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February Pattern and Storm Discussion


POWERSTROKE

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Please don't say the models have to heal.

I thought about that when I wrote that line....but not seriously. No, it seems that weather models have a weird habit of brewing up another big storm in the place that just had one, incorrectly I might add. I do think weather models struggle to adjust to the pattern after big storms. Problably has something to do with energy transfer and some other big physics vocabulary that only a met would know. So, I am wary of model output directly after a blockbuster.

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might be true for Kata fronts, but it it's a Ana type front then there is a chance. 

I don't think I've seen anything more than a token flurry from an ana front either. It takes a while for the real cold air to make it in, especially with the mountains. The story might be different in TN, KY and places like that, but nowhere in GA, NC, SC and probably VA outside of the mountains is going to see more than a few token flakes from any kind of cold front moving through.

 

The front probably isn't an ana front anyway. You just see it move so quickly that the 12-hour accumulated precip shows up north and west of the 850 zero line, which moves through at the END of the 12 hour period.

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The Euro last night was not too far off, the problem was it pushed that low down to Cuba and it didn't turn the corner until it was too late.  Still plenty of time to turn it around.

 

You're right, it did look pretty good, especially around 156 with an energy packed upper air trough moving east, orientation kind of stunk, but the vort is >30 1/s from southern TX up to IL.  The V-Day system is kinda development on the tail end of the storm moving through the GL in the next 2 days, the Euro then develops a weak wave on the tail end of the V-Day storm around 132hrs, taking it off the EC of FL, well in advance of the larger trough coming down.  We are kind of left with a bunch of disorganized mess, rather than a discrete coastal.  At 144hrs, the trough axis is from about NE IA back to central NM, then you have this second piece diving down in to the northern plains between 152-156hrs, sometimes you will see that piece assist in straightening the main trough out in to a more favorable tilt, not the case this run, enough separation between the two that by the time the second piece carves out over the TN Valley, our front is well off the EC.  There either needs to be more or less separation between the two in my opinion to get a good storm.  Good news, models tend to have a very difficult time predicting energy diving down from Canada 6-7 days out, so solutions will continue to change.

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You're right, it did look pretty good, especially around 156 with an energy packed upper air trough moving east, orientation kind of stunk, but the vort is >30 1/s from southern TX up to IL.  The V-Day system is kinda development on the tail end of the storm moving through the GL in the next 2 days, the Euro then develops a weak wave on the tail end of the V-Day storm around 132hrs, taking it off the EC of FL, well in advance of the larger trough coming down.  We are kind of left with a bunch of disorganized mess, rather than a discrete coastal.  At 144hrs, the trough axis is from about NE IA back to central NM, then you have this second piece diving down in to the northern plains between 152-156hrs, sometimes you will see that piece assist in straightening the main trough out in to a more favorable tilt, not the case this run, enough separation between the two that by the time the second piece carves out over the TN Valley, our front is well off the EC.  There either needs to be more or less separation between the two in my opinion to get a good storm.  Good news, models tend to have a very difficult time predicting energy diving down from Canada 6-7 days out, so solutions will continue to change.

 

There are also a lot of pieces floating around on both models. Probably gonna come down to when they can all get sampled properly.

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I don't think I've seen anything more than a token flurry from an ana front either. It takes a while for the real cold air to make it in, especially with the mountains. The story might be different in TN, KY and places like that, but nowhere in GA, NC, SC and probably VA outside of the mountains is going to see more than a few token flakes from any kind of cold front moving through.

When I was a teenager, we had some new hotshot ex-military TV met come to town who would sometimes mention the possibility of snow flurries behind an approaching cold front. I finally called him up and said, "Mister, you don't understand what it does to the population around here to hear a TV weather guy use the word 'snow.' And besides, it never snows behind cold fronts here." He yelled at me and hung up on me. But then he was out of that job in a very few months, and they got some other guy who knew better than to promise ana-frontal flakes.

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I don't think I've seen anything more than a token flurry from an ana front either. It takes a while for the real cold air to make it in, especially with the mountains. The story might be different in TN, KY and places like that, but nowhere in GA, NC, SC and probably VA outside of the mountains is going to see more than a few token flakes from any kind of cold front moving through.

 

The front probably isn't an ana front anyway. You just see it move so quickly that the 12-hour accumulated precip shows up north and west of the 850 zero line, which moves through at the END of the 12 hour period.

Yea, i know most are kata that come through here. i dont think anyone can tell just yet by looking at the quantified precip values and pressure isobars. interesting setup though...

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@144 snow across the Piedmont per the Euro...looks like Jerms arctic frontal boundary snow...looks like at least for this run the Euro has fallen to the GFS.

 

Much deeper than 0z, nothing really cooking off the EC, trough is not sharp enough, maybe some more energy diving in to ND/SD, but not going to help at this point, we would need enough contained at the base, or rounding the corner initially to pop something.

 

12zeurotropical500mbSLP144.gif

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 YOu won't hear me complaining about dry cold, if that's what comes...any kind of true cold wll be very welcome....T

 

 Like Tony and apparently unlike many here including Brick, I'm a big fan of a period of any kind of strong cold. Do the original 14 analog winters from the thread I started on 1/1 about the warm December give us a clue to the chances for it to actually occur this time despite a good number of false alarms this winter on the GFS (some on the Euro) and despite some waffling still occuring from run to run about the strength of the cold? Let's see:

 

 Of the 14 warm KATL Dec. analogs, an impressive nearly half (6) had a low at KATL that was 20 F or lower within one week of 2/17, the date for which the cold GFS/Euro runs have been centering the upcoming projected cold:

 

- 1901: 19 F on 2/24

- 1922: 20 F on 2/17

- 1923: 13 F on 2/18

- 1924: 19 F on 2/22

- 1993: 19 F on 2/19

- 2012: 19 F on 2/12

 

 So, whereas I'm not yet confident that KATL will get down to 20 F or lower (still a week away, models still waffling somewhat, and models have had false cold shots), it is a very believable possibility based on these analogs. If it occurs, I'm currently guessing that KATL would get down to ~17-20 F for the coldest around 2/17.

 

 Should it get this cold at KATL around 2/17, does that mean I'm giving up on teens in March? Absolutely not. Let's look at just these six winters going into March: 

 

- 1901 went on to have an even colder low of 17 F on 3/6

- 1923 went on to have a 17 F on 3/20

- 1993 went on to have an even colder low of 18 F on 3/14

 

 So, an impressive half of these six winters went on to have upper teens in March.

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Afternoon discussion from RAH:

 

<middle paragraph on mid-range>

IF THE SURFACE LOW DOES TRACK JUST TO OUR SOUTH AND EAST...THEN THE
BEST DEEP MOISTURE AND LOW LEVEL CONVERGENCE WILL BE CONFINED TO THE
SOUTHERN CWA...WHERE QPF IS FORECAST TO BE LESS THAN ONE HALF INCH.
THERMAL PROFILES AND PARTIAL THICKNESSES SUPPORT ALL-LIQUID
PTYPE...EXCEPT FOR ON THE TAIL END OF THE EVENT AS THE SURFACE LOW
TRACKS ALONG THE COAST AND COLDER AIR IS DRAWN SOUTH AND EAST ACROSS
THE AREA.  THICKNESSES WEDNESDAY AFTERNOON WOULD SUPPORT A
TRANSITION TO RAIN MIXING WITH SNOW...BUT AT THAT POINT ALL MOISTURE
IN THE ICE-NUCLEATION ZONE IS GONE...WITH LINGERING DRIZZLE MORE
LIKELY.  ON THE FLIPSIDE...THE NAM SURFACE LOW TRACK WOULD SUGGEST A
MIX AT ONSET TUESDAY NIGHT...QUICKLY BECOMING OVERWHELMED BY WARM
SOUTHERLY FLOW AND A TRANSITION TO ALL RAIN.  THE CURRENT FORECAST
FEATURES ALL RAIN.
 

<long term>

 

.LONG TERM /THURSDAY THROUGH SUNDAY/...
AS OF 255 PM SUNDAY...

THE LONGWAVE PATTERN IS EXPECTED TO FEATURE A BUILDING RIDGE ALONG
THE WEST COAST AND A DEEPENING DOWNSTREAM TROUGH OVER THE EASTERN
US.  THE GFS AND ECMWF STILL EXHIBIT FAIRLY SIGNIFICANTLY
DIFFERENCES IN THE AMPLITUDE AND SPEED AT WHICH THE TROUGH
DEEPENS...WITH THE GFS CURRENTLY SHOWING MORE CYCLONIC FLOW AND
LOWER 500MB HEIGHTS OVER THE SOUTHEAST US BY FRIDAY.  THE 12Z ECMWF
SEEMS TO BE A LITTLE MORE INLINE WITH THE GFS SOLUTION...BUT HAS
WAVERED A BIT FROM RUN TO RUN. CYCLOGENESIS ASSOCIATED WITH HEIGHT
FALLS AHEAD OF THE TROUGH SHOULD OCCUR OFFSHORE AND TO THE NORTHEAST
OF THE OUR AREA SATURDAY...WITH THE MAIN CHANCE OF PRECIP COMING
FROM MOISTURE STARVED BUT POTENTIALLY STRONG ENERGY ROTATING THROUGH
THE UPPER TROUGH. THERMAL PROFILES WOULD BE COLD ENOUGH TO SUPPORT
SNOW ...DEPENDING ON DIURNAL TIMING...AS NEAR NORMAL TEMPS THURSDAY
AND FRIDAY FALL TO TWO OR THREE CATEGORIES BELOW NORMAL SATURDAY
THROUGH SUNDAY.

&&
 

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