MikJournal Monday 11/26/2018...Terminology Explained

Good morning to you. Waking up this morning to a blustery start as temperatures have crashed overnight. My temperature at midnight was 51 degrees thus my high temperature for this day. However, presently at 10:15 a.m., I have a reading of 36 degrees, up one degree over the past few hours, and even experienced a few light snow showers.

Let me update you on Lexington's annual precipitation total. As I write this, a total of 65.57" has been tallied so far this year. The all-time record is 66.35" set in 2011. Therefore, a difference of just 0.78" is all that separates Lexington's all-time wettest year, or at least a tie.

A blast of cold air will reside in our region for a few days this week. In an earlier post, I mentioned about the Arctic Oscillation and its effects on our weather. Forecasts for a V-shaped signal caught my attention. Typically, I have noticed after the AO has taken a dive into negative territory, then quickly bounces back, rising toward the neutral line, an influx of milder air or return flow begins moderating our temperatures a bit. Often this introduces moisture into our region. Along with cold air trying to get out of the way, at times, the moisture overwhelms the cold air and we end up with a winter storm scenario.

But, this is normally seen during the winter months, at least this feature of the teleconnections. Of course, the other teleconnections like the NAO, PNA, and even the EPO have to be aligned as well. Since November has been behaving much like December and January at times, it seemed that this V-shaped signal would correlate better. However, all weather forecasts now are pointing toward a milder week after this cold snap. Any precipitation chances appear when the milder air is already in place thus just plain rain for our region.

Nevertheless, keep an eye on this exciting feature during the winter months as this is generally a precursor for wintry weather somewhere in our region. But, you know how Kentucky is, the battle lines between varying conditions of precipitation are always a source of contention and frustration for snow lovers and experienced forecasters alike.

One more thing. This is more about terminology than anything else. When you hear a meteorologist explain that the "strong winds are a result of low pressure with tightly packed isobars, or areas of equal pressure", that doesn't really spell it out for us very well, does it? It doesn't mean anything to me.

What is really happening? At the core of the low pressure, you have the lowest pressure reading. Surrounding that, perhaps only a few miles away, a different pressure reading is taken and shared by other locations surrounding low pressure. A few more miles away is a different pressure reading again shared by other locations surrounding the "low". Those are your isobars or areas of equal pressure. Behind the actual "low" is rising pressure. Ahead of the low is "falling pressure".

What causes the wind gradient? Well, simple physics tells us that pressure flows from high to low. It is either a steep rise or steep drop in pressure over a relatively short distance that produces the wind. The greater the difference between high and low pressure over a relatively small distance, the greater the force needed to equalize the pressure disparity. Eventually, winds will subside, because high pressure (also known as subsidence) will create more calm conditions in time.

Have a good week everyone. The busy season is upon us.

MS

Winter Storm Watch (teleconnections) Before Month's End

You have heard it first. I am forecasting a Winter Storm Watch for the region. Of course, this is still experimental, but teleconnections from the AO is forecast to show a definitive V-shape signal leading up to the end of the month.

Look to the right side of the V, as the AO should be trending higher toward the neutral line. Winter storms affecting our region have happened when this particular feature presents itself. Cold air will be in place but access to the Gulf of Mexico will cause a collision of air masses that can produce winter precipitation.

Best estimate is between November 28 and November 30. Stay tuned.

MS

MikJournal Monday 11/19/2018...More Below Normal Temperatures Coming

Another dreary Monday morning. Temperature at my place is 45 degrees at 7:00 a.m. Not looking like much rise in temperatures today with clouds and drizzle expected.

Lexington is closing in on its wettest year ever. As of last night, annual precipitation stands at 65.20". It is only the 3rd time on record that Lexington has surpassed the 65" mark. This is still the 3rd wettest year but closing in on 2nd with just a little over a half inch needed. Keep up with the total on the side of the blog as Lexington only needs 1.16" to set the all-time mark.

Louisville also is making puddles of its own. Of the 5 instances when the annual precipitation has exceeded 60" for any given year, 3 of those have now happened within the last 8 years (2011, 2015, 2018). The total of 62.32" is now the 5th wettest year. The all-time record may be hard to break though, since 68.02" is the mark to beat, nearly 5.70" away.

Snowfall for the month of November stands at 0.3" in Louisville. The last measurable November snowfall was in 2014/2015, a snow season that featured a still weak El Nino and a back-loaded winter (heaviest snow in February and March) that produced an impressive 27.6" for the snow year ending June 30. Again, most of that occurred in February and March 2015 when 22.8" was collected.

Just for fun, that would mean we would have to endure an uneventful December and January. While the first part of December looks cold, moderating temperatures seem poised to occur by the middle of the month. However, if it's just a brief speed bump, like what we have been seeing in recent months, the cold may become readily established once again with another shot of below normal temperatures by the holiday stretch. And you know what that could mean....

Presently, we are in a teleconnection pattern featuring a strengthening -AO, -NAO, and +PNA, a familiar and likely signal for below normal temperatures for the next several days after this week.

As we near the time when teleconnections mean something, I will be looking closely at the Arctic Oscillation (AO) index. What I have discovered over the last few years is when the AO is in a moderate to strong negative phase and forms a V-signature by quickly trending toward neutral. look for a snowstorm in our region as the AO is trending upward toward the neutral point. Typically, that means we already have cold air in place but warmer Gulf moisture is now available for something interesting.

That's all for now. Make it a good week. And don't overeat. I know, I know that's what everyone says.

MS

MikJournal Monday 11/12/2018...Looking Ahead

It's Monday. It was a tough day for sinus sufferers yesterday, including yours truly. Let's see if we can look ahead to what kind of weather we could have for the rest of the month.

First, the month of November has been dishing out the same kind of weather we began experiencing during the last 2/3rds of the month of October. Presently, Lexington and Louisville are running about 4.3 to 4.7 degrees below normal respectively. Over the weekend, I had my first hard freeze with 22 degrees Saturday morning and 19 degrees Sunday morning.

The persistent pattern we have seen is a result of an impressive ridge out west, partially responsible for the ongoing deadly wildfires in California. This ridge has carved out an atmospheric slope for us, allowing cold air to travel in waves with multiple precipitation chances and reinforcing shots of cold air. So, we cannot blame it on any blocking pattern to our northeast, which is typical for allowing cold air to reside so long in our region.

With colder air, snow chances have been increasing. I had my first duster by Friday morning. This week looks unstable, and precipitation chances are already going up for the region. Cold air in place may make forecasting tricky for parts of the region. I will say the best chance for some snowfall this week will be around the Wed/Thu time period. Again, a tricky forecast but does offer a chance for wet snow accumulation for some, especially central and east, perhaps a couple of inches of grassy accumulations. Stay tuned for that one.

However, this is just my observation, looking at current trends and modeling maps, the ridge out west looks to break down enough heading into Turkey Week to allow hopefully some welcome relief to the West. Also, the pattern should benefit our region with milder readings, at least more normal for this time of year. I would not be surprised to see a stretch of above normal readings heading into the last part of the month.

Where do we go from there? Well, as has been my custom for the past couple of years, I will be offering a monthly outlook for each of the winter months, one month at a time. While this is still not as accurate as a short term forecast, I believe it is a more realistic presentation than the sensational winter season forecasts put out by others. I say sensational, because people have become 'entertained' by these forecasts over the years, forecasts that include how many inches of snow your area will receive for an entire winter. Come on! Most of your experienced forecasters cannot even predict how much snow we will see in the next 7 days. It's just a guess, and it's just for entertainment.

Once I get these leaves put away, I'll be flipping my switch to snow mode. I can't stand having my fresh powder contaminated by wet leaves. Anyway, make it a great week.

MS