And here begins the December long-range forecast released by Northwest Ohio Storm Prediction Center!
I'm not going to go into detail about the long-range factors going into this forecast, as I well know that only true "weather geeks" really care about them. So for this, I will only make mention of the truly important factors.
Currently, the Equatorial Pacific is in the neutral ENSO phase, which us "weather geeks" like to sometimes call, "La Nada", which just references the fact that Neutral winters tend to have less affect on North American weather than do other variables. SST anomalies have been fluctuating, but have generally averaged just slightly above normal in the Equatorial Pacific. Current MJO forecasts (Madden Julian Oscillation, a weather pattern or frequency that occurs in the tropics, but can affect weather across the Pacific, as far away as the United States) suggest that in the next few weeks it will be going through phases 8,1, and 2. Phase 8 generally favors the strengthening of an El Nino, while phases 1 and 2 favor "La Nada's" and La Nina's. Another variable that I look at is the NAO, as well as the AO. The NAO stands for North Atlantic Oscillation, which is related to atmospheric pressure across the North Atlantic, and the AO stands for the Arctic Oscillation which is related to pressure anomalies across the Arctic (and including the stratospheric circulations). Both of these have been in the negative phase for nearly the ENTIRE fall. Last year, it was hard to keep the two negative. A negative AO/NAO couplet suggests a greater potential for cold weather to invade the Northern and Eastern United States, including the Midwest. Using a forecast of persistence, I can see the NAO staying near neutral or negative for the month of December (including the AO as well). Other variables related to my forecast include snow cover across Canada, the PDO index, the PNA index, solar cycle variation, etc. I will not go into detail on these.
As for the forecast, I'll start with the lower Great Lakes forecast. For the last few days of November and very beginning of December, long-range forecast models indicate that the pattern will become very "changeable", and is likely to go through a "pattern change" around the same time. In fact, it is all-together likely that this pattern change is marked by a major Arctic blast into the Great Lakes, which would usher in the first major lake effect snow event of the season. In the same time frame, both the NAO and AO are expected to go at least slightly negative, which supports the development of blocking across the North Atlantic, and thus a "stopped" and unchanging pattern. This could in fact allow arctic air intrusions to become more likely in December. At this point I do NOT believe that the December 2012 trough/ridge pattern will be very "blocked". This means that I do expect the pattern to still be rather "changing", but more likely to yield arctic air intrusions. In all, for the lower Great Lakes, expect slightly below normal temperatures, due to the Arctic air masses, but averaging in any "sustained" warm ups as well. As for precipitation, I expect near normal precipitation, as the storm track will favor Alberta Clippers into the region, but most "wet" storms will likely head south of the area. Areas downwind of the Great Lakes will likely see above normal precipitation and snowfall. For the rest of the Great Lakes and Ohio Valley, I think it will be definitely possible to see one decent snowstorm, but in light of recent events, most storm systems will likely feature a mix of ice/snow or heavy rainfall.
For the rest of the United States, expect below normal temperatures from the Northern Plains to the East Coast, with the core of the Arctic air still existing across Western Canada. An active southeastward storm track from the Northern Plains into the Ohio Valley and along the East Coast, will favor above normal precipitation in coastal cities, with near to below normal precipitation across the Southern Plains and Southwest United States. In the Great Lakes, precipitation will be near normal except for the Lake effect "belts". The Northern Plains will likely see near to above normal precipitation due to the storm track. This pattern I can see happening about two or three times during the month of December, each lasting about three or four days before a more transient trough/ridge pattern sets in, between these periods of Arctic cold. These will be the times when Midwestern storms make their way in, and a Great Lakes Cutter results, a storm that travels from the Central Plains into the Great Lakes region, bringing warmer conditions and heavy rains to the Ohio Valley and much of the East.
I will not yet release a Christmas Day forecast until December begins.
One point I would like to make and that is this: Once again, because of the fragile state of the ENSO phase especially, and the way the PDO has been trending, I can see that it is possible, that we see a storm track through the Ohio Valley, with near to above normal temperatures, but well above normal precipitation and potentially snowfall. This could in fact happen if a Western trough develops, which will eject disturbances into the Midwest region. I will keep an eye on this.
Here's the official forecast map:
And here is the snow cover maps.. Comparing this year to last year:
I'm not going to go into detail about the long-range factors going into this forecast, as I well know that only true "weather geeks" really care about them. So for this, I will only make mention of the truly important factors.
Currently, the Equatorial Pacific is in the neutral ENSO phase, which us "weather geeks" like to sometimes call, "La Nada", which just references the fact that Neutral winters tend to have less affect on North American weather than do other variables. SST anomalies have been fluctuating, but have generally averaged just slightly above normal in the Equatorial Pacific. Current MJO forecasts (Madden Julian Oscillation, a weather pattern or frequency that occurs in the tropics, but can affect weather across the Pacific, as far away as the United States) suggest that in the next few weeks it will be going through phases 8,1, and 2. Phase 8 generally favors the strengthening of an El Nino, while phases 1 and 2 favor "La Nada's" and La Nina's. Another variable that I look at is the NAO, as well as the AO. The NAO stands for North Atlantic Oscillation, which is related to atmospheric pressure across the North Atlantic, and the AO stands for the Arctic Oscillation which is related to pressure anomalies across the Arctic (and including the stratospheric circulations). Both of these have been in the negative phase for nearly the ENTIRE fall. Last year, it was hard to keep the two negative. A negative AO/NAO couplet suggests a greater potential for cold weather to invade the Northern and Eastern United States, including the Midwest. Using a forecast of persistence, I can see the NAO staying near neutral or negative for the month of December (including the AO as well). Other variables related to my forecast include snow cover across Canada, the PDO index, the PNA index, solar cycle variation, etc. I will not go into detail on these.
As for the forecast, I'll start with the lower Great Lakes forecast. For the last few days of November and very beginning of December, long-range forecast models indicate that the pattern will become very "changeable", and is likely to go through a "pattern change" around the same time. In fact, it is all-together likely that this pattern change is marked by a major Arctic blast into the Great Lakes, which would usher in the first major lake effect snow event of the season. In the same time frame, both the NAO and AO are expected to go at least slightly negative, which supports the development of blocking across the North Atlantic, and thus a "stopped" and unchanging pattern. This could in fact allow arctic air intrusions to become more likely in December. At this point I do NOT believe that the December 2012 trough/ridge pattern will be very "blocked". This means that I do expect the pattern to still be rather "changing", but more likely to yield arctic air intrusions. In all, for the lower Great Lakes, expect slightly below normal temperatures, due to the Arctic air masses, but averaging in any "sustained" warm ups as well. As for precipitation, I expect near normal precipitation, as the storm track will favor Alberta Clippers into the region, but most "wet" storms will likely head south of the area. Areas downwind of the Great Lakes will likely see above normal precipitation and snowfall. For the rest of the Great Lakes and Ohio Valley, I think it will be definitely possible to see one decent snowstorm, but in light of recent events, most storm systems will likely feature a mix of ice/snow or heavy rainfall.
For the rest of the United States, expect below normal temperatures from the Northern Plains to the East Coast, with the core of the Arctic air still existing across Western Canada. An active southeastward storm track from the Northern Plains into the Ohio Valley and along the East Coast, will favor above normal precipitation in coastal cities, with near to below normal precipitation across the Southern Plains and Southwest United States. In the Great Lakes, precipitation will be near normal except for the Lake effect "belts". The Northern Plains will likely see near to above normal precipitation due to the storm track. This pattern I can see happening about two or three times during the month of December, each lasting about three or four days before a more transient trough/ridge pattern sets in, between these periods of Arctic cold. These will be the times when Midwestern storms make their way in, and a Great Lakes Cutter results, a storm that travels from the Central Plains into the Great Lakes region, bringing warmer conditions and heavy rains to the Ohio Valley and much of the East.
I will not yet release a Christmas Day forecast until December begins.
One point I would like to make and that is this: Once again, because of the fragile state of the ENSO phase especially, and the way the PDO has been trending, I can see that it is possible, that we see a storm track through the Ohio Valley, with near to above normal temperatures, but well above normal precipitation and potentially snowfall. This could in fact happen if a Western trough develops, which will eject disturbances into the Midwest region. I will keep an eye on this.
Here's the official forecast map:
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| Temperature Anomaly Forecast Map. |
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| Snow cover for November 2011 |
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| Snow cover November 2012, well above what last year saw. |
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