February 2011 Thoughts: Another 'Atypical' La Niña Month

[uncle W]

Earlier in this thread, I suggested that the coming thaw would likely last 1 to no more than 2 weeks (probably starting around mid-month +/- a few days). Some quick additional thoughts:

1. After mid-month, the EPO is forecast to be declining. I suspect that it will go negative some time in the last week of the month (timing close to February-March 2001), opening the door again for some of the coldest air in the Northern Hemisphere to reload in Canada.

2. The signal for an AO+ is much weaker. Numerous ensemble members have the AO heading negative and/or staying negative prior to mid-month. I believe the redevelopment of blocking will ultimately lead to a strongly negative AO possibly in the last week of the month.

3. The objective analogs centered around 2/4 (GFS ensembles) are: 2/28/1956, 2/20/1976, 3/2/1974, 2/3/1965, 2/6/1979, 2/11/1999, 2/11/1994, 2/6/1959, 2/13/1967, and 2/3/1969. If one runs the composites, one finds:

Day 0 (centered around 2/14): Cool in the northeast, normal/mild in the Mid-Atlantic, warm in the Southeast; AO+

Day 5: The warmth is heading toward a peak with the entire eastern half of the U.S. above normal in temperatures, AO moving toward neutral

Day 10: A sustained cold pattern moves in; AO- and falling

4. Various runs of the operational GFS show colder air moving back toward or into the East at the end of the model's range.

Although the operational GFS might be rushing the cold back, the general idea is that the thaw should be temporary (no more than 1-2 weeks, perhaps around 10 days in duration). It will not be 3-5 weeks in duration, essentially meaning that winter is finished. Seasonal persistence with other "signals" of a dramatic shift in the pattern e.g., late December/early January, where such a shift proved of short-duration also argues for a temporary thaw, not an end to winter. Hence, at this point in time, I have added confidence that cities such as DCA, PHL, NYC, BOS, YOW, YUL, DTW, ORD will have overall cool anomalies for the month. Moreover, even with a "snow pause" in some areas during the lead up to the thaw and during the thaw, above to much above normal monthly snowfall still looks like a strong possibility for PHL, NYC, and BOS (BOS is already above 10" snowfall for the month and very likely en route to > 20" for the month). Finally, for the winter-starved Pacific Northwest, the duration of the thaw and perhaps a few days afterward could offer some periods of wintry weather. However, toward the end of the month (last week?) things could grow milder there.

Don, do you think the thaw will melt all or most of the snow pack?... 1947-48, 1960-61 and 1993-94 all had their huge snow pack's dwindle after a few days of 60 degrees...I'm not seeing it getting that mild but I could be wrong...If the thaw is minor with highs 50 or lower the snow pack might survive until the next onslaught...

[donsutherland1]

Don, do you think the thaw will melt all or most of the snow pack?... 1947-48, 1960-61 and 1993-94 all had their huge snow pack's dwindle after a few days of 60 degrees...I'm not seeing it getting that mild but I could be wrong...If the thaw is minor with highs 50 or lower the snow pack might survive until the next onslaught...

It might survive, especially if it can be rebuilt to some extent prior to the start of the thaw. I suspect that the warmest temperature will be less than 60°F in NYC and the thaw will probably see a number of days topping out in the upper 40s to lower/middle 50s, but that period won't be too lengthy.

[Kaner587]

It might survive, especially if it can be rebuilt to some extent prior to the start of the thaw. I suspect that the warmest temperature will be less than 60°F in NYC and the thaw will probably see a number of days topping out in the upper 40s to lower/middle 50s, but that period won't be too lengthy.

I'm a little confused at the time period you envision this thaw will occur. It appears we get "relatively" mild over the next week(temps around 40 at best in NYC) with a cold shot around day 5-6 and an additional storm with following cold shot day 8....

I'm assuming you're talking about mid month?

[donsutherland1]

I'm a little confused at the time period you envision this thaw will occur. It appears we get "relatively" mild over the next week(temps around 40 at best in NYC) with a cold shot around day 5-6 and an additional storm with following cold shot day 8....

I'm assuming you're talking about mid month?

Yes, mid-month. That's when the milder regime should lock in for a time (perhaps ~2/14-2/24? +/- a few days?).

[Kaner587]

Yes, mid-month. That's when the milder regime should lock in for a time (perhaps ~2/14-2/24? +/- a few days?).

thanks for the response...I think while it is possible we lose our snowpack, I think we come very close to breaking the record for consecutive days at 1+ snowcover in central park before it disappears (if it does at all).

[A-L-E-X]

Yes, mid-month. That's when the milder regime should lock in for a time (perhaps ~2/14-2/24? +/- a few days?).

Don, I'd love to know your thoughts for the potential storm for mid-late week next week. Early-Mid Feb has been a treasure trove of big storms, let's see if we can get that period to produce again.

[donsutherland1]

Don, I'd love to know your thoughts for the potential storm for mid-late week next week. Early-Mid Feb has been a treasure trove of big storms, let's see if we can get that period to produce again.

I believe a KU-type storm is a possibility this month. That storm certainly looks like a possible candidate, though things could still change markedly.

[Ottawa Blizzard]

Don, how do you see this warmup affecting Ottawa? Will we still be cold enough for snow, or will we surge into the 40s?

Also, do you think the big storm late next week could impact Ottawa? JB is drawing parallels to January 1966 and March 1993 lthough it should be emphasized that he is not saying it would be like those storms.

[nzucker]

Ladies and gentleman, I present you the arctic outbreak from hell:

Warm spell in February may be in trouble if the 0z GFS and 12z ECM have anything to say...looks as if the NAO/AO develops in time to save us from the SE Ridge.

[Isotherm]

Ladies and gentleman, I present you the arctic outbreak from hell:

Warm spell in February may be in trouble if the 0z GFS and 12z ECM have anything to say...looks as if the NAO/AO develops in time to save us from the SE Ridge.

Wouldn't that be something, all meteorological winter without a thaw in the Northeast. I don't believe it though, I think the PNA will be negative enough to at least pump the SE-ridge and give us more transient warm shots.

[nzucker]

Wouldn't that be something, all meteorological winter without a thaw in the Northeast. I don't believe it though, I think the PNA will be negative enough to at least pump the SE-ridge and give us more transient warm shots.

We did have a bit of a thaw over New Year's...I had one day with a high of 50F and two days in the mid 40s. It wasn't a massive torch, but by the standards of this brutal winter, it was pretty mild. I've really never seen such a combination of persistent cold, arctic cold, and snow here in NYC metro; it's quite remarkable given the years of above average winters we suffered in the 1990s. You can see the looks on people's faces when you talk about the next storm threat; there is just an incredible fatigue from the constant icy, windy, and cold conditions. We seem to be reverting to the Little Ice Age this winter with a consistent snow pack along I-95 such as was frequently the case during historic winters like 1816-17 and 1947-48.

After the storm next Thursday and an arctic outbreak (which may be intense), I believe we will enter somewhat of a gradient pattern as the NAO/AO revert to negative but a SE ridge tries to build due to the prevailing -PNA which often characterizes February during a La Niña. I think that the pattern will transition more towards SW flow events that benefit the interior with the potential for more icing along the coast. Temperatures will probably range from slightly above average in the Southern Mid-Atlantic to somewhat below normal in Northern New England with the PV stuck over Quebec and ridging in the North Atlantic keeping that cold airmass in place. I certainly don't see any signal for a torch as we had in January 1996 after the blizzard.

Overall, the 2010-11 winter will certainly be remembered as a cold and stormy one for the United States, with the Boxing Day Blizzard and Midwest Blizzard being the most distinguished events. According to RSS satellite analysis, January 2011 was the coldest January for the Lower 48 since 1988. February should also feature large regions of below average temperatures, potentially in places like the Southern Plains which could not expect to be cold in a strong La Niña.

[donsutherland1]

Don, how do you see this warmup affecting Ottawa? Will we still be cold enough for snow, or will we surge into the 40s?

Also, do you think the big storm late next week could impact Ottawa? JB is drawing parallels to January 1966 and March 1993 lthough it should be emphasized that he is not saying it would be like those storms.

Ottawa Blizzard,

I believe most days during the thaw will see readings < 40°F at Ottawa. There could be 1-2 days where the warmer air does push the thermometer above 40°, but that should be the exception.

As for next week's possible storm, the range of possible solutions is still large. Until the details concerning the phasing (timing/location) are better established, there are a lot of issues to be resolved. Nonetheless, setting aside the issue of qpf amounts, this is the type of storm that would probably bring precipitation to cities such as Ottawa and Montreal. The storm's track also remains to be seen. IMO, the 2/4 0z Euro is probably on the western side of viable solutions while the GFS is probably on the eastern edge. Something between those two ideas (perhaps from Norfolk to near/over Montauk Point to Nantucket to somewhere in the vicinity of New Brunswick/westernmost Nova Scotia?) might make sense.

[Organizing Low]

Don I am becoming increasingly concerned about the possible warmup.

I see the overnight GEFS guidance has backed off on the redevelopment of a NAO as the PNA tanks.

I am hopeful the PNA doesnt tank as much and we enter a zonal pattern rather than the big trough out west

Could the EPO help out, and what is the expected situation with the EPO at that time?

And if so and if you've got a moment, What is the setup in the east re: temps with a +NAO / + AO / - PNA and a favorable EPO in a Nina?

if we can keep the PV near hudsons bay, we should be OK, but i don't know how that plays out with upcoming indices.

[tamarack]

We did have a bit of a thaw over New Year's...I had one day with a high of 50F and two days in the mid 40s. It wasn't a massive torch, but by the standards of this brutal winter, it was pretty mild.

More of a torch, relative to norms, the farther north one looked. Jan 1&2 were each +18 IMBY (compared to only 12-yr avg), and CAR had +27, +24 for those 2 days. Thankfully it wasn't accompanied by a deluge.

[donsutherland1]

Don I am becoming increasingly concerned about the possible warmup.

I see the overnight GEFS guidance has backed off on the redevelopment of a NAO as the PNA tanks.

I am hopeful the PNA doesnt tank as much and we enter a zonal pattern rather than the big trough out west

Could the EPO help out, and what is the expected situation with the EPO at that time?

And if so and if you've got a moment, What is the setup in the east re: temps with a +NAO / + AO / - PNA and a favorable EPO in a Nina?

if we can keep the PV near hudsons bay, we should be OK, but i don't know how that plays out with upcoming indices.

OL,

I believe a thaw is going to unfold (even if the 0z GFS tried to keep the cold in place). In general, one would need a strongly negative EPO to offset a negative PNA, positive AO and positive NAO during a La Niña, unless the La Niña were collapsing. The EPO should be trending lower after mid-month, possibly going negative sometime during the final 7-10 days of February. I also suspect that the PNA will bottom out near mid-month +/- a few days and then begin a slow rise afterward. That rise could accelerate toward the close of the month.

Finally, as I suspect that the thaw will last only 1-2 weeks, there should still be plenty of opportunity for wintry weather well into March for areas running from Windsor to the Eastern Townships. Even during the thaw, there might be some snowfall opportunities in that general area, especially in cities such as Ottawa, Montreal, Trois Rivieres, and Quebec City.

[NJwinter23]

OL,

I believe a thaw is going to unfold (even if the 0z GFS tried to keep the cold in place). In general, one would need a strongly negative EPO to offset a negative PNA, positive AO and positive NAO during a La Niña, unless the La Niña were collapsing. The EPO should be trending lower after mid-month, possibly going negative sometime during the final 7-10 days of February. I also suspect that the PNA will bottom out near mid-month +/- a few days and then begin a slow rise afterward. That rise could accelerate toward the close of the month.

Finally, as I suspect that the thaw will last only 1-2 weeks, there should still be plenty of opportunity for wintry weather well into March for areas running from Windsor to the Eastern Townships. Even during the thaw, there might be some snowfall opportunities in that general area, especially in cities such as Ottawa, Montreal, Trois Rivieres, and Quebec City.

Don,

A negative AO appears to be developing over the next 10 days, at least according to gfs ensembles, with the blocking centered on the Siberian side of the north pole in about 10 days. this appears to trap that anomalously cold vortex on our side of the pole. Despite the potential for -PNA/+PNA, I would think this -AO type blocking could be a potential hinderance on any longevity/blow torching during this warm-up period for the northeast. Would you agree?

[donsutherland1]

Don,

A negative AO appears to be developing over the next 10 days, at least according to gfs ensembles, with the blocking centered on the Siberian side of the north pole in about 10 days. this appears to trap that anomalously cold vortex on our side of the pole. Despite the potential for -PNA/+PNA, I would think this -AO type blocking could be a potential hinderance on any longevity/blow torching during this warm-up period for the northeast. Would you agree?

I agree. I don't believe the thaw will amount to a long-duration blowtorch. I could see perhaps 1-2 days having temperatures topping out somewhere from the middle 40s to the lower 50s in northern NJ, NYC, and across Long Island. Most of the period will be somewhat cooler than that. I also don't expect the thaw to last more than two weeks.

[Organizing Low]

OL,

I believe a thaw is going to unfold (even if the 0z GFS tried to keep the cold in place). In general, one would need a strongly negative EPO to offset a negative PNA, positive AO and positive NAO during a La Niña, unless the La Niña were collapsing. The EPO should be trending lower after mid-month, possibly going negative sometime during the final 7-10 days of February. I also suspect that the PNA will bottom out near mid-month +/- a few days and then begin a slow rise afterward. That rise could accelerate toward the close of the month.

Finally, as I suspect that the thaw will last only 1-2 weeks, there should still be plenty of opportunity for wintry weather well into March for areas running from Windsor to the Eastern Townships. Even during the thaw, there might be some snowfall opportunities in that general area, especially in cities such as Ottawa, Montreal, Trois Rivieres, and Quebec City.

thanks Don

very informative and appreciated. we will be fine here as long as its not a big east coast ridge setting up and west coast trough.....hopefully that doesnt happen.

[donsutherland1]

Quick post-12z GFS/GGEM thoughts on the possible February 9-11 storm:

The GFS' shift to an off-shore solution and the GGEM's Miller B depiction just indicates that there remains a lot of spread in the possible solutions. While the 0z ECMWF idea is one viable solution, it is far from cast in stone. Other ideas are probably at least as likely. I do believe that there will be a fairly significant storm late next week with a large precipitation shield, but the details remain to be worked out. The extent, location, and timing of phasing will be critical and from this far out, no single model probably has a lock on such details. That most have a degree of phasing supports the idea that phasing will likely occur, hence my confidence in a fairly significant storm.

[A-L-E-X]

Quick post-12z GFS/GGEM thoughts on the possible February 9-11 storm:

The GFS' shift to an off-shore solution and the GGEM's Miller B depiction just indicates that there remains a lot of spread in the possible solutions. While the 0z ECMWF idea is one viable solution, it is far from cast in stone. Other ideas are probably at least as likely. I do believe that there will be a fairly significant storm late next week with a large precipitation shield, but the details remain to be worked out. The extent, location, and timing of phasing will be critical and from this far out, no single model probably has a lock on such details. That most have a degree of phasing supports the idea that phasing will likely occur, hence my confidence in a fairly significant storm.

Once you have a chance to look at the 12z Euro, your thoughts on it would be welcome, Don.

[am19psu]

Quick post-12z GFS/GGEM thoughts on the possible February 9-11 storm:

The GFS' shift to an off-shore solution and the GGEM's Miller B depiction just indicates that there remains a lot of spread in the possible solutions. While the 0z ECMWF idea is one viable solution, it is far from cast in stone. Other ideas are probably at least as likely. I do believe that there will be a fairly significant storm late next week with a large precipitation shield, but the details remain to be worked out. The extent, location, and timing of phasing will be critical and from this far out, no single model probably has a lock on such details. That most have a degree of phasing supports the idea that phasing will likely occur, hence my confidence in a fairly significant storm.

Agree with this 100%, Don. The only thing I feel confident about at this time is that wherever it goes, it is going to be a deep, large low pressure.

[donsutherland1]

Agree with this 100%, Don. The only thing I feel confident about at this time is that wherever it goes, it is going to be a deep, large low pressure.

I agree. The 2/5 0z GFS notwithstanding, I continue to believe that the synoptic environment is favorable for a significant storm. It should also be noted that the 2/5 0z run of the GFS has trended toward a greater impact than the preceding two runs.

[Srain]

Don, from a historical perspect, our currect Arctic intrusion was most impressive. HGX offered a summury through yesterday...

CLIMATE...

THE FIRST 4 DAYS OF FEBRUARY HAVE BEEN BRUTALLY COLD. THE AVERAGE

TEMPERATURE HAS BEEN ABOUT 20 DEGREES COLDER THAN NORMAL. THE LAST

TIME HOUSTON RECEIVED 5 CONSECUTIVE DAYS WITH MIN TEMPS EQUAL TO

OR BELOW 28 DEGREES WAS FEB 1989. THIS IS THE 4TH COLDEST START TO

FEB FOR THE CITY OF HOUSTON. ONLY FEB 1-4 IN 1985...1951 AND 1996

WERE COLDER.

[donsutherland1]

Don, from a historical perspect, our currect Arctic intrusion was most impressive. HGX offered a summury through yesterday...

CLIMATE...

THE FIRST 4 DAYS OF FEBRUARY HAVE BEEN BRUTALLY COLD. THE AVERAGE

TEMPERATURE HAS BEEN ABOUT 20 DEGREES COLDER THAN NORMAL. THE LAST

TIME HOUSTON RECEIVED 5 CONSECUTIVE DAYS WITH MIN TEMPS EQUAL TO

OR BELOW 28 DEGREES WAS FEB 1989. THIS IS THE 4TH COLDEST START TO

FEB FOR THE CITY OF HOUSTON. ONLY FEB 1-4 IN 1985...1951 AND 1996

WERE COLDER.

I agree with you. It is disappointing, though, that the snow never made it to Houston.

[donsutherland1]

Just a few quick thoughts:

1. It appears that GFS's early depiction of an off-shore solution for Thursday has become increasingly likely. There may still be some modest shifts, but I believe a blockbuster event is unlikely.

2. Tuesday's event could bring some accumulations of snow to the north and west of Philadelphia into southern New England. The largest accumulations will probably be to the north and west of the big cities, though a short period of snow can't be ruled out for the cities. Boston would have the best prospect of picking up a few inches of snow, but the soundings are still uncomfortably warm there.

3. The thaw continues to appear on the modeling.

For now, today is one of those dreaded "melting days." The snow is dissolving under the sun's heat and the mercury has pushed above 40° in much of the Mid-Atlantic/southern New England regions.

[ayuud]

Just a few quick thoughts:

1. It appears that GFS's early depiction of an off-shore solution for Thursday has become increasingly likely. There may still be some modest shifts, but I believe a blockbuster event is unlikely.

2. Tuesday's event could bring some accumulations of snow to the north and west of Philadelphia into southern New England. The largest accumulations will probably be to the north and west of the big cities, though a short period of snow can't be ruled out for the cities. Boston would have the best prospect of picking up a few inches of snow, but the soundings are still uncomfortably warm there.

3. The thaw continues to appear on the modeling.

For now, today is one of those dreaded "melting days." The snow is dissolving under the sun's heat and the mercury has pushed above 40° in much of the Mid-Atlantic/southern New England regions.

do you think the thaw will reach buffalo? 0z gfs max temp for next week is only 33F

[Ottawa Blizzard]

The 0z GFS keeps the cold in place in eastern Ontario/NNY/NNE and s Quebec pretty much righ tthrough the run. The 540 thickness line runs right along the I-80 corridor at times - JB might nail the patteern!

[donsutherland1]

do you think the thaw will reach buffalo? 0z gfs max temp for next week is only 33F

I do. It won't be a blowtorch there, but readings will run above normal for a period. It would not surprise me if 1-2 days saw a high temperature at around 40° or a little above despite what the GFS is currently showing.

[donsutherland1]

The 0z GFS keeps the cold in place in eastern Ontario/NNY/NNE and s Quebec pretty much righ tthrough the run. The 540 thickness line runs right along the I-80 corridor at times - JB might nail the patteern!

Ottawa might have little impact from the though, perhaps only a few somewhat milder than normal days. The polar vortex will help limit the encroachment of warm air into the vicinity of Ottawa.

[Ji]

Ottawa might have little impact from the though, perhaps only a few somewhat milder than normal days. The polar vortex will help limit the encroachment of warm air into the vicinity of Ottawa.

are you on board that winter is over 40 South?