North American Mesoscale Model Verification on January 26-27...
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
Reader Comments
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Fine with me. If it's not going to snow, it might as well be warm, and anything else in between just isn't fun.
I like Syracuse- 95 straight hours of snowfall. Maybe Heavy should consider moving to that hotbed of economic and social activity...
http://www.webmd.com/cold-and-flu/cold-guide/cold -becomes-sinus-infection
I read about it here and you need to call your dr. gotta be well soon cause it is almost time to start planting!
Blizz - said back in early January I think that March and April will be warmer than normal. Then a few weeks later he changed his prediction.
Did anyone see those pictures of Lead, South Dakota back in early January of the snow they got. Truly amazing.
Anyone having a problem with having to sign in all the time here on Wunderground? It happens to me all the time the last couple of weeks. What a PIA.
putting a few test taps for sap today.
My dang family won't go. Jerks. hahahahahaha.
Syracuse? Hmmmmmm, Rochester maybe. Glens Falls? Okay. Tug Hill Plateau, I'm there!
Three storms in 123 years? That hardly worries me. Are we looking at a hot/cold/hot/cold 70s/30s/70s/30s pattern March through April? When can I plant my garden, play golf, and go mountain biking?
Bring on Spring.
If letting my guard down means a higher risk for a three-foot snowfall, then consider my guard down. Way down.
not quite yet a surprize is possible after big thaw
wait watch see
bwi maybe down in your area the ground is unfrozen, but up here in springfield it's going to take a lot more than 7 days of 40s to melt the snow.
Just back from Chicago - missed you there, shipweather. :) Got home in time for this beautiful, warm day! Good to be home!
Too many posts to read through all of them - Has Blizz shown up? Any word about the surprise?
National Weather Service Albany New York
451 PM EST Monday Feb 14 2011
Synopsis...
a strong cold front will sweep through the region this evening
ushering in very cold air and strong gusty winds. Temperatures are
expected to drop as much as 50 degrees from mondays highs by
Tuesday morning. High pressure will begin to build in on Tuesday
and will dominate our weather through middle week. Temperatures are
expected to be chilly through Tuesday night and then warm to well
above normal before the end of the work week.
gotta love these rollercoaster temps spring is coming
Thanx
There's been a lot more than that. Thay're just a couple "Storm of the Centuries"
: MAX MIN SNOW SNOW
:ID LOCATION TEMP TEMP PCPN FALL DEPTH
:
:...NORTHERN NEW JERSEY...
12N : ANDOVER : 56 / 30 / 0.00/ M/ M
TTN : MERCER COUNTY AP : 59 / 42 / 0.00/ M/ M
FWN : SUSSEX AIRPORT : 57 / 35 / T / M/ M
TEB : TETERBORO AIRPORT : 57 / 38 / 0.00/ M/ M
CDW : CALDWELL : 57 / 39 / 0.00/ M/ M
EWR : NEWARK INTERNATIONAL : 60 / 41 / 0.00/ M/ M
SMQ : SOMERVILLE AIRPORT : 57 / 26 / 0.00/ M/ M
BLM : BELMAR AIRPORT : 59 / 43 / 0.00/ M/ M
:
:...SOUTHERN NEW JERSEY...
ACY : ATLANTIC CITY AIRPORT : 65 / 44 / 0.02/ M/ M
VAY : MOUNT HOLLY AIRPORT : 61 / 44 / 0.00/ M/ M
WRI : MCGUIRE AFB : 60 / 42 / 0.00/ M/ M
NEL : LAKEHURST NAS : 62 / 42 / 0.00/ M/ M
MIV : MILLVILLE AP : 65 / 41 / 0.00/ M/ M
WWD : WILDWOOD AIRPORT : 63 / 43 / 0.00/ M/ M
ATLN4: ATLANTIC CITY MARINA : 62 / 42 / 0.00/ M/ M
:
:...EASTERN PENNSYLVANIA...
PHL : PHILADELPHIA AP : 62 / 42 / 0.00/ M/ M
ABE : LEHIGH VALLEY INTL : 52 / 26 / 0.00/ M/ M
RDG : READING AP : 55 / 36 / T / M/ M
MPO : MOUNT POCONO AP : 49 / 36 / T / M/ M
AVP : WILKES-BARRE AP : 50 / 39 / T / M/ M
PTW : POTTSTOWN AP : 59 / 45 / 0.00/ M/ M
NXX : WILLOW GROVE NAS : 56 / 43 / 0.00/ M/ M
DYL : DOYLESTOWN AP : 55 / 42 / 0.00/ M/ M
PNE : NORTHEAST PHILADELPHIA : M / M / 0.00/ M/ M
SEG : SELINSGROVE AP : 53 / 32 / 0.00/ M/ M
THV : YORK : 58 / 43 / 0.00/ M/ M
LNS : LANCASTER AP : 54 / 39 / 0.00/ M/ M
LOM : BLUE BELL : 58 / 44 / 0.00/ M/ M
UKT : QUAKERTOWN : 55 / 39 / 0.00/ M/ M
:
:...DELAWARE AND EASTERN MARYLAND...
ILG : WILMINGTON AIRPORT : 62 / 42 / 0.00/ M/ M
GED : GEORGETOWN AP : 67 / 43 / 0.00/ M/ M
ESN : EASTON AIRPORT : 66 / 46 / 0.00/ M/ M
NAK : ANNAPOLIS : 66 / 48 / 0.00/ M/ M
DOV : DOVER AFB : 67 / 42 / 0.00/ M/ M
OXB : OCEAN CITY AP : 69 / 47 / 0.00/ M/ M
SBY : SALISBURY : 67 / 39 / 0.00/ M/ M
BWI : BALTIMORE AIRPORT : 67 / 48 / 0.00/ M/ M
:
.END
:
.BR PHI 0214 E DH00/TAIRZX/DH07/TAIRZP
:
:...OTHER COASTAL OBSERVATIONS...
SDHN4: SANDY HOOK : 53 / 41
PTPN4: POINT PLEASANT : 60 / 40
BGLN4: BARNEGAT LIGHT : 60 / 40
NWWN4: NORTH WILDWOOD : 61 / 41
CAPN4: CAPE MAY HARBOR : 61 / 42
CMAN4: CAPE MAY FERRY : 50 / 42
LWSD1: BREAKWATER HARBOR : 65 / 46
CAMM2: CAMBRIDGE : 65 / 46
TCBM2: TOLCHESTER BEACH : 55 / 44
DELD1: DELAWARE CITY : 63 / 46
PHBP1: PHILADELPHIA PIER 12 : 62 / 43
NBLP1: NEWBOLD ISLAND : 58 / 43
he did say it wasn't any big deal.
Too bad I had to spend it inside with bronchitis. At least I have a bottle of sweet, delicious sizzurp to keep me company.
Exactly my thoughts. Wonder if he knows his blog is being highacked.
Didn't Blizz say he was interested in any supposed link between solar activity and climate change?
Link:
NOAA Space weather
I wouldn't be surprised if it gets warmer than that later in the week. Yesterday, as you said, was 62 here, yet they were predicting mid 50's. Today, on the other hand, is downright bitter compared to 24 hours ago, especially with that biting wind. I opened the door to the balcony this morning and it literally pulled me outside.
Here's to 65 on Friday!
Yay! I'm liking the little bit of spring, and one more snowstorm would be perfect. Early enough, also, to not destroy anyone's garden. (I think - my husband's the gardener in our family.)
Yeah, I'm starting to get that spring fever, but I'd be up for snow in July if you ask me.
This interesting low pressure system is still a week away and there is some huge model spread between the GFS, ECMFW and CMC. One thing they have in common is that they project a zonal flow from the plains to the east coast, meaning west to east storm movement with little to no amplification. The GFS & ECMFW suggest a decent amount of moisture with the system with a west to east swath of moderate to heavy. The GFS has trended north from the 6Z to 12Z run and is the northern-most of the 3 models, bringing the low offshore at New Hampshire and favoring northernmost New England with heavy snow. The ECMFW brings the low off the NC/VA coast and looks like it favors the mid-atlantic with moderate to heavy snow. The CMC is the least impressive of the 3 and brings the low off shore at southern NC. All 3 solutions push the low off shore with no coastal redevelopment. What a spread!
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