Friday, January 22, 2016

Before a Would-Be Historic D.C. Blizzard, Some Cautionary Thoughts on Those Improbable GFS Snow Amounts and the KDCA Big Snow Record

**This entry was posted January 22, 2016.**

The Sterling (LWX) county warning area (CWA) most likely snowfall range forecast valid from 7AM January 22, 2016 - 7AM January 24, 2016.

Nearly the entire District of Columbia is, incredibly, in the 24 to 30 inch range.


So at this 4AM hour, the entire Baltimore/Washington region remains under a BLIZZARD WARNING for what has the potential to be a historic snowstorm -- one that, if the relentless output of the operational GFS model is to be believed, challenges the Knickerbocker Storm itself when 28.0 inches fell because of (to paraphrase CWG's Jason Samenow) the "improbably high" numbers (in this case, right at KDCA itself).

Map of the 0Z Jan. 22, 2016 GFS snowfall for the northeastern U.S. valid through hour 72 / 0Z Jan. 25, 2016 based upon a 1:10 ratio.

Map created by the Tropical Tidbits site. If you click on it, you'll see snow totals in the 36 to 48 inch range -- and in places where they shouldn't be (such as the parts of the Virginia Northern Neck).


For the 0Z runs, the GFS produces what I view as unrealistic amounts of snow, as the above snow forecast map image and the histograms below show.

Here are the numbers and maps (as prettied up by the Tropical Tidbits and using a 10-1 ratio):

0Z 1/22/2015 GFS
KDCA: 2.942 --> 29.4 inches
KBWI: 2.533 --> 25.3 inches
KIAD: 3.637 --> 36.4 inches

0Z 1/22/2015 NAM
KDCA: 2.527 --> 25.3 inches
KBWI: 2.159 --> 21.6 inches
KIAD: 2.512 --> 25.1 inches

The bottom line is that the GFS numbers -- which that model has been almost consistently screaming for the past four days -- would result in a snowfall that tied or broke the Knickerbocker Storm total of January 1922.


Keep in mind that since records have been kept at KDCA (starting in 1945 or thereabouts), the single greatest snowfall ever there was the Feb. 1979 Presidents Day Storm when 18.7 inches fell, and even this was just the 3rd greatest snowfall in D.C. after the 20.0 inches in Feb. 1899 (a pre-KDCA record).

In the "Snowmaggedon" event (also called the North American Blizzard) of Feb. 5th - 6th, 2010, when Dulles Int'l Airport (KIAD) recorded its greatest single snowfall -- a gargantuan 32.4 inches -- frickin' KDCA had only a little more than half that at 17.8 inches.

The top 10 days 1 - 3 snowfall events for Washington, D.C. (KDCA), Baltimore, Md. (KBWI), and Dulles Airport (KIAD).

I assume that refers to a single snow event that lasted anywhere from 1 to 3 days.


And when Baltimore/Washington Int'l Airport (KBWI) had its greatest single snowfall -- 26.8 inches in the Feb 16th - 18th, 2003 "Presidents' Day II" storm, KDCA came in with just 16.4 inches.

In the two other biggies -- Feb. 1983 and Jan. 1996 -- KDCA recorded 16.6 inches and 17.3 inches, respectively, while the KIAD had 22.8 inches and 24.6 inches, respectively, and KBWI had 22.8 inches and 26.6 inches.

KDCA 180-hour cumulative snow total based upon the 0Z January 22, 2016 run.


The Knickerbocker Storm total was measured at 24th and M Street NW, location of the old Weather Bureau office. I'm uncertain of where the 1899 event was measured but certainly not at National Airport, which did not exist.

My point is that in the present era, KDCA simply has never recorded anywhere near the amounts that the other stations get. Why that is the case has to do with its location (and resulting micro-scale weather including during major snowstorms) and also, possibly, issues with how the snow is measured. But that's not important right now.

KBWI 180-hour cumulative snow total based upon the 0Z January 22, 2016 run.


It is for this reason that I am having a hard time fathoming the forecasted amounts in the GFS and, to a lesser extent, NAM runs.

The 0Z Euro (ECMWF) apparently shows less (CWG's Ian Livingston said 20 inches instead of 30 inches), but it isn't clear. I can't really tell from all the back-and-forth embedded deep down in the comment peanut gallery of this CWG entry (link embedded): Winter storm takes shape over the South, models continue to suggest it will become a severe blizzard.

KIAD 180-hour cumulative snow total based upon the 0Z January 22, 2016 run.


The Tropical Tidbits page doesn't really have much useful info for the Euro because of the coarseness of the resolution of the data that the European Centre makes publicly available.

In short, if the GFS verifies, this will be a truly unprecedented event for D.C. itself, including its National Airport climate station. If the storm busts, the GFS will be severely and perhaps irrevocably discredited.

Anyway, I just wanted to get that out there tonight before any would-be history-making blizzard starts tomorrow.

The Sterling (LWX) county warning area (CWA) weather advisories as of 3:20AM EST January 22, 2016. The bright "international orange" (or rather, vermilion) represents a blizzard warning.

As I noted in my previous entry, you will not often see the entire Baltimore / Washington area under a blizzard warning.


Oh, yes, the entire frickin' region is closing down including the Metro system (rail and buses). Most schools are closed tomorrow and the Metro is closed all Saturday and Sunday. Of course, you might not notice anything all THAT different with regard to Metro ...

I shall be teleworking on Friday from home. And if this blizzard materializes in anywhere near the magnitude it is supposed to, I suspect I will be doing it again on Monday.

Animated gif loop simulated the upcoming mid-Atlantic blizzard for Jan. 22 - 23, 2016.

This map is based upon the GFS output -- either the 12Z or 18Z from Jan. 21st, I would assume. It shows MSLP and precipitation by type and intensity. I'm not sure what the blue and pink lines are showing.


I made it to the gym tonight and had a good multi-part workout (except core, which I couldn't do as there was no available empty side room), but I am assuming I won't be going (indeed, I'm not planning on going) on Saturday. Actually, my weight clicked down almost a pound to 145.8 from the oddly nearly constant 146.4 pounds it has been in recent weeks (as measured on different digital readout scales).

The 0Z Jan. 22, 2016 GFS showing 6-hr average precipitation rate (in mm/hr), MSLP, and 1000mb-500mb thicknesses valid at hour 36 / 12Z Jan. 23, 2016 for the northeastern quadrant of the U.S.

This image was created by the Tropical Tidbits site.


Gary is planning on stranding himself without his vehicle around Dupont Circle for the storm's duration. (He lives up 16th Street near Carter Barron Amphitheatre.) He will be staying with me tomorrow night and Kristof on Saturday night (unless, as Kristof said in a text to me, we have a custody battle over him). On Sunday, he might stay with me again or at Howie's.

He is assuming three days away from home.

U.S. Lower 48 national composite radar loop from 0608 - 0718UTC January 22, 2016.

The culprit storm system is really starting to crank up, although the coastal low won't form until late today or early Saturday.


As I got paid today (the money direct deposited in my account), I will go grocery shopping at the Safeway (assuming also there is any food and supplies to be gotten given the frenzied shopping of the past few days, although the little market on U Street next to my apartment has at least some stuff).

All U.S. National Weather Service weather advisories updated 0625UTC January 22, 2016.

This does not include the color-coded legend. All the deep pink are winter storm warnings and the blue-purple are offshore storm warnings. The D.C. area blizzard warning vermilion is not very visible against all the deep pink.


I suggested to my mom that she and Ray stay in a hotel -- perhaps in Annapolis or by BWI Airport -- during the duration of the storm rather than being snowbound in their small trailer in Millersville, but she has opted to "shelter in place," as it were. As long as the power doesn't go out, they should be fine.

Needless to say, Ray cannot do any physical exertion whatsoever. It is a profoundly bad idea given his condition. I'd go there myself to help shovel snow (the only time I would ever do such a pointless task), except then I'd be stranded for 3 or 4 days, and I really don't want to do that.

OK, I guess that's all for now. My concluding thought -- even as the waxing gibbous Moon is shining serenely down on the wee hours world of Washington on a cold January night -- let's get this snow party started ...


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