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Feb 7 Winter Storm


Brick Tamland

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I live in between Myrtle beach and Conway. I can verify there's

No word of winter weather. Even ole Ed Piatrowski said just a cold rain earlier today. Assuming that's the safest bet until told otherwise

 

Jaydog is all over it.....http://www.wmbfnews.com/weather

 

That said Jaydog ya need to head back up to eastern NC your severe storm coverage is sorely missed......

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No it didn't, maybe earlier that evening somewhere but it started as light snow at RDU....there's a -RA at 1750 but it didn't last long

 

RDU 2000-01-24 17:51 -RA

RDU 2000-01-24 18:51 M

RDU 2000-01-24 19:51 -SN BR

RDU 2000-01-24 20:51 M

RDU 2000-01-24 21:51 -SN BR

RDU 2000-01-24 22:51 -SN BR

RDU 2000-01-24 23:51 -SN BR

RDU 2000-01-25 00:51 +SN FZFG

RDU 2000-01-25 01:51 +SN FZFG

RDU 2000-01-25 02:51 +SN FZFG

RDU 2000-01-25 03:51 +SN FZFG

RDU 2000-01-25 04:51 +SN FZFG

RDU 2000-01-25 05:51 +SN FZFG

RDU 2000-01-25 06:51 -SN BR

RDU 2000-01-25 07:51 +SN FZFG

RDU 2000-01-25 08:51 SN FZFG

RDU 2000-01-25 09:51 SN FZFG

RDU 2000-01-25 10:51 -SN BR

RDU 2000-01-25 11:51 -SN BR

RDU 2000-01-25 12:51 -SN BR

RDU 2000-01-25 13:51 -SN BR

RDU 2000-01-25 14:04 -SN

 

It definitely started as Rain in N. Raleigh.  Western wake saw close to 2 feet. Eastern wake could have cut that total in half, but when it switched to snow, it was glorious.  Ended up with 16" at my parents house in N. Raleigh

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Going to take a couple minutes and cover trough axis's.  I know we have some who may not understand when we talk about tilt, and we have many guests stopping by so this seems like a good point to cover the basics.  In order to understand troughs you have to focus on the upper levels, you should not look at surface maps which show precipitation and surface pressure to determine what an upper level trough is doing. In the world of weather, it is best to take a top down approach.  You will here us refer to H5 a lot, aka 500mb.  That is the air about 15,000' above us.  300mb is even higher, about the altitude airplanes fly at, 30K'.  

 

Let's use the 22z (Zulu, Greenwich mean time) RAP for this system as an example.  One has to locate the 500mb trough axis of the embedded short wave.  This comes from experience, if you look at enough H5 maps over time it will get easier.  Many of us have been looking at this stuff for 10-15 years, QC started looking at it when he was a baby, Brick still has not looked at it.  Shaded areas of vorticity (basically spin, turbulence at that level, here it is 15K'), should be taken in to account but you really need to focus on the isohypses, lines of equal geopotential height.  With all this being said, one can orient the base (bottom) of the shortwave trough to the left, when compared to the center-point.  It takes time, I know, but after seeing enough of them folks who do not know, who have interest, will get the hang of it.  From the graphic below, we can clearly see the trough is positively tilted (22z RAP +18hrs).

 

post-382-0-84141200-1454717368_thumb.jpg

 

So lets move on to neutral and negative tilt, which my MS Paint skills have crudely tried to illustrate in a Wilkesboro dud type esque.  I will start with this, the sign of a maturing  trough (and system in general) is the trough turning from neutral to negative tilt.  Neutral tilt is when the axis orientated N-S, as shown above, negative is when the base of the trough is right of center.  

 

Depending on where you live in the SE, you want this to occur at a certain point.  For us here in Eastern NC it is AL/MS (FL Panhandle), for the MA and NE, it is right around the MS River, or just east.  Cutters turn neg well west of the MS River, Apps runners are just west of the MS River.  A late turn, like the one we are seeing here, is good for E SC, and results in an OTS (out to sea) track as there is not sufficient upper level forcing to take the LP further up the coast.

 

Many I know already know this, but for some this is a little learning, that's all. 

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^^ Good post man. One thing that there is also frequent confusion about is what to root for in terms of the thing cutting off more west vs more east. Usually, we tend to pull for a close-off more west, but someone mentioned to other day (may have been you) that we want it to stay open longer, as it may help the axis turn negative sooner. Just a thought.

Nice injection of funny too. :)

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^^ Good post man. One thing that there is also frequent confusion about is what to root for in terms of the thing cutting off more west vs more east. Usually, we tend to pull for a close-off more west, but someone mentioned to other day (may have been you) that we want it to stay open longer, as it may help the axis turn negative sooner. Just a thought.

Nice injection of funny too. :)

 

Open longer, usually a sign of more energy rounding the base, aiding in a sharper turn when it occurs.  As opposed to a cutoff where more energy is absorbed in to the center mass, which tends to limit the overall turn.  Hope that makes sense.

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Open longer, usually a sign of more energy rounding the base, aiding in a sharper turn when it occurs. As opposed to a cutoff where more energy is absorbed in to the center mass, which tends to limit the overall turn. Hope that makes sense.

It does. Open and diving is the way to go this time.

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Since we're talking about the 2/7 storm in this thread, this just came through out of ILM... from their latest HWO

 

731 PM EST FRI FEB 5 2016THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHEAST NORTH CAROLINA AND NORTHEAST SOUTH CAROLINA..DAY ONE...TONIGHT.NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME..DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY.RAINFALL AMOUNTS OF 1 TO 2 INCHES POSSIBLE SUNDAY...HIGHEST NEAR THE COAST. ACCUMULATING SNOW POSSIBLE WELL INLAND ON SUNDAY.
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Open longer, usually a sign of more energy rounding the base, aiding in a sharper turn when it occurs.  As opposed to a cutoff where more energy is absorbed in to the center mass, which tends to limit the overall turn.  Hope that makes sense.

 

In this scenario, when would the RDU area want the low to cutoff? I know it's unlikely for us to see much of anything at this point, but one can still hope.

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Researching the ARPEGE leads to knowledge that it is 4dVAR.. and a lot of collaboration with the ECMWF people and data.  interesting to see how it performs.  even back in 1993 it was successful forecasting vs other guidance they were working with.. it's been around for quite the while.

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Researching the ARPEGE leads to knowledge that it is 4dVAR.. and a lot of collaboration with the ECMWF people and data.  interesting to see how it performs.  even back in 1993 it was successful forecasting vs other guidance they were working with.. it's been around for quite the while.

I just hope you're further along than me.  Still trying to figure out the models, but same area as you.

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Our favorite weenie model, the French Model, is not backing down. The 18z run...

It's a bit further west with the precip shield than the prior run and CLT gets a decent bit of virtual snow.

 

That is mighty close to the coast, imagine that precip shield would extend to the ENE after 48hrs, potential to be the catch phrase coming out of this winter, ARPEGE

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KCHS is closely monitoring this scenario and at this time will not hoist up winter storm watches. However, the afternoon AFD was a very good read and well thought out and includes the potential for convective elements causing bursts of quick accumulating wet snow.

Temperatures tomorrow and when clouds fill in in this region could also have significant impacts on how much or little things need to cool down the SFC and atmosphere but this is going to be a highly dependant rates and dynamic cooling event.

CAE even mentions the s word  :D  

 

.SHORT TERM /6 AM SATURDAY MORNING THROUGH SUNDAY NIGHT/...

SURFACE HIGH PRESSURE WILL REMAIN ANCHORED OVER THE FORECAST AREA

THROUGH THE WEEKEND WHILE ANOTHER POSITIVELY TILTED...HIGHLY

AMPLIFIED UPPER TROUGH MOVES INTO THE REGION SATURDAY NIGHT AND

CROSSES THE FORECAST AREA AS A CLOSED LOW SUNDAY. THE APPROACHING

UPPER TROUGH WILL INDUCE STRONG CYCLOGENESIS OFF THE SOUTHEAST

COAST FROM LATE SATURDAY AFTERNOON THROUGH SATURDAY NIGHT AND

THEN THE LOW WILL BEGIN TO LIFT NORTHEAST AWAY FROM THE REGION

SUNDAY. THE LATEST GFS AND ECMWF WERE REASONABLY CLOSE WITH

PLACEMENT OF THE SURFACE LOW OFF THE CAROLINA COAST ALTHOUGH THE GFS

MAY BE JUST A BIT FARTHER TO THE WEST.

ATMOSPHERIC MOISTURE WILL REMAIN QUITE LOW WITH ONLY THE EASTERN

MIDLANDS SEEING PRECIPITABLE WATER VALUES RISE ABOVE 0.25 OF AN

INCH TO AS HIGH AS 0.60 OF AN INCH LATE SATURDAY NIGHT INTO EARLY

SUNDAY MORNING. ISENTROPIC LIFT WILL INCREASE ALONG THE COAST AND

EXPECT LIGHT RAIN TO DEVELOP AND LIFT NORTHWARD...POSSIBLY

IMPACTING MAINLY THE EASTERN MIDLANDS SATURDAY NIGHT INTO SUNDAY.

WILL CONTINUE TO CARRY LOW CHANCE POPS AT THIS TIME. THE NAM WAS A

LITTLE COOLER COMPARED TO THE GFS INDICATING A GREATER CHANCE OF

SNOW. SOME SREF MEMBERS INDICATED SNOW. THE CONSENSUS INDICATES

LIGHT AMOUNTS AND MARGINAL TEMPERATURES. WE HAVE FORECASTED A

SLIGHT CHANCE OF A RAIN AND SNOW MIX LATE SATURDAY NIGHT INTO

SUNDAY MORNING IN THE EAST PART OF THE FORECAST AREA.

THE UPPER LOW WILL PUSH OFF THE COAST SUNDAY AFTERNOON WITH ZONAL

FLOW RESUMING OVER THE REGION. TEMPERATURES WILL BE BELOW NORMAL

THIS PERIOD. USED THE GUIDANCE CONSENSUS FOR THE TEMPERATURE

FORECAST.

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Not to mention the fact that temps will be 45-50 Sunday afternoon

Down here between the Conway/Myrtle beach area highs for Sunday have dropped from low 50s to between 39-43 depending on the source. And that was just from this morning to this evening. Sadly the lows haven't shifted much, sitting between 33-36

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Down here between the Conway/Myrtle beach area highs for Sunday have dropped from low 50s to between 39-43 depending on the source. And that was just from this morning to this evening. Sadly the lows haven't shifted much, sitting between 33-36

Don't get to caught up in temps, your high could be at midnight with a thick cloud deck, and your low could be during the heaviest precip shield.

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