12/26/15

Update 12/27/15 - Look for a New Battle of Air Masses and Jets to Commence at the Week's Open to Top off an Exceptionally Warm December!

 Update - 12/2715 

Freezing Rain and Strong Easterly Winds to Cause Problems in Areas with the Longest Periods of Freezing Rain Monday Afternoon into Early Night

Very little change to original analysis: 
If anything I am even more definite on the freezing rain and associated problems along with the strong gusty easterly winds which will accompany the battle of the systems mentioned below. Look for mixed precipitation to over spread Southeast Lower Michigan from south to north during the afternoon on Monday. Most of the freezing precipitation from this system should be in the form of sleet then freezing rain as a thicker warm wedge of air surges north quickly on the southern jet over the colder, relatively drier Polar air. Freezing rain will become rain during the evening into night from south to north with time.

Strong high pressure in excess of 1040+ MB will but-up against the deep but slowly weakening low pressure over the middle Mississippi and cause a decent period of freezing rain. Most of the region, especially away from the Southeast corner has the biggest risk of ice build-ups up to around .2" with some "hold-out freezing or below temperature areas" from Detroit suburbs northward of around .2" - to as much as .4 - .5" of ice possible. This along with strong easterly winds of 20 to 30 mph with gusts to near 40 will bring the risk of icy roads and falling weaker tree limbs and power outages where conditions hold on the longest before the changeover. Temperatures hovering from upper 20s to lower 30s early in the event will gradually rise into the lower to mid 30s by evening.


Original Post 12/26/15

Earlier in the month, I sent out a blog about how the second half of the month would see a resurgence of the battle of the two distinct air masses that would dominate our winter weather. I stated it would not all be about El Nino this winter and from time to time, an impressive battle would brew between the Pacific energized El Nino jet stream and the Polar/Arctic jet stream. All indications are a new battle will commence in style early this upcoming week but first; lets look at this exceptional December...

Thus far this December has held true to form for an El Nino December with unseasonably warm weather, so much so, it should be at the top of the warmest Decembers on record at all three sites; Detroit, Flint and Saginaw! Even though cooler weather is expected this upcoming week; it shouldn't be enough to knock Detroit's standing out of first place while both Flint and Saginaw are more than safe.

In our analogue section for this winter; December had the best chance at being above normal and notably so - but admittedly, not ranking in first place. In the December analogues, there were three distinct very mild Decembers; 1877 - 38.1, 1940 - 35.6 and 1982 - 37.3. Overall; early in the game, the Winter of 1940-41 seemed to be the best analogue fit for the entire winter but with the two very strong El Nino's of 1982-83 and 1997-98 contending for very close seconds. In winter of '97-98, which arguably has had a very good showing for similar Pacific "goings-on" this past summer into early winter, its December locally though was not all warm as this years - nor the other three mentioned. December of '97 had an average temperature of just 32.2 (didn't even make the top 20 warmest Decembers). The exceptional warmth occurred later in that Winter of '97-98.

Top 20 Coldest/Warmest Decembers in Southeast Lower Michigan
Rank Detroit Area* Flint Bishop** Saginaw Area***
Coldest Warmest Coldest Warmest Coldest Warmest
Temp Year Temp Year Temp Year Temp Year Temp Year Temp Year
1 17.8 1876 42.2 2015 16.1 1989 42.42015 16.2 1989 40.62015
2 18.0 1989 40.6 1881 16.6 2000 37.2 1982 17.2 2000 35.3 1923
3 19.2 2000 39.3 1889 17.4 1976 36.8 1923 18.8 1983 34.5 1982

The second half of December has not all been tranquil and nice as our former air mass battle that occurred last week; brought an outbreak of severe weather over the Midwest and South - and a very rare tornado in Southeast Lower Michigan near the border of Canton and Plymouth. Never had a tornado been reported in Michigan during the month of December - a very rare bird indeed! This severe weather outbreak across the country was preceded by record warmth over the Midwest and East. Detroit broke an very old record high from 1893 /56/ with a 58 on the 23rd...while Flint topped the 60 mark with a 61 for both the 23rd/24th. Its previous records occurred in 1982 (an analogue) with 55 and 56 respectively. Other warm records occurred during the month and can be found here.

Now on to our new battle...

This time around an intense low pressure center over Texas expected to produce a news worthy blizzard over portions of eastern New Mexico and western Texas (see map) overnight into Sunday.

Dawn Sunday 12/2715



The deep low will track north northeast aided by a strong jet streak over the south which came aboard from the Pacific. Note the 135K jet feeding into the storm at 250 MB at that time.



As the low approaches, the cold dome of high pressure will glide across Southern Canada. Timing of these systems, along with cold air in place after being advected in Sunday by the high pressure will determine what sort of mess  (snow, sleet and freezing rain) will be on the docket for Monday and Monday evening. in addition; ground temperatures are unusually warm for late December which only complicates matters. At this time, the risk of mixed precipitation will be the greatest at the onset of the approach of the low later Monday.

The surge of moisture remains robust even with the cold, dry air and subsidence advected in by the 1040+ high pressure - a fairly impressive strength. And thus, our battle commences locally between the deep low moving north northeast toward
western Illinois/eastern Iowa and large Polar high to our northeast in Canada. this will also create strong easterly winds across the region. One thing noted at this time is the remarkable agreement with various models on positioning and affects of the aforementioned systems.

It's interesting and passing to note, a few days ago this storm was progged to move more northeast into the Ohio Valley, which would have put Southeast Lower Michigan in heavy snow and/or a possible ice storm. That solution remains more transitory at this time as the air masses and jets have become bettered sampled. That is not to say Southeast Lower Michigan is out of the woods for mixed precipitation and possible icing, just not extent that was telegraphed a few days ago. This system appears to have enough wind at its sail to surge far enough northward to drag milder air back over the region.

At this time; the best chance for mixed precipitation runs from Monday afternoon into mid evening; the map below /Mon, early eve/ shows the classic mixed precipitation of snow, sleet and freezing rain set up when the clash of air masses takes hold over a the region. Picture warm, moist air being pushed northward aloft while colder, around freezing or below air remains trapped below near the ground. If a stand-off develops, an extended period of mixed precipitation, including destructive freezing rain as it accumulates on surfaces. The warm air is expected to win the battle and therefore, an extended period of freezing rain is not anticipated. However, the situation will be watched as new guidance and actual events unfold.



 
In any event, look for a mix of precipitation to move into the region later Monday into Monday evening with icing to affect mainly "exposed in the air items" as opposed to warmer ground surface areas, including roadways. Temperatures should hover in the lower to mid 30s for a time until the low pressure and jet streak has enough "umph" to push aside the cold residual affects of the high pressure. Any mixed precipitation accumulation is expected to be limited and transitory over extreme Southeast Lower Michigan with a slower change over time as one moves into Detroit's northern suburbs and points north and northeast toward Saginaw and the Thumb. At this time I look for ice to accumulate any where from a trace over the extreme southern regions to up around a 1/4" possible further north before any changeover to rain.

Various model solutions for Mon eve:











 Any important updates will be forthcoming for this holiday period.

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



12/19/15

Ghost of Christmases Past; The Whitest of Christmases and Other Christmases Past - 2015 version

The Whitest of Christmases and Other Christmases Past 
 
By: William R Deedler; Southeast Michigan Weather Historian
Date: 4PM Saturday Dec 19th, 2015
 

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 /19th/, at this time it is highly unlikely for a white Christmas across Southeast Lower Michigan even though temperatures should drop some for Christmas after a cold front pushes through, reading should still be above normal into the 40s with no or little precipitation. In fact, at this time the weather looks very conducive for holiday travel across Southeast Lower Michigan with tranquil weather.

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.  Now officially there must be an inch of snow on the ground Christmas MORNING at 7am. That is how the official "white Christmases" have been tallied in the past. So 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 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.

Last year's December /2014/ and Christmas time was very similar to this year's with record setting low amounts of snow for the month (in the top 5 snowless) and the chances for a white Christmas last year, also being almost non-existent. Even with the normal snowfall throughout last winter, officially on 12/25/14 at 7am; Detroit Metro Airport only a TRACE of snow that fell for the month with nothing on Christmas nor on the ground at Detroit Metro Airport. Most areas into the remainder of Southeast Lower Michigan had a few tenths 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. 

Previous recent Christmases:

In 2013even 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 115 (including 1900) Christmases in Detroit, 54 (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 2016! 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

12/9/15

Will the Battle Reignite?

 Will Second half of December Resemble the Second half of November?

Back in mid November; El Nino energized central Pacific Jet along with the normal dive of the late autumn Polar Jet created a stormy battle across the country as the two patterns competed for dominance. It now appears this will again commence during the second half of December as both air masses and associated jets begin to carve out deeper upper level troughs over the West (were the initial battle will commence) and push northeast in time across the country into the Great Lakes. As time wears on, heights drop across the country and the Polar jet/air mixing with the Pacific Jet becomes more established, basically from the US Southwest to the Northeast. Of course this is a favored storm tracked for storm lovers as the churning of jets and air masses brew storms. This track of storms will bring rain, snow and likely difficult driving conditions depending on each particular storm and available cold, warmth and moisture - and where. Early in the battle anyway, it appears the systems will bring mainly rain to Southeast Lower Michigan but as colder air filters in behind systems, this would set up the region for snow.

As an example of the jet configurations the GFS model 18z 12/09/2015 is projecting, it is easy to see the strong El Nino Pacific enhanced jet gradually becoming mixed with the lowering heights and colder air from the polar region. Note; not only the jet express from the Pacific but also toward the end of the period, the large ridge block developing over Alaska. I would initially take this strong block with a moderate grain of doubt this far out but examining the upper pattern daily for weeks now, suggests at least transitory ridging developing with time toward Christmas in that region as heights lower across the lower 48. One thing that has been trending toward the negative is both the NAO/AO with time which reflects the lower heights..




Check out the loop of the 250MB Jet 18z GFS 12/09/20115 (click on arrow). Of course this will dance around with exact features and storm tracks the next couple of weeks but we are mainly interested in the trend, which shows a definte lowering of heights with time as the NAO/AO appraoch negative territory. How much they move into negative territory will strongly dictate the amount of cold air delivered into the country. Anorther factor I'm watching is the EPO which so far remains positive.



In any event; the second half of December is beginning to look very active and changeable - something holiday travelers will want to watch, especially after mid month.

I'll return with a new blog when specifics become more apparent and affecting the region.

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