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dmillz25

February 2017 Discussion & Observations

1,353 posts in this topic

10 hours ago, dmillz25 said:

With February a few days away, models are showing a better pattern for winter weather. Discuss away

Basically the make or break month for 2016/2017. If we can pull of a solid February it will not be a complete disaster. February has been absolutely solid the last decade on average 

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With respect to the pattern, my confidence continues to grow that this winter is gradually improving rather than a maintenance of status quo. Displacement induced tilting will not be sufficient to force a major zonal wind reversal in the coming days, but reconsolidation will be slow / painful, with IMO, an increasingly likelihood of a follow-up wave-2 convergence about a week or so later. This isn't really being detected by the model data yet,  but it should in the coming days. The vortex will be extremely susceptible in early February, and we're entering a regime for further robust driving. When a boxer attempts to knock someone out, it's much easier do to so after several hard punches, rather than waiting until the opponent regains his/her footing and strength. Not too dissimilarly, a delay in follow-up wave driving permits rapid reconsolidation, but the entrance into a propitious precursor regime implies an already depressed vortex state will be threatened with potentially fatal blows.

 

The first real threat has been 2/6 period to me, but even if that one doesn't work out, I tend to think the tropospheric pattern may become more blocky as we progress into mid / late February. The lack of NAM / NAO cooperation has been detrimental for the East Coast in times of WPO/EPO pulses. Contemporaneous geopotential height response would yield a significantly more auspicious set-up for coastal snowfall. The tropical forcing progression, additionally, looks good to me for renewed ridging near Alaska, after this initial cut-off block retrogrades away.

 

The long and short of it is as follows: February will be our best month of the meteorological winter this year. The extent to which the sensible weather is pleasing for winter lovers will be largely a function of effective stratospheric activity and other variables. But I am willing to say at this point that February looks much closer to normal temperature wise, with likely at least normal snowfall for the month. March could either resume January's furnace is the strat progression falls apart, or feature a nice late winter regime. 1973-74 still looks great as an analog.

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Seems like, in the past few years, we always manage to secure blocking in the springtime when most of us don't want it.  Does the data support my memory here?

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16 hours ago, Eduardo said:

Seems like, in the past few years, we always manage to secure blocking in the springtime when most of us don't want it.  Does the data support my memory here?

No, the last few springs have been above average temps. Last April did start really cold with light snow events but ended +1 at KNYC. May 2015 was the warmest on record. The last really cold spring was 2007.

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The forecast EPO-/PNA+/AO+ pattern has measurable snowfall frequency that is, on average, above climatology for the 2/1-15 period. For example, in New York City, days with measurable snow were more than 40% greater than climatology and days with snowfall amounts of 4" or more were more than 50% above climatology.

Frequency of Select Snowfall Amounts (2/1-15/1950-2016):

Boston (% days with given snowfall amounts):
Measurable snow: 27.3% (climatology: 22.8%)
4” or more: 9.1% (climatology: 3.6%)

New York City (% days with given snowfall amounts):
Measurable snow: 21.2% (climatology: 14.7%)
4” or more: 4.5% (climatology: 2.9%)

Philadelphia (% days with given snowfall amounts):
Measurable snow: 25.8% (climatology: 16.2%)
4” or more: 4.5% (climatology: 2.5%)

With the subtropical jet's being more active, especially as the first week of February progresses, the idea that there could be at least one or two opportunities for storminess is something to watch for even if some of the current guidance (>1 week away) suggests a lack of storminess. The GFS ensembles are suggesting that the February 4-11 period could be wetter than normal, so there is support among at least some of the guidance for what could be a period with snowfall potential. 

Such patterns also typically result in normal to somewhat colder than normal temperatures.

Approaching or moving beyond mid-February, there remains a real risk that the EPO could go positive. If that happens, the second half of February could wind up warmer than normal.
 

 

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2 hours ago, donsutherland1 said:

The forecast EPO-/PNA+/AO+ pattern has measurable snowfall frequency that is, on average, above climatology for the 2/1-15 period. For example, in New York City, days with measurable snow were more than 40% greater than climatology and days with snowfall amounts of 4" or more were more than 50% above climatology.

Frequency of Select Snowfall Amounts (2/1-15/1950-2016):

Boston (% days with given snowfall amounts):
Measurable snow: 27.3% (climatology: 22.8%)
4” or more: 9.1% (climatology: 3.6%)

New York City (% days with given snowfall amounts):
Measurable snow: 21.2% (climatology: 14.7%)
4” or more: 4.5% (climatology: 2.9%)

Philadelphia (% days with given snowfall amounts):
Measurable snow: 25.8% (climatology: 16.2%)
4” or more: 4.5% (climatology: 2.5%)

With the subtropical jet's being more active, especially as the first week of February progresses, the idea that there could be at least one or two opportunities for storminess is something to watch for even if some of the current guidance (>1 week away) suggests a lack of storminess. The GFS ensembles are suggesting that the February 4-11 period could be wetter than normal, so there is support among at least some of the guidance for what could be a period with snowfall potential. 

Such patterns also typically result in normal to somewhat colder than normal temperatures.

Approaching or moving beyond mid-February, there remains a real risk that the EPO could go positive. If that happens, the second half of February could wind up warmer than normal.
 

 

The EPS is extremely ugly. It shows a deep vortex developing over Alaska (++EPO) by February 12th

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4 minutes ago, snowman19 said:

The EPS is extremely ugly. It shows a deep vortex developing over Alaska (++EPO) by February 12th

It's so hard to trust anything.  2 days ago it showed that the it stopped now it's showing it again 

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1 hour ago, snowman19 said:

The EPS is extremely ugly. It shows a deep vortex developing over Alaska (++EPO) by February 12th

 

There is  lot going on before mid month .

Several wintry possibilities over the next 15 days are modeled .

 

There is plenty of time to look at the second half of the month . As is it the guidance has a -4 SD WPO and begins to turn the AO neg thru the 10th .

 

There is the possibility that you will just hand off the blocky EPO to the Atlantic if the NAO can slip neg.

 

 

 

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2 hours ago, snowman19 said:

The EPS is extremely ugly. It shows a deep vortex developing over Alaska (++EPO) by February 12th

That would fit the seasonal trend of 5-10 days of cold and then back to the warm base state here.   Miss that warm blob in the pacific that favored a negative -epo all winter 

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Just now, Brian5671 said:

That would fit the seasonal trend of 5-10 days of cold and then back to the warm base state here.   

The GEFS has us below normal the whole entire run so we are still looking for a below average regime with a storm every few days. 

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8 minutes ago, WeatherFeen2000 said:

The GEFS has us below normal the whole entire run so we are still looking for a below average regime with a storm every few days. 

That's great but models had a big cold pattern for January amd verification was 5 days.  Let's see if we can get February to verify longer and stronger 

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I continue to be quite intrigued by the potential stratospheric progression over the next couple weeks, which may lead to situation whereby NAM values reach their minima in the second half of February into the first half of March. The models are slowly but surely beginning to detect what I've been noting over the past week concerning the more effective wave-2 follow up, subsequent to the initial ongoing w1/displacement event. The susceptibility of the stratospheric vortex to further attacks will be increased via the w1, but it will be insufficient insofar as significant tropospheric geopotential height reversal in the NAM/NAO domains. However, the wave-2 precursor should induce an upward propagating splitting wave, possibly in the 2/8-2/15 period. Dual action from the Eurasian and Pacific sides could effectuate a fairly rapid tropospheric response by mid February and onward.

 

I am not yet at the inflection point of pulling the trigger on this evolution definitively, in terms of stratospheric progression and subsequent tropospheric response, but my confidence on the probability of its occurrence is increasing. The resultant impacts could be our most negative NAO/AO period of the winter, circa 2/15-3/15. The NAO and AO are neutral to positive for the first half of Feb.

 

As far as the synoptic set-ups for snow prior to 2/15, 2/6 still looks like a time frame to monitor for a moderate event. I am not as interested in 2/6 as I was in prior days, but it still holds potential certainly.

 

Regardless, an intriguing period of tracking from a meteorological, academic perspective at the very least. Changes are clearly afoot with the BDC and O3 transport, although the WQBO will attempt to destructively interfere, its modulation will be lessened by the double-jab wave flux. I expect stratospheric charts to become more impressive again in the D10+.

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I also forgot to note that the concurrent MJO pulse reaching possibly phase 8 circa 2/12 should work synergistically with the w2, lending further credence to the possible -NAO/AO development Feb 15+ with the more significant storm risk (maybe) coming thereafter due to lag.

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There is now strong consensus on the guidance that the first 10-15 days of February will likely see a mean EPO-/PNA+/AO+ pattern. That typically means readings that are somewhat below normal to near normal in the northern Mid-Atlantic and southern New England regions. Such patterns also have a higher-than-climatological frequency of measurable snow events.

But afterward, there is a growing signal on the ensembles that the EPO- will flip to EPO+ as a strong vortex develops in the Gulf of Alaska. The PNA+ pattern seems more likely than not to continue courtesy of a PDO+ and continued weakening of the La Niña. There remains uncertainty concerning the Arctic Oscillation (AO). A lot of the guidance suggests that the AO will go negative for a sustained period of time. However, such forecasts have failed to verify during much of the winter, so that idea is far from assured. To date, 88% of days this meteorological winter have seen a positive AO.

An EPO+/PNA+/AO+ pattern would favor warmer than normal readings in much of the East. In general, an EPO+/PNA+/AO- pattern would favor somewhat colder than normal readings. However, if one looks more closely at such patterns, ridge placement is crucial. Such patterns can see the ridge extend so far south that warmer than normal readings predominate in the Middle Atlantic and New England areas. February 15-28, 1981 and February 15-29, 1984 provide two such cases from the 1981-2010 climatological period.

Overall, if one calculates the share of days when both the EPO and PNA were positive, 57% of such days (2/15-29/1981-2010 period) saw the AO+ or a “warm” AO- set up. In short, should the EPO go positive, the second half of February could wind up warmer to possibly much warmer than normal.

All said, the probability that February will wind up warmer than normal despite a somewhat cooler than normal start has increased. Such an outcome remains more likely than not.

AO01302017.jpg

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CFS as usual is not paying any attention to these stratospheric changes because the vectors are not reaching the troposphere yet (ever?) and analog years have not changed yet (ever?)   A generous interpretation of their presentation of the 28 days of Feb. right now shows 12BN days.   Second halve of month needs a plastic surgeon, a hairdresser and a speech coach, before it can even enter the contest.  LOL.

wk3.wk4_latest.NAsfcT.gif

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22 minutes ago, CIK62 said:

CFS as usual is not paying any attention to these stratospheric changes because the vectors are not reaching the troposphere yet (ever?) and analog years have not changed yet (ever?)   A generous interpretation of their presentation of the 28 days of Feb. right now shows 12BN days.   Second halve of month needs a plastic surgeon, a hairdresser and a speech coach, before it can even enter the contest.  LOL.

On the contrary, I actually believe the latest run of the CFS reflects the stratospheric changes. If one looks closely at the GFS animation, one finds that the above normal 10 mb height anomalies develop over eastern Canada. If one then goes to the February 15-28, 1981 500 height anomalies (93% days had an AO-), one finds the positive anomalies centered in the same region. That was a warm pattern almost CONUS-wide and the extended range of the ensembles seem to suggest just such an outcome. So, if the first half of February winds up somewhat colder than normal to near normal, the second half warm anomalies could result in a monthly warm anomaly. Of course, things can still change, but it appears that February will more likely than not have yet another warm anomaly (probably closer to normal than January's much above normal figure).

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48 minutes ago, CIK62 said:

CFS as usual is not paying any attention to these stratospheric changes because the vectors are not reaching the troposphere yet (ever?) and analog years have not changed yet (ever?)   A generous interpretation of their presentation of the 28 days of Feb. right now shows 12BN days.   Second halve of month needs a plastic surgeon, a hairdresser and a speech coach, before it can even enter the contest.  LOL.

wk3.wk4_latest.NAsfcT.gif

 

 

 

The CFS says week 1 - 2 are below normal 

 

 

 

wk1.wk2_20170129.NAsfcT.gif

 

That`s a pretty big change from it`s week 3 and 4 forecast from 2 weeks ago ..

 

wk3.wk4_20170116.NAsfcT.gif

 

 

 

 

 

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That is because this is an analog.   Which LR model has done better?   Point is:  ANYONE OR ANY MODEL that predicted a BN month in the last 22 months would have been wrong. (I count June 2015 as above normal since its last 22 days behaved like the other AN months anyway).

Since every year and every month on a worldwide basis is now the hottest ever or in the top ten (since 1880), it is best to take a strike and say it is going to be AN if asked.  Next BN month will probably be an accident.     A volcanic eruption could be needed for a worldwide temperature reduction.

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The 12z GFS took away the PV split. Instead, it begins to consolidate the stratospheric PV, which would fit with the predominant tendency of a strong stratospheric PV this winter.

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45 minutes ago, donsutherland1 said:

The 12z GFS took away the PV split. Instead, it begins to consolidate the stratospheric PV, which would fit with the predominant tendency of a strong stratospheric PV this winter.

The GFS and Euro have both backed off the idea of a major SSW and have the vortex reconsolidating and strengthening again after the elongation. A mid month warmup to above normal and possibly well above normal again is looking more and more likely. 2/15 - 2/28 looks like another warmer than normal period. Whether there is a flip to cooler afterwards, come March, remains to be seen but by then you are running out of time as the seasonal changes will be quickly taking over 

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25 minutes ago, bluewave said:

You can also see the same thing with the TPV. Ensemble means split the TPV over the Kara this week and reconsolidate it again near Alaska day 11-15.

So we are back to the same pattern all season with very strong EPO swings determining our sensible weather. The cold and snow potential has been limited 

all winter to near the strong -EPO drops. Once the EPO goes positive again the warmth returns. Hopefully, we can cash in on on the current -EPO

interval for decent snows before milder temps return again.

 

Very volatile EPO this winter

epo.png

 

 

Furthermore to the consistency of this winters pattern, we have received 2 1-inch events and 2 5-inch events with 2 plus week mild intervals. Tomorrow we could very well see 1 inch and Monday 5 inches. We should see one more period in March. Hopefully we all could benefit and reach average.

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depressing if true, but it fits the seasonal trend of a quick cold shot lasting 5-10 days and then a return to the warm base state.   these strat warming/polar vortex splits are always iffy, so hate to put all my eggs in that basket.   Also, the -NAO modeled in the 8-10 day range is mostly phantom.   That leaves us with the EPO and without that warm blob, it's hard to keep it negative for long this year.  On the plus side the WPO is forecast deeply negative, but is it enough?

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9 hours ago, CIK62 said:

That is because this is an analog.   Which LR model has done better?   Point is:  ANYONE OR ANY MODEL that predicted a BN month in the last 22 months would have been wrong. (I count June 2015 as above normal since its last 22 days behaved like the other AN months anyway).

Since every year and every month on a worldwide basis is now the hottest ever or in the top ten (since 1880), it is best to take a strike and say it is going to be AN if asked.  Next BN month will probably be an accident.     A volcanic eruption could be needed for a worldwide temperature reduction.

I think you make some points that are difficult to dismiss. These temps are worrisome.

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