Coldest day of winter tomorrow? January thaw next week

This week may be about as cold as it gets this winter.

It's too early to declare with certainty that tomorrow will be the coldest day of winter, but I'd say there's at least a 50/50 chance.

Rock bottom? Wednesday morning as the mercury bottoms out near minus 15 in the metro, with minus 30 in Minnesota's traditionally frigid nooks and crannies like Embarrass, Ely and Tower. We batten down the hatches for a few more days, as our string of sub-zero mornings grows to seven days by this weekend. Last winter we had already endured 19 sub-zero starts by this date.

• -23 degrees one year ago today at Minneapolis-St Paul International Airport. (coldest temperature recorded at MSP last winter)

In this modified (weak) El Nino winter, the chances of us getting stuck in a polar rut for weeks on end is much lower. There are already growing signs of a significant January thaw by late next week. Hope of the horizon for the winter weary. Light at the end of a cold dark wintry tunnel.

Hang in there!

Weather headlines for Tuesday Jan. 6

• Glaze ice/black ice coating Minnesota roads today with overnight snowfall and sub-zero temps

• Coldest day of winter possible tomorrow with temps near  minus 15 in metro, minus 30 in northern Minnesota

• Wind chill warnings tonight until 11 a.m. Wednesday (chills of minus 30 to minus 40 by tonight)

• 7 sub-zero mornings so far this winter at MSP Airport including today (average is 8)

• Sub-zero mornings continue through Saturday morning

• January thaw increasingly likely late next week - highs in the 30s above zero

• National Oceanic and Atmospheric Administration on the verge of major 2015 computer upgrade should improve forecast model outputs

Rock bottom

Purple is generally not a pleasant color on your local weather map. Our current cold snap bottoms out tomorrow morning, as wind chill values plummet to minus 35 in the metro and minus 50 around International Falls, Minn.

The most dangerous window for life threatening wind chills? Tonight through Wednesday morning.

Freeze warnings extend deep into Dixie as this air mass will penetrate all the way south to the Gulf Coast.

Siberian express: Train 1052 rolls south

This is what it looks like when arctic high pressure surges south deep into Dixie. A "1052 millibar" central pressure high pushes cold air all the way to the Gulf Coast. Watch the national newscasts as 200 million people share in Minnesota's January polar pain.

Here's a more detailed breakdown of temps this week. Most of Minnesota will not reach the zero mark Wednesday. The coldest day of winter? Quite possibly.

Pattern change ahead: January thaw late next week?

For those dreaming of milder days and easier commutes I have some news. A major pattern change looks likely by late next week, as a Pacific breeze blows in much milder air by way of Seattle, instead of the Yukon.

Here's a look at NOAA's Global Forecast System surface map for next Friday Jan.  16. Westerly breezes and red dashed lines equal temps above freezing in Minnesota.

Here's the GFS temp output for late next week. A string of days with highs in the 30s looks increasingly likely by late next week.

From wind chill values of minus 35 tomorrow morning, to temps near 35 above a week from Friday? Temps will feel as much as 70 degrees warmer by late next week.

Often the magnitude of these warm ups is underestimated. I won't be shocked to see temps hit 40 degrees again in Minnesota by late next week. More melting and green grass by the middle of January?

Stay tuned.

Weather wars: NOAA announces major supercomputer upgrade 

Call it the Superstorm Sandy upgrade.

NOAA just announced a major upgrade in computing power. The $45 million upgrade includes the purchase of new Cray supercomputers that will produce a tenfold increase in NOAA's computing power by October. The big win? Faster calculations and improved resolution of NOAA's GFS model from 33 km down to 13 km out to 10 days.

Here are some key excerpts from NOAA's release.

Today, NOAA announced the next phase in the agency’s efforts to increase supercomputing capacity to provide more timely, accurate, reliable, and detailed forecasts. By October 2015, the capacity of each of NOAA’s two operational supercomputers will jump to 2.5 petaflops, for a total of 5 petaflops – a nearly tenfold increase from the current capacity.

“NOAA is America’s environmental intelligence agency; we provide the information, data, and services communities need to become resilient to significant and severe weather, water, and climate events,” said Kathryn Sullivan, Ph.D., NOAA’s Administrator. “These supercomputing upgrades will significantly improve our ability to translate data into actionable information, which in turn will lead to more timely, accurate, and reliable forecasts.”

Ahead of this upgrade, each of the two operational supercomputers will first more than triple their current capacity later this month (to at least 0.776 petaflops for a total capacity of 1.552 petaflops). With this larger capacity, NOAA’s National Weather Service in January will begin running an upgraded version of theGlobal Forecast System (GFS) with greater resolution that extends further out in time – the new GFS will increase resolution from 27km to 13km out to 10 days and 55km to 33km for 11 to 16 days. In addition, theGlobal Ensemble Forecast System (GEFS) will be upgraded by increasing the number of vertical levels from 42 to 64 and increasing the horizontal resolution from 55km to 27km out to eight days and 70km to 33km from days nine to 16.

The increase in supercomputing capacity comes via a $44.5 million investment using NOAA's operational high performance computing contract with IBM, $25 million of which was provided through the Disaster Relief Appropriations Act of 2013 related to the consequences of Hurricane Sandy. Cray Inc., headquartered in Seattle, plans to serve as a subcontractor for IBM to provide the new systems to NOAA.

NOAA's new supercomputer capacity could be the ninth fastest in the world according to Top500.com. Still, the European Centre for Medium-Range Weather Forecasts is also upgrading, and will have capacity that is still 3 times what NOAA has by later this year.

Stay tuned.