The Empire of Warmth Begins to Decay But Will Not Fall Soon

[donsutherland1]

Over the next week to ten days, it will seem that the “Empire of Warmth” that has imposed its tyranny on the eastern United States is invincible. By January 18, the brief chill that attempted to liberate the East will have been thoroughly vanquished and a firm trough in the West-ridge in the East alignment established. To some, it will seem like it is January 1932 or January 1950 all over again.

But if there’s the prospect of Greenland ridging, that signifies trouble in the Spring Paradise. Therefore, even as the “Empire of Warmth” rises toward its high tide, there are already subtle signs of decay. And for those enjoying a honeymoon with early spring, things could get worse as the month comes to a close.

The first domino to fall was ENSO situation. It has been at La Niña-ish levels for December and CPC expects that to continue through the rest of the winter. For warm weather lovers, weak La Niña winters have often proved barbaric, both in terms of cold and snow. The second domino to fall was the switch in the PDO to positive. Down the road, if it is sustained, the tendency for a positive PNA could be on the increase. The third domino that is still standing but could fall as the month progresses is the NAO. The GFS ensembles have cautiously but steadily moved more and more toward a negative NAO late in the month.

Ensembles:
The GFS ensembles have been very consistent with regard to the development of a trough in the West and ridge in the East for more than a week with strong support from the Canadian ensembles. Hence, I have very high confidence in the evolution toward such a situation. The mild pattern also is well-supported on some of the extended range models i.e., the GSM and RSM models.

MEI:
There are six seasons in which the average monthly difference in the MEI from the 2005 levels came to less than 0.350 over the past four months: 1959-60, 1966-67, 1981-82, 1983-84, 1984-85, 2000-01. All six saw the second half of January average colder than the first half. The median difference was 1.7° and the mean difference was 2.5°. In 4/6 (67%) cases, the difference was less than 2.5°. Hence, I believe the second half of January will prove moderately colder than the first half but remain on the mild side overall.

NAO:
The ensembles have grown gradually more aggressive with a falling NAO and the Arctic Oscillation is forecast to fall to negative levels, as well, which typically correlates with a negative NAO. A sharply negative NAO will probably not develop before the end of January. However, what is intriguing is that 4/6 (67%) of the above MEI analogs saw the development of a sustained strong block at some point in February (NAO: -2.00 or below for 10 days or more). Could this suggest the potential for a very cold period in the February 10-20 period, which might also fit well with the MJO’s evolution? That’s an issue for later, but there is at least some possibility that February might break on the cold side, but I want to see more supporting data before reaching such a conclusion. For now, I’m reasonably confident that a negative NAO could develop toward the end of January.

On a final note concerning the NAO, the British Met Office expected an NAO that would average < 0 for Winter 2005-06. While it has been generally > 0 from mid-December on, it should be noted that in December the monthly average came to -0.201. If a strong block were to develop in February, it could well wind up averaging < 0 for the December-February period.

Conclusion:
Overall, during the second half of January, the brief shot of cold will rapidly be replaced by more warmth. A ridge will rise in the East and a trough in the West. That configuration will probably hold for a sustained period of time but then crumble late in the month as a trough suddenly gets established in the East possibly preceded by an important storm.

In my view, one can reasonably expect the following for the remainder of January:
∙ January 16-27: warmer than normal with colder shots generally transient and not severe.
∙ Toward the end of the January 16-27 period, one or more days of much of above normal readings are possible with high temperatures reaching or exceeding 60 degrees in Richmond and Washington, DC and in the 50s in such cities as New York, Philadelphia, and Newark as the trough in the West/ridge in the East configuration reaches its climax.
∙ After January 25 there will be at least one or more opportunities for accumulating snow, especially from Philadelphia northward. However, it likely won’t be until February when meaningful snows become more commonplace
∙ The closing 3-5 days of January will likely grow cooler, particularly in the Mid-Atlantic, New England, and Ohio Valley states. Severe cold is not likely through the remainder of January.

[mike815]

yeah very brief cold shots and warm air returns great analysis. i knew it there is no winter this year

[boca]

We don't get winter down here in Florida just episodes of fall once in a while. High today in summerlike Boca Raton in the low 80's. What is winter? At least if its warm let it rain, it hasn't rained down here in 40 days.

[Extremeweatherguy]

I think that the cold comes sooner than the last 4 days of the month. I am predicting Jan. 20-23rd for the start of a colder period.

[donsutherland1]

Mike,

If you're looking for a fairly widespread freeze in Florida, one will probably have to wait for February before there is a chance for such an event.

[Stephanie]

Mike - that's not what don said, but you can believe whatever you want to.

Anyway, we've seen here in the Mid Atlantic some pretty significant snow storms around the President's Day weekend and of course, in March. I won't get lulled into a false sense of security with this current warm period.

I do hope that the trough in the West is deep enough to bring those storms further south so the NW coast can get a break and the SW, Texas and OK can get some beneficial moisture.

[Scorpion]

We don't get winter down here in Florida just episodes of fall once in a while. High today in summerlike Boca Raton in the low 80's. What is winter? At least if its warm let it rain, it hasn't rained down here in 40 days.

I think the fronts this month are pretty powerful, I don't remember it going into the 30's twice in one week.

[Tyler]

yeah very brief cold shots and warm air returns great analysis. i knew it there is no winter this year

OMG, did you even read his superb analysis? Did you not read that he stated that there could be a VERY cold period in February that could last a while. In no way did he say there will be "no winter this year".

[Tyler]

We don't get winter down here in Florida just episodes of fall once in a while. High today in summerlike Boca Raton in the low 80's. What is winter? At least if its warm let it rain, it hasn't rained down here in 40 days.

I think the fronts this month are pretty powerful, I don't remember it going into the 30's twice in one week.

They have been powerful for you and only you (lucky). Everywhere else, they have been considered weak, only able to knock temperatures to normal.

[Gord_on_snow]

Well if we're going to be warm for the 2nd half of January, lets have a bit of sunshine to go with it..i'm a pre-school teacher and it would be fanatastic to get the kids outside at this time of year!

Hopefully things will change for Fenruary, i cant see any reason why they cant. This is only my 2nd winter in the US and is proving very different to my 1st one here. I've looked through some recent years for Ohio to see how winters pan out and i cant stop looking at 1998 which had a very dull winter throughout (thoug it wuld be wrongt to compare that to this winter as i notice December 1997 wasn't that great, but December 2005 was). But on the flip side, i cant stop looking at February 2003 either!

All i conclude is that its all still there to play for this winter.

Also, thanks for analysis Don, in my 2 years in the United States, its posts like yours that really help me to learn the weather around here. I'm returning to live back home in the UK this year but i will still be reading what you have to say, just out of interest!

[AnthonyC]

Hey Don!

Any thoughts for the PNW during this period? Any possibility of lowland snow in Seattle? Or will this nonstop rainy pattern continue?!

Anthony

[donsutherland1]

Gord_on_snow,

Good luck on your return home to the UK. I very much hope you had a great stay in the U.S.

Best wishes.

[donsutherland1]

AnthonyC,

I'll take a closer look at the Pac NW tomorrow.

[donsutherland1]

With the second half of January now commencing, the prospects for a late-month pattern change have increased:

∙ The GFS ensembles send the Arctic Oscillation crashing. In 21/21 (100% cases) when the Arctic Oscillation averaged -1.00 or below in February, the NAO also averaged negative.
∙ The GFS ensembles are continuing to show a negative NAO toward the end of January, with some members taking it toward -2.00 by month's end.
∙ The NCEP ensemble mean 500 mb height anomalies are now showing a trough developing in the East just before the end of January.

So, all in all, things still continue to look good for late-month pattern change and those prospects have improved in recent days. Nonetheless, before then a generally mild pattern is likely to prevail. But even then, there might be some snowfall opportunities, especially from the northern Mid-Atlantic region into New England.

[donsutherland1]

DT, among others, has raised a crucial point as to the importance of the development of blocking as the calendar moves into February.

I'll use New York City as an example.

February 1-15 Mean Temperature:
NAO:
> 0: 34.2°
0 to -0.99: 34.0°
-1.00 to -1.99: 30.8°
-2.00 to -2.99: 30.0°
-3.00 to -3.99: 29.0°
-4.00 or below: 28.2°

Coldest: -4.00 or below and PNA > 0: 26.8°

Frequency of High Temperature < 40°:
NAO:
> 0: 45%
0 to -0.99: 46%
-1.00 to -1.99: 57%
-2.00 to -2.99: 66%
-3.00 to -3.99: 63%
-4.00 or below: 75%

Most frequent: -4.00 or below and PNA > 0: 88%

Frequency of Low Temperature < 20°:
> 0: 20%
0 to -0.99: 23%
-1.00 to -1.99: 30%
-2.00 to -2.99: 28%
-3.00 to -3.99: 31%
-4.00 or below: 47%

Most frequent: -4.00 or below and PNA > 0: 54%

Conclusions:
∙ In terms of mean temperatures, readings become markedly colder once the NAO is at -1.00 or below.
∙ When the NAO falls to -1.00 or below, high temperatures stay below 40° on more than half the days. At -2.00 or below, the figure rises to more than 60% of days. During extreme blocks (-4.00 or below), high temperatures stay below 40° on 75% of days. When extreme blocks are accompanied by a PNA > 0, 7 out of every 8 days see the high temperature stay below 40°.
∙ The greatest tendency for severe cold (lows < 20°) occurs during extreme blocks (-4.00 or below). In cases when such blocks are accompanied by a PNA > 0, more than half the days see lows fall to severely cold levels (< 20°).

In short, a block, particularly one in which the NAO goes to -1.00 or below could prove crucial in determining just how cold the first half of February could grow. Currently, the GFS ensembles are in good agreement that the NAO will likely go negative by the start of February and there is a cluster of ensemble members that take the NAO below -1.00.

At this time, there remains the potential for significant cold in February. As noted in the opening post of this thread, 4/6 (67%) of the above MEI analogs saw the development of a sustained strong block at some point in February (NAO: peaking at -2.00 or below for 10 days or more). 3 had a peak negative NAO of -4.00 or below (2 such blocks were prior to mid-month).

[pawxguy]

Quite a bullish statement (in disguise) that favors an active month of February. Favors. Not a guarantee.

[Tyler]

Donsutherland, I really appreciate your analysis. They are fun to read and I learn alot from them! I have a question, with the expected pattern change toward the end of the month, do you think that Texas may finally see temperatures much cooler and actually average below normal for once, perhaps maybe even a shot at some true arctic air, or is this pattern change primarily only going to effect the northeast?

[donsutherland1]

Tyler,

In the next few days, I'll be looking at other parts of the USA other than the East. With the pattern change finally growing more likely, it might soon be time to examine its impact nationwide.

[Tyler]

Ok, thanks Don!

[pawxguy]

With new data streaming in this evening, Pacific influence will be felt as far east as Wall, SD. Trough in the east for the first part of Feb. No 1050mb., though, making its way down from the arctic.

Tyler,

In the next few days, I'll be looking at other parts of the USA other than the East. With the pattern change finally growing more likely, it might soon be time to examine its impact nationwide.