Officially, at 1pm today, O'Hare reported no measurable snow on the ground.
And at 2pm, the official Chicago temperature was 11°C, the warmest we've seen since December 4th.
If only they weren't predicting more snow tomorrow...
In the hopeless war between spring-like warmth and the ice still covering Chicago, the heat has almost prevailed. Officially at 7am O'Hare had only 25 mm of snow left after an overnight temperature rise to 6°C.
The end is near. Those last few millimeters have no chance of surviving the day, between nearly 12 hours of sunlight and a predicted high of 14°C.
Still, today is the 71st consecutive snow-covered day here. No one under 30 has ever seen this in Chicago before. And it's unlikely anyone ever will again.
You had a good run, winter, but it's over now. Go home.
It looks like we're going to go 71 days with snow on the ground before it all melts. But a couple of subtle yet telling things have happened since I last griped.
First, the temperature has gone up since sunset, as forecast. It hasn't gone up a lot, but the influx of warm air from the Gulf of Mexico will continue through tomorrow, to the detriment of all the snowdrifts in Chicago.
It's hard to get your mind around how much heat the atmosphere moves around. A human being can generate about 6-8 megajoules as heat every day. (A food calorie is about 4,200 joules.) Your car or office can generate tens of megajoules to keep you warm. But when an air mass comes up along the Mississippi to Chicago, it's dragging so much energy that we need to review exponents. We're talking about petajoules.
Which brings up the second point. We're not talking about an inch of fluffy ice crystals on a flower. We're actually talking about megatons of ice covering...everything. Not snow; ice.
Take a 10m square of ice just 50 mm thick—meaning just about any square of lawn in the Chicago area right now. So, that's 100 square meters times 50 mm (0.05m), which yields just 5 cubic meters of ice. It turns out, to change just that small amount of ice—oh, wait, that's five tons of ice (do the math)—into water takes 16.5 gigajoules of energy.
Also, when the energy goes into melting ice, it doesn't go anywhere else. I'll hold off on the physics for the moment, except to say that energy can't be created or destroyed, so when it goes into changing the state of a large mass of water without changing its temperature, it's pretty much unavailable for anything else. (Physicists reading this, please be kind; it's close enough.)
This is just a long way of saying: those last millimeters won't go quietly. The last bits of "snow" that the official weather observers measure aren't really snow, they're ice; and ice takes a lot of heat to melt. (Snow is easier to melt because it has so little mass for the same volume.)
Still, if the temperature gets up to its predicted 14°C tomorrow, that's a lot of heat fighting a lot of ice. It might get rid of the official snow cover at the airport, even. And that would leave us with nothing more than the two-meter snowbanks pushed up by all the plows for the last ten weeks. Joy.
When we got a few centimeters of snow on December 29th, no one expected it would still be on the ground after we changed the clocks in March. Yet there it is, officially 50 mm for the last 24 hours.
The 11am temperature at O'Hare was -0.6°C, and the forecast calls for the temperature to pop up to 7°C this afternoon and then stay above freezing until Tuesday night—possibly even getting up to 14°C tomorrow afternoon. If the little snow we've still got can survive that onslaught, then I will be impressed.
And the best part about this forecast? I won't write anything more about how many consecutive days of snow we've had. You're welcome.
Snow-cover reports come out every six hours. (The next report is due at 1pm.) I'll post as soon as the ground is officially snow-free.
Just one more moan: It's 18°C and sunny in London. But I won't be there for almost two more weeks.
Update: At 1pm the official snow depth was still 50 mm, but the temperature was up to 2°C. I'll check back in six hours.
Yesterday Chicago got warm enough to melt almost all the snow. We had just 50 mm on the ground at O'Hare (not including the waist-high drifts along all our major streets) when the cold front hit overnight. We woke up this morning to another "dusting" covering every surface of the city, just enough below freezing to make us ask "why?"
The Weather Service promises 12°C on Monday, which should end our 10-week ordeal of boots and salty paws temporarily. But I won't believe we're through winter until we have a solid week of warm weather. And I have no illusions this will happen before the end of May.
We still have snow on the ground, and now we've got a "hostage situation" counter up in our office about it. Sixty eight days ago, Chicago was snow-free. Since December 29th, we've worn boots every day, wiped our dogs' feet every day, squished across streets every day, and squelched down sidewalks every day.
There's a glimmer of hope. The temperature is up to -0.6°C, very nearly freezing. It might even get up to 7°C tomorrow and even stay above freezing for two days early next week.
And yet, we'll still have snow on the ground, possibly until April. Or May.
Enough already.
Just because we've had snow on the ground for 66 days (since December 29th) doesn't mean we didn't all want to see this on our morning commutes today:
We got another 50 mm overnight, on top of the piles already on the ground, and it's not forecast to get above freezing until late tomorrow.
We'd better have a cool frickin' summer or I'm going to write a very strongly-worded letter to the climate.
Update: Today is our 45th measurable snowfall this season—a new record. Yay.
It's killing invasive insects:
"This winter has been a godsend for the hemlock. Overnight temperatures dipped to minus 15 [Fahrenheit, or -26°C] here in Amherst [Massachusetts], and that’s cold enough to guarantee almost complete adelgid die-off," Joseph Elkington, a professor at the University of Massachusetts, Amherst, told the Worcester Telegram.
Elkington says that in some parts of North Carolina, subzero temperatures have killed 100 percent of the adelgids. In Massachusetts, around 80 percent of the population should die, according to a state official. Gypsy moths and emerald ash borers are similarly vulnerable to extreme cold; the U.S. Forest Service estimates that 80 percent of Minnesota’s emerald ash borers died in January. Other invasive insects, such as the southern pine beetle, which has been ravaging New Jersey, and the Asian stinkbug, may be dying off as well.
In fact, this nearly tops the reasons I like living in a temperate climate. Malaria? Not in Chicago, ever. Kudzu? Nope. Emerald ash borers? Die, you green vermin, die.
There's a problem, though:
The cold may also kill off predator insects that forest officials have been releasing to take out invasive insects. For instance, parasitoid wasps that are supposed to control the emerald ash borer population in Michigan and other states are even more vulnerable to the cold than their prey, whose populations might recover more quickly as a result.
Plus, we've had snow on the ground for 65 days now.
So it's not all perfect. But at least the cold has done something useful for us.
If I have time, I'll read these articles today:
Now, to work.
The third-worst winter in history ended (meteorologically) on Friday. And yet we woke up this morning to more snow and an overnight low of -19°C.
Even better, today I have to drive out to Suburbistan for a meeting. In the snow. Both ways. Uphill.
The meeting is in about two hours, so I guess I should get going now...