Incredible Cold

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It’s hard to believe we are even going to entertain the idea of February 2015 being the coldest month ever recorded in the Hartford area. In the current climate regime, plus urbanization around climate sites, it’s even more impressive that we are running more than a half degree ahead of the exceptional cold from February 1934.

To put 15.9 degrees in perspective, the average February temperature in the Hartford area is 29.7 degrees which is a full 13.8 degrees below normal! This monthly mean temperature is also colder than a typical February in Minneapolis, Burlington (VT), and Anchorage. In fact Anchorage’s average February temperature is 18.7 degrees!

So will we beat the 1934 record? Using raw model guidance from the GFS MOS and our current temperature departure we can get an idea at how things will shake out through 2/26. With average highs in the low 40s by the end of February – maintaining such a wildly negative departure is very, very, very hard to do.

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Using this model guidance, today’s likely high and low, and the previous 18 days I get a mean temperature of 16.31 degrees through 2/26. We will most certainly be within striking distance of the coldest month on record.

If it’s going to be so damn cold we might as well break this exceptionally impressive and long standing record! If we break the record in the Hartford area we will likely break the record in Bridgeport as well since they are currently running 1.4 degrees colder than the previous coldest month on record January 2004.

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While this incredible cold is gripping the northeastern U.S. the rest of the globe is looking mighty toasty. By far the coldest location relative to average this month is right here in our backyard. Very warm temperatures continue across most of Asia, north Africa, the middle east, and the western U.S.

An Icy Mess or a Rainy Mess?

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Our streak of snowstorms is coming to an end this weekend. Even with 10″-30″ of snow on the ground across the state it’s not out of the question we’ll be dealing with rain on Sunday. How can this be!?

A powerful shot of Arctic air with sub-500dm thicknesses is once again plowing into the Lower 48. This shot will be accompanied by a near 1050 mb high over the northern Plains. Instead of crossing the international border near the eastern Great Lakes this one will be much farther west. To the north of New England there’s no cold high pressure or confluence aloft to shunt a storm system underneath us.

Instead, we’re left with what will likely be a cutter.

Cutters come in all shapes and sizes. Some cutters are weak enough that they only bring light rain after some initial snow and icing. Weak ones like the GFS shows for this weekend would bring a bit of everything with temperatures that struggle out of the low 30s.

The Canadian model (which has had a good winter) forms a more powerful low that cuts well to the west and brings temperatures well into the 50s!

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While not the most likely scenario this is certainly possible! Snow cover will do nothing to keep the storm from cutting well west with no high to our north and no mechanism to suppress the storm track. What is concerning about this setup is that the storm is strong enough near Buffalo to bring a sizable push of warm air in and would start rapidly melting snow. Flooding issues and roof collapses would be the likely result – especially toward Boston.

While deep snow pack can help maintain a cold surface with a weaker storm system that cuts to the west – a stronger storm (driven by mid-level processes and almost totally independent of snow depth) could care less about a couple feet of snow on the ground. Rain to Montreal!

This certainly has happened before. The epic January 1996 cutter resulted in some of the most incredible snow melt we have seen. It is a blight on what was otherwise a fabulous winter.

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As for what will happen with this storm I think odds favor a weaker storm (more like the GFS) which would bring a period of snow followed by icing with temperatures in the low to mid 30s. Ground temperatures are cold enough that ice would be an issue on the roads. Most of the GFS ensemble members show this kind of scenario.

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Bottom line – watch forecasts for this weekend closely. A bit of snow, ice, and rain all appear likely. Hopefully we can avoid getting a big thaw in here – a more gradual thaw is definitely preferable!

Impressive Cold

Extreme Cold, brutal cold, dangerous cold, bitter cold, frigid cold. I generally hate adjectives placed before the word cold – more often than not it’s a bunch of hype. This shot of cold, however, may actually deserve a few of those adjectives!

Our computer models are showing some eye-popping numbers. Getting to -10 in parts of Connecticut on a radiational cooling night isn’t that impressive – being able to do it on a night where the wind stays up IS impressive.

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So, how cold will it get? I’m willing to bet Bradley Airport gets to -5 with winds sustained around 20 mph tomorrow morning. Brrrrrrrrrrrrrrr. There’s an outside chance that Bradley will dip to -10 for the first time since January 19, 1994. In Bridgeport temperatures will probably get to 0 degrees tonight for the first time since 2011. In January 2004 the mercury reached -2.

The one station I’ll be watching most carefully is Central Park. While getting to 0 is unlikely if it happens it would be the first time since 1/19/1994.

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The 925mb temperature in Atlantic City (the closest upper air site) that morning was -24.7C – which is colder than what is modeled tonight (-22C). However, north of the city in Albany the 925mb temperature was -25.5C while tonight the forecast is a -27C temperature at 925mb. If you interpolate the two -Hmmmmmmmm.

 

Blizzard Warnings Posted

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No real change in the overnight forecast with some questions still remaining. The National Weather Service upgraded parts of coastal Connecticut to a blizzard warning – though I expect they will fall short of blizzard warning criteria (wind will be there but visibility won’t be under 1/4 mile). The more I look at this storm the more I get the feeling it will come in 2 parts with a sizable lull in between.

Part 1 will be this afternoon and this evening with a gusty southerly wind (right of the Sound) as the bitterly cold air from this morning is replaced by milder air from the ocean.

bufkitprofileI wouldn’t be surprised to see this overperform in areas with a few inches of snow falling in a relatively short period of time later today. There’s a bit of instability and temperatures above the lifted condensation layer are quite cold and in the dendritic growth zone (that means efficient snowflake production – AND snow flakes that are able to accumulate easily).

Most of our computer models show a lull after the first burst of snow this afternoon and evening and then another period of snow in the pre dawn hours tomorrow. There’s a high amount of uncertainty here.

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The GFS keeps the snow going all night as an “inverted trough” sets up northwest of the offshore low. Notice the precipitation from Connecticut back  toward the Finger Lakes of NY along that kink of the isobars? Our high resolution RPM model also agrees with this output.

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If this is correct we will have a fabulous bust in snowfall totals with many areas picking up over 10″ of snow. Most computer models, however, have a much weaker feature like this, some keep it over New York City, and others don’t have it at all. The typically Teflon Euro model bears little resemblance to this forecast and the regional Canadian model (RGEM) has nothing remotely like this (the RGEM has had one hell of a winter too).

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The HRRR which is our very high resolution and near-term computer model shows a similar setup to the above mentioned models with a heavy band of snow along the inverted trough and another up with the mid level forcing toward Maine. In between there’s one heck of a sucker hole over northeastern areas and parts of Massachusetts.

So bottom line is watch this one. I think it has a few tricks up its sleeve.

 

Friday Update

In a possible ominous sign I woke up this morning from a nightmare in which the 17.5″ of snow I have on the ground outside my house had melted entirely. Not even a snow pile to be found at the end of the driveway. Clearly, this is yet another sign I suffer from the illness known as “weather obsession.”

What this portends for the weekend storm I do not know. A surprise burst of very heavy snow or a storm that winds up being a bust?

Let’s try to answer that question the best I can. Let’s start out with the short range ensemble forecast or SREF. I normally don’t find these terribly valuable in southern New England during the cold season but this winter I haven’t found them totally awful.

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This shows the amount of liquid expected to fall in Windsor Locks from a number of high resolution computer models – each with different physics and parameterizations. The ensemble mean is close to 0.5″ while the best “clustering” of ensemble members is around 0.35″. You can see some outliers that produce much higher precipitation totals. Assuming a liquid:snow ratio of 12:1 you’re looking at about 4″ of snow for the majority of the ensemble members.

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The most impressive solution here in southern New England is the GFS model which develops the most intense low pressure near eastern New England. Here about 10,000 ft off the ground you can see a back-bent warm front which is a classic sign of a mature storm. Along that front strong “lift” in the atmosphere can produce heavy snow.

In addition the GFS shows very impressive “snow growth” with the strongest lift centered around -15c from Saturday evening through Sunday morning.

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This is a VERY impressive signature and if it were to verify our snowfall amounts would be underdone significantly. However, other models are not nearly as bullish with the amount of “lift” modeled in the atmosphere. You need lift (we call it omega) to get precipitation!

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The NAM insists on keeps 2 areas of lift/precipitation on either side of Connecticut. Consider this solution the 7-10 split.The best forcing along the mid level warm front takes place across Maine and the sea coast of New Hampshire while the best low level forcing occurs in a narrow band across Long Island and into Fairfield County and the Hudson River Valley along what is known as an inverted trough.

So, which solution is right?

Hard to say. The track and strength of the mid and upper level lows is impressive. There will be several bands of heavy snow nearby and the atmosphere is cold enough with a deep layer near -15c that any bands of snow that do develop could be quite heavy. Additionally, the wind will be impressive. The GFS model (shown below) shows a deep mixed layer with the potential for gusts up to 60 mph Sunday morning. This is likely a bit overdone.

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The European model sort of splits the difference with a more “in the middle” solution. Not nearly as robust as the GFS and not nearly as paltry as the NAM. I think our snowfall map looks pretty good with 3″-6″ for most of Connecticut and 6″+ for northeastern areas. Let’s see how this one develops!