Chicago Severe Weather Updates: 2018

Sunday, November 25, 2018

Blizzard Warning

Sorry for one more email but this is really exceptional: NWS just added Cook and Dupage to a Blizzard Warning until 9:00 tomorrow morning.

The low continues to deepen and conditions are atrocious in Iowa. Many major roads are closed and impassable. The switch to snow is beginning across Chicago and the snow will intensify from west to east around 5-6pm. The worst conditions will arrive with heavy snow and winds over 40 mph (gusting to 50+) from 9pm through midnight. Snow totals are largely unchanged from prior models (see below; I'm taking the under by an inch or two, especially along the lake, but that doesn't change the fact that this is a big, nasty storm).

The very sharp line between rain/snow and light/heavy remains in place, running SW to NE right through the area. 10+ inches of heavy, wet snow will be separated by only 10-20 miles from a little slushy accumulation.

The airports are already a mess and by 8-9pm tonight the roads will be very tough. Hopefully crews can catch up by tomorrow morning but we'll see...

(Reminder: a blizzard is actually a specific term defined by three or more consecutive hours of 35+ mph sustained winds that cause blowing or falling snow to create visibility below 1/4 mile. There is no threshold for snowfall accumulation that pertains to a blizzard.)

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last storm update

This powerhouse storm is still barreling across the middle of the country, although the forward motion has slowed. Rain this morning will be later to transition to snow this afternoon. Best guess is rain or a rain-snow mix until 12-2 pm far NW, 2-4pm near suburbs, and after sunset in the city.

Best guess remains 8+ inches far NW -- Lake and McHenry counties remain in the bull's-eye -- with amounts tapering rapidly to the SE. 3-6+ inches for most suburbs toward O'Hare, and 1-2" right along the lakefront from Lincoln Park south to the Indiana border.

One moderate change is that the wind field is expanding and intensifying. Gusts of 45+ mph are likely across the whole area tonight. Airports will have a very tough time after sunset, and even driving will be a challenge tonight in many places.

The Winter Storm Warning is in effect from noon today until 9:00 tomorrow morning. The good news is that we should get a few more hours in the "good" travel window this afternoon on the roads and at the airports, but the morning commute could be somewhat of a problem tomorrow. The worst conditions will arrive well after sunset and be gone by sunrise, but lingering snow showers and the cleanup effort could make for slower travel times tomorrow.

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Saturday, November 24, 2018

Winter Storm Warning

Well, so much for the under – the entire area is under a Winter Storm Warning from late morning Sunday to pre-dawn Monday, and the snow totals are looking more impressive with each iteration. This is a serious storm.

Here is the best guess for now:

Temps in the 40s will support rain developing near dawn. Light, on/off rain will continue through the morning before the switch to snow begins some time after noon (beginning in the W/NW).
Areas to the far west and northwest will see snow first, near or shortly after noon, and even if snow melts at the onset the snowfall rates of 1+ inch/hour will quickly overwhelm road crews. Travel will be problematic by mid-afternoon. Flights – especially at O’Hare – are going to be a mess beyond 12:00 or so. Expect widespread cancellations and delays.
- Totals near O’Hare and the areas to the west and north – especially McHenry and Lake counties – could run to 8+ inches.
The city will see a later switch to snow, and the rain-snow line will be set up roughly parallel to I-55. Snow may be as late as 3-4pm in the city. Totals could range from 4-8” in the far NW sections to 1-2” in the Loop and southern areas.
Areas to the far SE, near the lake and Indiana border, will see the least snow and may not get much beyond a slushy inch or so
Snow will be very heavy and wet.
Winds will gust to 30-40+ mph. Power outages are a distinct risk.
Thundersnow is possible!

A quick note of caution is needed. If you wanted to create a difficult forecast, you’d want a powerful, developing low with a shifting track; early-season conditions, with an urban heat island and a warm lake; and a very sharp rain-snow line across a densely populated area. We have all of that with storm. The “bust potential” with the storm is low – there is a powerhouse coming, it’s just a matter of the precise location – but a tiny difference of 5-10 miles could mean the difference between one inch of snow and one foot of snow. Keep that in mind with everything for tomorrow.

Winter Storm Watch -- Sunday night

Snowvember rolls on after a brief shot of mild air yesterday and today, and we've just been upgraded to a Winter Storm Watch tomorrow (Sunday). This storm has been monitored for days, but it is really coming together and tracking south of its original projection.

With temps pushing 50 today it may not feel like winter, but our exceptionally cold November will return tomorrow after morning temps near 40 start to slide and rain changes to snow. Winds will also be an issue, gusting to 30-40+ and causing visibility issues (especially in open areas). Snow will be heaviest to the west, and totals will decrease rapidly from northwest to southeast. There is a good chance of 6+ inches far west toward DeKalb, while areas in Chicago -- especially near the lake -- will see far less accumulation. For now, I'd put the 50% probability total at 4-6 inches in far NW and N suburbs; 3-4 inches at O'Hare; 1-3 inches at Midway and Loop; and a trace to 1" far S and SE. Some projections are already up to 6-9" NW and 3-6" right through the city, but I'll take the under on that for now. It is still early, the track has been shifting, and as with all early-season storms the bust potential is significant. I will send an update tonight or tomorrow morning as details come together.

Especially at the onset of the rain-to-snow transition the snow will be heavy and wet. Warm surface temps should help it melt at first, but heavy snowfall rates will likely overwhelm road crews by mid-/late-afternoon, causing at least some problems on the roads. The timing in general is terrible given the busy travel schedule on the Sunday after Thanksgiving. Air travel will see delays given that heavy snow will be impacting areas from the central Rockies to the Upper Midwest. Chicago airports Driving west, especially through western Illinois, Iowa, and northern Missouri, is going to be problematic.

The good news is that the snow should end overnight, so hopefully roads will be clear and travel will be OK but the Monday morning rush. It will be cold, though, with near-record temperatures

Note: this is old and the Winter Storm Watch has been extended to the west and south to include Chicago.

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Thursday, November 8, 2018

snow/cold and winter outlook

Yes, there is some (very light) snow on the way tonight. Normally this would not merit any attention, but given that it’s early in the season and this is the first real snow, it is getting a lot of attention.

Snow arrives near or after midnight and exists tomorrow morning after rush hour.
A dusting to maybe an inch of snow could accumulate in some locations.
Given the date and warm surface temps I would not expect much if any accumulation on the roads, especially in the city and near the lake.
Visibility should be decent, so even though there could be some minor traffic delays on the roads and the airports tomorrow morning it shouldn’t be terrible.
This is going to be a wet/slushy snow and a lot of leaves are still on the trees, but amounts will be so light that I don’t think there will be any issue with power lines.

Beyond the next seven days, which look very cold for the season, the outlook is mixed. There are no major warm-ups showing up just yet, but I would bet more to the mild side toward Thanksgiving. Beyond that there isn’t much to say. The various prognosticators/soothsayers probably have some strong and useless forecasts, but I would ignore them all. We do know that a weak/moderate El Niño is somewhat likely this winter (see below), and we do know that El Niño winters are correlated with mild-ish winters in Chicago.* Beyond that it is safe to pay attention to details within a day or two, broad trends and outliers to 10-14 days, and ignore the rest.

* Here is the evergreen reminder that the atmosphere is endlessly complex and we cannot prove causation, let alone model it with precision in the future, when it comes to El Niño or any other specific event. El Niño winters may come with better-than-average odds for a mild winter, but no two events are alike. In any case, an El Niño winters doesn’t mean we will be free of (big) snowstorms or occasional cold snaps. And even if we get an El Niño, and even if the correlation holds up over time, please don’t confuse a winter that turns out to be cold/snowy with what “should” or was “supposed” to have happened. We had a moderate/strong El Niño in 2015-16, and that was a very mild winter in Chicago. But 2009-10 was a moderate El Niño and Chicago actually had a slightly colder than average winter.

So maybe the most important thing to remember about El Niño is this analysis from The Weather Channel’s “WeatherScope” segment:

http://www.nbc.com/saturday-night-live/video/el-nino/2861308

EL NIÑO/SOUTHERN OSCILLATION (ENSO)

DIAGNOSTIC DISCUSSION

issued by
CLIMATE PREDICTION CENTER/NCEP/NWS
and the International Research Institute for Climate and Society

8 November 2018

ENSO Alert System Status: El Niño Watch

Synopsis: El Niño is expected to form and continue through the Northern Hemisphere winter 2018-19 (~80% chance) and into spring (55-60% chance).

ENSO-neutral continued during October, despite widespread above-average sea surface temperatures (SSTs) across the equatorial Pacific Ocean [Fig. 1]. All four Niño regions showed increased SST anomalies in October, with the latest weekly values near +1.0°C in the Niño-4, Niño-3.4 and Niño3 regions, and +0.2°C in the Niño-1+2 region [Fig. 2]. Positive subsurface temperature anomalies (averaged across 180°-100°W) also continued [Fig. 3], due to the persistence of above-average temperatures at depth across the eastern half of the equatorial Pacific Ocean [Fig. 4]. However, atmospheric convection remained slightly suppressed near the Date Line and over Indonesia [Fig. 5]. Low-level westerly wind anomalies were observed over the eastern Pacific during October, while weak upper-level westerly wind anomalies were present over the far western Pacific. The traditional and equatorial Southern Oscillation indices were near zero. Despite the above-average ocean temperatures across the equatorial Pacific Ocean, the overall coupled ocean-atmosphere system continued to reflect ENSO-neutral.

The majority of models in the IRI/CPC plume predict a Niño3.4 index of +0.5°C or greater to continue through the rest of the fall and winter and into spring [Fig. 6]. The official forecast favors the formation of a weak El Niño, with the expectation that the atmospheric circulation will eventually couple to the anomalous equatorial Pacific warmth. In summary, El Niño is expected to form and continue through the Northern Hemisphere winter 2018-19 (~80% chance) and into spring (55-60% chance; click CPC/IRI consensus forecast for the chance of each outcome for each 3-month period).

Wednesday, October 10, 2018

Hurricane Michael

I’ve been hesitant to send anything about Hurricane Michael because I haven’t had any questions about it, unlike with prior hurricanes. (As a reminder, the threshold here is severe/disruptive weather in the Chicago area, with occasional exceptions for national weather catastrophes that are likely to rank in the top 25 all-time for damage.)

But unfortunately this does require a quick note, because Hurricane Michael is likely to be a true disaster.

Later today Michael is going to make landfall on the Florida coast as a Category 4 storm. Unlike Harvey and Florence – both of which were horrendous storms that killed dozens of people and did tens of billions of dollars in damage – this storm is packing a flooding threat and a terrifying wind field. Current *sustained* winds are 145 mph. If that carries through to landfall this will be one of the strongest storms to ever hit the U.S. Damage at that level is catastrophic. And it does look likely that the storm will retain its strength, if not strengthen further, before making landfall in a few hours.

This is also a worst-case scenario because unlike Florence, for example, Michael has exploded in intensity just before landfall. I hope I’m wrong, but there seems to be much less attention on this storm compared to others. The track and overall threat has been in discussion for over a week now, but the rapid intensification – always the trickiest part – is coming at the last moment and may be catching people off guard. The area at risk is highly populated and vulnerable to flooding. Michael is large – nearly 2x the area of hurricane-force winds as Andrew had in 1992 – and producing a storm surge that could be 10-12 feet.

It doesn’t get much worse than this for the Florida Panhandle.

Monday, October 1, 2018

severe storm and heavy rain threat

Clouds and occasional sun will dominate the afternoon, but precip should be limited to just a passing storm or light drizzle. Tonight, a line of strong storms associated with a cold front will pass through the area and main bring heavy rain, frequent lightning, and the potential for damaging winds. Areas to the north and west are most favored for storms, as points from the city to the south and east may be spared. Unfortunately, 2-4+ inches of rain could fall over still-waterlogged areas in the northern suburbs and into Wisconsin.

Daytime temps this week will oscillate between the 60s and 80s as a front flips back and forth through the area, bringing ongoing chances for rain too (but not all-day washouts).

One model at just after 9:00 pm local:

Tuesday, September 25, 2018

severe thunderstorm warning

Well, so much for that idea – these storms are sticking together and packing a punch. Essentially the entire area is under a severe thunderstorm warning until 6:00.

Winds 60-70+ mph have been recorded just west of us, with widespread tree damage and some power outages. Expect impacts now in the western suburbs, with storms moving ~50 mph (so closer to 5:30 in the city). This line of storms isn’t giving any room to the airports either, so both are likely to be on extended ground delay and/or stop programs right in the evening rush. Even traffic on the roads is going to be impacted a little bit as visibility temporarily drops in some of the heavier downpours.

severe thunderstorm watch

The entire area is under a severe thunderstorm watch until 10pm. Damaging winds are the main threat from a line of storms that is likely to move through the area from late afternoon through early evening (see below). I think the risk of a severe storm in any one spot is actually quite low, even if the risk of at least one severe storm somewhere in the watch area is meaningful. Keep an eye on outdoor plans between ~5:00 and 9:00, but there is nothing extraordinary about this set up. ATC delays at the airports could well be the most notable effect of these storms.

Thursday, September 13, 2018

Hurricane Florence

Hurricane Florence is approaching the Carolina coast today, and there is some good news and a lot of bad news.

The good news is that we may avoid some of the worst wind damage. Sustained winds were most recently measured at 110 mph, and that’s obviously better than 130+. Wind was never the primary threat, but every little bit of relief is welcome.

The bad news is…bad. The lower core wind speed is nice, but it comes with a much bigger storm. And size matters. The wind field has expanded considerably, and the wall of water being pushed by the storm has also grown. Tropical storm-force winds extend an insane 200 miles from the eye, and hurricane-force winds extend 80 miles. That is a massive, massive storm.

The track is also bad. In a true fluke, there are “blocking ridges” – areas of high pressure – spread in perfect alignment across North America such that Florence is likely to slow down, possibly stall, and then grind its way to the *southwest* into South Carolina. This storm will have 1-2 days to dump rain on the area before it finally exits this weekend. The exact location of landfall (the point where the lowest pressure in the eye of the storm meets land) is hard to pinpoint. It may be on the North Carolina shore, or there may not be a landfall until late Friday or early Saturday in South Carolina. The details will matter for any single location, but the big picture is pretty clear. Here are the threats that are extremely likely to develop:

A deadly storm surge along the SC-NC coast. It could be only a few feet toward Charleston, but it could be 6-12+ feet in parts of North Carolina.
- I don’t think it has been verified, but there is a small town on a barrier island in the Outer Banks of North Carolina that is only 3-5 feet above sea level and home to 100 or more residents who apparently refused to evacuate. There is no road/bridge, the ferry has stopped running, and the Coast Guard and EMS have pre-warned that no rescues are going to be possible.
Horrendous rain and flooding. There is an unreal amount of water coming with this storm, and the rainfall is going to be exacerbated by the slow forward motion of the storm. Many places from Myrtle Beach to Wilmington will see one to three feet of rain. A few places could see 40 inches. The numbers on the map below are likely understated given that the models have never seen any storm follow a track like this. And given saturated soils and drainage problems from the surge, the flooding is going to be a massive problem.
Widespread power outages. Even if winds top out at “only” 90-105 mph in the populated areas, there will be at least a few hundred thousand to a few million people who lose power. It may take days or even weeks to get it back.
The analogy to this storm is not Andrew or Camille. It’s some combination of Harvey, Ike, and Sandy. Each of those storms killed scores of people and did tens of billions in damage. Everyone in the path should be taking this very seriously.

Monday, September 10, 2018

Hurricane Florence -- travel disruptions at best, natural disaster at worst

After a very quiet start to the season a potential catastrophe is looming. Hurricane Florence is undergoing explosive intensification and the forward track looks ominous at best. Currently a Category 2 storm, Florence could be a Category 4 hurricane as soon as tomorrow – the water in its path is very warm, and there is almost no shear aloft to disrupt the convection and circulation.

Of course, the standard caveat applies: we are still several days out, and the atmosphere is unpredictable. That said, the data and models are quite reliable down to a reasonable band of location and strength, and the consensus is strong and growing that a major hurricane will make landfall this week on the East Coast. This is an unusual storm, and if the current forecasts verify it would become just the 11^th major (Category 3/4/5) hurricane to make landfall on the east coast since 1851. Given the immense population and property development in the path it could easily become one of the most destructive storms on record.

A summary of where things stand:

Category 2 hurricane with Category 3-4 strength likely within 24 hours
A projected landfall (greater than 70% confidence) of at least a Category 3 landfall on the East Coast on Thursday/Friday
- The current best estimate from is a Category 4 storm with sustained winds of 140 mph at landfall somewhere near or north of the South Carolina and North Carolina border. For now the most likely track takes it into North Carolina, but a 25-100 mile wobble will have massive implications and cannot be predicted this far in advance. And areas that are hundreds of miles from the exact landfall will suffer damaging winds, surge, and flooding.
  - The 72-hour projection from NHC has Florence at a catastrophic 150 mph sustained. Only one storm on record has ever had 150 mph sustained winds at such a northerly latitude (Helene in 1958).
  - Category 4 at landfall in NC would be the all-time record for northern latitude for a storm of such strength. North Carolina hasn’t seen a landfalling storm of such intensity since 1954. And there are reasonable parallels in terms of intensity to Hurricane Hugo in 1989.
Soils along much of the Mid-Atlantic coast into the Northeast are already saturated after days of heavy rain in recent days/weeks/months. The forward motion of Florence is likely to be slow, and the rainfall totals – even dozens or hundreds of miles from the ocean – could be disastrous. There are no exact parallels between storms, but as we saw with Harvey last year 20-30+ inches of rain can have horrendous consequences in areas far from any wind threat. The odds of disaster-level flooding on the East Coast are even higher than those of a landfalling hurricane.

Anyone living in the area should make plans now to secure property and/or evacuate. Anyone else with travel plans anywhere in the U.S. on Wednesday-Saturday should be prepared for significant delays and disruptions. There are also three more tropical storms (two in the open Atlantic, one in the Gulf) that need to be monitored.

Monday, September 3, 2018

More downpours

Another round of torrential downpours is approaching from the west. Given that many areas — especially north and NW suburbs — have seen 4-10" of rain in recent days this is not good.

At the moment O'Hare is almost closed. Runways and taxiways have standing water. And the expressways in/out are all flooded too.

Expect on and off storms the rest of today. Slight chances tomorrow and Wednesday too before the hot and humid pattern breaks Thursday.

On Sep 3, 2018, at 2:00 PM, Philip C. Ordway <pordway@anabaticllc.com> wrote:

A severe thunderstorm warning is in place for radar indicates 60 mph winds. Will, southern DuPage, into Cook. Prolific lightning and torrential downpours but wind is actually marginal.

Over northern Lake a tornado warning is in place for radar indicated rotation. Storm is weakening but needs to be monitored. Near Fox Lake and Round Lake Beach.

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Severe thunderstorm warning

A severe thunderstorm warning is in place for radar indicates 60 mph winds. Will, southern DuPage, into Cook. Prolific lightning and torrential downpours but wind is actually marginal.

Over northern Lake a tornado warning is in place for radar indicated rotation. Storm is weakening but needs to be monitored. Near Fox Lake and Round Lake Beach.

This email is confidential and intended only for the recipient(s). If you have received this message in error, please notify the sender at compliance@anabaticllc.com and delete this message and any attachments. This message is provided for informational purposes only and should not be construed as a solicitation or offer to buy any financial instruments. Please see the full disclaimer at www.anabaticllc.com.

Saturday, September 1, 2018

Flash flood watch

An area of very heavy rain is setting up tonight over cook and dupage. Areas north of I-80 are most favored. Many areas will see 1-3" and in spots that get stuck under repeated storms 4-5" is possible. Storms will begin this evening and continue into the overnight.

Much drier and still warm tomorrow and Monday.

This email is confidential and intended only for the recipient(s). If you have received this message in error, please notify the sender at compliance@anabaticllc.com and delete this message and any attachments. This message is provided for informational purposes only and should not be construed as a solicitation or offer to buy any financial instruments. Please see the full disclaimer at www.anabaticllc.com.

Tuesday, August 28, 2018

Severe Thunderstorm Warning

There are two current warnings that cover almost the entire area. The southern warning is more for hail than anything else, while the northern warning is more for wind. Either way this line of storms is packing a decent punch — nothing too crazy but certainly among the more intense storms we've had in the past year or two. They are prolific lightning and rain producers as well. Storms are approaching from the west along a line from Gurnee to Buffalo Grove to Wheaton to Naperville and will impact the whole area through the next 1-2 hours.

On Aug 28, 2018, at 7:56 PM, Philip C. Ordway <pordway@anabaticllc.com> wrote:

The entire area is under a severe thunderstorm watch until midnight. Severe warnings are in place just 50-100 miles west of us, and the main line of storms should come through between roughly 9:00 and 11:30. The hope is that these storms will weaken slightly but I'm not so sure. They have an impressive history of wind damage and conditions remain favorable for storms. Widespread wind damage and power outages remain possible, and the airports are already a mess. Rain totals will also be impressive across most if not all of the area.

To the north Wisconsin is suffering from massive flooding problems. Multiple interstate closures are in place and travel is not recommended.

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