2/29/16

* Storm Snowfall Totals - 1 PM 3/2/16 - New Week, New Storm - March Comes in With the Bite of the Lion!

STORM SNOWFALL TOTALS-

http://www.weather.gov/dtx/march12016winterstorm



-Update 1 PM
Latest suite of this morning's models continue to advertize with more vigor the ongoing band of snow across portions of Southeast and East-Central Lower Michigan. A deepening low over Ohio this afternoon and evening; along with strong convergence will dump moderate to heavy snow over the aforementioned area below. Maximum snowfalls of 8 - 12" are now likely over the area along and north of a line from around Lansing to just north of Pontiac and Port Huron north into Saginaw and the Thumb Region. Traveling in this region will become extremely difficult as the afternoon unfolds.

The remainder of the region remains unchanged.

-Update Midnight

Latest upper air and model runs are intimating a band of slightly heavier snow across portions of Southeast Lower Michigan's central and northern areas. A band of 4 - 7" with isolated spots of around 8" are possible through Tuesday in the area along and north of a line from Lansing to Pontiac to Mt Clemens. The central portion of this region seems to be the best primed for the heavier band.

Otherwise; no change in the current forecast with generally 3 - 6" of snow likely over the remainder of Southeast Lower Michigan.

The aforementioned low pressure system will gain strength as she moves across the extreme northern Ohio Valley during the day and into Ohio by this evening. A snow band will streak out north and ahead of the low during the early morning hours as the low flings moisture up across the above region. Look for this area to fill in across all of Southeast Lower Michigan as the day progresses.

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Original blog 2/29/16


The projected busy end of the winter continues to unfold across Southeast Lower Michigan as another low pressure and storm center takes aim on the Lower Great Lakes and Northern Ohio Valley.

Our latest storm will take a similar path as last weeks (but with a bit more of an east trajectory) and will contain less snow than the maximum amounts measured last week of 8-12". Still, the low pressure is expected to deepen somewhat as the center moves across the Northern Ohio Valley. As with last weeks system; there is a risk of mixed precipitation across the far southeast corner of Lower Michigan but more snow should accumulate over last week's in the far southeast corner.

Generally across the entire region; 3 - 6" of snow is likely with this system with areas a little less or more depending on the exact track and ground temperatures. Look for the snow to advance across Southeast Lower Michigan mainly during forenoon hours (around sunrise and noon) of Tuesday with the best of the snowfall occurring during the late morning into the afternoon. Temperatures should hover in the mid to upper 20s north to lower 30s extreme south as the system moves across the region. Therefore; temperatures on average will be colder by a few degrees than last weeks system.

Because of the warm temperatures over the weekend; snowfall over the area should be somewhat sloppy and slippery on roadways during the daylight; especially those heavily traveled and or treated. However; on the flip side; snowfall over secondary/side-streets and rural areas will be slippery and greasy because of the mild roadways causing a melting/freezing process. The evening rush hour will be the most affected by the system and with a little luck; the morning rush hour should be least affected, especially further east areas.

The rest of the week should be on the cold side so the snow should stick around awhile; at least as much as can be expected with the early March sunshine.



Any notable changes as the system gets bettered sampled by this evening's radiosonde data, look for updates.

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


2/23/16

2/24/16 - Update - Winter Storm Affecting the Lower Great Lakes Heavy Snow and Rain; Critical Temperatures Creating Dividing Line For Snow Accumulations

2/25/16
Storm Smmary and Snowfall totals:

http://www.weather.gov/dtx/February24-25SnowfallSummay


Update 2/24/16 Noon
Little change in overall forecast area delineations for snow but with a few inch adjustments in overall final snowfalls as storm appears to be tracking a bit further east. Latest noon surface observations/trough position due to pressure falls indicate a track more toward central (rather than west central Ohio) and then subsequently northeast Ohio.


Updated Forecast Through Thursday

Snowfalls of 2 - 4" are likely across the mildest areas of Southeast Michigan over the Southeast corner Lower Michigan with mixed rain and snow including the east and Southeast portions of Metro Detroit; most of which will fall overnight Wednesday into Thursday. The least amounts of snow being near the Ohio border. 

Areas away from the Southeast corner;  including much of the western suburban Metro Detroit areas, west into Ann Arbor and north into Pontiac and Port Huron are likely to see 4" - 8" of the snow (generally highest amounts over western and northwest areas).  Snowfalls further west, northwest and north toward South - Central Michigan and up into Flint, Saginaw and Michigan's Thumb can expect general snowfalls of 7"- 11" (local areas of higher snow amounts are possible especially downwind of Lake Huron) with all precipitation, snow. 

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Previous blog 2/23/16

Latest morning guidance continues to advance major storm toward Lower Great Lakes and Southeast Lower Michigan. The biggest problem of forecasting precipitation type continues to be where the rain/snow line will set up across Southeast Lower Michigan during the heaviest precipitation from the storm. All areas will still see snow on the backside of the system later Wednesday night and Thursday. The dilemma comes in during the first half of the period when the heaviest precipitation should moves into the region during the day Wednesday into Wednesday evening. This itself (daytime arrival in late February) suggests the more likelihood of rain or rain mixed with snow over extreme Southeast Lower Michigan as precipitation advances into the region during the daylight, when the air mass will be naturally be a bit warmer. Another problem that comes is how close the low pressure gets to Southeast Lower Michigan. The closer it gets, the more likely slightly warmer air is pushed northward into the region. Models continue to vary somewhat on the air column /profile/ above the ground over Southeast Lower Michigan and its temperature distribution.

However; a nudge to the northwest has been noted in general which will affect snowfall amounts over the region during Wednesday and Wednesday evening. Note the model maps..


GFS

 Top map above is Wednesday early afternoon, the second is Wednesday evening.

NAM



The above map is Wednesday Evening

EURO


The above map, the European also has the R/S line (light blue) advancing slowly northward into Southeast Lower Michigan as the low tracks northeast across northern Ohio (see track above).

Add to this; it must be remembered that the column of air will be cooling aloft later toward the evening as colder air in the higher levels of the atmosphere advances across the same region;while the ground temperatures are steady to slowly falling

All this in mind; I'm pushing the better snow amounts away to the northwest from the Southeast corner and Detroit Metro area.

Previous Forecast

At this early juncture; snowfalls of 3 - 5" are likely across the mildest areas of Southeast Michigan over the Southeast corner Lower Michigan. Areas away from the Southeast corner; which includes much of the Metro Detroit Area west into Ann Arbor, Brighton, Howell, Flint and areas west and north where general snowfalls of 5"- 9" (highest amounts will be further away from the Southeast Lower Michigan corner where isolated higher snow amounts are possible). Besides of snow of course, will be the very strong northeast winds of 20 - 30 mph with gusts near 40 will cause problems with power and tree limbs along with the heavy snow.

 

Updated Forecast

Snowfalls of 1 - 3" are likely across the mildest areas of Southeast Michigan over the Southeast corner Lower Michigan including the east and Southeast portions of Metro Detroit; most of which will fall overnight Wednesday into Thursday. The least amounts of snow being near the Ohio border. Areas away from the Southeast corner;  including much of the western suburban Metro Detroit areas, west into Ann Arbor and north into Pontiac and Port Huron are likely to see 3" - 7" with most of the snow falling later Wednesday afternoon into Thursday.  Snowfalls further west, northwest and north toward South - Central Michigan and up into Flint, Saginaw and Michigan's Thumb region remains unchanged where general snowfalls of 6"- 9" (where areas of higher snow amounts are possible) with most if not all precipitation, snow. 

 

Besides of rain and snow of course, will be the very strong northeast winds of 20 - 30 mph with gusts near 35 will cause problems with power and tree limbs along with the heavy snow in areas indicated.

Keep in mind that all guidance and logic points to a rather sharp line of accumulation snow to rainy wet areas.  This continues to be a changing situation and therefore updates will be sent; whether or not the snowfall amounts change

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 Previous blog

As mentioned yesterday, tomorrow we'll update the current expected major storm with the latest 12z guidance (Feb 23rd, 2016 -7AM EST) and adjust expected storm affects on the region by mid afternoon.

Below; we'll compare our present day storm with the storm that started it all for me as far as a fascination with snowstorms and thus, increased my desire to study weather. It ironically, occurred on the same date as our expected storm this week - The anniversary of Snowstorm of February 24-25th 1965! Just passing it's 50th anniversary last year, I remember the day well.

The best part, besides obviously the snowstorm ,was being off two days from school. In fact; those two days, February 25-26th 1965 were the only two days back in the old days (well before kids started to get off of school for anything weather related) that I ever was let off of school in grade or high school. I went to a Catholic grade school in northwest Detroit /St. Monica/ and high school /Bishop Borgess/ therefore; getting let out of school because of a snowstorm was rarely heard of anyway.

Anyway; on the morning of the 25th, which my memory recollected was a Thursday (and checking back on my computer verifies this) we were awaken to a heavy snow cover along with drifts I had never seen in the Detroit metro area growing up my 10 years previously. Snowfalls varied across the metro Detroit area but most were with a few inches of a foot. Officially in the far northwest part of Detroit, I measured a foot in several places around the house. Besides the heavy snow cover were the moderately strong, gusty winds which built drifts in the city lots/yards to up to 2 1/2-3 feet in places from my memory.

Let's take a look at new items from that memorable day for many...


SNOWSTORM Feb 24-25TH 1965

There are close similarities in the expected modeled storm this week, 51 years later and the actual Snowstorm of February 24-25, 1965.  Besides the obvious dates; ironically the Storm of '65 in its infancy was also a Gulf Low that developed in the same region as the models are predicting this weeks storm development on Wednesday, the 24th. The  storm development is expected down over the Louisiana/Gulf Region. The upper air appears very similar as does the surface low development and movement. One major difference with this week's weather is the milder temperatures expected ahead of/and during the storm which could obviously cut down on snowfall amounts. This especially will be noted where rain or rain mixed with snow falls

From the Toledo Blade, which gives a fairly thorough synopsis of the Feb 24-25th, 1965 storm...

"This could be called the "Midwest/Ohio Valley Snowstorm of 1965" 7.8" at Toledo, 11" at Detroit, 12.9" at Flint, 9" at Jackson MI, 10.3 " at Lansing, 17.9" at Saginaw, 7.5" at Grand Rapids, 12.7" at South Bend, 7.5" at Fort Wayne, 12.5" at Indianapolis, 10" at Chicago, 7.6" at Peru IN, 9.8" at Lafayette, 8.4" at Evansville, 6" Bowling Green KY, 3" Cincinnati, 7" Paducah."

"The surface low tracked from Louisiana to Cincinnati to north of Pittsburgh to north of Montreal. The rain-snow line was near a Toledo to Indianapolis line. It was a strongly deepening low from around 1002mb to 983mb in 24 hours, to 976mb in 30 hours.

It was 12 degrees and windy at Toledo after the storm ended. It is interesting to note this situation was along with a strong Greenland block but the upper level flow off the East Coast did not allow a coastal low to develop. This was a definite problem for transportation in Toledo, according to the Toledo Blade. It was also the largest single-storm total snowstorm at Toledo in the previous 14 years, according to the Toledo Blade."

500 MB Heights 



Surface


Detroit after the '65 Storm

 

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



_____________________________________________________________________________
Previous blog 2/22/16

Major Late Winter Storm Likely to Impact Southeast Lower Michigan With Strong Winds and Heavy Snow!

After several days on various tracks of the possible impending storm, better sampling of the atmosphere is indicating very strong dynamic system with copious moisture will affect the region. A more definitive track is beginning to emerge even though this system is still a good few days away, it appears all models have a better handle on the outcome now.

Still; the exact track of the storm/low will have a major impact of snowfalls across Southeast Lower Michigan and Lower Michigan, as a whole. Along with the crucial track of the low determining snowfalls will be the existing relatively mild temperatures ahead and during the early stages of the storm on Wednesday when rain, mixed rain and snow is expected. All precipitation is expected to change over to all snow by Wednesday night into Thursday morning.

At this early juncture; snowfalls of 3 - 5" are likely across the mildest areas of Southeast Michigan over the Southeast corner Lower Michigan. Areas away from the Southeast corner; which includes much of the Metro Detroit Area west into Ann Arbor, Brighton, Howell, Flint and areas west and north where general snowfalls of 5"- 9" (highest amounts will be further away from the Southeast Lower Michigan corner where isolated higher snow amounts are possible). Besides of snow of course, will be the very strong northeast winds of 20 - 30 mph with gusts near 40 will cause problems with power and tree limbs along with the heavy snow.

This storm has more of a Gulf Low characteristic which generally contain the best moisture access along with a very strong southern jet streak in the upper atmosphere; classic of the deeper, more intense low pressure. It has been awhile since a true Gulf Low has affected the Lower Great Lakes and in fact, much of the country as most storms on the East Coast this winter have been Coastal Storm development with impulses originating from the West or Northwest. We saw numerous cousins of the Gulf Low over the Texas/Oklahoma/Arkansas region during the severe winter of 2013-14 and late last winter.



All indication are the storm will take shape over Southeast Texas/Louisianan/Gulf of Mexico as an intense subtropical jet streak containing impressive winds of 120-130 knots at the higher levels of the atmosphere /250-300 MB, or 33Kft-35Kft/ and strong horizontal and vertical velocities. It's certainly without question; the most impressive low pressure/storm center projected to affect the region in this benign winter season, anyway!

Next will take a look at specific upper winds and storm tracks of the 12Z/022316 models along with and a little Weather Historian history.  Look for updates during the next few days on this impending storm!

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

2/22/16

This Week's Projected Snowstorm Lands on the Anniversary of the Snowstorm of '65 - February 25th, 1965 - A Storm That Started My Facination With Snowstorms

As mentioned yesterday, tomorrow we'll update the current expected major storm with the latest 12z guidance (Feb 23rd, 2016 -7AM EST) and adjust expected storm affects on the region by mid afternoon.

Below; we'll compare our present day storm with the storm that started it all for me as far as a fascination with snowstorms and thus, increased my desire to study weather. It ironically, occurred on the same date as our expected storm this week - The anniversary of Snowstorm of February 24-25th 1965! Just passing it's 50th anniversary last year, I remember the day well.

The best part, besides obviously the snowstorm ,was being off two days from school. In fact; those two days, February 25-26th 1965 were the only two days back in the old days (well before kids started to get off of school for anything weather related) that I ever was let off of school in grade or high school. I went to a Catholic grade school in northwest Detroit /St. Monica/ and high school /Bishop Borgess/ therefore; getting let out of school because of a snowstorm was rarely heard of anyway.

Anyway; on the morning of the 25th, which my memory recollected was a Thursday (and checking back on my computer verifies this) we were awaken to a heavy snow cover along with drifts I had never seen in the Detroit metro area growing up my 10 years previously. Snowfalls varied across the metro Detroit area but most were with a few inches of a foot. Officially in the far northwest part of Detroit, I measured a foot in several places around the house. Besides the heavy snow cover were the moderately strong, gusty winds which built drifts in the city lots/yards to up to 2 1/2-3 feet in places from my memory.

Let's take a look at new items from that memorable day for many...


SNOWSTORM Feb 24-25TH 1965

There are close similarities in the expected modeled storm this week, 51 years later and the actual Snowstorm of February 24-25, 1965.  Besides the obvious dates; ironically the Storm of '65 in its infancy was also a Gulf Low that developed in the same region as the models are predicting this weeks storm development on Wednesday, the 24th. The  storm development is expected down over the Louisiana/Gulf Region. The upper air appears very similar as does the surface low development and movement. One major difference with this week's weather is the milder temperatures expected ahead of/and during the storm which could obviously cut down on snowfall amounts. This especially will be noted where rain or rain mixed with snow falls

From the Toledo Blade, which gives a fairly thorough synopsis of the Feb 24-25th, 1965 storm...

"This could be called the "Midwest/Ohio Valley Snowstorm of 1965" 7.8" at Toledo, 11" at Detroit, 12.9" at Flint, 9" at Jackson MI, 10.3 " at Lansing, 17.9" at Saginaw, 7.5" at Grand Rapids, 12.7" at South Bend, 7.5" at Fort Wayne, 12.5" at Indianapolis, 10" at Chicago, 7.6" at Peru IN, 9.8" at Lafayette, 8.4" at Evansville, 6" Bowling Green KY, 3" Cincinnati, 7" Paducah."

"The surface low tracked from Louisiana to Cincinnati to north of Pittsburgh to north of Montreal. The rain-snow line was near a Toledo to Indianapolis line. It was a strongly deepening low from around 1002mb to 983mb in 24 hours, to 976mb in 30 hours.

It was 12 degrees and windy at Toledo after the storm ended. It is interesting to note this situation was along with a strong Greenland block but the upper level flow off the East Coast did not allow a coastal low to develop. This was a definite problem for transportation in Toledo, according to the Toledo Blade. It was also the largest single-storm total snowstorm at Toledo in the previous 14 years, according to the Toledo Blade."

500 MB Heights 



Surface


Detroit after the '65 Storm

 

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



_____________________________________________________________________________
Previous blog 2/22/16

Major Late Winter Storm Likely to Impact Southeast Lower Michigan With Strong Winds and Heavy Snow!

After several days on various tracks of the possible impending storm, better sampling of the atmosphere is indicating very strong dynamic system with copious moisture will affect the region. A more definitive track is beginning to emerge even though this system is still a good few days away, it appears all models have a better handle on the outcome now.

Still; the exact track of the storm/low will have a major impact of snowfalls across Southeast Lower Michigan and Lower Michigan, as a whole. Along with the crucial track of the low determining snowfalls will be the existing relatively mild temperatures ahead and during the early stages of the storm on Wednesday when rain, mixed rain and snow is expected. All precipitation is expected to change over to all snow by Wednesday night into Thursday morning.

At this early juncture; snowfalls of 3 - 5" are likely across the mildest areas of Southeast Michigan over the Southeast corner Lower Michigan. Areas away from the Southeast corner; which includes much of the Metro Detroit Area west into Ann Arbor, Brighton, Howell, Flint and areas west and north where general snowfalls of 5"- 9" (highest amounts will be further away from the Southeast Lower Michigan corner where isolated higher snow amounts are possible). Besides of snow of course, will be the very strong northeast winds of 20 - 30 mph with gusts near 40 will cause problems with power and tree limbs along with the heavy snow.

This storm has more of a Gulf Low characteristic which generally contain the best moisture access along with a very strong southern jet streak in the upper atmosphere; classic of the deeper, more intense low pressure. It has been awhile since a true Gulf Low has affected the Lower Great Lakes and in fact, much of the country as most storms on the East Coast this winter have been Coastal Storm development with impulses originating from the West or Northwest. We saw numerous cousins of the Gulf Low over the Texas/Oklahoma/Arkansas region during the severe winter of 2013-14 and late last winter.



All indication are the storm will take shape over Southeast Texas/Louisianan/Gulf of Mexico as an intense subtropical jet streak containing impressive winds of 120-130 knots at the higher levels of the atmosphere /250-300 MB, or 33Kft-35Kft/ and strong horizontal and vertical velocities. It's certainly without question; the most impressive low pressure/storm center projected to affect the region in this benign winter season, anyway!

Next will take a look at specific upper winds and storm tracks of the 12Z/022316 models along with and a little Weather Historian history.  Look for updates during the next few days on this impending storm!

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

Major Late Winter Storm Likely to Impact Southeast Lower Michigan With Strong Winds and Heavy Snow!

After several days on various tracks of the possible impending storm, better sampling of the atmosphere is indicating very strong dynamic system with copious moisture will affect the region. A more definitive track is beginning to emerge even though this system is still a good few days away, it appears all models have a better handle on the outcome now.

Still; the exact track of the storm/low will have a major impact of snowfalls across Southeast Lower Michigan and Lower Michigan, as a whole. Along with the crucial track of the low determining snowfalls will be the existing relatively mild temperatures ahead and during the early stages of the storm on Wednesday when rain, mixed rain and snow is expected. All precipitation is expected to change over to all snow by Wednesday night into Thursday morning.

At this early juncture; snowfalls of 3 - 5" are likely across the mildest areas of Southeast Michigan over the Southeast corner Lower Michigan. Areas away from the Southeast corner; which includes much of the Metro Detroit Area west into Ann Arbor, Brighton, Howell, Flint and areas west and north where general snowfalls of 5"- 9" (highest amounts will be further away from the Southeast Lower Michigan corner where isolated higher snow amounts are possible). Besides of snow of course, will be the very strong northeast winds of 20 - 30 mph with gusts near 40 will cause problems with power and tree limbs along with the heavy snow.

This storm has more of a Gulf Low characteristic which generally contain the best moisture access along with a very strong southern jet streak in the upper atmosphere; classic of the deeper, more intense low pressure. It has been awhile since a true Gulf Low has affected the Lower Great Lakes and in fact, much of the country as most storms on the East Coast this winter have been Coastal Storm development with impulses originating from the West or Northwest. We saw numerous cousins of the Gulf Low over the Texas/Oklahoma/Arkansas region during the severe winter of 2013-14 and late last winter.




All indication are the storm will take shape over Southeast Texas/Louisianan/Gulf of Mexico as an intense subtropical jet streak containing impressive winds of 120-130 knots at the higher levels of the atmosphere /250-300 MB, or 33Kft-35Kft/ and strong horizontal and vertical velocities. It's certainly without question; the most impressive low pressure/storm center projected to affect the region in this benign winter season, anyway!

Next will take a look at specific upper winds and storm tracks of the 12Z/022316 models along with and a little Weather Historian history.  Look for updates during the next few days on this impending storm!

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





2/8/16

Cuddle Alert! Coldest Air of the Season Likely This Valentine's Weekend! And, What About Longer Term into March?

The more mixed pattern forecast and discussed recently has come to fruition the past month or so with a "sometimes mild, sometimes cold" pattern pattern taking hold. The biased however, continues to be on the mild side as El Nino continues to greatly influence our winter. However; the second player discussed for the winter, the Polar Vortex has been intermittently sticking its cold beak into our weather regime since January and thus, has been tempering somewhat our as an extraordinary mild winter! This resulted in January actually averaging just slightly above normal (as compared to December's double digit above normal departures) with colder air masses making an appearance. Actually; this month's pattern looks to be very similar to January's through mid month with a very mild week opening the month; only to be replaced by a cold one by mid month - and this is about to commence again.



A deepening low pressure system in formation over the Eastern Great Lakes into mid week will begin to draw down colder, Arctic air into the region by mid week with the coldest of the air arriving this Valentine's Weekend. Temperatures this weekend are anticipated to plummet from around the 50 degrees we felt this past weekend /Sunday/ to morning lows of single digits; above and below zero by Valentine's morning, this upcoming Sunday. Indeed, this would be the coldest air of this mild winter's run thus far. The colder air will be accompanied by light snow and snowshowers as moisture is fed into the system from the east and Great Lakes. The cold, cyclonic flow will aid in pulling down the much colder air that is in place over eastern Canada. The best snowfall amounts will naturally be downwind of Lakes Superior, Michigan and Huron where several inches could accumulate. In and around Southeast Lower Michigan away from Lake Huron and the Thumb Region; I'd look for generally one to three inches depending location through mid week. This expected snow cover will have more of an impact on overnight lows come this weekend, with the coldest mornings occurring in conjunction with snow cover, clearing skies and lighter winds.

Note the low temperatures projected for the coming weekend; granted these could change some but our past cold weather in mid January could see some competition this weekend. After; look for milder weather to again return to the region.




Rest of February into March 

Of interest to meteorological buffs; a very strong stratospheric warming has taken place over the Arctic as unseasonably warm air surged north into the highest of altitudes of the stratosphere. This pattern is generally associated with a dislodgement of the Polar Vortex normally over or close to that region. Latest indications are the Polar Vortex in in the process of splitting (as the GFS has picked up on) with one heading toward southeast Canada while the other heads over to Europe or further east.

"Major Sudden Stratospheric Warming"

These occurs when the westerly winds at 60N and 10hPa (geopotential height) reverse, i.e. become easterly. A complete disruption of the polar vortex is observed and the vortex will either be split into daughter vortices, or displaced from its normal location over the pole.

Longer Term
 
For a longer term through the rest of February and into March; note the following discussion by Atmosphere and Environmental Research /AER/.

AER scientists provide researchers and enthusiasts real-time insights on one of North America’s and Europe’s leading drivers for extreme and persistent temperature patterns. Author Judah Cohen, Ph.D., works at Atmospheric and Environmental Research (AER), a division of Verisk Analytics.

"Longer term we continue to expect that variability in the polar vortex (PV) to strongly influence Northern Hemisphere (NH) weather patterns.  Our confidence continues that a troposphere-stratosphere-troposphere coupling event (T-S-T) is underway (Cohen et al. J. Clim., 20, 5335, 2007), which is resulting in a sudden stratospheric warming (SSW) and is reversing the AO from positive to negative in the stratosphere.   The T-S-T should culminate with the negative phase of the AO favored in the troposphere from after the SSW peak through the end of winter.

General temperature trends across the NH should mirror trends in the AO.  As we have discussed many times previously, while the vertical energy transfer is active, the positive phase of the AO is favored in the troposphere.  The atmospheric energy transfer is now predicted by the weather models to be active through mid-February and even to achieve record values next week.  The record strong energy transfer is also predicted to bring record warm temperatures to the polar stratosphere next week making for an impressive SSW.  This SSW has been evolving for an unusually long time but is likely to peak with the record warm polar stratospheric temperatures next week.  The strengthening SSW should force a negative AO in the stratosphere. 

Our research and that of other scientists shows that the negative phase of the AO in the troposphere is favored, with a ten to fourteen-day delay, for the following four to six weeks after a SSW and a negative stratospheric AO. The evolution of the SSW or polar vortex weakening is likely to modulate which regions are favored for colder temperatures across the NH continents for the remainder of winter. The models are predicting for the PV to slide from its current position over northern Eurasia into the North Atlantic and then stretch out towards eastern North America. As the PV pinballs towards the North Atlantic, the models also predict geopotential heights to strongly build across the North Pacific side of the Arctic in the stratosphere.  This should result in a tropospheric reflection of strong positive geopotential heights across the North Pacific of the Arctic.  Strong geopotential height rises across part or all of the Arctic basin favors lower geopotential heights across Eastern Siberia, eastern North America and Northern Europe.  Lowering geopotential heights in eastern North America and East Asia coupled with ridging to the west will promote a northerly flow of cold air for those regions".


This forecasted pattern fits very well with the Winter Outlook where analogues indicated colder, but still variable temperature conditions likely to dominate the remainder of the cold season through March. The key here is how El Nino plays into this Polar pattern. Will it continue to be strong enough to influence the Pacific jet and allow mild, Pacific air to surge well east across the country; at least at intervals? While I believe the Polar Vortex has now become a viable contender to the El Nino influenced Pacific jet; both should remain in contention as spring approaches. That being said; this battle (as first mentioned back last fall in the Outlook) could very well intensify into a more stormy pattern not seen this winter in our neck of the woods. Again; WHERE these atmospheric battles take off is largely dependent on these two dominant patterns and if, when and where phasing takes place. It has been our observance this winter that notable winter storms have been basically all around the Lower Great Lakes - west, south and east - therefore it will be extremely interesting to see if that established pattern hangs tough the rest of the cold season or breaks down.


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