Posted at 5:54 PM on February 4, 2013
by Paul Huttner
We're mixing metaphors in Updraft today.
The next in a series of Alberta Clippers (a sailing ship) rolls in overnight. These systems are like boxcars (on a train), each one dumping a payload of powdery snow. What can we expect from the next 2 systems this week?
Warmer air pushes back this week, and 30s ahead. The trusty European model is hinting at significant snow on Sunday. Why do we tend to pay such close attention to the Euro model?
Clipper #4 rolls through Minnesota overnight into Tuesday AM
Another 1" likely in much of the Twin Cities area by sunrise
2" to 4" snowfall totals likely in the northern half of Minnesota
Rising temps overnight as milder air pushes north
30s by Wednesday
Sunday snow? Euro paints snowy scenario Sunday
If it's dark, it must be snowing.
That's the conclusion you would draw if there were no weather maps...no radar these days.
Our next in a series of "Sunset Clippers" rolls in overnight like clockwork.
Our 3 weekend Clipper systems were centered on the Twin Cities more or less. This one takes a slightly more northerly track, with the Twin Cities on the southern edge.
That means we could see a decent "snowfall gradient" across the metro, with amounts increasing as you move north. Around 1" (give or take) seems like a good general snowfall forecast for the metro by Tuesday AM. The south metro may have to be happy with a coating, while there could be some 2" totals as you move through the north metro up I-35 and I-94.
Snowfall should taper off as AM rush gets going Tuesday...but there could be some slick spots once again Tuesday AM, especially in the north metro.
Clipper #5: Wednesday Arrival
It's been a while since I can remember a "stable" persistent jet stream pattern that delivered snowfall to Minnesota with such regularity.
The last in our series of 5 Alberta Clippers in 5 days arrives Wednesday. This system also appears to favor the more northerly track with the Twin Cities on the southern edge.
Snowfall totals from the next 2 systems favor highest accumualtions north of the metro, where more than 6" could fall between the two systems by Wednesday evening.
Meteorologically speaking, Wednesday's system is slightly different than the previous 4. It marks the start of a transition to a milder southwest flow aloft as warmer air pushes north.
These "warm advection snows" are produced when warm air rides over the top of a colder air mass near the ground. It's a little different mechanism than a "pure" Clipper which normally features a shot of arctic air behind....but the result is the same. You'll still have to shovel it off your walkway.
Milder Days Ahead:
Last Friday I said the worst of winter's cold seems to be over. That logic seems to be holding this week.
As milder air oozes north, we'll actually see slowly rising temps tonight. It will be warmer when you wake up...and 20s will feel nicer Tuesday.
By Wednesday the next surge of milder air should push readings into the lower 30s.
Did you add windshield washer fluid?
Euro Model: Snowy Sunday
This falls under the "big maybe" category 6 days out, but the Euro model suggests significant snowfall potential for Sunday into Monday morning.
Monday's runs wind up a fairly potent low in western Kansas early Sunday, and track it ENE into eastern Iowa by 6 AM Monday.
If that track verifies, the band of heavy snow would lay out in the southern half of Minnesota...and would include the Twin Cities. The Euro is cranking out 11.8mm of mostly frozen precip. That's 0.46" for us Americans.
If that's close to reality...that could add up to "several inches" of snowfall Sunday into Monday.
The GFS is still playing catch up as usual, but cranks out .20" liquid right now.
So why do give the Euro Model (ECMWF) so much respect?
Vastly superior computing power (10 times more than GFS), higher resolution, better "initialization parameters" and twice daily runs (instead of 4x day) make the "Euro" a better product on most days than NOAA's GFS.
You may recall it was the Euro that first picked up on Superstorm Sandy's unprecedented track.
The Euro also did the best job with Isaac...taking the westward path. At AMS I saw a set of facts that NOAA's GFS was the most accurate with hurricane tracks "overall" in the 2012 hurricane season. The 2 worst storms for GFS in 2012? Isaac and Sandy...both of which made devestating U.S. landfalls. Ooops.
As a long time user, (someone who has looked at models almost every day for 30 years) you can just see the GFS get "lost" after about a week. "Pattern recognition" is part of synoptic meteorology. There are patterns that make sense...and though it sounds non technical, a good forecaster can see when a pattern just doesn't "fit."
I talked with University of Washington Professor Cliff Mass at AMS in Austin, TX last month about the Euro's advantages. I'll let him dig into the details of "petaflops" but the bottom line is the ECMWF has at least 10 times the computing power...and much better model resolution that NOAA's medium range GFS model.
You can read Cliff's entire post here, but I wanted to pull a few key excerpts that I think make his overall point best.
In previous blogs, I have documented the profound inadequacy of the computational resources used for operational numerical weather prediction by the National Weather Service (NWS) and the serious implications this deficiency has for the quality of weather forecasts in the U.S. I have described how the world-leading European Center for Medium Range Weather Forecasting (ECMWF) now has more than ten times the computer power as the U.S. Environmental Modeling Center (EMC), how U.S. skill in global prediction is in second or third place, and how the lack of computer resources is crippling the NWS's ability to move forward in probabilistic prediction, the next major area of development. (Reminder: EMC, part of the NWS, is the operational weather prediction entity of the U.S.)
For EMC to serve the nation in a reasonable way, I believe they need the computational resources to do the following:
(1) Run a global ensemble system at 12-15 km resolution (currently they are at roughly 50 km). (Remember ensembles is when you run a model many times with different starting points and model physics, this allows one to get at the uncertainties in a forecast). This ensemble needs to be running the best physics possible, unlike the inferior physics used in the current U.S. global ensemble system.
(2) Run convection resolving high-resolution ensembles over the U.S. (1-4 km resolution). Currently, the U.S. ensemble system is at 16 km resolution. Many of the runs of the current use inferior physics to save computer time.
(3) Run a rapid-update system (like ESRL's HRRR) at 3 km resolution. Eventually, (2) an (3) should be combined.
(4) Lowest priority but useful. Run a global model at 2-4 km resolution.
Doubling resolution takes about 8 times the computer power. My back of the envelope calculation is that the above is doable if EMC had 5-10 petaflops of computer power (well within the range of recently acquired machines by others). The plan below will give it to EMC for operational use and maintain high reliability.
How to Fix the Problem Quickly
First, EMC needs to get their house in order and reduce the waste in their current schedule, which I estimate is roughly 25% of their current computer.
EMC will get an upgrade this summer of their two .07 petaflop machines (the vendor is IBM, one operational and one backup) to .2 petaflops. This is helpful, but not nearly enough. Congress just passed the Hurricane Sandy relief bill for roughly 50 billion dollars. Within this bill is 25 million for enhanced hurricane weather prediction and data assimilation and 50 million for hurricane research...money that is going to NOAA. One thing we learned is that good global weather prediction is the key for hurricane forecasting--that is why the European Center Global Model was the best during Sandy. So you want to help hurricane forecasting? USE ALL OF THE 25 MILLION TO UPGRADE EMC's COMPUTER RESOURCES.
Let me be blunt: the state of operational U.S. numerical weather prediction is an embarrassment to the nation and it does not have to be this way. Taiwan, Germany, England, the European Center, Canada, and other nations have more computer power for their weather prediction services. Our nation has had inferior numerical weather prediction for too long. New computers are an obvious and relatively easy first step, because they make everything possible. For the price of a single warplane we could have greatly improved weather prediction that would save lives and property.
As a user who would like to see the GFS become every bit as reliable as the Euro I say... Amen Brother Cliff!
Happy National Weatherpersons Day, Updraft bloggers!
My husband says that Alberta Clippers cause strong winds and low temps so he thinks these storms are erroneously being called Alberta Clippers. Can you set him straight, Paul?