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February 12-13 Storm, Part II


stormtracker

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an increasingly strong signal -- it's interesting when analogs based on a forecast deviates a bit from the model evolution -- CIPS are a neat tool

It has mixed utility IMO but it has been neat to see how it's consistently west of the op it runs off of.. probably because the mid levels looked better than the sfc for a while.  

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Just some thoughts, RE: the ECMWF...

It hasn't been the greatest performer this cool season 60-144 hours out, at least in terms of verification comapred to it's ensemble mean or even the GFS and GEFS mean. I understand some "tinkering" was done recently to the model; I'm wondering if we're seeing some grid scale feedback issues because of that (?)

 

it's foolish to label any model changes as "tinkering" -- they are exhaustively tested, especially in the case of the ECMWF -- and are never implemented if they don't show "positive" impact -- that doesn't preclude issues on a case-by-case basis. Not every deviation between models can be traced back to some "bias". 

 

Regarding performance -- it's still the best performing model by just about every verification metric -- doesn't make it right here, as the case with any model, it's just guidance. When you say it hasn't been the greatest performer -- is that just a qualitative inference or something that's got some meat behind it?

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It has mixed utility IMO but it has been neat to see how it's consistently west of the op it runs off of.. probably because the mid levels looked better than the sfc for a while.  

 

yeah i haven't followed it enough to really have an opinion from an operational tool -- do they show the spread of the analog mean anywhere?

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This is what I wrote on Facebook for the general public:

 

Time to comment on this storm - Just thoughts - not committed to anything - all subject to change

- Start time would likely be Wednesday mid to late evening
- It will probably be a long duration event - 18hrs+
- We will start as snow but will likely mix and change to sleet in DC for a period and then perhaps back to snow
- Surface will be fine for 1st 6-8 hours of storm and we will accumulate easily
- Thursday could be 33-34 at surface so may cut down on accumulations a bit at the end
- The American models have a more easterly track with less precipitation but higher percentage snow
- The European model, which is the best model, is the furthest west, the wettest, and I would lean slightly toward that solution, though it could shift east a bit

Very low confidence loose guess for DC proper - 

Feels like a 6-10" event with most of that coming in the first 8 hours, then accumulating sleet, then back to snow with perhaps 1-3" during the day on Thursday....

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Once this gets going the surface will not be a problem. I found the DCA commenter to be smuga nd that is part of the problem down there. You will never, ever, never be able to convice me that in Feb 2010 with area wide heavy snow and temps in the mid 20's that DCA recorded 16" and everthing else around it was 24"+.

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I am basing it on the monthly verification scores that our Development and Training Branch provides us within WPC each month. I'm admittingly making a broad assumption here from viewing just a handful of ppt slides the last few month (500 and sfc)

it's foolish to label any model changes as "tinkering" -- they are exhaustively tested, especially in the case of the ECMWF -- and are never implemented if they don't show "positive" impact -- that doesn't preclude issues on a case-by-case basis. Not every deviation between models can be traced back to some "bias".

Regarding performance -- it's still the best performing model by just about every verification metric -- doesn't make it right here, as the case with any model, it's just guidance. When you say it hasn't been the greatest performer -- is that just a qualitative inference or something that's got some meat behind it?

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First watches up to the SW. 

 

URGENT - WINTER WEATHER MESSAGE
NATIONAL WEATHER SERVICE BLACKSBURG VA
200 PM EST MON FEB 10 2014

...HIGH POTENTIAL FOR HEAVY SNOW WEDNESDAY INTO EARLY THURSDAY...

.A DEEP LOW PRESSURE SYSTEM DEVELOPING ALONG THE GULF COAST WILL
FORCE LARGE AMOUNTS OF MOISTURE NORTHWARD ALONG THE ATLANTIC
SEABOARD AND ACROSS THE APPALACHIAN CHAIN. COLD AIR ALREADY IN
PLACE DURING THAT TIME WILL CAUSE THIS PRECIPITATION TO FALL AS
SNOW. STRONG UPSLOPE FLOW INTO THE MOUNTAINS...IN ADDITION TO THE
POTENTIAL FOR HEAVY SNOW BANDS TO DEVELOP ACROSS THE AREA...WILL
LEAD TO THE POTENTIAL FOR 5 TO 8 INCHES SNOWFALL ACCUMULATIONS
ACROSS THE MOUNTAINS TO THE BLUE RIDGE...AND 6 TO LOCALLY 10
INCHES ACROSS THE PIEDMONT. THESE VALUES MAY BE ADJUSTED LATER
BASED ON UPDATED FORECAST MODEL GUIDANCE.

VAZ011-018>020-022>024-034-035-045>047-059-WVZ042>045-110300-
/O.NEW.KRNK.WS.A.0002.140212T1100Z-140214T0300Z/
GILES-CRAIG-ALLEGHANY VA-BATH-ROANOKE-BOTETOURT-ROCKBRIDGE-
BEDFORD-AMHERST-CAMPBELL-APPOMATTOX-BUCKINGHAM-CHARLOTTE-MERCER-
SUMMERS-MONROE-GREENBRIER-
INCLUDING THE CITIES OF...PEARISBURG...NEW CASTLE...
CLIFTON FORGE...COVINGTON...HOT SPRINGS...ROANOKE...SALEM...
FINCASTLE...LEXINGTON...BUENA VISTA...BEDFORD...AMHERST...
LYNCHBURG...APPOMATTOX...KEYSVILLE...BLUEFIELD...FLAT TOP...
HINTON...HIX...UNION...LEWISBURG...QUINWOOD...DUO...RAINELLE
200 PM EST MON FEB 10 2014

...WINTER STORM WATCH IN EFFECT FROM WEDNESDAY MORNING THROUGH
THURSDAY EVENING...

THE NATIONAL WEATHER SERVICE IN BLACKSBURG HAS ISSUED A WINTER
STORM WATCH...WHICH IS IN EFFECT FROM WEDNESDAY MORNING THROUGH
THURSDAY EVENING.

* LOCATIONS...AREAS OF VIRGINIA AND SOUTHEAST WEST VIRGINIA NORTH
OF HIGHWAY 460.

* TIMING...WEDNESDAY MORNING THROUGH THURSDAY EVENING.

* HAZARDS...HEAVY SNOW.

* ACCUMULATIONS...SNOW ACCUMULATIONS OF 5 TO 8 INCHES ARE POSSIBLE
WEST OF THE BLUE RIDGE...WITH 6 TO 10 INCHES POSSIBLE FURTHER
EAST ACROSS THE PIEDMONT.

* MAIN IMPACTS...HEAVY SNOW CAN LEAD TO SLICK AND HAZARDOUS
TRAVEL CONDITIONS AS SNOWFALL ACCUMULATES ON ROADWAYS. THE SNOW
IS EXPECTED TO BE HEAVY AND WET...AND MAY WEIGH DOWN ON TREE
LIMBS AND POWER LINES. SPORADIC POWER OUTAGES ARE POSSIBLE.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A WINTER STORM WATCH MEANS THERE IS A POTENTIAL FOR SIGNIFICANT
SNOW...SLEET...OR ICE ACCUMULATIONS THAT MAY IMPACT TRAVEL.
CONTINUE TO MONITOR THE LATEST FORECASTS.

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Been looking at GFS and NAM forecast soundings, IAD seems to stay all snow throughout the entire event.  DCA appears to have an isothermal layer at 0 C between 850-950mb.  So DCA *might* stay all snow (verbatim) but could be low-ratio wet snow instead of changing outright over to IP or RA.  Could be a problem for power lines.

 

Don't have access to euro or its soundings.

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Once this gets going the surface will not be a problem. I found the DCA commenter to be smuga nd that is part of the problem down there. You will never, ever, never be able to convice me that in Feb 2010 with area wide heavy snow and temps in the mid 20's that DCA recorded 16" and everthing else around it was 24"+.

 

DCA recorded 18" and area around it was generally 19-23"....so a little low comparatively, but not at all what you are suggesting....I got 22" well into NW DC at 210'...I think you can definitely make an argument, but when you skew the facts it makes your argument much less compelling and you have a tendency to do just that

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This is what I wrote on Facebook for the general public:

 

Time to comment on this storm - Just thoughts - not committed to anything - all subject to change[/size]- Start time would likely be Wednesday mid to late evening[/size]- It will probably be a long duration event - 18hrs+[/size]- We will start as snow but will likely mix and change to sleet in DC for a period and then perhaps back to snow[/size]- Surface will be fine for 1st 6-8 hours of storm and we will accumulate eas[/size]ily

- Thursday could be 33-34 at surface so may cut down on accumulations a bit at the end

- The American models have a more easterly track with less precipitation but higher percentage snow

- The European model, which is the best model, is the furthest west, the wettest, and I would lean slightly toward that solution, though it could shift east a bit

Very low confidence loose guess for DC proper - 

Feels like a 6-10" event with most of that coming in the first 8 hours, then accumulating sleet, then back to snow with perhaps 1-3" during the day on Thursday....[/size]

I think its extremely unlikely qpf being advertised yields anything less than 8 inches, except at the runway at the airport. 8-14 seems fairer and less cynical

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I am basing it on the monthly verification scores that our Development and Training Branch provides us within WPC each month. I'm admittingly making a broad assumption here from viewing just a handful of ppt slides the last few month (500 and sfc)

 

 

that's cool -- no worries -- would have liked to hear about those -- just the first i had heard about feedback issues with the newest version 

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I think its extremely unlikely qpf being advertised yields anything less than 8 inches, except at the runway at the airport. 8-14 seems fairer and less cynical

I actually agree.  I think it's a little bearish, but safe.   If it were a perfect scenario, we'd be looking at almost 2 feet.   Even with a prolonged period of sleet and low ratios, 8 to 12 seems like a good call...and that's with the Euro's track.

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I think its extremely unlikely qpf being advertised yields anything less than 8 inches, except at the runway at the airport. 8-14 seems fairer and less cynical

 

If you throw out the american guidance and hug the euro verbatim, then I agree...but who would do that 54 hours out?....Not the I am accountable to the public, but I have been forecasting a long time, and 8-14" is way too bullish at this range when you have a major model giving us 0.75" with mixing

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I actually agree.  I think it's a little bearish, but safe.   If it were a perfect scenario, we'd be looking at almost 2 feet.   Even with a prolonged period of sleet and low ratios, 8 to 12 seems like a good call...and that's with the Euro's track.

 

Its what I sent out to our staff here... my email basically mirrored what Zwyts said... I stated 4-8 very early guess of snow... but potential for much more

 

15z SREFs should be out any minute now

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Once this gets going the surface will not be a problem. I found the DCA commenter to be smuga nd that is part of the problem down there. You will never, ever, never be able to convice me that in Feb 2010 with area wide heavy snow and temps in the mid 20's that DCA recorded 16" and everthing else around it was 24"+.

The problem is people like yourself who dont have a clue and make foolish comments. Do you even know where they measure snow at DCA?

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