North American Mesoscale Model Verification on January 26-27...

By: Zachary Labe , 10:34 PM GMT on January 29, 2011

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The North American Mesoscale Model (NAM) is a high resolution model courtesy of the National Center for Environmental Prediction. Another very common and referenced name for the model is the Weather Research and Forecasting Model (WRF). They are the same model and run out to 84 hours. The purpose of the model is to run a higher resolution determining mesoscale features that often cannot be picked up by the global models due to their larger scale. The NAM can be run on an 80km resolution with a broad view of the United States, or 40km which allows the viewer to zoom in on a localized region to put up on mesoscale features. Also a very high resolution form of the NAM exists using a 12km parametric and can zoom into different states. The model is released four times a day at 0z, 6z, 12z, and 18z. Keep in mind that time is zulu or more commonly known as greenwich mean time.

Computer models are critical to forecasting the weather as they use parametric and other mathematical equations to derive the current and predicted state of the atmosphere using a physical and chemical explanation as the background for the predictions. The NCEP is associated with the National Oceanic Atmospheric Administration (NOAA) to be the developer of these computer models. Each meteorological organization worlwide uses their own developed computer models to serve as a basis for the forecasts. Without computer models, we are not able to derive predictions on the weather greater than 24 hours out.

Like all computer models, the NAM shows all layers of the atmosphere in maps determining positioning and speed of the jet stream, surface precipitation amounts (quantitive precipitation forecast QPF), temperatures throughout the entire core of the atmosphere, convective indices, simulated radars, etc. Due to the higher resolution of the NAM, several problems do exist. It often produces convective elements in many middle latitude cyclones and these are known as convective feedback problems. This is where it developed these unstable regions and often associates them as surface lows causing the surface depiction to be distorted. This was a problem in the recent prediction of the January 26-27 winter storm and will be noted below. Also the NAM has a tendency to produce higher than normal precipitation amounts. I typically find myself cutting totals nearly by 30% as shown on the NAM. Finally the NAM has a bias to overamplify a low pressure and close them off to early particularily on eastern United States cyclogenesis off the coast.

The January 26-27 winter storm featured many model headaches do to some interesting variables. Early on it appeared likely for a low pressure to track up inland along the coastal plain. There was a lacking 50/50 low, unfavorable position of the western trough axis, neutral NAO, natural baroclinicity along the coastline, and stale antecedent cold air mass. This would produce rain along I-95 with heavy snows inland. The 500mb synoptic pattern showed very strong signals for this time of setup with most computer model guidance also in support. The GGEM and ECMWF led the pack with the heavy snows from I-81 on westward. The GFS suffered major problems with varying solutions for each run. But then the computer models began to delay the storm. In fact it was delayed nearly 48-60 hours from the original starting time. This caused a different scenario to unfold. The lacking high pressure to the north was still a problem as the anticyclone zoomed east-northeast, but now a high pressure and associated shortwave out ahead of it allowed sunk east-southeast across the Midwest and western Great Lakes. This acted as a 'kicker' helping to push the cyclonegenesis farther off the coast. This in turn allowed for a colder scenario along with precipitation to occur farther east. Therefore a turn of events allowed for a major I-95 snowstorm with 6in+ totals from Washington DC to Boston. This was very fortunate for snow lovers in that corridor due to pure luck given the poor synoptic setup.

Given the NAM's high resolution, it often overanalyzes prognostics post hour 60. It tends to enhance QPF, overamplify lows, and pick up on mesoscale features that really do not exist. Therefore I typically throw out hours 60-84. It would be a rare event where you would find the NAM 84 hour verifying anywhere close to accurate. But in the near term range, the NAM does an excellent job locating temperature thermals, QPF ranges, and picking up on mesoscale features; coastal fronts, enhanced convection, deformation bands, etc. But in this recent storm, it suffered a plethora of problems and even the 6 and 12 hour surface maps had poor verification especially in the QPF department.

Let us first look at the actual accumulated precipitation totals for the storm.

Given this is a 24 hour accumulated precipitation amount, about .01-.1in of additional precipitation fell south of the Mason-Dixon line in the previous 24 hours.

Here are the preceeding NAM total QPF forecasts...


(January 24; 18z) (January 25; 6z)


(January 25; 12z) (January 25; 18z)


(January 26; 0z) (January 26; 6z)

As you can see, the NAM had a lot of variance with the northwestern sharp precipitation gradients. These tight gradients this year have been caused by the rapid intensification of the coastal lows allowing the heaviest moisture to be confined closer to the center of circulation. Also in this instance, a very cold and dry air mass along with associated cold front was quickly advancing southeast across the Great Lakes and was even picked up on by the 700mb RH charts. This allowed the flow out of the northwest to dry up some moisture for areas more inland.

The NAM simulated radar vs. the forecast QPF did not match up. Often the NAM simulated radar showed the heavier mesoscale bands lining up in northern Maryland and southern Pennsylvania where as it only showed total QPF to be .25in-.5in. In fact looking at total verification, the NAM did very well for its simulated radar.


(Actual NEXRAD National Radar) (6z NAM January 26 Simulated Radar)

The NAM did seem to have a hold on the 500mb map showing the negatively tilted trough producing the coastal low along with the placement of the upper level low and associated shortwave kicker just to the west.


(18z NAM January 24; 500mb) (0z NAM January 26; 500mb)

In general the differences in the 500mb maps were very subtle with just a general strengthening in the closed 500mb low, which verified a tad north of the January 24 18z model run.

The NAM did a very excellent job in identifying mesoscale band using the UUV/700mb RH charts.

(6z NAM January 26; 700mb)

It indentifed the enhanced snow growth over southeastern Pennsylvania up through New Jersey and New York City. The problems with the NAM generally existed in the QPF fields. The model likely suffered a very convective feedback issues in QPF totals. This is why it is important to note other maps than surface maps to help locate the heaviest precipitation. The 700mb map screamed that snow totals would be farther inland with the enhanced deformation band and UUV rates. In general the high resolution models handled this the best with the HRR scoring an amazing victory for QPF along with the ECMWF. The GFS/NAM did a very poor job for QPF, but as noted above QPF does not always tell the story. Sometimes it is important to note other layers of the atmosphere to help make a forecast. This point is why many forecasters missed the boat. Many forecasters (especially broadcoast meteorologists) are drawn to the easy to understand QPF/surface maps, but one has to look at all layers of the atmosphere to make a prediction.

Lower Susquehanna Valley Doppler...

(Courtesy of WGAL)

"Here northeast of Harrisburg 2010-2011 winter statistics"
(Snow Stats)
Current Snow Cover- 0-3in
Monthly Total (November)- Trace
Monthly Total (December)- 0.6in
Monthly Total (January)- 18.90in
Monthly Total (February)- 1.35in
Seasonal Total- 20.85in
Winter Weather Advisories- 7
Winter Storm Warnings- 2
Ice Storm Warnings- 0
Blizzard Warnings- 0
Freezing Rain Advisories- 1
Winter Storm Watches- 2

(Temperature Stats)
Lowest High Temperature- 23.7F
Lowest Low Temperature- -1.7F
Wind Chill Advisories- 0
Wind Chill Warnings- 0

(Snow Storms Stats)
First accumulating snow - December 10 - 0.50in of snow
Clipper light snow - January 7-8 - 2.25in then another 1in of snow
Double Barrel Low - January 11 - 4.5in of snow
Coastal Low - January 17-17 - 1.8in of snow/sleet
Arctic Front - January 20-21 - 2.1in of snow
Upper level/coastal low - January 26 - 5.75in of snow
Two clippers - January 28-29 - 1.5in of snow

Ice Storm 2011... (Blizzard92)
.4-.5in of freezing rain
Ice Storm 2011...
Ice Storm 2011... (Blizzard92)
.4-.5in of freezing rain
Ice Storm 2011...
Ice Storm 2011... (Blizzard92)
.4-.5in of freezing rain
Ice Storm 2011...
Ice Storm 2011... (Blizzard92)
.4-.5in of freezing rain
Ice Storm 2011...
Ice Storm 2011... (Blizzard92)
.4-.5in of freezing rain
Ice Storm 2011...
Ice Storm 2011... (Blizzard92)
.4-.5in of freezing rain
Ice Storm 2011...
Ice Storm 2011 (Blizzard92)
Melting begins...
Ice Storm 2011
Ice Storm 2011 (Blizzard92)
Melting begins...
Ice Storm 2011

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"All good things arrive unto them that wait - and don't die in the meantime" M. Twain.

Blizz/Zack, it has been so amazing watching you develop over the last couple years--best of luck, you earned it! Plus you have the best blog going on WU! Woo Hoo. we will have a party!
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Quoting Matlack:


I stayed with Moosehead - used to ride my bike to the liquor store to buy a 6 before each party. Now I brew my own...


i forgot about Moosehead....there was Molson Golden as well and Labatts...those were over $3 easy. I can remember also that Coors (a brew i never cared for) was hard to get. I brewed my own once, but found it was too much trouble. easier to buy what i like. My favorite these days is Paulaner Original. There is actually a great deli/bar in my neighborhood. The have 6 microbrews on draft and they also have a 40' wall of beers on shelves. all kinds of beer from all over the world and they will chill it for you in 4 mins if you desire. it's really doing well
Member Since: January 26, 2007 Posts: 72 Comments: 6243
Quoting PengSnow:
I look forward towards next weeks weather extremes and I will now be relocating back to the burgh from the east(you got to love the corp world)----Go Steelers and Go Penguins, I now won't have to listen to Philly sports anymore, even though I will miss watching Vick and you got to like the flyers because their owner has always put a phyically tough team on the ice.  But the burgh will always be my home!!!  I already purchased a home

 


Welcome back neighbor! It gets lonely here being on the outer fringes of the mid-atlantic. I think I'm the only PA regular here West of the mountains. I would argue that this area is its own region; neither Northeast, Great Lakes, Midwest or Mid-Atlantic. The weather here is significantly different from our Eastern counterparts. Congrats on your new home.
Member Since: October 14, 2006 Posts: 1 Comments: 639
Quoting bwi:
I'm terrible at interpreting model results, but the ECMWF seems like a parade of storms up the east coast. Hopefully some will be snowy. Looking forward to a discussion of next week's weather -- Blizz I hope you have time to post an analysis?

Yep, I should have a new blog out tomorrow.
Member Since: December 14, 2007 Posts: 281 Comments: 15071
1112. bwi
I'm terrible at interpreting model results, but the ECMWF seems like a parade of storms up the east coast. Hopefully some will be snowy. Looking forward to a discussion of next week's weather -- Blizz I hope you have time to post an analysis?
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Did I miss the surprise or do I need to wait until tomorrow?
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nice ice pics blizz
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Cold morning today with a low of 8F.
Member Since: December 14, 2007 Posts: 281 Comments: 15071
1108. crowe1
Thanks for the Albany snow map P451, 4ish for me on that. Apparently trending N and warm, yuck.
Member Since: January 26, 2007 Posts: 15 Comments: 921
1107. crowe1
Stop me if you've heard this...

Short term /7 am Saturday morning through Sunday night/...
12z models runs came in significantly different than previous runs.
Precipitation amounts are now running between a third and three-quarters of
an inch for the upcoming event...with the highest amounts now
displaced well north of where it had been forecast over the past few
days. They have also brought above freezing middle level air much
further north.
Member Since: January 26, 2007 Posts: 15 Comments: 921
I'm thinking maybe the surprise was the new photo and it accidentally came out early.
Member Since: December 17, 2009 Posts: 0 Comments: 796
1105. Matlack
Quoting TheRasberryPatch:


hmmmmm....back then Michelob was supposed to be one of the highest alcohol content for beer. you know when you are 16 or was it 15...hahahaha. drinking age was 18 for beer and wine. heineken? not in college...college was whatever the party was serving hahahaha that was pretty much the same in high school. wow the parties back in the late '70s


I stayed with Moosehead - used to ride my bike to the liquor store to buy a 6 before each party. Now I brew my own...
Member Since: January 1, 2006 Posts: 0 Comments: 358
Hey, P451 - Missed your re-entry, I think. Welcome back! Good to see your postings.
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Quoting PengSnow:
I look forward towards next weeks weather extremes and I will now be relocating back to the burgh from the east(you got to love the corp world)----Go Steelers and Go Penguins, I now won't have to listen to Philly sports anymore, even though I will miss watching Vick and you got to like the flyers because their owner has always put a phyically tough team on the ice.  But the burgh will always be my home!!!  I already purchased a home

 

I'll miss your observations here, PengSnow. You can still root for our teams even out west there!
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Clouds moving in after what has been another glorious bright (though nippy) day.
Member Since: October 14, 2006 Posts: 1 Comments: 639
Quoting Blizzard92:

But the ECMWF slams us with heavy snow especially I-95.


I like the ECMWF scenario!
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18Z still has no storm for the East Coast next Thurs/. Friday.
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I look forward towards next weeks weather extremes and I will now be relocating back to the burgh from the east(you got to love the corp world)----Go Steelers and Go Penguins, I now won't have to listen to Philly sports anymore, even though I will miss watching Vick and you got to like the flyers because their owner has always put a phyically tough team on the ice.  But the burgh will always be my home!!!  I already purchased a home

 
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1097. cchamp6
Just saw a map of Ct. that showed nearly 50 reported roof collapses.
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1096. cchamp6
Back in from shoveling my roof for the 3rd time in the last two weeks. Have had enough of that thankyou. This past weeks storm delivered around 7-8" in round one and about 4" of snow and mostly sleet with a thin layer of ice on top of that. This morning it got down to -8.8 degrees. Many roofs collapsing in Ct. I still have to shovel my garage roof tomorrow morning before the next round of snow. I love snow but I am throwing up the white flag. Enough. Stop. Warm up gradually because we will need archs with the amount of snow pack around here if it ever gets real warm and rains.
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Quoting Blizzard92:

But the ECMWF slams us with heavy snow especially I-95.


more model disasters? hahahaha this winter
Member Since: January 26, 2007 Posts: 72 Comments: 6243
Quoting originalLT:
Good afternoon Blizz, did I see right that the 12Z GFS took away our big storm for Thurs/Fri.?

But the ECMWF slams us with heavy snow especially I-95.
Member Since: December 14, 2007 Posts: 281 Comments: 15071
Good afternoon Blizz, did I see right that the 12Z GFS took away our big storm for Thurs/Fri.?
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Quoting TheRasberryPatch:
reading the WWA it doesn't sound like much and did I see 41 one day - was it Monday?

good afternoon Blizz

Yep, Sunday and Monday look quite warm before arctic air moves along with the cold front Tuesday.
Member Since: December 14, 2007 Posts: 281 Comments: 15071
reading the WWA it doesn't sound like much and did I see 41 one day - was it Monday?

good afternoon Blizz
Member Since: January 26, 2007 Posts: 72 Comments: 6243
Good afternoon! Storm tomorrow looks worthless. Computer surface models are a complete mess.
Member Since: December 14, 2007 Posts: 281 Comments: 15071
Quoting TheRasberryPatch:


I hope I didn't come across as harsh. texting and posting has a way of making things sound like preaching or something. I was just making a decree


FIFY
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Quoting hurigo:
thank you for saying that Patch. You make sense. I would like to change my answer please!

just want the best for him -- and I have a hard enough time figuring that out for myself. He doesn't have to live by my biases but discover it all on his own. That boy is so talented, if he does do TV he may even be part of something that improves masscom!

Again, thank you.


I hope I didn't come across as harsh. texting and posting has a way of making things sound like preaching or something. I was just making a comment
Member Since: January 26, 2007 Posts: 72 Comments: 6243
1087. hurigo
thank you for saying that Patch. You make sense. I would like to change my answer please!

just want the best for him -- and I have a hard enough time figuring that out for myself. He doesn't have to live by my biases but discover it all on his own. That boy is so talented, if he does do TV he may even be part of something that improves masscom!

Again, thank you.
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Quoting hurigo:
Hi Ya'll.
Finally I got to see Blizz's new mugshot. I can see it using IE but not Fox.

Blizz, new photo looks great. Hope we aren't driving you a little crazy with all the commentary about it. Surely you have a good head on your shoulders and can handle this. You're amazing kiddo. (Please don't take a job in TV - I'm hoping that the surprise will be much more exciting than that--something where you really get to learn as well as receive recognition for your achievements thus far.)


why can't he learn from TV. part of getting a degree in meteorology is understand all aspects. broaden the horizons. at least if he interned on TV he could get that taste out of his system and in turn learn about the culture of masscom.
Member Since: January 26, 2007 Posts: 72 Comments: 6243
1085. hurigo
Hi Ya'll.
Finally I got to see Blizz's new mugshot. I can see it using IE but not Fox.

Blizz, new photo looks great. Hope we aren't driving you a little crazy with all the commentary about it. Surely you have a good head on your shoulders and can handle this. You're amazing kiddo. (Please don't take a job in TV - I'm hoping that the surprise will be much more exciting than that--something where you really get to learn as well as receive recognition for your achievements thus far.)
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Well, on the 12Z run of the GFS, the big storm for next Thurs/Fri. is gone. The GFS giveith and taketh away!
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Quoting zotty:


that, my friend, is why it would be a surprise.

TRP- your first beer was Michelob? seriously? wow, your are high class. did you move on to Heineken when you went to college?


hmmmmm....back then Michelob was supposed to be one of the highest alcohol content for beer. you know when you are 16 or was it 15...hahahaha. drinking age was 18 for beer and wine. heineken? not in college...college was whatever the party was serving hahahaha that was pretty much the same in high school. wow the parties back in the late '70s
Member Since: January 26, 2007 Posts: 72 Comments: 6243
I still see it. Senior Picture from the looks of it. Dude has definitely hit that "spurt" from the Mt Washington pic.
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Quoting originalLT:
Yeah, 717, I asked Blizz to post the picture itself on the blog, so everyone could see it, because some are having trouble, but he hasn't yet. Maybe he will this weekend.


I couldn't see it yesterday but I can see it today, so maybe WU updated it for everyone?
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Yeah, NJHurricanez, I noticed that on the last run of the GFS. Blizz said however he thinks it may be an in-land runner up the coast be cause of the La Nina situation, or come up just off the coast, keeping the I95 corridor in mostly rain, but snow inland.
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I'll take a tee shirt, and I'm looking forward to another 6 inches of snow here in Worcester tomorrow!

*crosses fingers*
*shines up snowshoes*
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Yeah, 717, I asked Blizz to post the picture itself on the blog, so everyone could see it, because some are having trouble, but he hasn't yet. Maybe he will this weekend.
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Does anyone have any thoughts on next Thursday's storm? It looks like it could be a nice snow maker for NJ/NY/CT...
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I SEE IT!!!! Emptying my cache didn't help. I had to log out and then I saw it. When I logged back in, it kept the new picture. I have no idea why that that would happen but there you go.

Blizz sure has grown up since the previous picture!
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Quoting originalLT:
717 Weatherlover, I see the old Picture of Blizz on my home computer, but while at work, I see the new one, can't figure it out!---Wrong quote came up? I was answering post #1064

Quoting Snowmog: This new version of WU is weird, all your postings are cropped and the ones that are hidden I can't unhide like I used to be able to. Is anyone else having these problems?

My son designs web sites and programs and, with most new launches, there's a few days of debugging. I'm sure WU will fix the glitches, and it doesn't hurt to let them know issues you're having.
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Wonder if I need to clear my cache or something? I sure would like to see the new picture as my son told me Bliz doesn't look like the old one anymore.
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Quoting shipweather:



Yea!!! Let's go sledding!!!
717 Weatherlover, I see the old Picture of Blizz on my home computer, but while at work, I see the new one, can't figure it out!---Wrong quote came up? I was answering post #1064
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1072. Snowmog
This new version of WU is weird, all your postings are cropped and the ones that are hidden I can't unhide like I used to be able to. Is anyone else having these problems?
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1070. zotty
Quoting PhillySnow:
Our forecast is for snow mixed with freezing rain, then snow, then rain, then freezing rain mixed with rain, then rain and snow with little to no snow accumulation at any time. Temps range from 29 degrees to 36 in daytime. Anything could happen here!


Forecast for lower westchester co, ny not much different. I'm heading to Mt Snow this weekend, though, so I am sure I will have more ice to chip through when I get back...
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Our forecast is for snow mixed with freezing rain, then snow, then rain, then freezing rain mixed with rain, then rain and snow with little to no snow accumulation at any time. Temps range from 29 degrees to 36 in daytime. Anything could happen here!
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1068. zotty
Quoting PalmyraPunishment:


Shenanigans. Nobody likes Milwaukee's Best.


that, my friend, is why it would be a surprise.

TRP- your first beer was Michelob? seriously? wow, your are high class. did you move on to Heineken when you went to college?
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Maybe an internship working for noaa?

I thought blizz didn't like cameras
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About Blizzard92

Cornell University- Atmospheric Sciences Undergrad; Research Assist.- Onset of Spring Indices Toolbox; Interests- Small spatial scale climatolology

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Linglestown, PA
Elevation: 520 ft
Temperature: 24.2 °F
Dew Point: 15.2 °F
Humidity: 68%
Wind: Calm
Wind Gust: 9.0 mph
Updated: 10:37 AM EST on January 18, 2014

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