In the midst of January's wild roller-coaster ride of frequent up and down temperature swings; came just as many resulting weather phenomena - some typically seen and some not during January. Snow and cold of course, ranks on the side of normalcy in January; whereas balmy spring-like temperatures interspersed through the month, thunderstorms and many dense fog days do not. Oh sure they happen in January; and if at any time, usually during our cyclical January thaw which comes regularly enough to nudge up temperature records in past data during mid to late month for several days. However, there's certainly been more than a weeks duration of thawing weather this January with several notable upward temperature swings during the month. So much so, that even with the bitter cold experienced earlier in the month, readings are averaging 4 - 5 degrees above normal and enough so; that we are beginning to enter the top 20 warmest January's list at all three stations in the bottom (upper teens to 20). Three thunderstorm days have ranked up this month thus far at Detroit, an unusual amount being its the dead of the winter. Dense fog days have just eclipsed (6/5-as of the 22nd) the number of snow days thus far in January with nearly a week total in days where visibilities at Detroit Metro Arpt dropped down to a 1/4 mile or less. Last night (21st-22nd) being the foggiest I've seen it in quite awhile around metro Detroit. Dense fog advisories have been carried/existed since Saturday evening /21st/ (now Sun eve night, 22nd).
The snow machine sputtered the first ten days of the month but then died completely after the tenth. What had been a relatively snowy winter thus far into early January went bye-bye since, with 4.6" recorded the first ten days at Detroit. Flint did a bit better with 5.7" and Saginaw topped it with 7.4" To be fair; all three climate stations still are above normal for the snow season of 2016-17 by about 2-4" - but don't look for much of any addition this week as temperatures hold basically above normal with mainly rain expected until about Friday. The better chances for any addition of light snow will be across the northern portions of Southeast Michigan but then, rain is expected to mix with the snow, which should cut down any appreciable accumulations. Actually more rain than snow days have been observed this month with all of Southeast Lower Michigan having a wet January thus far. Detroit is nearly an inch above normal (a decent departure for January); Flint is nearly an inch and a half above while Saginaw rests at about three quarters above average.
Climate thus far in January at Detroit
There are changes in the offing....
While the week should basically continue mild for January; a gradual cool-down is expected to commence after Tuesday as a storm center pushes through the southern Great Lakes on its way into Canada. It will bring more rain to the region to add to the already above normal totals measured this month. cooler temperatures will push slowly into the area during mid-week with a colder air mass arriving for the last weekend of January!
Note the prevailing upper wind patterns projected for the up coming week at different runs; it's interesting to see the GFS model attempt to forecast these changes while amplifying and/or phasing the main upper weather features discussed in the Winter Outlook back in November.
1-Strong southwest trough approaches Tues Eve (forecast date 1/20 18z).
2-Jet from southwest moves off over New England and opens the door to northwest jet and Polar trough spilling colder, Polar/Arctic air south from Canada (forecast date 1/20. 18z)
3-A full-lat trough has now evolved over North America bringing cold air to much country east of the Rockies by the first day of February (forecast date 1/20. 18z)
4-Way out in "la la land" our GFS develops this huge block over North America with high over Alaska and deep Polar Vortex over Eastern Canada while both are under-cut by a mid Pacific jet (again, forecast date 1/20. 18z).
1- Later on the 01/21/ 00z run, a huge trough has also evolved in "la la land", this time ridging is a bit further east, less of a block shows up now while the Pacific undercut is weaker.
2-Then the next morning's run (01/21/ 12z) decides to shunt the energy in two places back out over SW Canada and another piece, though much weaker toward the eastern US. keep in mind this is all in a 24 hour forecast period the 20th-21st.
What's the point? Models regularly dance around with the jet (500 MB) and surface solutions days out? Yes of course they do, the point is.. the prevailing patterns that have evolved this winter, much of what showed up in the prevailing analogue winters are "competing" (if you will) in model-land for evolution in time. Given the upper air patterns dominating this winter and also prevailed in our set of analogues!
From the Winter Outlook...
"The upper wind anomaly pattern from all analogue winters shows a marked difference in jet preferences and placing upper Lows and ridging when compared to a typical La Nina pattern. While the semi-permanent eastern Canadian Low is represented by the lobe of negative anomalies south of Hudson & James Bays; the most predominate departures in the upper wind anomalies materialized over western Canada and the Northwestern US. It's almost like the typical La Nina upper wind trough pattern shifts back west at times and creates the negative departures over that region. Referring to the typical La Nina map (above), the ridging is dominant on the West Coast of Canada and to a lesser extent, the US which would negate the coldest of winters".
Resulting Storm Tracks This Winter
"Main
upper air feature positions along with generated storm tracks by my
analysis per analogue data is on the map below. The upper lows and
troughs are depicted in black; while the resulting storm tracks are in
red. As you can see, the generated storm tracks to our southwest are
mainly Kansas and Texas Panhandle Lows which have a tendency to track
near or over Southeast Lower Michigan. If the impulse generated is far
enough south, some Arkansas or even Louisiana lows are possible but they
are not expected to be a main player this winter. East Coast storms
should be more the result of Ohio Valley and mid Atlantic phasing".
In any event, it looks as though the roller-coaster will be revving up again and where it ultimately settles for this period is questionable in model-land. However; we do have the trends this winter and history in analogues to suggest the ultimate outcome - again.
Next up; will see what GFS forecast pattern becomes more dominant with time (later in the week) and ultimately should win out.
Making weather fun while we all learn,
Bill Deedler - SEMI_WeatherHistorian
