent history has shown us.  The setup is a bit different than it was then, and it isn't looking as nearly as scary as it was back then, either, so this could wind up being a paper tiger.  I just won't discount it until I have more model runs and data to analyze.

Update: To be fair, I had yet to read the SPC's day 3 outlook in its entirety before I made this post.  They do specifically mention a potential upgrade in later outlooks, but that the impact of morning thunderstorms makes predictability too low at this time:  

   
   HAVE INTRODUCED A MARGINAL RISK AREA...BUT AN UPGRADE TO HIGHER PROBABILITIES IS
   LIKELY AT SOME POINT IN FUTURE UPDATES ONCE UNCERTAINTY REGARDING
   EVOLUTION OF EARLY THUNDERSTORMS AND THEIR IMPACT ON THE MESOSCALE
   ENVIRONMENT HAS BEEN MITIGATED.

This outlook was likely issued before the 06z (2am) run of the NAM and GFS was complete, so I can't fault them for the want of more data before delineating a higher risk area.  With that in mind, without significant changes to the forecast, I have a suspicion their Sunday outlook will look a bit like mine come tomorrow.

Severe weather in Michigan possible Monday August 3rd

SCP index from last three consecutive GFS model runs, in order of appearance.  The model has predicted more favorable conditions for severe weather in Michigan with each run.

The last three consecutive GFS model runs have demonstrated likelihood for severe thunderstorm development in Michigan this coming Monday, with each successive run suggesting a more robust threat.  This leads me to believe that changing dynamics favor a possible severe weather event in Michigan, possibly even a widespread straight-line wind event.  It's too early to tell for sure, but late last night and this morning's runs especially are hinting at such a scenario.

MCD just released for Thumb & SE Michigan - Watch unlikely

PROBABILITY OF WATCH ISSUANCE...20 PERCENT

The Storm Prediction Center has just put out a mesoscale discussion regarding the potential of a severe thunderstorm watch in the next hour.  Click here to read the full text.

Strong thunderstorms affecting Tri Cities, heading for the Thumb & SE Michigan - likely to intensify

The small cells which formed over Mid Michigan have rapidly intensified into a multicell line and are entering an even more unstable environment as they move east.  Instability will only increase with time ahead of these storms.  I fully expect at least one or two of these cells to be severe warned shortly as wet micro bursts may begin to occur; the one just north of Flint in particular has an echo top reaching 50,000 feet.  So far, I'm only seeing indications of moderately heavy rains, though.  The storm near Birch Run looks like it may drop some hail, too, but I doubt it will be severe hail.

Thunderstorms initiating across Mid Michigan

Several clusters of storms are beginning to pop up across northern and central lower Michigan.  No MCDs have yet been issued by the Storm Prediction Center, though the Marginal Risk has been extended to cover northeastern lower Michigan as well.  I fully expect these storms to intensify a bit as they move east into an even more unstable environment.  Heavy rain and gusty winds are almost a given.

Chance of severe storms back on for the Thumb area today

The SPC has updated their day 1 outlook to include the Thumb area once again.

No widespread rain nor clouds this morning will definitely cause instability levels to go up.  The NAM4KM simulated radar is definitely looking meaner than it was yesterday.  More as it develops.

Severe storms still questionable, but something different/troubling possibly ahead

Chances are looking good for thunder this coming weekend, possibly as early as Friday, but whether or not said thunder will be accompanied by severe weather hazards remains in question.  As of now, I'm leaning toward a less robust storm mode spread out over several days rather than one big whopper, which will likely mean lower chances of severe weather.

Looking ahead, I am noticing something a bit discouraging for the month of August, and it has nothing to do with thunderstorms.  The last few long term model runs are beginning to hint that the upper air pattern for August is going to change significantly from the one we were experiencing in July.  What's troubling to me is that it resembles less of what we tend to see in the summer, and more like what we've seen over the last couple of winters.

Hello, Old Man...

See that red circle?  Yep, that's a chunk of our old "friend", Mr. Polar Vortex.  If this forecast should verify, we can expect the "summer-like" temperatures we've been having for the past little while to disappear.  Night time lows could even sink as far as the 40s in some places.

Expect surface temperatures to plummet should this forecast verify.

What really gets me about this is that it's demonstrating that the pool of warm air in the Gulf of Alaska not only remains, but remains very strong.  It also seems to be having a greater impact on our weather patterns than even the moderately strong El Niño that has developed in the Pacific.  Normally, during a moderately strong El Niño, we can expect a mild winter in Michigan.  This could still be the case, however, should this pattern persist into the winter, what we may wind up with instead is the same pattern we saw the last couple years with brief warm-ups accompanied by potentially stronger-than-average clipper systems, which are able to take advantage of extra moisture provided by El Niño, and the occasional winter storm whopper from the south. 

Andrew, a blogger I've followed extensively over the past couple years, released his preliminary 2016 winter forecast the other day.  Sure enough, he mentions both of these phenomena, and suggests that winter could pretty much go either way in our neck of the woods.  This lowers my confidence in the previously widely-anticipated "mild winter" I was (and I'm sure many other Michiganders were) hoping for.

As far as the remainder of summer goes, I'd expect a pattern like this will also likely increase thunderstorm chances, but for now the GFS is suggesting that most of the stronger storms will be to our south in the Ohio valley, where warmer, more unstable air will be present.  This could be disrupted by the "heat dome" building to our south rather than surging northward into Montana as is currently predicted.  In that case, our chances for big thunder and severe weather will skyrocket.  Those hoping for super-hot 90°+ days will likely be out of luck.

Severe weather across the state looking more likely August 2nd/3rd

Both the ECMWF and GFS are suggesting that conditions will be ripe for severe weather across the state - including the U.P. - this coming Sunday or Monday.

As of now, the models are leaning more toward Sunday for the big storms, but the models are far enough out and there's been hints from run to run that a delay may push this into Monday.  As always, it's going to be all about timing.  If the storm system powering this comes along during the overnight, the chances of severe weather will be less.

Severe outlook for Wednesday downgraded, more severe possible next week

Latest day 3 outlook from the SPC

Short range models are beginning to suggest that severe storms this Wednesday are looking less likely in Michigan.  A combination of cloud cover and remnants from previous day convection should temper instability a bit, and the wind profile doesn't look quite mean enough to cause trouble in the absence of serious instability.  This is due to the strong storm system moving further north, as I suggested last week could 86 severe thunderstorm likelihood in the state.

Supercell Composite Index for around 5PM August 5th, taken from 8am GFS run 07/27/15

Meanwhile, there may be a couple opportunities for severe storms to pop up in the state next week, as we continue our stormy pattern into August.  The GFS suggests that Southeast Michigan could house some very unstable air on August 3rd, and more highly unstable air could be present throughout the state between August 5th and August 7th.  Wind profiles are not too spectacular, but I still think it's enough to suggest the likelihood of potentially strong to severe thunderstorms.

Storms with heavy rain, gusty winds on track to plow across SE Michigan

I can speak for two things regarding today's thunderstorms: they're windy, and they're rainy.  About an inch of water covered M-25 as I drove home through the core of one of these.  There was a lot of cloud to ground lightning, too.  Be careful outside this evening.

MCD issued for SE Michigan, watch unlikely

There's a 20% chance of a severe thunderstorm watch within the next hour.  These storms have some very brisk gusty winds (I can say from experience), but if you ask me they're just shy of severe limits.  Some decent pictures on the way when I get home tonight.

Broad rotation in some of these storms

Be advised that these storms are starting to look a bit meaner.  Currently on the road looking for action.

First thunderstorms of the day popping up, will affect northern Huron County

The first storms of the day are popping up right where the NAM4KM model said they would.   Might try to intercept these in the coming hour.

Not one, but two major storm systems may affect Michigan next week

I'm still fairly confident that Michigan should see at least some degree of severe weather in the coming week, when two major low pressure systems will begin to affect our weather.

ECMWF's forecasted position and intensity of storm system #1 for next Wednesday

GFS's forecasted position and intensity of storm system #1 for next Wednesday

Temperatures are likely going to skyrocket as this storm approaches and pulls up hot, moist air from the Gulf as it does

The first storm system looks to be a negatively tilted monster which looks to center itself around southeastern Manitoba by Wednesday, July 29th.  Both the ECMWF and the GFS are in close agreement regarding the timing and placement of this system, so at this point I'd call it all but a sure thing.  While this storm system definitely looks to be the more powerful of the two, I'm a little less concerned about it, as it may drive too far to the north to bring its full weight and power down onto Michigan.  I'd still expect thunderstorms out of this one, but if a storm system like this were to be placed a little further south, I'd be much more concerned.  There are a few reasons why this one may give us some trouble, though.  The first is that the "heat dome" is looking like it'll be positioned directly to our south again; a strong area of high pressure is looking to be centered right over the Florida panhandle and Alabama.  Combining this feature with a strong storm system usually has chances for severe weather in Michigan go up considerably.  I'll be watching this one closely.

GFS's forecast for storm #2.  Confidence isn't as high in this one, but I'd still call it very reasonable.

Severe chances might be a bit higher with this one due to the storm's position.

The second storm system doesn't look to be as strong, and isn't nearly as much of a sure thing, but should it arrive where the GFS is placing it, it'll be in a much better position to drive big thunderstorms in our state.  The GFS is also forecasting it to have a slight negative tilt, so it could strengthen as it approaches.  So far, it's not suggesting that the system will drive temps quite as high as the first one will, but I'd still expect some very warm (if not quite hot), humid conditions to be in place as it plows through.

All and all, given the features of both systems, I'd say we have a pretty good chance of seeing some major thunderstorms in the state next week.  Hopefully they'll be timed just right and I'll be able to get some more beautiful pictures without them causing any trouble for anyone.

Concern growing about potential end-of-July severe weather outbreak

Literally one month ago Michigan was on the receiving end of one of the nastiest batches of thunderstorms we've had in quite some time, with several tornado touchdowns, one of which was strong, and which people are still recovering from.  The system that caused that outbreak began to show signs of being troublesome a week and a half before it happened.

I'm beginning to grow concerned that another system like that one may impact Michigan in the coming weeks, albeit I'm not yet sure to what degree.  Above is the GFS's supercell composite index prediction for the time frame of August 1st to 8PM on August 2nd.  So far, it doesn't look quite as strong as what menaced us last month yet, but it's approaching that point.  Several GFS runs thus far have introduced a disturbance around this time, but this run is by far the strongest in terms of severe potential for Michigan.

Since the GFS has shown run-to-run consistency in this feature for about two days now, I've increased my severe risk assessment to "Severe thunderstorms likely" for this time frame.  With that in mind, this feature has disappeared completely from this morning's run, so this could change drastically, but with the last two day's worth of runs suggesting something potentially big on the horizon, I'm not going to lower the flag based on one run's output.

Likelihood of severe weather for Michigan on Saturday plummeting

Mid-range models are beginning to indicate that timing will not favor much severe thunderstorm potential in Michigan this Saturday.  My confidence in any real threat has all but vanished. 

Severe storms are increasingly likely to our west, and there's a chance that they may propagate into northern/central Michigan through the overnight hours, but chances are that by the time they get here they'll have weakened substantially, or even dissipated completely to the point that only rain will be left over.  Storm initiation still looks possible in the evening as the cold front comes through, but the models don't appear to be suggesting much.  The front is expected to stall into a quasi-stationary front which may bring thunderstorms on Sunday, but it remains to be seen what the timing will look like and whether or not there's any chance of severe development. 

July 31st to August 3rd Potential Severe Thunderstorms

Models are starting to show some run-to-run consistency regarding the advancement of a storm system which should affect the lower Great Lakes next weekend, which could bring some potentially strong to severe thunderstorms to eastern Michigan.

My current expectation of severe weather potential based on the model data.

Latest GFS run's SCP index predictor.  Other runs are a bit less formidable looking, so only introducing isolated risk at the moment.

These storms look to target the state between Friday and Monday, but it's too soon to tell exactly when they'll strike, or what kind of storm mode we'll be seeing.  For now, shear is looking to be unidirectional, meaning damaging winds would be the most likely hazard.  The latest ECMWF run appears to be a bit faster in timing, so this could evolve to include Thursday, but since that model is only just now getting close to being able to view the time frame, and because the GFS has shown fairly good consistency, I'd still expect any storms to occur between Friday and Monday.

Thunderstorm outlook widget

In the upper right hand corner of this blog, you'll find an outlook regarding thunderstorms and severe weather probabilities in Michigan.  In the winter time, this will switch over to winter storm/heavy snow potential (barring the insane chance of a mid-November severe weather outbreak a la 2013, in which case I'd go back to the thunderstorm outlook).

Note that this outlook may or may not match with what the SPC puts out for their outlook.  I'll likely match any day 1 through 3 categorical risk values unless I strongly disagree with them.  Day 1 through 3 thunderstorm potential will always be displayed.  If one of those days has thunderstorm potential but others don't, those days will be skipped. The outlook will also reference upcoming potential severe weather events (4-10 days out) that I believe have a good chance of affecting the state. If there is no day 1 through 3 thunderstorm potential and nothing on the horizon that looks interesting, you'll see a smiley "no thunderstorms forecast" face instead of the outlook.  I'll do my best to update the image at least once per day, unless no changes are apparent in the forecast and no upcoming events are moving into the day 1-3 time frame.  The categories pretty much match what the SPC designates, though the wording will be a bit different:

• █ Thunderstorms possible - Exactly what it says; thunderstorms should be possible in any area highlighted in light green.  This includes a very small chance of a severe thunderstorm, as any time a thunderstorm forms, it can pick up steam given the right parameters.

• █ Isolated severe t-storms - Thunderstorms are possible, with a slightly higher chance of a thunderstorm crossing the severe threshold.  This means one or two thunderstorms out of ten to twenty have a chance of producing winds greater than 60mph, hail greater than 1 inch, or a tornado.

• █ Severe thunderstorms likely - The "Slight Risk" equivalent. Storms that form within or enter these areas will likely be severe in nature.  They shouldn't be potentially long lasting or intense, but some isolated and/or light damage is to be expected.

• █ Widespread severe possible - The "Enhanced Risk" equivalent. It's highly likely that storms will form in or move into highlighted areas and it's likely that they will be severe in nature. Widespread damage is not necessarily a sure thing, but it is possible, and general preparations should be made by people residing within these areas (i.e. have "power outage kit", plenty of non-perishable food, and bottled water ready).

I will not use the categories listed below unless the Storm Prediction Center releases them in their outlook: 

• █ Widespread severe likely - The "Moderate Risk" equivalent. Significant severe weather is almost a sure thing. Widespread damage to property is expected. Power outages and other resource strains are likely.  Emergency and utility crews are likely to be dispatched.  Rehearse emergency preparedness plans, restrict long distance travel unless traveling out of risk zone and make appropriate preparations for long-term power outages that may last several days.  Stay close to substantial shelter throughout the duration of the outlook.

• █ High risk of significant severe weather - The "High Risk" equivalent.  A major severe weather outbreak is expected or underway.  THIS IS A PARTICULARLY DANGEROUS SITUATION.  Consider keeping children home from school, and stay close to very substantial underground shelter.  Pay close attention to NWS-issued watches and warnings, and consider keeping a NOAA weather radio on hand at all times.  The types of severe hazards seen on high risk days include 80mph+ wind gusts, hail greater than 2" in diameter, and/or widespread EF2+ rated tornadoes, with EF4 and EF5 tornadoes possible. Significant widespread property damage is likely, and entire neighborhoods may be damaged or even completely destroyed. Do not travel, unless you plan to travel far away from the risk zone and are absolutely certain the timing of your travel will not coincide with the location of thunderstorms. If traveling, keep an emergency survival kit with you. If stranded by flood waters or structural damage such as trees or power lines on the road, stay with your vehicle until emergency crews arrive if possible. Keep up to date on weather by using mobile devices equipped with doppler radar applications such as RadarScope, as well as CMAS alerts. Carry a NOAA weather radio if possible. If a tornado or severe thunderstorm is approaching your vehicle, abandon it and move to the nearest substantial shelter available. More weather related fatalities occur on high risk days than usually occur on every other non-high-risk-day of the year.

I hope that I can do my part to help people understand what's coming and when to act.  These outlooks, I believe, would do people a lot more good if they knew where to find them and what they meant.    

Raw, unedited photos from yesterday's storms

The storms that blew through my back yard yesterday were among the most beautiful and stunning that I've ever photographed.  Brief areas of broad rotation also lead to something I've yet to capture until now - a wall cloud.  Note that none of these storms were severe warned (the one with the wall cloud probably would've been had I called it in, but I did not feel that it was a real threat), but they definitely had some gusty winds.  Later I plan on uploading a video or two which should highlight that.

Below is the reward of skywatching.  Enjoy!

Just to give a scope on the size of the storm.  Anvil to the right, invisible as it is too high.  Flanking line to the center/left.

Looking up at the flanking line from the southeast.

Shelf cloud behind the windmills.

More of the shelf cloud.

Shelf cloud again, with rainshaft in background.

Shelf cloud/rain shaft.

Again.

Shelf cloud from a different angle.

Coming up on the shelf cloud.

Closer.

Even closer.

There it is - rotating wall cloud to the left, and almost looks like the beginnings of a funnel.

Another angle of the wall cloud.

Getting right up on this thing.  Almost due east of it, looking west at it.  Rain to the north/east begins to interfere with my view quickly.

Final picture.  Video of it coming soon.