6/1/21

Will Variable Spring Weather Lead to a Variable Summer?

If the weather the past few months seemed unusually erratic -even for spring- with cold spells and frost, hot spells with near record highs, dry spells going on for a couple weeks without rain then only to be deluged in a week’s time or less with a couple inches of rain recently; that was our spring - now how about summer?

Strangely enough, while the summer analogues are initially saying the same thing; variable - the picture becomes clearer as we delve deeper into the analogues and computer guidance. It’s really not surprising that on the surface; the initial data intimates the same thing for a few reasons. We are going into a season that is least likely to be affected by hemispheric patterns, an ENSO that is outright neutral and analogues that seem to reflect various patterns. Since that is the case; further investigation, then the weighted years and trends must be uncovered and decided for this Outlook. After this researching, the following is forecast for the summer...

TEMPS:

Above normal temperatures should dominate the overall general pattern with occasional significant cooler shifts in temperatures due to retrograding and/or wavering upper air patterns. Still, I look for temperature departures from normals /1971-2010/ +1.0 to +2.5. For summer trends in temperatures; see Analogue section.

RAINFALL:

Summer rainfalls and departures are probably the most difficult to predict due to the majority of the rains being convective.  That being said; I look for quite variable rainfalls; below normal to above. Current trends suggest the better rains to fall from the Thumb Region to Ann Arbor and  southeast to the Michigan/Ohio border. Again; summer trends are discussed in the Analogue section


ANALOGUES FOR LA NINA TO NEUTRAL WINTER TO SUMMER 2020-21

Mainly because of the warming the latter quarter of the 20th century into the early 21st century; analogues from earliest periods have been generally discounted or less weighted than the later period analogues. Basically; many of the earlier analogues have been considered too cool for our present warmer period the past several years. However; all analogues are considered for patterns and timing. Note the average summer temperature of the highlighted warmer summers is 72.5/+0.8


Analogues highlighted are more weighted than others.

TEMPS/TRENDS

All Monthly trends of the summers reflect cooler Junes, warmer July's and normal August's. When discounting the cooler analogues; then leaning more toward the yellow highlighted years gives a different picture. Preferred, highlighted Junes averaged above normal, 70.6/ +1.2; July's 74.5/+0.9 and August's 72.4/+0.4. All averaged above normal with June's the largest departure at +1.2. July was a close second with a departure of +0.9. while August came in at +0.4.  Keeping one eye on the analogue data and the other on the projected upper air maps; early to mid summer has the best chance to average above normal with mid to late summer around normal. This matches well with a retrograding ridge mid to late summer and troughing also shifting west with time. (see maps).

RAIN/TRENDS

Rainfall is again, like many summers; feast or famine. When all rainfalls are averaged; they average  near normal (within a inch), 9.24"/-0.65; but there still was a decided slant to below normal by the departure and four summers being drier than average (more than an inch below normal). Only one summer was wetter and the other three were near normal. I feel there is a stronger than average case for below, above and normal rains this summer - location, location, location.

COMPUTER GUIDANCE

Generally upper high pressure is a dominant player during the summer; allowing only intermittent low pressure and surface fronts through the country. If upper air projected patterns are correct; this should become more common later in the summer. Upper air guidance from the CFS for the season and monthly shows the following scenario.

 SUMMER 2021


High pressure aloft focuses on the east-central area of the country early in the summer with a gradual retrograde westward mid-late summer. Note each month's map.

JUNE

1- Late May into June; a semi-permanent, subtropical area of high pressure in the North Atlantic off    the East Coast, normally spreads west across the Eastern and Central U.S.

 

JULY

 2- As the high pressure retrogrades westward; this allows troughing into the Northeast with time.

AUGUST

3- Later in the summer, troughing shifts westward into the Lakes.


Maps from CFS for temps/pcpn for the summer




 Enjoy the summer! Look for other notable weather write-ups and trends through the summer if conditions warrant.

Making weather fun while we all learn,
Bill Deedler -SEMI_WeatherHistorian




5/27/21

Winter 2020-21; A Rather Uneventful, Mild Winter - That is Until February

Winter of  20 - '21 was a somewhat boring, slow and mild winter with February the only "real winter month" of the three.

There was a rather mild intro to winter from the get-go in December that carried right on through January. Temperatures averaged several degrees above normal both months across Southeast Lower Michigan and it looked as though we were going "skate" through another relatively balmy winter as we had the winter before /Winter of 2019-2020/. All three winter months in that winter averaged above or well above normal. This left Detroit with its 9th warmest winter with 32.6 degrees; Flint had its 5th warmest winter with 31.5 and Saginaw checked in at 29.8 degrees/7th warmest winter. 

Our most recent winter didn't change direction until early in February with much colder weather; heralded in by a drastic shift in the predominant upper air pattern to the Arctic. Before the change; a rather persistent upper air troughs routinely pushed into the West Coast; as discussed in my Winter Outlook; 

Pacific/North American /PNA/ Pattern

 A negative /-PNA/ generally reflects a trough over the western portion of the US with ridging and warmer weather in the East.

The Pacific Jet Stream remained dominant much of the early to mid winter and thus; only occasionally allowed colder, polar air into the eastern part of the country. For much of December and January; colder and stormier weather slammed into the northeast Pacific; then down into the Rocky Mountain range (note white path and arrows in the negative PNA pattern above). This also encouraged a mild to warm, upper and surface wind flow from the southwest and south into the Ohio Valley and Great Lakes.

During February; the PNA shifted to a dominant positive pattern bringing the stored up, Arctic cold in the form of several polar vortexes pushing down into the center part of the country, then spreading out east and south. It was at this time; notable record cold and snow occurred mid month with the influx of the "blue norther".

 

 



Statistics for the Winter 2020-21

WINTER TEMPS



2020-21 SEASON SNOWFALL



 Winter Forecast & Analogue Performance

Closer to home; let's take a look at the winter statistics for Detroit, Flint and Saginaw and compare it to the Winter Analogue statistics...and most important; the forecast.

Forecast was for:

Temperatures - Normal to Above (or -1.0 to +2.5 temp departure)

Most analogue winters averaged normal to slightly below with an average sitting at 26.5 (30 year norm @ 27.9 or -1.4 below). Taking into account the more recent La Nina winters (including Modoki La Ninas), computer guidance and recent trends; I look for a normal to above normal temperature winter. This is both for the winter (Dec-Feb) and cold season (Nov-Mar). 

This projected milder winter average/departure verified well with the average for Southeast Lower Michigan coming in at 27.6. The normal for the area is 25.8; therefore the departure for the winter in Southeast Lower Michigan was +1.8 degrees. Keep in mind the normal range is for a departure -1.0 to +1.0 for our purposes. Expanding to the cold season, November thru March temperatures were also above normal with November averaging just above normal and March well above normal. Therefore; with the exception of only February; the entire cold season period averaged above normal.

Not only did the Winter Outlook temperature departure verify for the winter; so did the temperature and snow trends

The Forecast Winter Trend read:

Temperatures and Snowfall:

Most analogue winters averaged normal to slightly below with an average sitting at 26.5 (30 year norm @ 27.9 or -1.4 below). Taking into account the more recent La Nina winters - Modoki La Nina winters- computer guidance and recent trends; I surmise the average of the winter analogues are on the cooler side and therefore; I look for a normal to above normal temperature winter. This is both for the winter (Dec-Feb) and cold season (Nov-Mar). The analogues contained front-end loaded, mid-loaded or back-end loaded winters regarding temperatures (coldest relative to norms) and snowfall (relative to averages). There were twice as many snowier winters (8/4) as there were snowless (see analogues and legends below). Potential for a major snowstorm or two in the snowy La Nina analogues was slightly greater in every month Dec-Mar with a lean toward late season.

In descending order; back-end loaded (roughly late Jan-Mar) winters were favored in regard to colder temperature and/or heavier snowfall.

And one more thing; there are enough well below normal (or "snowless") months that showed up in every set of analogues to be concerned about a bust on the snowfall prediction but I'll hang tough with the normal to above - for the time being anyway.

Both colder temperatures and heavier snows did fall in all areas in February; especially across the Flint area. Detroit more than doubled its normal snow for February with 21.6" this was 11.6" above the norm /10.2'/. Up around Flint; snowfall for February was a whopping 29.7. This was nearly triple the norm of 10.8" /+18.9"/. Saginaw recorded 18.1" of snow for February; which was more than double /+9.5/ their normal amount of 8.6"

In spite of the heavy snows in February; the snow totals for the season just caught up to around normal at both Detroit and Flint (see analogue chart - stats for Winter 2020-21) - which shows just how dry and snowless much of the winter was up until February. Saginaw's seasonal snowfall still came in well below normal with 32.3" or 9.2" below normal. Snowfalls at both Detroit and Flint came close to their analogue means (Detroit - 44.9/48.8" & Flint 48.6/52.4"); whereas Saginaw was well below its snowy mean of 52.0" with just the 32.3". The storm track clipped the Flint and Detroit regions with the best snows of the season.

Analogues & Actual Winter 2020-21 Data

 

 

Precipitation and Snow Amount Forecast:

The most surprising trend of the winter was the lack of precipitation and a lesser extent; snowfall leading to below normal precipitation for the winter right into the spring and normal to below normal snowfall. This part of the forecast did not verify.  La Nina winter's are notoriously wet in the Ohio Valley into the Lower Lakes but not this time with much of this area being drier than average.

 


Reasoning and deductions as to why the La Nina precipitation and in some areas, snowfall didn't verify along with a longer, mild winter

 
Map I & Map III
 
First off; La Nina forecast intensity was not only off; so was the prime area it was to affect in the Pacific. The forecast and thus; the analogues used were for a weak to moderate La Nina. The La Nina generally was weak thru its life. Second and more important; La Nina was forecast to peak in the eastern and central Pacific early-mid winter. Not only did the La Nina weaken, it migrated into the central and western Pacific. This placement further west; at least partly affected our temperatures which remained above normal for two thirds of the winter season. The Pacific jet stream remained strong and shifted further inland and thus; cut off the polar and Arctic jet into the lower 48 (ironically, not unlike an El Nino).  Note the studies on La Nina placement in the Pacific. Note; La Nina mild winters in example #3 with the core of  La Nina over the central-west region of the Pacific. This; in conjunction a NAO which was neutral to positive until February, precipitated our mild winter.

Map II

Another sideline but just as important was the lighter westerly QBO never dominated during the winter as expected. In fact at one point; it looked as though the QBO may start shifting to an easterly phase (negative) toward spring. Negative QBO's are notorious for aiding colder and stormier winters in the eastern two-thirds of the country. As of this writing; next winter looks more promising for a easterly QBO

 Map I


 

Map II


 QBO and WinterTemperatures Trends

 

Map III


 

Next up shortly the Summer Outlook

Making weather fun while we all learn,
Bill Deedler - SEMI_Weather Historian

 

5/5/21

Another Lousy May To Start off the Garden Season?

May of 2020 is all too familiar in the minds of gardeners across the Great Lakes and Michigan. The unseasonable cold weather last May that covered the region mid month with freezes and snow is still fresh in many of our minds. To recap; https://www.climatehubs.usda.gov/.../6.2...
 
So what about this May; are daily temperatures expected now to remain cool and average below normal? On average high temperatures in early to mid May in Southeast Michigan generally rise into the mid 60s to around 70; while lows fall into the mid 40s to around 50. Thus far; temperatures have actually averaged above normal for the month but May is only a few days old.
 
Latest weather guidance into at least early next week is not too encouraging for warm weather. Temperatures are expected to average 5 to 10 degrees below normal. And; there is still the risks of scattered frosts or freezes.
 
Latest estimate of temperatures through mid next week /May 12th/ are on the first map; while the reason for the cool weather is on the second map. The reason is in the form of an upper 500 mb cool low that remains trapped over Ontario and the Great Lakes (and routinely being recharged with polar air).
 
This anomaly map /Map 2/ shows the below normal heights/temperatures with the upper low with time. Fortunately; the cold low does migrate to the east-northeast and allows warmer weather to push back into the region toward the end of this period, next week.
 
Another period of cool weather is beginning to show up on extended models later in the month but at this time it remains further north and it's too far out to be reliable, anyway.
 

 

 
Making weather fun while we all learn,
Bill Deedler -SEMI_WeatherHistorian

4/6/21

April 6th ~ Too Late For Big Snows? 😁

 

     April 6 1886 Super Snowstorm In Detroit

    Written by: William R. Deedler, Weather Historian

While the Snowstorm of April 6th 1886 had been written about in the past,  I am now able to include the weather maps drafted at that time, so long ago. At the time I wrote about the storm (along with the storm of December 1st, 1974), I had to estimate the weather map just by local surface observations available from Detroit. I wrote about some similarities between the two storms (1886 & 1974). And now, looking back at the roughly drawn weather maps from 1886, you could also toss in our big blizzard of January 26th, 1978 for good measure. All three storms involved some sort of strong, deep upper low pressure system /500 MB Low/ over the Upper Ohio Valley, most like negatively tilted (which would help explain the backing of the storm to the north-northwest and it’s ability to draw Atlantic, along with Gulf, moisture north and westward into the Great Lakes). Obviously, there was no upper air data way back in 1886 but just by looking at the evolution of this massive and late season snowstorm, an estimate of the upper level system could be drawn (along with fine tuning the available surface maps) from April 4-6th, 1886 7AM EST surface analysis.

APRIL 1886 SCENARIO

By early April 1886, some residents of Southeast Lower Michigan had most likely started on spring outdoor activities. High temperatures frequently pushed well into the 50s from mid March on; the last hint of snow fell nearly two weeks before on the 23rd. No doubt the growing season's new green vegetation was well underway.
 
The weather days proceeding the massive and incredible snowstorm hinted little of what was yet to come; however, there were some subtle signs of trouble brewing. The first was a fresh, brisk northeast wind that blew continuously for nearly three days prior to 6th (generally, an easterly wind along with a falling barometer in this region, foretells of foul weather approaching the area). On the 4th into the 5th, observations including temperatures, wind flow and pressure changes indicated an unseasonably cold high pressure system pushing slowly into Southern Canada and the Northern Great Lakes. This persistent and strengthening northeast wind along with an extended period of steady, then slowly falling barometric pressure, during the three-day period (3rd, 4th and 5th), indicates this high was a fairly strong, resilient and a blocking type of high pressure. A second and more foreboding sign of what was to come was indeed a rapidly falling barometric pressure later on the 5th, which foretold of the major storm approaching Southeast Lower Michigan. The surface observations late on the 5th indicated a low pressure and storm center approaching the Southern Great Lakes from the south or southwest (most likely from Illinois, Indiana or Ohio) as the cold high to the north slowly retreated.
 
The afternoon high on the 5th reached only 38 degrees (about 15 degrees below normal) and then held nearly steady into the evening. Increasing high cirrostratus clouds mingled with the sunset but then, quickly lowered to altostratus and nimbostratus as midnight approached. Light snow began to fly just after midnight and remained light until becoming heavy during the predawn hours. Note the following taken from the actual Detroit Weather Log dated April 6th, 1886:
"Snow began at 12:30 AM and fell light until about 4:30 AM when it began to fall heavy and a tremendous fall of snow continued all day, ending at 9:00 PM. The fall at 7:00 AM was 4.6" and at 3:00 PM was 17.1" and at 11:00 PM, 2.4" making the total of 24.1 inches melted from the snow gauge. The rain gauge was soon snowed full and was practically useless. Total fall of the snow on the level was 24.5 inches. The snow was badly drifted by the heavy gale. The drifts in some places were 12 feet high and the snow in the street was from 10" to 40" inches deep. A heavy north gale set in at 1:45 AM and raged in fury all day reaching 40 miles north at 2:15 PM and continued all the remainder of the day. Its force with the snow was appalling. It blew the snow in fine particles against the face, cutting like a knife."
The synopsis continues with a description of numerous street cars that were abandoned, strewn about and laying in all sorts of positions. As one might expect with the snow falling in April, the snow contained a high water content (2.43") and, therefore, it was very heavy and packed down well. Obviously, wading through the snow to get around on foot was extremely difficult - so much so that it became necessary to use crowbars and ice picks just to clean a path on the street. Maneuvering through, or just moving the snow, was such a monumental chore that even several ton railroad cars were "held prisoner in their houses". On the train tracks, freight cars were immobilized and abandoned across all of Southeast Lower Michigan. Temperatures held in the upper 20s to around 30 through the entire snowfall, with over two feet of snow reported on the ground. The strong northeast to north gale sculptured towering drifts of snow up to 12 feet high across the landscape .The howling wind averaged over 30 mph during the 24 hour period. The lowest barometric pressure reading noted was 29.60 inches at 11:00 AM on the 6th. This reading isn't too terribly deep or severe (the lowest pressure ever observed in Detroit was 28.34 inches during the late January blizzard of 1978), but the pressure was taken only five times daily (7:00 AM, 11:00 AM, 3:00 PM, 7:00 PM and 11:00 PM), so it likely fell lower. As the center of the low pressure drifted further north into the Great Lakes on the 7th, milder air from the south was drawn into Southeast Lower Michigan. The sky cleared as the wind shifted to the south and the temperature rose to 40 degrees, in spite of the very heavy snow cover. In the days following the storm, temperatures managed to push up well into the 50s and even reached the mid 70s by mid month, after all, this was April, right?
 
This storm stands as Detroit's biggest and severest snowstorm and is well summarized by the following quote in the journal and actually would still stand to this day. . .
"The storm was unprecedented in fierceness, snowfall and blockades in the history of the service and the oldest inhabitants can recall nothing to equal it".
 MAP 1 

Note copies of the 120 year old maps below, all under the "War Department" seal at that time. On the morning of the 4th, a large Arctic high pressure system /30.41"/ dominated much of the central and northern part of the US. The air with this high was unseasonably cold for early April with readings in the teens and 20s under it. A station in the western U P in Michigan reported 10 degrees. It was around the 20 degree mark here in Southeast Lower Michigan (normal lows average in the mid 30s for Detroit). Meanwhile, a north/south front over the Ohio Valley appears to have stalled with areas of low pressure riding up the front as a strong, southerly low level jet surges northward ahead of the front.

April 4th, 1886 7AM EST 


MAP 2

Note the series of low pressure systems that ride north-northeast out of the Gulf of Mexico in an upper air pattern that is also showing signs of stalling and deepening as an upper low pressure trough /500MB/ seems to be digging and forming into the Ohio and Tennessee Valleys. Our monster has now shown its face and of all places, far to the southeast over the panhandle of Florida !

April 5th, 1886 7AM EST


MAP 3 

On the morning of the 6th, note the massive surface storm system covering pretty much the eastern half of the country. This is also reminiscent of the our January 26-28th, 1978 storm in its deepening  intensity (though the ’78 storm central pressure bottomed-out deeper), estimated upper air pattern and extent of coverage.  Note the area of heavy snow and blizzard conditions over the Eastern Great Lakes with sky obscured in heavy, driving snow (shaded round circles, not black) as surface troughing extends northward up into Lake Huron as the surface low backs toward the Lakes Region.  This heavy snow scene replicates that of our 1974 storm   with its "conveyor-belt " analogy of moisture drawn from the Atlantic westward into the Eastern Great Lakes . The heaviest snow fell across extreme Southern Ontario, extreme Southeast Lower Michigan and extreme Northwest Ohio with the ’74 storm also and note how that same area is shaded here in  the 1886 storm. An estimated position of the 500 MB low is included (most likely very close, if not identical to the 1978 and 1974 storm) somewhere in the Upper Ohio Valley (Kentucky northward into the Eastern Great Lakes).  Note, the high pressure system has been squeezed northwestward into the classic "horseshoe" shape pattern, also reflective of the 1974 storm.

April 6th 1886, 7AM EST



Snowstorm and Cold Wave of April 5-6th 1982


April of 1982's weather started out normal enough across Southeast Lower Michigan with highs in the mid 50s and decent weather. Along about the 4th, the pattern began to change as an Arctic air mass hibernating across northern Canada began to push southeast in earnest, approaching the northern border states of the US. By the 5th, the high pressure made inroads into the Northern Plains and Great Lakes while a low and storm center began forming over Oklahoma with a trof northeast toward the southern Great Lakes. Temperatures in the Lakes region had plummeted into the teens and 20s that morning of the 5th.

By the morning of the 6th; the low had deepened and moved rapidly east northeast across the northern Ohio Valley pushing a wide area of snow into the cold air over the region. As the storm moved into the Northeast over Pennsylvania that morning; the central pressure had dropped to 992 MB. Across Southeast Michigan, generally 4-8" of snow fell over the area by mid day on of the 6th with temperatures in the lower 20s.  

April 5th 1982 Weather Map 





April 6th 1982 Weather Map




DETROIT LCD 1982



FLINT LCD 1982


April - Detroit Records 1874 - Present
April Normals
(1980-2010)
Maximum Minimum Average Daily
Temperature
Precipitation
Date Max Min Avg Record
High
Lowest
Max
Highest
Min
Record
Low
Highest Lowest Greatest Date
1 53 34 44.0 80/2010 27/1911 57/1967 14/1923 64/2010 24/1923 1.30/1959 1
2 53 35 44.0 83/1963 29/1899 58/1963 17/1881 71/1963 24/1881 1.44/1945 2
3 54 35 44.0 77/1999 30/1954 57/1981 14/1954 66/1981 22/1954 1.06/1980 3
4 54 35 45.0 74/1921 30/1881 54/1928 9/1874 64/1921 20/1874 1.06/2003 4
5 55 36 45.0 79/1921 29/1874 59/1929 16/1881 68/1929 24/1881 2.59/1947 5
6 55 36 46.0 83/1929 27/1982 65/1929 18/1982 74/1929 23/1982 2.41/1886 6
7 56 36 46.0 83/1991 25/1972 63/1929 10/1982 72/1929 21/1982 0.92/2010 7
8 56 37 46.0 79/2001 32/1920 59/2001 11/1982 69/2001 24/1982 0.94/2002


April - Flint Records 1921 - Present
April Normals
(1980-2010)
Maximum Minimum Average Daily
Temperature
Precipitation
Date Max Min Avg Record
High
Lowest
Max
Highest
Min
Record
Low
Highest Lowest Greatest Date
1 51 31 41.0 79/2010 32/1992 56/1967 7/1923 66/2010 21/1923 1.14/1929 1
2 51 31 41.0 82/1963 32/1992 55/2010 16/1924 69/1963 26/1992 1.62/1945 2
3 52 31 42.0 79/1999 28/1954 57/1981 11/1954 67/1999 20/1954 1.03/1926 3
4 52 32 42.0 77/1921 30/1944 56/1928 13/1995 65/1928 0/1999 1.51/2003 4
5 53 32 42.0 80/1921 28/2007 57/1929 13/1995 67/1929 25/2007 2.05/1947 5
6 53 32 43.0 83/1921 27/1982 64/1929 16/1975 73/1929 23/1982 1.73/2010 6
7 54 33 43.0 83/1929 27/1972 60/1991 6/1982 72/1929 18/1982 0.87/2010 7
8 54 33 44.0 76/1991 32/2007 52/1991 8/1982 64/1991 23/1982 0.91/2002 8


April - Saginaw Records 1912 - Present
April Normals
(1980-2010)
Maximum Minimum Average Daily
Temperature
Precipitation
Date Max Min Avg Record
High
Lowest
Max
Highest
Min
Record
Low
Highest Lowest Greatest Date
1 49 31 40.0 81/2010 29/1924 55/1999 8/1923 67/2010 22/1923 1.09/1959 1
2 50 31 41.0 82/2010 30/1936 58/2010 15/1954 70/2010 25/1936 1.17/1945 2
3 50 32 41.0 82/1999 26/1954 56/1981 11/1954 64/1981 19/1954 1.20/1982 3
4 51 32 41.0 76/1921 29/1982 55/1929 15/1954 64/1921 23/1982 1.13/1947 4
5 51 32 42.0 79/1921 28/1982 59/1929 14/1995 68/1929 23/1982 1.45/1917 5
6 52 33 42.0 81/1929 28/1982 66/1929 16/1982 74/1929 22/1982 0.93/1988 6
7 52 33 43.0 81/1991 26/1972 60/1991 12/1982 71/1991 23/1982 0.84/1928 7
8 53 33 43.0 74/1931 29/1914 50/1981 17/1950 59/1929 24/1914 1.19/1991 8


Making weather fun while we all learn,
Bill Deedler -SEMI_WeatherHistorian


1/30/21

Mild and Relatively Boring Winter Thus Far ~ Does Second half of Winter Still Look Busier (or Back-end Loaded)?

It's been a mild and slow winter in regards to snowstorm activity in Southeast Lower Michigan. How were the analogues in regard to the the winter thus far?

From my Outlook:

I look for a normal to above normal temperature winter. This is both for the winter (Dec-Feb) and cold season (Nov-Mar).  With the variability in these type of La Nina's; leaves me with a two-tier temperature forecast - normal to above.

Check

We're good here as temperatures have generally been normal to above normal with a mild winter overall.  The mild weather has actually been an overachiever this winter so far and I expected it to pull back some through February. I underlined overall since that doesn't mean the winter wouldn't be without its cold snaps. In fact; sharply colder air masses were introduced from time to time and more likely the second half of the winter.

 

From the Outlook 

 

In descending order; back-end loaded (roughly late Jan-Mar) winters were favored in regard to colder temperature and/or heavier snowfall.

 

Snowfall prognostication this season is more problematic than precipitation as a whole since storm tracks affecting the region will be north, over Southeast Lower Michigan and south over the Ohio Valley. This leads to snow, rain, rain to snow, snow to rain depending on the system. The unusually strong mid Pacific jet (for a La Nina) will lead systems to bring in milder Pacific/Gulf of Mexico air and thus; mixed precipitation should be a frequent visitor. 

 

In descending order; back-end loaded (roughly late Jan-Mar) winters were favored in regard to colder temperature and/or heavier snowfall.

 

And one more thing; there are enough well below normal (or "snowless") months that showed up in every set of analogues to be concerned about a bust on the snowfall prediction but I'll hang tough with the normal to above normal; for the time being anyway.

 

Check

Snowfall -and actually precipitation on the whole- has been more problematic thus far through January 30th with below normal precipitation and snowfall across the entire region. This is unusual for La Ninas but we still have 2 1/2 months. But then again; in back-end loaded winters, you'd expected that the winter precipitation would be off to a slow start. In keeping with the forecast of a back-end loaded winter; we'd look for a pickup in storms. I think we finally are beginning to see that this last part of January. A two tier seems most suitable in keeping with the normal to above.


So what's been happening meteorological-wise (maps) and what's it looking like the rest of the winter?

 

Well one thing that has evolved the past few months has been the positioning of our La Nina. We started the winter season with a east-central seasonal La Nina (generally normal temps, above normal precipitation) which has evolved to a central-west La Nina (above normal temps and above normal precipitation). Note that the La Nina area considered is a rather narrow area over the Pacific.


Last 3 months stream of the SST (note the colder, dark blue waters migrate west in the La Nina region with time)>>>




Updating the positioning of the La Nina from seasonal winters to mild winters positioning.

 

Updating the Winter and Cold Season Forecast

Temperatures

As stated; this mild winter scenario actually plays into the Winter Outlook. And, I see no reason to drastically change it. In regards to the original temperature forecast departure;  Temperatures - Normal to Above (or -1.0 to +2.5 temp departure); however that range can be raised and tightened to just above normal. 

 

I look for both the entire winter and cold season temperatures to average above normal over Southeast Lower Michigan with a departure of +1.5 to +3.0. Regardless; I'll keep the temperature trend for the remaining part the winter and cold season (through March) with colder and closer to normal. That being said; I see no reason to dismiss the strong westerlies off the Pacific (and one the main reasons we've been so mild) which will be at least part of the equation into spring. This does bring the potential prospect of a more active spring severe weather season than seen the last several years.


Precipitation (Rain and Snow)

One of the memorable forecasters I worked with much of my career used to have a saying "let's give the forecast time to work" and I believe this is one of those times; at the very least the snow part of the precipitation forecast. My original forecast read as follows; 

 

"In descending order; back-end loaded (roughly late Jan-Mar) winters were favored in regard to colder temperature and/or heavier snowfall. Potential for a major snowstorm or two in the snowy La Nina analogues was slightly greater in every month Dec-Mar with a lean toward late season".

Still keeping with that view and original forecast; I look for snowfall to average around normal (departure -5.0 > +5.0) to locally above (departure better than +5.0). for the entire snow season.  

 

Now entire precipitation (rain/freezing rain/sleet/snow) has been problematic also with below normal amounts thus far. This is unusual for a La Nina which generally by trade is wetter than average. 

 

Original forecast for precipitation:

Precipitation - Above

Analogue guidance and computer model guidance from numerous sources overwhelmingly call for a wetter than normal winter.

 

I do feel with the increase in activity we'll make up some precipitation but still I'm inclined to drop the category to below (1.00" or more below normal) to around normal ( or -1.00" > +1.00") for the winter and cold season.

 

Look for forecast on notable storms/trends/patterns to continue on Facebook and here into spring. Keep those snow blowers/shovels handy.

 

BTW ~ Take a look at the Jekyll/Hyde Winter of 1899-1900 as an example of what started out as a boring, slow winter through January that picked up with a vengeance the second half!

https://weatherhistorian.blogspot.com/2011/12/dr-jekyll-mr-hyde-winter-of-1899-1900.html?showComment=1612024152410#c6423598471122289426

 

Making weather fun while we all learn,
Bill Deedler - SEMI_WeatherHistorian


 

12/23/20

The Whitest of Christmases and Other Christmases Past and Chances for a White Christmas - 2020

Frequently during the Christmas Season, meteorologists are asked; Are we going to have white Christmas?  Generally, it is agreed among meteorologists that in order to "officially" have a white Christmas, an average of an inch of snow must cover the ground, but not necessarily have to fall on Christmas. 

At this time /Wednesday/; December 23rd, 2020 chances of a white Christmas across all of Southeast Lower Michigan have improved -slightly- just recently across the region. Up until these past few days, it looked as though another brown, boring looking Christmas would greet Southeast Michiganders. This may still be the case, since the chances this year are still well less than 50%. However; a storm developing upper Midwest will slam a cold front through the area early Christmas Eve day /24th/ bringing abruptly colder weather. Rain is expected ahead of the front but the colder air flooding in behind is expected to change any residual rain over to snow showers Christmas Eve into Christmas Day. Remember; at least an inch of snow is needed on the ground Christmas morning as of 7am est for an official white Christmas. The amount of snow that falls will depend on the residual moisture available that streams up from the south and east on the upper winds - as a wave of low pressure zips up along the front. How far west the system throws back the moisture will determine if we get any system snow. Lake effect snow showers are also possible. Keep your fingers crossed!
 
Last Christmas /2019/ there was no white Christmas to be had and back in /2018/ again around Metro Detroit, there was no white Christmas. In fact; temperatures pushed up into the 40s and 50s in the few days following Christmas. Further north from the Flint area into the Saginaw Valley and Thumb Region however; a inch or two remained on the ground for a white Christmas across that region.

Over the years, extreme Southeast Lower Michigan has averaged about a 50 percent chance for a white Christmas.  Some years it's already on the ground, some years not, some years it melts while other years it falls on the day. However, theoretically, you could actually have nothing on the ground Christmas morning and have a snowstorm dump a foot on the region during the day and still have NO official white Christmas under the standing morning rule. It works the other way too; you could have a several inches on the ground at 7am 12/25 but warmer air and/or rain melts it away by afternoon or evening and still officially have a white Christmas.

Three years ago /2017/; an unexpected white Christmas was had in spades as low pressure system overachieved; developing robustly over the southern Great Lake/northern Ohio Valley. The system developed into a notable little snowstorm falling mainly on Christmas Eve over the southeast area as seen in this map, bringing snow for a picturesque, classic Christmas scene. The only negative - and a notable one - was the lousy driving conditions Christmas Eve into early Christmas Day but with improving conditions later for Christmas dinnertime.


For more on the system from the NWS; see here.

In 2016; even with mild weather with temperatures in the 30s; Southeast Lower Michigan was able to hold on to a white Christmas as the snow (generally 2-5") slowly melted. In fact; the day after Christmas, warm air surged into the region and pushed temperatures into mainly the 50s and took care of any remaining snow! Back in December /2015/; it was a mild and snowless Christmas with a high temperatures near 50. Of course, the year before, /2014/ contained our record breaking warm El Nino December, therefore the hopes for a white Christmas were low anyway. Back on Christmas 2014, the chances for a white Christmas were very similar to 2015 with record setting low amounts of snow for the month (in the top 5 snowless). Officially on 12/25/14 at 7am; no snow was on the ground with a trace of light rain on the date. Only a TRACE of snow had fallen up to that day in December /0.1 for the entire month/.  Most areas over the remainder of Southeast Lower Michigan had a few tenths of snow Christmas eve or Christmas but with less than the amount needed and mild temperatures rising into the upper 30s to around 40...none of the area saw a white Christmas.

More Previous Christmases back to 2004:

In 2013;  even with all the snowfall throughout last winter, officially on 12/25/13 at 7am Detroit Metro Airport had only a TRACE of snow on the ground. Most areas into the remainder of Southeast Lower Michigan had some residual snow and ice on the ground for a white Christmas. Back in 2012, enough snow did fall at Detroit Metro Arpt (an inch of fresh snow Christmas Eve) to make it an official white Christmas was on the ground as of 7AM. The necessary inch or more was also on the ground at both Flint and Saginaw. Ironically the day after Christmas, the best snowstorm of the winter season hit the region...a day late and several inches short for Christmas. A year earlier in 2011, it was a relatively mild Christmas with temperatures in the 40s and no snow on the ground; so no white Christmas. However back in 2010; residents across Southeast Lower Michigan did enjoy a white Christmas with generally 1” to 6” of snow across as temperatures hovered in the 20s. Then further back in 2009, much of the Detroit area south did not have a white Christmas but points north across Flint, Saginaw and the thumb region generally had a 1” to 3” snow cover. Back in 2008, we saw a “sloppy, melting white” Christmas. That white Christmas involved the melting of a heavy snow cover from past snows that accumulated throughout December. The best of the snowstorms came before Christmas on the 19th (with another, lesser intense snow falling on the doorstep of Christmas, 23rd -24th). After, however, the heavy snow cover melted in earnest as milder air overspread the region Christmas Eve right through the 26th. Christmas of 2007, saw temperatures rise into the mid 40s to mid 50s a couple of days prior to Christmas and that, combined with light rain, pretty much took care of any hopes for a white Christmas as then, like the later Christmas of 2008, the  previous heavy snow cover melted (but this time in its entirety before Christmas). Some scattered light snow did return, skirting the landscape on Christmas Eve but most areas around Southeast Lower Michigan still only had a trace of snow for Christmas. At White Lake and Saginaw, however, the official inch of snow to make it a white Christmas was barely attained in 2007.

Going back further to the Christmas of 2006; it was also mild and therefore, there was no white Christmas. In 2005, we just barely squeaked out a white Christmas (at Detroit Metro Airport, anyway) as a mild spell moved in just before Christmas along with rain, melting the snow down from 4” to 1” by Christmas morning. Originally, there had been 8” of snow on the ground on the 15th. The last really scenic (no slop)  with fresh white snow for Christmas occurred in 2004. A snowstorm brought heavy snow (ranging from 8”at Detroit to around 4” in Saginaw and Flint) on the 23rd, which left the region with a nice white cover for Christmas. It was also a cold Christmas also with highs only in the teens and overnight lows below zero. 


Looking over historical weather records of Christmases past since 1900, a wide range of weather conditions were found. While most people would like to believe that Christmas in the Detroit area should be snowy-white and picturesque, more often than not, they're not. Over the past 120 (including 1900) Christmases in Detroit, 56 (or just barely 47%) have been what would be called "white" with an inch or better of snow on the ground. Keep in mind however, these records are for Detroit; farther north in Flint, the chance of a white Christmas jumps to 56 percent, while in Saginaw and the Thumb region it rises to 61 percent.

Based on the Detroit records, the Santa award for the "whitest" (most snow on the ground) and also the second snowiest Christmas (snow falling on Christmas) goes to the Christmas of 1951! Just over a foot /13 inches/ of snow was recorded on ground late Christmas day with 6.2 inches of the snow falling on Christmas. Temperatures held well below freezing (HI-26/LOW-18), so what snow did fall, remained. A close second to the "whitest" Christmas, occurred the Christmas after the big stock market crash in 1929. Eleven and a half inches of snow was measured December 25th, 1929 at Detroit but only three tenths /.3/ fell on Christmas. Recently, the Christmas of 2000 was very white indeed, but as to how much of a white Christmas (snow depths) is where the confusion came in. Let me elaborate, officially at Detroit Metro Airport, just six inches of snow was recorded on the ground at 7AM Christmas Day. However, just about anywhere west/north and in the city of Detroit itself, amounts were considerably higher with generally 8 to at least 15 inches. At the National Weather Service in White Lake, 15 inches was observed on the ground Christmas 2000 morning. No additional snow fell on Christmas Day (nor was anymore really wanted with the surplus already at hand). In any event, for Detroit and surrounding communities, the six inches at Detroit Metro Airport is the official snow depth used for the area.

The snowiest Christmas (most snow falling on Christmas), occurred in 1915 when 6.4 inches fell with a snow depth of seven inches on the ground. The timing of this snowfall was impeccable for Christmas with it actually starting Christmas Eve around sunset. Then, it continued to snow through the night into Christmas day. Actually, even more than the 6.4 inches fell from the entire storm with an additional 1.6 inches falling on Christmas Eve. This gave a snowstorm total of eight inches.  A little light rain did mix with the snow during the forenoon hours of Christmas but with a high temperature of only 33, it did little to mar the "Christmas card" scene. Speaking of "Christmas card" scenes, another heavy wet snowfall blanketed the area just after the turn of the century early on Christmas in 1901. The scene is described in the historical weather books as follows:

    "Night of the 24 - 25 cloudy; moist snow continued,
     heaviest between hours of 1:30 and 4:30 am, ended
     at 6 am. amount of precipitation .62 inches. The
     street cars ran all night to keep the tracks open.
     the snow adhered to trees etc, and made a very
     beautiful scene. Depth of snow on ground at 8 am,
     5.5 inches".

 This "Norman Rockwell Christmas scene" was further enhanced by a heavy coating of frost deposited on the buildings and windows Christmas Eve due to the moisture-laden air. But just like memories of some Christmases past, this majestic Christmas scene quickly faded (melted) during the day as temperatures climbed to 41 degrees, leaving just slush , slop and water. During the Christmases of 2002 and 2003, the weather was similar to both of the white Christmases mentioned above /1901 & 1915/. Here again in 2003, snow started falling Christmas Eve and lasted into at least part of, if not all of Christmas Day. On Christmas Day 2003, snowfalls ranged from at least an inch in the far southeast corner of Lower Michigan to as much as six inches across Detroit's northern suburbs, extending northward across Flint and Saginaw. On Christmas Day of 2002, total snowfall at Detroit Metro Airport was measured at 6.4” inches for both days (Christmas Eve and Christmas) with 3.4” of it falling on Christmas Day, itself. Across all of Southeast Lower Michigan snowfalls generally ranged from four to seven inches. A picture perfect Christmas was created both years with the freshly fallen snow. Like the Christmas snowstorms of 1901 and 1915, the snow Christmas 2002 was also somewhat heavy and wet with high temperatures in the lower 30s and lows only in the mid 20s.

Probably one of the slushiest and sloppiest Christmas Days happened in 1973. What started out as a white Christmas with a heavy 7 inch snow cover, quickly melted to a meager 2” slush mess by nightfall. To add insult to injury, it rained nearly a half an inch during the day.The wettest Christmas on record occurred in 1945 when 1.16 inches of rain fell. The rain actually began Christmas Eve as a light freezing rain and continued freezing until nearly dawn on Christmas, when the temperature pushed above freezing. Until the ice melted, a few tenths of an inch of ice coated everything by Christmas dawn. Needless to say, walking and driving early the Christmas of 1945 was treacherous but Santa was in and out of town in a flash!

Without a doubt, and still in the memories of long term inhabitants of Southeast Lower Michigan, is the warmest Christmas on record, the Christmas of 1982. It was as though the whole area was shipped to Florida for the holiday! The official record high at Detroit was 64 degrees, while Flint did one degree better at 65! These readings are about normal for Tallahassee, Florida! Scenes of shirt sleeved people with shorts running or riding bikes, instead of visions of sugar plums, made the Christmas of 1982 to some Michigan Christmas traditionalist, very hard to take.  This spring-like day was complete with scattered showers and, of all things, thunderstorms! Ironically, the bitterest cold Christmas came just a year later in 1983! Maybe a payback from Mother Nature for the warm weather we were treated to, the Christmas past? The temperature plummeted Christmas eve to a record low of -9 at Detroit and was accompanied by a stiff west wind averaging 25 to 30 mph, creating life threatening wind chills at times of near 40 below zero! Santa certainly brought the North Pole with him the Christmas of 1983, when he made his rounds very early that morning. In addition to the record low Christmas eve, another record low /-10/ was established during the very early morning hours of Christmas.

These Christmases past discussed are more the extreme than the norm across extreme Southeast Lower Michigan. But they do show the variable weather that can occur at Christmas (or any other time for that matter). The "normal" (or average) highs in extreme Southeast Lower Michigan Christmas Day are in the lower 30s, while lows average in the upper teens.

And now, I'd like to wish all who read this a very Merry Christmas and/or Holiday Season and the best in 2021!  I plan on continuing my blog for the new year if the fates allow and look forward in reaching out to more people (and hear their comments and ideas) across the globe.

Making weather fun while we all learn,
Bill Deedler - SEMI_WeatherHistorian