And the NAM Says...?

Anyone who has read the posts on here knows I often use the NAM model in the winter, especially when the event is between 24 and 36 hours away. Of course, I still like to see what the other models are showing. But nearly 80 % of my confidence is placed in this model at 24-36 hours ETA, especially when it's all snow.

The Sunday time frame might bring many their heaviest snowfall for the next few days, not like last month, of course.

Look for at least Advisory snows going into effect soon. Depending on what the next run of the NAM shows, some may be upgraded to Warning status for snowfall of at least 4" in a 24-hour time span.

And the NAM says...
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9:45 a.m - Still looks very snowy for Kentucky. Awaiting graphics....for Sunday and overnight.

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10:00 a.m - From the Weather Prediction Center...through Monday morning...

http://www.wpc.ncep.noaa.gov/wwd/day2_psnow_gt_04.gif

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10:10 a.m - Here's a graphical look at accumulations for Sunday into Monday morning...the numbers are in millimeters. Convert to centimeters by dividing by 10 then divide that by 2.54" to get a liquid equivalent and multiply by 10 to get a 10:1 snow to liquid ratio number in inches...

http://meteocentre.com/models/get_accum.php?mod=nam&run=12&type=SN&hi=024&hf=048&mode=latest&lang=en&map=na

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2:00 p.m - Still no Advisories or Warnings yet.

The only reasons I can think is perhaps one more model run or trying to figure out a time scale for issuing either an Advisory or Warning without causing interference with the southern stream system that may or may not be as impactful. Plus coordinating these advisories/warnings might be a challenge among the Weather offices in our region.

Nevertheless, I would already plan on accumulating snowfall in Kentucky for tomorrow into tomorrow night, at least get an Advisory out there...upgrade to Warning status later if necessary.

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Lexington KY's Snowfall History Since 01/01/1990

Well, that was an interesting project. I picked apart the last 25 years or so of the calendar years and official snow seasons that run from July 1 through June 30 of each year and came up with some revealing totals for Lexington KY. Find out which day of each month had the most days of measurable snow >0.1" during the winter season of December through February over all those years. How about which days of the winter season did not record any measurable snow greater than a trace amount. And of course, the efficiency numbers. I'll explain that in a little bit.

	Days of Snow	Total Inches		Inches/Day
1-Feb	2	1.1		0.55
2-Feb	4	6.1		1.53
3-Feb	5	8.4		1.68
4-Feb	6	14.6		2.43
5-Feb	5	3.9		0.78
6-Feb	6	7.0		1.17
7-Feb	4	5.8		1.45
8-Feb	6	5.1		0.85
9-Feb	6	6.6		1.10
10-Feb	8	5.3		0.66
11-Feb	4	6.8		1.70
12-Feb	3	1.8		0.60
13-Feb	5	2.7		0.54
14-Feb	5	2.5		0.50
15-Feb	3	10.2		3.40
16-Feb	4	11.3		2.83
17-Feb	3	3.3		1.10
18-Feb	2	5.5		2.75
19-Feb	1	0.1		0.10
20-Feb
21-Feb	2	1.1		0.55
22-Feb	1	1.8		1.80
23-Feb	3	0.7		0.23
24-Feb	1	0.8		0.80
25-Feb	4	8.3		2.08
26-Feb	4	1.6		0.40
27-Feb	1	0.2		0.20
28-Feb	1	0.3		0.30
29-Feb	1	0.5		0.50
	100	123.4		1.16

This is just a sample of what my spreadsheet looks like for February since 1990, ending in 2015. As you can see, the 2nd column shows the number of instances with measurable snow greater than 0.1" for that date. The 3rd column displays the total snowfall that has occurred for that date. Then, the last column shows the efficiency number, or how many inches of snow accumulated during each instance for that date.

The most productive snow days fall right in the middle of the month. Since 1990, February 15 and 16 typically average between 2.8 and 3.4" per snow event.

During any given year, February 10 has proven to be the likeliest day you will have measurable snow. Yesterday, as a matter of fact, Lexington received 0.5" of snow for this February 10. Of course, that is not included in the table above, since it only runs through 2015. But, now you can chalk up another day, at 9 now, that it has snowed on February 10 since 1990.

The 123.4" that has accumulated during the 1990-2015 time period is the snowiest month of the winter and subsequently the calendar year. Yes, it beat out the month of January, which has more days, and every day of that month has seen some type of measurable snow throughout the aforementioned time period.

At the moment, February 20 is the only day that has not registered any measurable snow since 1990.

MS

MikJournal Monday 02/08/16

I want to show you what I have been working on this past week. It's been a lot of fun though a bit tedious at times.

Briefly, this snapshot of my spreadsheet shows Lexington Kentucky's snowfall amounts since February 1990 through 2015.

	Days of Snow	Total Inches		Inches/Day
1-Feb	2	1.1		0.55
2-Feb	4	6.1		1.53
3-Feb	5	8.4		1.68
4-Feb	6	14.6		2.43
5-Feb	5	3.9		0.78
6-Feb	6	7.0		1.17
7-Feb	4	5.8		1.45
8-Feb	6	5.1		0.85
9-Feb	6	6.6		1.10
10-Feb	8	5.3		0.66
11-Feb	4	6.8		1.70
12-Feb	3	1.8		0.60
13-Feb	5	2.7		0.54
14-Feb	5	2.5		0.50
15-Feb	3	10.2		3.40
16-Feb	4	11.3		2.83
17-Feb	3	3.3		1.10
18-Feb	2	5.5		2.75
19-Feb	1	0.1		0.10
20-Feb
21-Feb	2	1.1		0.55
22-Feb	1	1.8		1.80
23-Feb	3	0.7		0.23
24-Feb	1	0.8		0.80
25-Feb	4	8.3		2.08
26-Feb	4	1.6		0.40
27-Feb	1	0.2		0.20
28-Feb	1	0.3		0.30
29-Feb	1	0.5		0.50
	100	123.4		1.16

The second column highlights how many times measurable snow of at least 0.1" has occurred for each day of the month. The third column displays the total snowfall that has occurred for that date over the years since 1990. Finally, the last column shows what I call the efficiency number, or how much snow fell per measurable snow event for that date.

Of course, the totals are displayed at the bottom. Just to let you know, since 1990, February has been the most productive month of the winter for snowfall in Lexington. Yes, despite less number of days than January and including no measurable snowfall for the 20th of February, the month beat out January in total snowfall during this period.

As a side note, if you look at the date of February 10, you will note that there have been 8 instances of measurable snow for that date, the most of any day for the month of February. And you know what? We may add to that, since snow showers are expected to occur over the next few days, including the 10th.

In future posts when nothing is going on, I'll display more spreadsheet views of the other winter months of December and January. Actually, I'm just about done with February, so that one will be available this week. But, the spreadsheet view you see above is what will be displayed during that post.

For the next few days, regionally, we will be dealing with off and on snow showers and squalls. We call them snow showers because of the convective nature of the type of snow. Lots of instability between the surface and the air above will promote and foster bursts of, at times, heavy snow and wind with some of the stronger bands or squalls.

For the most part, the major arteries of our highway systems in Kentucky should be able to handle the light to moderate bands that occur during the daytime, but if these squalls are still kicking up a fuss during the nighttime hours, travel will become more negatively impacted.

In addition, the heavier squalls with strong winds at times, will reduce visibility suddenly. Drivers will likely be slowing down dramatically at times. So, do not think that since the weather is not bad where you are currently driving is going to be that way for the rest of your travel. A distance of a few miles or less will have no snow at times to intense, near white-out conditions at other times. And if you are just plowing along at normal highway speed when you come upon drivers that have had to slow down, well, you know what can happen. Don't be that driver. Use common sense and plan ahead for travel issues. You are not the only driver on the road. I know, that's hard to believe, isn't it? I have to tell myself that all of the time. So, be careful out there.

MS

AO Negative to Positive Alert

Ok, what a strange sounding title for a post. However, one of the patterns I have noticed is when the Arctic Oscillation is in a significantly negative mode (-3 to -5) but trending positively toward neutral, milder air is attempting to return to our region after a stout cold blast.

Often associated with milder air will be a storm system that gathers moisture from the Gulf. As long as the track of the low pressure area does not take a route to the Great Lakes, which should not happen in this case but is still possible, some type of significant wintry weather will occur in our region.

However, I really would not say that this storm system, if it can develop, will be as memorable as the January Jukebox when everyone was doing snow dances to the sound of snowflakes piling up in their neighborhoods.

Look, this storm system has not developed yet, but the AO will be trending toward neutral at about the same time the models are developing a potential winter storm. But, the other teleconnections that I like to use are pretty much out to lunch or are on vacation.

The NAO, EPO, and PNA will all be positive. Therefore, if it does snow, look for a heavy perhaps wet snow, good-packing unlike last month's snowfall for many that was more dry and powdery.

Since snow ratios will be lower in number due to the high water content, I would expect lesser accumulations as the snow will pack down an already existing base.

IF this storm system develops and will produce snow for our region, which could happen in the vicinity of February 14.

At this time, it would be impossible to peg amounts. I am just letting you know that this storm system does have a teleconnection that favors a winter storm for someone, hopefully our region if of course you're a snow lover like me.

MS

MikJournal February Prediction

Welcome to the last in a 3-part series of the MikJournal's winter prediction. I find this monthly format to be far superior than a single snapshot of what the entire winter season will be about without any specific time periods mentioned and impending storm systems to worry about. Plus the data is more fresh and useful in actually providing readers with a better assessment of the state of our climate as we progress throughout the winter season. In other words, there is more accountability with a monthly projection than some long-range outlook that just does not do much for the average reader, who will quite likely forget what the outlook said over the course of a few months.

I have been pleased with my December and January predictions. The averages have been accurately achieved and a general description of how teleconnections are associated with general weather patterns have been explained and realized.

Moving into the month of February, we have already seen quite a bit of precipitation. Plus, we are beginning to experience the first of perhaps several transitions for the month when it comes to temperature variability.

Let me explain.

Part of the delay in the issuance of this report was due to the need for the freshest data possible, since there has been mixed thus conflicting data about how cold the month of February may become.

This first week of February looks quite normal for the month, except the hefty rain totals realized late yesterday and overnight.

By the time we get into the second week, temperatures look to average several degrees below normal. In addition, clipper type systems will provide intermittent light snowfall during the time period. I back this up with the teleconnection patterns that I often refer to in my assessments.

The Arctic Oscillation, the Keeper of the Cold, should be entering the negative phase, joined by a negative EPO and a positive PNA. But, it only peaks out for a few days. Why? So far, the postive NAO is not on board yet with setting up our region for a long-term progression of below normal temperatures. Remember, we need a good blocking pattern near Greenland, and this is where the NAO can become most useful being in a negative phase.

Therefore, the third week looks to average out near normal in terms of temperatures as the AO begins to bottom out and trend more positive while the EPO becomes positive and the PNA trends negative late in the period, suggesting milder air interspersed with cold shots from the still negative AO.

Next, the fun part. This is what held me up for the longest time in getting this report together.

The AO, is expected to transition to positive for a brief time. As you found it last month, this transition from deep negative AO toward neutral and positive AO can produce exciting winter weather for our region.

The data I see for the fourth week of February does not suggest a record-setting snowfall like we had in January. However, this looks to be the greatest opportunity to see a significant snowfall for the month. Obviously, I cannot foresee actual accumulations this far out, but the potential is there for a decent storm system.

After a brief thaw from a possible snowpack and resulting frigid overnight temperatures, the AO should trend sharply negative for the latter half of the month, plunging our region well below normal again in terms of temperature

This is in part due to a phenomena in the Arctic region called a Sudden Stratospheric Warming. A transfer of energy from the troposphere to the stratosphere will have a pronounced effect on the Polar Vortex. The latest data suggests the Polar Vortex will likely become displaced as the belt of winds weaken. However, the primary displacement looks to be over Europe/Asia. Nevertheless, Arctic air will become readily available for most, as along as the other teleconnections align., such as +PNA, -EPO, -NAO, and of course the -AO.

I do expect temperatures for the month to average below normal.
I expect precipitation to average near normal to below normal.

MS

NOWCAST 02/02/16 Severe Weather Possible

The numbers will be there....All available data may show support for severe weather for our region. But will we see any widespread issues with this setup?

Analogs do not support a widespread severe weather outbreak, but the numbers are pretty scary. Nevertheless, the best chances for tornadoes appear to be west and south of Kentucky. But, isolated tornado chances still exist across the state, especially west and south.

The more sun we get, the windier it will be today, more instability. The caveat...say it with me, THE CAP. Just like spring and summer, the dreaded cap will stall initial development of thunderstorms. But, once the cap breaks, storms fire up quickly and may reach severe limits.

It will be interesting to see how many severe reports we get from this system. I'm not too impressed but do believe a few strong tornadoes are possible where the SPC has been highlighting the greatest risk, generally west and south of I-65. Look for the updates below....
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Update 1:30pm
Quick update...a few showers not severe have broken out during the last couple of hours. While a few downpours can be expected, nothing threatening with these cells. In fact may hamper instability for a time reducing severe threat for some.
Winds will eventually get cranking soon.
Tornado Watch for Western Kentucky...not an impressive Watch box as far as probabilities go for tornadoes. 50% chance for two or more within that large Watch box. Low end for strong tornadoes.

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Update 3:20pm
No warnings locally or regionally for that matter.
A couple of tornado warnings in Mississippi, don't know if any are confirmed yet or just radar-indicated.
A growing line of storms moving across western Kentucky with heavy rain.
Perhaps these less intense storms may rob the atmosphere of the needed instability for severe weather.
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Update 4:10pm
New Tornado Watch till 11:00pm est
Includes Breckinridge, Hardin, Meade, and Nelson counties in Louisville CWA.
Jefferson County not included.
More info later.
Also Tornado Warning not too far from Clarksville Tennessee, moving northeast.
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Update 5:15pm
Not too many damage reports coming in...except in a few counties of Mississippi, possibly a tornadic cell affecting the few counties involved.
Otherwise, are getting radar indicated tornado warnings for parts of western Kentucky, but no damage reports received nor confirmed touchdowns.
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MikJournal Monday 02/01/16

Good Monday morning. What a nice preview of spring over the weekend. Just awesome!

In fact, I did not have time to finish up my February Prediction...well, that was not the only reason. Actually, I am still awaiting a suite of data to help me figure out how the second half of the month may go down. Previous data suggests a conflict in how the month will unfold. And it all centers around the Arctic Oscillation.

The latest data was revealing a significant development in the Arctic region. It's a very technical term, closely related to the Polar Vortex. It is called a Sudden Stratospheric Warming Event, or SSWE. It involves a dynamic transfer of energy from the troposphere to the stratosphere which in turn affects the troposphere again with pronounced effects on the Polar Vortex, the belt of winds that circle the outer fringes of the Polar region.

Not trying to get too technical, but what happens is that the Polar Vortex is either completely displaced, or it splits into two smaller vortices. This can have major ramifications on our winter weather going forward here in the United States.

But, the latest data was incomplete as to whether the SSWE was going to cause a split or just an overall displacement of the Polar Vortex. Hopefully, that will be resolved within a couple of days. Regardless, the belt of winds are going to weaken around the Pole, the pressure difference between the Pole and mid-latitudes will go negative, and cold air is going to dive somewhere. But where? Just have to wait and see.

Some references suggest at least a 3 week lag from a SSWE to affecting our weather around here. So, it does look more likely that the second half of February extending into March may be a period of cold, at times brutal cold, possibly.

So, yes. You have just expanded your weather vocabulary. Get used to this term, again, called Sudden Stratospheric Warming or a Sudden Stratospheric Warming Event.

Another conflict is related to the teleconnections, as they are not aligning themselves properly for an extended outbreak of cold air. I will discuss more of that in my February Prediction.

In the meantime, I'll be glancing periodically on any updates about severe weather chances for the region and include these in a separate post. Busy busy.

MS