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Dec 10 Morning Crusher (obs/nowcasting)

yoda

By yoda,
in Mid Atlantic

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WinterWxLuvr

WinterWxLuvr

Posted
Posted

How much snow did you get both days?

Not sure if I know what you mean by both days. The two this week were 6.75 and 5. I can't remember exactly when the RAP yanked away my hopes. It might have been the Thanksgiving storm. Looked really good at about 10 hours and in one run was completely different...and was exactly right.

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phil882

phil882

Posted
Posted

The best thing about the HRRR and RAP is they show something different every hour. You're bound to get one run that nails it.

 

There was a substantial amount of consistency in various HRRR runs that there would be a mesoscale band developing and propagating upstream to the NW of DC. You can go back and look at the individual runs, they are all available (use the drop down bar to change the hour run).

 

http://rapidrefresh.noaa.gov/HRRR/

 

 

 

seems to be the case with mesoscale models in general.  see the NAM. they do have their use but they can be wildly varied run to run. not sure i'd assign any great victory to the hrrr here but i didn't watch it all night or anything.  there was plenty of guidance/climo knowledge pointing to the area that got the most snow today getting the most snow.  our issue around here wasn't so much mixing which was very short lived in the grand scheme as much as lack of consistent rates and temps too warm.  if temps were like 4 colder we probably would have doubled our total as it was today. partly where we got duped was just assuming that some sort of megaband was going to roll east. though the very beginning of the storm also had that weird dc gap where it was snowing all around us but not here for a while. 

 

I think where the HRRR and RAP has its most utility is being able to track down if there is any systematic error that exists from run to run. Model "trends" as most people interpret them, don't really exist. When you are looking at a deterministic solution, often you are only seeing one potential solution in the PDF curve of possible ensemble solutions. Thus when model solutions appear to waffle back and forth you are just seeing the control run sampling different portions of the curve. In reality the majority of the the new model run (e.g. 00z GFS) is created off the previous forecast of the previous model cycle (6 hr forecast of the 18z GFS). Only a small portion (15-20%) of the new model initial conditions (ICs) are actually based off ingested data that is new from the previous run.

 

With that said you do often see "trends" in model data that lead to adjustments in one particular direction as a model forecast gets closer to the initial time. This is due to systematic error in the initial conditions of the model. This is most likely to occur in a data sparse region where limited observations are received and thus the model must make its best guess based off error covariances of the limited data available. This is oftentimes where you see model biases play a part resulting in a faulty forecast. For example, its not uncommon to see models under forecast the magnitude of subtropical ridging (such as what occurred with this past week's snowfall events). This is because in most cases there are very in-situ observations (through radiosondes) in this region, and satellite radiances don't always do the best job when assimilated to depict this. 

 

http://www.atmos.albany.edu/student/kgriffin/maps/dprog/A102/500vort/namer/500vort_namer_dprog.html

 

Note that even in the last 24-48 hours before verification, the model little by little keeps building the surface area of the 588 dm contour. These tiny changes don't seem that significant in the early house, but errors always continue to grow upscale both in magnitude and horizontal extent leading to large forecast differences in longer time frames. 

 

Thats great with global models, but what about utility of the mesoscale models (e.g. RAP, HRRR). First of all the initial conditions of these models ingest global model data outside of their domains (the HRRR uses the IC of the RAP), so what the global models do can often be important to what the mesoscale models do. Next, both the RAP and HRRR assimilate radar data and attempt to create vertical thermal profiles based off estimated latent heat release of both stratiform and convective precipitation elements depicted by radar. The HRRR has the added benefit of being able to explicitly resolve convection, which is important if you want to physically interpret the diabatic heating profile of radar reflectivity. 

 

The added benefit of actively ingesting radar data is that if there are significant short term deviations in radar from the initial conditions of the global model output, it can attempt to correct for this and produce a short term forecast that understands the current "nowcast" precipitation distribution. Thus, the systematic error in this case are related to how well radar reflectivity diabatic heating profiles are assimilated with the current ICs. 

 

So lets say the southeast is convectively more active ahead of a forthcoming shortwave. In this case, the HRRR can potentially pick this up through its radar assimilation and give a realistic extrapolation of what that enhanced convective activity will translate to downstream. It would likely happen incrementally as the model receives new IC to supplement the previous model cycle, leading to a possible trend. 

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Deck Pic

Deck Pic

Posted
Posted

Everything looking good. 850 temps are still high but the crash should coincide with the precip arrival. Still wouldn't surprise me to see some initial rain/sleet quickly changing over. I'm gonna try and get another 45 min sleep. Good luck everyone!

 

 

radar looks great

 

 

yup

 

making a beeline right at us...might be sleet/rain 1st esp for DC....850temps were +3 last hour...they should be closer to +1 now

 

 

me and you are in a really good spot..We could get flushed, but either we we are going to do well...I wouldn't be surprised if we are jackpotted

 

 

makes sense..this storm is a stone cold assassin.  and we are about to be assassinated

 

 

Do you think this could be the start of some more consistent banding over MoCo and surrounding area? 

 

attachicon.gifRadar1.png

 

 

IMG_1651_zpsdf9c82d5.jpg

 

IMG_1650_zps9a39e389.jpg

 

IMG_1649_zps3d0e17ec.jpg

 

IMG_1654_zps6d133922.jpg

 

 

IMG_1636_zps2b951aab.jpg

 

IMG_1644_zps19cfc018.jpg

 

:axe:

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Bob Chill

Bob Chill

Posted
Posted

Coming off the multi year drought definitely made it hurt worse than it should have. After the first half of Jan nobody cared about this one anymore (thankfully).

I'm totally ready to track a VA to ME miller A. Another Dec 10th? No thankyou. Time to go big or go home this year.

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hosj III

hosj III

Posted
Posted

Coming off the multi year drought definitely made it hurt worse than it should have. After the first half of Jan nobody cared about this one anymore (thankfully).

I'm totally ready to track a VA to ME miller A. Another Dec 10th? No thankyou. Time to go big or go home this year.

What do you call 2-12/13?

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gymengineer

gymengineer

Posted
Posted

Coming off the multi year drought definitely made it hurt worse than it should have. After the first half of Jan nobody cared about this one anymore (thankfully).

I'm totally ready to track a VA to ME miller A. Another Dec 10th? No thankyou. Time to go big or go home this year.

 

This storm was almost comedic after 3/5-6 from the previous March. Everything from the Fed Gov't closing (every outlet including CWG warned of the morning rush-hour blitz) to the short-range models ramping-up....I got a day off of work, so I wasn't too sad :) 

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T. August

T. August

Posted
Posted

Too many losers up and down the coast. It wasn't a classic. The storm matured and occluded too early. I want one to bomb off obx/va capes and smoke everyone up and down.

I don't now about everyone else, but my snow melted an inch per hour. It hurt me every time I looked out the window at a wet driveway and heard the sound of melting snow all day long.

 

:(

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Bob Chill

Bob Chill

Posted
Posted

People love to talk about "classic" DC-Boston clobberings, but how many times has that actually happened? 1996? And?

I'm not talking about historic. Just widespread. 6-12 with 18 jackpots spread in the mix. An event the ma-sne can enjoy together. We've had plenty but it's been too long

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Bob Chill

Bob Chill

Posted
Posted

Forgot that one.

Didn't 2/12-13 fit the bill?

In some ways yes and others not as much. Too much taint and lull. I loved it in my yard but the ull lagged too much. Boston only got 3" although not too far away got much more. Too much dripping during the day.

I guess it fits the bill overall but a cold smoke 6-12 and cold dry air on the heels would have been sweeter. That dripping lull kinda took some fun out of the storm. Luckily I took a long walk at 3am. Best hour of 13-14 for sure.

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PrinceFrederickWx

PrinceFrederickWx

Posted
Posted

DC meh? Everyone but us got smoked. My best was St. Paddy Day Magic. Yeah, it's imby, but like some in here openly proclaim, I don't give a damn what other people get when it comes to snow. It is ALL about me and my yard lol.

 

The St. Patricks day storm was the biggest one IMBY too- one of my all time favorite storms. We got mostly screwed here too with 2/13/14.

 

I remember how hopeless this winter felt after the Dec. snow fails and especially after the Dec. 21-22 heatwave... boy did that change lol

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hosj III

hosj III

Posted
Posted

In some ways yes and others not as much. Too much taint and lull. I loved it in my yard but the ull lagged too much. Boston only got 3" although not too far away got much more. Too much dripping during the day.

I guess it fits the bill overall but a cold smoke 6-12 and cold dry air on the heels would have been sweeter. That dripping lull kinda took some fun out of the storm. Luckily I took a long walk at 3am. Best hour of 13-14 for sure.

Completely agree. Walking the dog at 3 AM was awesome. The deathbanding over the area just continually got crazier and crazier. Remember the HRRR runs showing widespread 12+ that we all laughed at at first? 

 

The warmth really was a buzzkill. Quickest I've ever seen 14.5" of snow melt. You could walk outside the next day in shorts. The ULL also sucked IMBY. I was thinking I could get 4-6" out of it but that sort of thing will always have winners and losers. It's not like 3/17 lasted that long either, and 1/21 was a little small for my tastes (If it was more like 8-10" I could get behind it at as my favorite event.)

 

So 2/12-13 was the king of the winter.

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AlaskaETC

AlaskaETC

Posted
Posted

Completely agree. Walking the dog at 3 AM was awesome. The deathbanding over the area just continually got crazier and crazier. Remember the HRRR runs showing widespread 12+ that we all laughed at at first? 

 

The warmth really was a buzzkill. Quickest I've ever seen 14.5" of snow melt. You could walk outside the next day in shorts. The ULL also sucked IMBY. I was thinking I could get 4-6" out of it but that sort of thing will always have winners and losers. It's not like 3/17 lasted that long either, and 1/21 was a little small for my tastes (If it was more like 8-10" I could get behind it at as my favorite event.)

 

So 2/12-13 was the king of the winter.

Agreed, I consider the 2/12/-2/13 storm my first "true" Nor'easter and it was a magical night for me. I was in heaven. Here's hoping for a better one this winter.

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Deck Pic

Deck Pic

Posted
Posted

Coming off the multi year drought definitely made it hurt worse than it should have. After the first half of Jan nobody cared about this one anymore (thankfully).

I'm totally ready to track a VA to ME miller A. Another Dec 10th? No thankyou. Time to go big or go home this year.

 

 

I did...I was bitter all winter and still am 

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