It's getting to be the time of the year for dangerous weather, and this may be the first widespread severe weather outbreak of the late winter season. The severe weather we'll be watching will be to our west today and no real threat for us in Georgia, but some of this could get pretty nasty.
Storms are already breaking out over Texas and Oklahoma, but right now (when I was typing this) there was no severe weather being reported.
Most of the action will occur later this afternoon and evening once the atmosphere gets stirred up a little.
I have four HRRR model images showing some of the severe parameters we'll be facing today.
Here's a look at the current radar from two different radar applications.
SPC Convective Outlook
This is a pretty long Day 1 Severe Weather Outlook... These can always be found on the Storm Prediction Center's website or here at DaculaWeather.com.
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0609 AM CST Sat Feb 24 2018
Valid 241300Z - 251200Z
... THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
NORTHEAST TEXAS... NORTHWEST LOUISIANA... ARKANSAS... SOUTHEAST
MISSOURI... SOUTHERN ILLINOIS... FAR SOUTHWEST INDIANA... WESTERN
KENTUCKY... WESTERN TENNESSEE... FAR NORTHWEST ALABAMA... NORTHERN
MISSISSIPPI... AND NORTHERN LOUISIANA...
... THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SURROUNDING THE
ENHANCED RISK,AND EXTENDING WEST INTO NORTH TEXAS...
... THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SURROUNDING THE
ENHANCED AND SLIGHT RISK AREAS...
Severe thunderstorms are expected to develop today through tonight
across northeast Texas and the Arklatex region, east northeastward
through the lower Mississippi and lower/middle Ohio Valleys. The
storms will be accompanied by potential for damaging wind gusts and
a few tornadoes, a couple of which could be strong. Hail will also
be possible across the Texas and Arklatex portions of the outlook.
Large-scale troughing will persist over the western and central U.S.
this period, while ridging holds fast across parts of the Southeast
and adjacent western Atlantic. At smaller scales, an energetic
short-wave trough -- embedded within the larger-scale cyclonic flow
-- is crossing the central and southern Rockies, and will progress
east-northeast across the Plains, reaching the upper Great Lakes by
the end of the period.
At the surface, a rather weak/ill-defined pattern is evident at this
time, per latest surface analysis, with a very weak low over far
northeast Oklahoma, a warm front extending roughly eastward to
Kentucky, and a cold front extending southwest across eastern
Oklahoma and north central Texas into the Concho Valley and Big Bend
area. With time, as the upper system shifts east-northeast, the
northeast Oklahoma low is progged to gradually deepen/shift slowly
north-northeast across Missouri today, and then advance more rapidly
north across Illinois into the western Upper Great Lakes region
overnight. As this occurs, a strengthening cold front will move
eastward in the wake of the low, extending across Arkansas and
eastern Texas by sunset, and then accelerating east to reach a
position just to the lee of the Appalachians by the end of the
period (early Saturday morning). This front will focus a zone of
strong/severe storms through the period.
...Portions of North Texas east across the lower Mississippi and
Tennessee Valleys, and northeast to the Mid-Ohio Valley...
Elevated Convection has begun to develop across the eastern
two-thirds of Texas this morning, as large-scale ascent increases
atop a still-stable boundary layer as the southern Rockies upper
system advances. With steep lapse rates over the area supporting
moderate CAPE and strengthening mid-level flow, a few of these
storms will pose a risk for producing large hail.
Several complicating factors with respect the evolving severe risk
-- primarily centered around the developing Texas convection and
more widespread storms which have been ongoing from the Ozarks east
across the Ohio Valley states. Resulting cloud cover and
reinforcement of cool air to the north of the warm front will affect
potential for any later-day heating/destabilization, and so later
adjustments to the outlook may be needed as the environment evolves.
With that said, very strong/veering wind profiles with height --
already indicated particularly over western portions of the region
-- will continue to strengthen, as stronger flow aloft associated
with the advancing upper trough overspreads the outlook area. By
afternoon, very large, sickle-shaped low-level hodographs --
representative of low-level shear highly favorable for updraft
rotation -- can be expected, suggestive of tornado potential with
any sustained/stronger storms. However, as implied above,
thermodynamic concerns will temper overall risk to some degree.
At this time, expectations are that ongoing Texas convection to
spread northeastward across eastern Oklahoma/Arkansas with time,
with new storm development late this morning/afternoon occurring
across northeast Texas/southeast Oklahoma/the Arklatex region.
While storm mode should trend toward a linear configuration near the
front, supercells -- perhaps just ahead of the line but particularly
within what is likely to be a complex line with LEWPs and bows --
are expected to evolve. Along with risk for fairly widespread
damaging winds, a few tornadoes will be possible. Greatest tornado
risk -- including potential for a couple of strong tornadoes -- is
expected within a corridor from the Arklatex area northeast across
Arkansas into the southeast Missouri/southern Illinois/western
Kentucky/western Tennessee area this afternoon and evening.
Greatest wind risk will exist along a similar corridor.
Overnight, as convection spreads east across the Mississippi Valley,
storms will eventually begin to diminish in intensity -- due both to
a decrease in instability, as well as low-level flow becoming
aligned more parallel to the front as the upper system shifts
northeast toward the Upper Great Lakes region, away from risk area.
Until then however, risk for a tornado or two within the complex
convective line along with damaging wind risk can be expected into
the western Kentucky/western and Middle Tennessee/northwest
Alabama/northern Mississippi/northern Louisiana areas.
Looking at the teleconnections this morning and what I see would be pretty historic if it actually comes to fruition. Instead of showing you all of the teleconnection charts, let's look at the numbers and try to put those into perspective.
I've captured the data from the 00Z model runs from the Euro, Euro ensembles, GFS, GFS ensembles, and the Canadian, and ballparked the values from the charts. I then compared the average of those runs to the historial March records as well as all time records to see how the current forecast stacks up. It appears from the charts, the AO and NAO start taking a dive on or around the 23rd, so I would expect changes in our weather shortly after that. A few of the long term analogs are from http://madusweather.com
Arctic Oscillation - AO
As we've talked about before, a negative AO is the result of higher pressures over the polar region, and in this case, it is caused by the stratospheric warming which is still underway.
The model average is well below the historical average and would be a new March record if it holds true. The record minimum was set in February of 2010 and that record is also in danger of being broken.
Thes records go back to 1950, and there are only three years that had a negative AO in March, 1969, 1978, and 2013, so a very small sample size, but the image on the left below shows how the temperatures responded.
North Atlantic Oscillation - NAO
The models are going wild with the NAO, and this is exactly what would be expected during an Easterly QBO with Stratospheric Warming. Strong pressures over Greenland and parts of the North Atlantic are responsible for this.
As you can see, we've never had a March with a -NAO less than -2.470, so the implications are pointing toward extreme amplification of the Greenland block. These numbers would set the all time (since 1950) record for NAO values. Not much I can show except the one year that set the March record, no other year in March has gone below -2.00. I would think values of -4 would change things considerably toward colder.
I've include two images below, 1962 on the left and 20 years of -NAO years on the right.
Eastern Pacific Oscillation - EPO
The models are thinking the same way about the EPO, but the GFS is taking it off the charts. The Euro is headed down but not as negative at the same point in time. Because EPO daily data is in a different format, I can't show any comparison to past data.
You can see the difference between a positive and negative EPO for March in the two images below. Historically, it doesn't seen to have much influence on the southeast during the month of March.
All of the values in the charts I've posted are up to March 1. The models have the PNA pretty negative at this point, and that is NOT good for cold here. Keep in mind, as we approach March the PNA is on its way up to neutral or even positive while the EPO is trending negative.
You can see examples of the PNA in its different phases. It would make sense that if the PNA goes positive, the EPO would go more negative, as the trough over the western US retrogrades west and is replaced by higher pressures. According to some meteorologist, the cold for the eastern US will be due to the retrograde of the cold over Europe, and would build in from the east to west over time. Right now the current phase of the PNA is the one teleconnection not in our camp yet.
Here's a look at years with a positive PNA, neutral PNA, and negative PNA.
While technically the MJO is not a teleconnection, it's an important driver for our weather here. We have been stuck in a warm phase 7 for a record amount of time, but it now looks like the MJO is going to continue its progression through the phases that are more favorable for cold, phases 8, 1, and 2.
The current pattern is always a combination of all the various patterns and teleconnections. The state of the La Nina/El Nino, teleconnections, stratospheric conditions... it's all a big interactive puzzle that is constantly changing and morphing.
I'm very much looking forward to the first couple of weeks of March, I just get the impression that there will be some wild weather across the US, and it will be interesting to see where it all ends up.
Temperature records are going to be challenged this week as our warmest period of the winter is about to get underway.
A pair of dueling 1038 mb high pressure areas (image #2), one out in the Atlantic and one over the central plains, are battling to see which one will be the strongest, and for us in the southeast, the one in the Atlantic is going to win out. A warm moist flow around the periphery of the high pressure will keep our temperature anomalies running 15-20 degrees above normal for highs and 20-25 degrees above normal for our lows.
In between, a precipitation battleground is shaping up with large quantities of rainfall (image #3) on the southern edge and heavy snow (image #4) on the northern side. Some of this precipitation could be heavy and some areas across the central part of the country could see upwards of 8 inches of rainfall (image #5) over the next 7 days. When we have these types of clashes between two very different air masses, severe weather is usually a by-product, and there will be a slight change for severe across the middle of he country, especially on Tuesday.
All images from WeatherBELL
These are some of the high temp records that may be broken this week across the southeast. Click to enlarge.
There will also be many max low temp records set this week, and the max low temp records will continue on through the weekend. Click to enlarge.
It's been warm this month, no question about that. But how warm has it really been and where do we stand as far as our warm records go?
The big world picture shows that for the month to date, February is running about 0.25º C above normal. This data comes from Temperature analysis (T319) from Japanese Met Agency (JRA-55 Reanalysis) and graphics from Dr. Ryan Maue's new website at http://wx.graphics/.
So far the year to date anomaly is 0.28º C or about 0.50º F above normal.
Lets look at February and see where we stand for the month. The three images below are the temp anomalies for the month and they show the max, min, and avg temp anomalies from left to right, and as always, you can click on any image to enlarge it. As you can see, the cold air has been confined to the central part of the country for the most part, while both coast basked in very warm temperatures. Overall the lower 48 states have averaged about 0.7º above normal. I would suspect the anomalies will go up some over the next 7-10 days before we return to more normal or even below normal temps.
The three images below come from the Southeast Regional Climate Center. Instead of showing temps or anomalies, these images show the temperature ranking for various sites across the southeast so far for February. Max is left, Min is center and Avg is right. So a ranking of 1 would be the warmest period in that sites data records.
The images below are the temperature anomalies for the month to date from the official sites. Again, max, min, and avg from left to right.
So we know February has been a little warm, but if we go back to the start of 2018, we begin to see a slightly different picture. We still see that the western part of the country was warm, but the east was normal to below normal. Keep in mind that these three images also include the warm February temps, so despite the warmth we've had so far, our year to date temps are still right around normal here, while a good part of the country was below normal.