Network News

X My Profile
View More Activity
The new Washington
Post Weather website
Jump to CWG's
Latest Full Forecast
Outside now? Radar, temps
and more: Weather Wall
Follow us on Twitter (@capitalweather) and become a fan on Facebook
Posted at 9:45 AM ET, 02/ 8/2010

The incredible output of Snowmageddon

By Ian Livingston

Feb. 3-6, 2010: Simulations, satellites, radars, and maps

*** Remarkable winter brings new threat: Full Forecast ***

* Winter Storm Watch Tues.-Wed. for most of metro area (map) *
* A closer look at next snow threat: SLCB | Watch out for ice dams *
* Measuring Snowmageddon's depth | NWS totals | CWG snow reports *
* Power outage maps for Dominion Electric | Pepco | BG&E *
* Outside now? Radar, temps & more: Weather Wall *
* News, traffic & storm coverage: Local home page | Get There *


Radar estimated liquid equivalent totals (generally 1.5-2.5" inches of liquid) from the historic Snowmageddon which dropped as much as 2 to 3 feet of snow across the region. Note, radar does not always accurately demonstrate real totals; numbers on the edges of the radar scope are likely underestimated. Image courtesy: Weather Underground.

After Snowpocalypse in December, it would have been hard to imagine it would only end up "one of the biggest" storms of winter 2009-2010. But that was before Snowmageddon came along with its massive amounts of moisture. While the large-scale pattern was similar, and aided us in our high level of forecast confidence that a historic storm was in the offing, the way it came together was a little different. The moisture sources it tapped were far-reaching, ultimately helping it produce historic amounts of snow over the area.

Continue on for more imagery related to the historic February 2010 storm.

Though we had been advertising that a significant snowstorm was likely for several days, by February 3rd and 4th it was apparent this storm would have little trouble topping the typical output of a large winter storm around here. Satellite imagery indicated that the system was drawing moisture deep into the tropics even before tapping the Gulf of Mexico and Atlantic. Radar showed a ton of rain gathering in and around Texas.


Northern hemisphere water vapor loop showing moisture for the eventual Snowmageddon streaming north from the deep tropics. Loop runs from 11:30 a.m. through midnight on February 4th. Image courtesy: Unisys.


1 a.m. on February 4, 2010. Radar courtesy: WSI Corporation.

While a brief look at the imagery above might have led some to believe this system would head to the north and west, pushing warm air northward resulting in a mix or rain (whereas many of our big snowstorms begin somewhere in the northern Gulf of Mexico or off the lower Southeast Coast) the cold air locked over eastern North America (due to a high latitude blocking pattern, where high pressure over Greenland helps to bottle up cold over the East) kept the storm on a favorable southern track.

The cold air in place coupled with the effects of El NiƱo's juiced southern jet stream provided the large-scale set up for the storm. CWG meteorologist Matt Rogers reviewed a similar set up after the December 19 "Snowpocalypse" storm, so reading his post again is worth the time. We also mentioned these features as ingredients in our snowy outlook for the winter -- which has become more even more snowy than we anticipated.


Northern Hemisphere plot at 0z February 5 (7 p.m. EST Feb. 4). Image courtesy: Unisys.

An avid reader of CWG's comment section will note that three and four letter acronyms get thrown around a lot -- NAM (North American Model), GFS (Global Forecast System) and SREF (Short Range Ensemble Forecast) are American models among the group. Critics of their sometimes wild swings aside, these tools have helped forecasting ability progress as they are refined and continue to have more power which allows finer detail.


0z NAM February 5 (7 p.m. EST Feb. 4). Image courtesy: NCEP.


21z SREF February 4 (4 p.m. EST). 24-hour totals near 2.5" across the area and 36-hour numbers toward 3". Image courtesy: NCEP.

The quantitative precipitation forecast above, from the North American Model on the final evening prior to the beginning of Snowmageddon, suggested that up to 2-3" of liquid (manifested in the form of snow) could fall in or near the area. Even being conservative on liquid-to-snow ratios these numbers would lead to widespread 1.5-2' snows with some places higher. Often there will be guidance suggesting outlandish numbers. Many times, forecasters will assume that it is overdone. In this case there was significant support for such numbers beforehand as upwards of 3-4" of rain was being reported along the Gulf coast.

Like most big storms around here, Snowmageddon arrived with only a brief period of lighter snows before it quickly started piling up. Unlike many storms in these parts, it began producing multi-hour snowfall rates of up to 2-3" per hour prior to midnight on the 5th. These continual super bands ejecting north around the strengthening low pressure off the coast contained whiteout conditions and instances of thundersnow, both typically associated with the most powerful winter storms on the East Coast.


Radar late on February 5 into early February 6 shows continual high-moisture bands pushing through the area as the rain/snow/mix line stays generally just to the south. Radar courtesy: Weather Underground.


February 4 GFS 500mb loop showing upper-level energy swinging by in an optimal fashion for "backlash" snow on the coastal system. Image courtesy: NCEP.

After the heavy bands on the northern envelope of the developing low, additional and fluffier snowfall occurred through a good portion of Saturday largely thanks to the upper level energy associated with the system. CWG team knowledge of previous big-league storms for the D.C. metro area combined with model data led our pre-storm forecasts to note two main parts to this historic event.


Surface loop of Snowmageddon as it travels up the east coast and then rotates around offshore just to our east before departing. Images courtesy: HPC.

Measuring a big storm is difficult work. Both National and Dulles (0.99" and 1.6" reported) seem to have had equipment issues as can be the case with larger snowfalls such as the one in December. If either needs correction it will likely be done through data obtained by certified local observers. Baltimore-Washington International's final liquid tally was 2.13" and appears more representative. The Community Collaborative Rain, Hail & Snow Network (CoCoRaHS) reports from February 6 do validate the high liquid numbers on a large scale. As if we all needed validation after looking outside!


Satellite the day after Snowmageddon reveals plenty of white across this area and the northern extent of the precipitation shield. Image courtesy: Terra/MODIS satellite imagery.

By Ian Livingston  | February 8, 2010; 9:45 AM ET
Categories:  Recaps, Snowmageddon  
Save & Share:  Send E-mail   Facebook   Twitter   Digg   Yahoo Buzz   Del.icio.us   StumbleUpon   Technorati   Google Buzz   Previous: Forecast: Remarkable winter brings new threat
Next: Alert: Serious snow/wind a risk late Tues into Wed

Comments

Wow! Thanks for posting this collection. Down here on earth in Falls Church, no power from sometime early Sat morning until 5:28 pm last night. (And I feel for those still without power!)

Posted by: erbele | February 8, 2010 10:13 AM | Report abuse

How the heck am I supposed to work when you post excellent analyses like this?

Posted by: wiredog | February 8, 2010 10:15 AM | Report abuse

Thank you. Great images. Will never forget watching those amazing precip bands pivoting around & around DC on radar Saturday morning.

Posted by: FIREDRAGON47 | February 8, 2010 10:22 AM | Report abuse

Positively superb overview, Ian

Posted by: SteveT-CapitalWeatherGang | February 8, 2010 10:28 AM | Report abuse

OUTSTANDING! This is what I like about the CWG. Factual, unbiased and thorough forecasts with willingness, even a compelling need, to review actual versus forecasted conditions and openness to sharing the information for all of us to learn from the analysis. Thank you very much...

Posted by: djm-01 | February 8, 2010 10:42 AM | Report abuse

Meanwhile, according to Reagan National, we only had 18 inches. There is no point to continuing to use an "official" measuring site that bears no relation to what everyone experienced. When will this be fixed?

Posted by: sparman | February 8, 2010 11:06 AM | Report abuse

What a great recap! Funny how none of us (me anyway) wanted to believe the liquid output predictions of the NAM, either in December or over the weekend.

I couldn't help but notice some pretty impressive liquid quantities showing up on recent NAM runs for tomorrow's storm...I'm just saying.

We are soon going to have an unbelievable 3 1/2 foot snowpack in my backyard in Darnestown. If this patterns flips and it gets warm quickly, we can all expect to be talking about flooding, I fear.

Posted by: curtmccormick | February 8, 2010 11:14 AM | Report abuse

If metro is running below ground only tomorrow....which has a chance of happening...what's the FedCast look like for Tuesday?

Posted by: DaLord | February 8, 2010 11:15 AM | Report abuse

WEATHER Channel just said we are looking at 12-18in...is that right?

Posted by: MAYFREE34 | February 8, 2010 11:25 AM | Report abuse

That liquid equivalent total map does accurately reflect the "hole" over National Airport.

Posted by: bdeco | February 8, 2010 11:36 AM | Report abuse

how does this year's total snowfall compare with other cities? i wonder if we've gotten more snow this year than, say, chicago or boston.

Posted by: bddf | February 8, 2010 11:37 AM | Report abuse

TWC just said 6-12" for DC/Baltimore, and more for Philly. Sounds like your basic East Coast Nor'easter. As much of a snow lover as I am, I almost wish they're wrong.

Posted by: Juan-John1 | February 8, 2010 11:37 AM | Report abuse

bdeco, some spost close to the beam get undermeasured by radar as well. It's not perfectly exact. During storms you can often see some clear spots around the center. I doubt National got 18:1 ratios in this event given how heavy and wet it was.

Posted by: Ian-CapitalWeatherGang | February 8, 2010 11:39 AM | Report abuse

Hopefully we will have a gradual warming of temperatures so everything is not flooded.

The NWS is saying a possibility of 5 inches. Why are they saying 12-18 on the weather channel?

I was thinking 1-5 inches, not 12.

(Since when does 5 sound like a little snow)

Posted by: celestun100 | February 8, 2010 11:39 AM | Report abuse

Sorry Ian, meant to say "doesn't" accurately represent. It was meant as a joke, but I suppose jokes come out much better when you actually type what you were trying to say.

Posted by: bdeco | February 8, 2010 11:46 AM | Report abuse

TWC is probably looking at the 12Z NAM and GFS--both with over an inch liquid for us. Yipes.

Posted by: jkuchen | February 8, 2010 11:49 AM | Report abuse

Tom Kierein on Channel 4 just said 3-5, while Channel 5 says "potential for 5-10+" and Channel 7" is doing the spectrum 4-6 most likely, then upwards to 10 possible. Heh, looking for these "models to come into agreement."

Posted by: ArlingtonSnowGal | February 8, 2010 11:51 AM | Report abuse

The midday models are all coming in quite intense. Blizzard?

Posted by: Ian-CapitalWeatherGang | February 8, 2010 11:51 AM | Report abuse

Guys, what is going on? The posters on Eastern WX are talking about a huge hit from the most recent model runs. 1" QPF. Very cold and high ratios.

I mean, it seems like something major in the works again? Or is it just hype?

Posted by: AndrewRockville | February 8, 2010 11:53 AM | Report abuse

There seems to be lots of confusion about what is going to happen tomorrow.. But should emergency managers begin preparing the public for another crippling event? It would only take 6 inches at this point to be crippling, but some models show lots more than that along with an even windier storm than over weekend? How long do mets have before sounding alarm?

Posted by: realclear | February 8, 2010 11:56 AM | Report abuse

Remarkable analysis. I hope CWG will assemble this and the other extraordinary CWG posts from this winter into a single, multi-part document and keep online for the foreseeable future.

Or alternatively extrapolate and publish in WeatherWise, so this historically important information is available to meteorologists, researchers, weather mavens, etc. in both print and online formats.

Whatever, please don't let this information disappear into cyberia.

Posted by: JerryFloyd1 | February 8, 2010 11:56 AM | Report abuse

NWS notes as of a couple hours ago (before, one would imagine, the midday models came in):

CSTL LOW SHUD BE TAKING OVR TUE NGT...BACKING WNDS NE. SUCH A
FLOW...W/ DROPPING H8 TEMPS AND A S/WV ABT TO KICK THRU...WUD
ENHANCE LLVL COLD AIR...CHGG PTYPE BACK TO SN. SNW WL CONT INTO
WED...BEFORE DRY SLOT WORKS IN. STRONG CAA KICKS IN THEREAFTR. FOR
NOW...HV REVISED WND DIR/PTYPE TUE NGT...AND ADDED UPSLP SNW POTL
WED-THU. TUE NGT-WED MAY BE WINDIER THAN CRRNTLY FCST...AND WL
REVISIT THAT LATER TDA AFTR REVIEWING 12Z GDNC.

WATCH WL HOLD AS IS FOR NOW. WL LOOK AT ITS AREAL CVRG AND THE ACCUM
POTL FM THIS SYSTM NXT CPL UPDATES.
-- End Changed Discussion --

Posted by: Juan-John | February 8, 2010 12:00 PM | Report abuse

I guess those of us that live in Manassas, will not have to worry about the snow, since PW County and the City of Manassas are not included in the winter storm watch?

I suppose we'll have sun and warm temps, right?

Posted by: irish031 | February 8, 2010 12:05 PM | Report abuse

Ian you used the "B" word.
You are scaring me.
Haven't seen a plow now for over 48 hours. Three - five foot ice spears hanging from most roofs this morning.
Had hoped to try to bust out of the neighborhood for a supply run this afternoon. Forecast make re-supply critical before next weather event hits.
Will heaviest snow hit after evening rush hour?

Posted by: FIREDRAGON47 | February 8, 2010 12:07 PM | Report abuse

latest update from nws as of 11:58, trending bigger...

URGENT - WINTER WEATHER MESSAGE
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
1158 AM EST MON FEB 8 2010

DCZ001-MDZ003>007-009>011-013-014-VAZ042-053-054-WVZ053-090100-
/O.EXT.KLWX.WS.A.0005.100209T1700Z-100211T0000Z/
DISTRICT OF COLUMBIA-WASHINGTON-FREDERICK MD-CARROLL-
NORTHERN BALTIMORE-HARFORD-MONTGOMERY-HOWARD-SOUTHERN BALTIMORE-
PRINCE GEORGES-ANNE ARUNDEL-LOUDOUN-FAIRFAX-
ARLINGTON/FALLS CHURCH/ALEXANDRIA-JEFFERSON-
INCLUDING THE CITIES OF...WASHINGTON...HAGERSTOWN...FREDERICK...
WESTMINSTER...GAITHERSBURG...COLUMBIA...BALTIMORE...ANNAPOLIS...
LEESBURG...FAIRFAX...ALEXANDRIA...FALLS CHURCH...CHARLES TOWN
1158 AM EST MON FEB 8 2010

...WINTER STORM WATCH NOW IN EFFECT FROM TUESDAY AFTERNOON
THROUGH WEDNESDAY EVENING...

THE WINTER STORM WATCH IS NOW IN EFFECT FROM TUESDAY AFTERNOON
THROUGH WEDNESDAY EVENING.

* PRECIPITATION TYPE...SNOW.

* ACCUMULATIONS...POTENTIAL FOR 8 OR MORE INCHES OF SNOW. THERE IS
A GOOD LIKELIHOOD OF SNOW IN EXCESS OF 10 INCHES.

* TIMING...MID TO LATE AFTERNOON TUESDAY THROUGH WEDNESDAY.

* TEMPERATURES...TEMPERATURES NEAR FREEZING AT THE ONSET TUESDAY
AFTERNOON. TEMPERATURES WILL DROP INTO THE UPPER 20S TUESDAY
NIGHT AND WEDNESDAY.

* WINDS...LIGHT SOUTHEASTERLY WINDS TUESDAY BECOMING NORTH-
NORTHWESTERLY 15 TO 25 MPH WEDNESDAY.

Posted by: danog224 | February 8, 2010 12:09 PM | Report abuse

irish031 - PW County is included in the winter sotrm watch. Actually, it's been expanded to include Stafford and other southwest counties in VA.

This is just in from the NWS:

...WINTER STORM WATCH NOW IN EFFECT FROM TUESDAY AFTERNOON
THROUGH WEDNESDAY EVENING...

THE WINTER STORM WATCH IS NOW IN EFFECT FROM TUESDAY AFTERNOON
THROUGH WEDNESDAY EVENING.

* PRECIPITATION TYPE...SNOW.

* ACCUMULATIONS...POTENTIAL FOR 7 OR MORE INCHES OF SNOW. THERE IS
A POSSIBILITY OF LOCAL AMOUNTS IN EXCESS OF 10 INCHES.

* TIMING...MID-AFTERNOON TUESDAY THROUGH WEDNESDAY.

* TEMPERATURES...TEMPERATURES NEAR FREEZING AT THE ONSET TUESDAY
AFTERNOON. TEMPERATURES WILL DROP INTO THE MID TO UPPER 20S
TUESDAY NIGHT AND WEDNESDAY.

* WINDS...LIGHT SOUTHEASTERLY WINDS TUESDAY BECOMING NORTH-
NORTHWESTERLY 15 TO 25 MPH WEDNESDAY.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

Posted by: ZmanVA | February 8, 2010 12:09 PM | Report abuse

@zman.

Thanks. So much for the warm temps.

Posted by: irish031 | February 8, 2010 12:11 PM | Report abuse

Sweet mama. Why don't the schools and government just call it now, and close everything down for the rest of the week?

Posted by: Juan-John | February 8, 2010 12:18 PM | Report abuse

Channel 7 just noon forecast just rated "6-12" as "best chance, 12=15" "possible". And if you live NE of Baltimore, you may be looking at the sequel to Snowpocalyse and Snowmageddon.

Posted by: JerryFloyd1 | February 8, 2010 12:22 PM | Report abuse

Great summary Ian! I also saved a lot of radar and satellite loops from the storm. By the way, check out today's radar loop compared to your Intellicast loop posted above from 1am Feb 4. Here's the current loop:

http://www.intellicast.com/national/radar/current.aspx?animate=true

Posted by: Kevin-CapitalWeatherGang | February 8, 2010 12:23 PM | Report abuse

Prediction: if we get 12-16 inches or more snow, they are going to need to mobilize the Nat. Guard and a lot more military construction equipment to get things dug out.
(That is, if there is any left here that isn't overseas.)

Posted by: AndrewRockville | February 8, 2010 12:28 PM | Report abuse

C'mon, folks, aren't we going to name tomorrow's storm yet? I would like to nominate Snowzilla.

I'm OK. I managed to get to RiteAid so I have now stocked up on ibuprofen and am ready to shovel. I have candles, a flashlight, lots of blankets, and a gas grill to cook on in the back yard if necessary. But this is one year when I will be really, really, really happy to see Spring.

Posted by: ChickenLady | February 8, 2010 12:54 PM | Report abuse

Dear CWG.... I was thinking as I made some money shoveling people out today that there need to be a weather re-cap web site. I guess I haven't been reading you too much!!! You analysis was such a joy to read. I follow radar every 30 mins to an hour, but the system is so much more complicated. You really enlightened me on what happened. So so cool.
Good luck with the rest of the winter!!!!!!!

Posted by: bt_134 | February 8, 2010 5:04 PM | Report abuse

I say shut the government down for as long as possible. Maybe something positive will come out of this. Obviously, nothing good happens when it is active, except for stuffing a few already over-stuffed pockets. TFL, Ken

Posted by: kentigereyes | February 8, 2010 10:30 PM | Report abuse

The comments to this entry are closed.

 
 
RSS Feed
Subscribe to The Post

© 2012 The Washington Post Company