DCA's storm total doesn't make sense

[Deck Pic]

And they have been so good this winter and last.

Timeline -

4:40: They report 2.6" in the afternoon CLI. Not sure when this measurement is taken and conveyed to LWX, but certainly can't be any later than 4:40

4:42: I make a post with the numbers in the OBS thread

4:52: DCA reports snow at 27 degrees, with 0.5 visibility. We all are getting yellow banded before the flip. I pick up roughly 0.5-0.6 between 4:40 and when I flip close to 5:30

12:47: CLI indicates DCA's storm total is 2.6" which is exactly what they measured no later than 4:40 (and likely before that)

So you are telling me that DCA did not pick up even 0.1" after the 4:40 CLI?

Is there an explanation for this? Observer waited until after the flip to measure again and there was compaction? Someone accidentally dropped a piece of luggage on the snowboard? (which we all know is outside terminal A).

I don't have a problem with the measurement itself per se. It might be a tad low, but I imagine they had to do a bit worse than me (3.5") near downtown. Though an Alexandria spotter reported 3.1" at 5:13 which doesn't mean much but is probably closest measurement to DCA. But the timeline makes no sense. Hopefully we aren't going back to the days when DCA's measurements were suspect.

ETA: it was 3:55 when they reported 2.6"

http://forecast.weather.gov/product.php?site=NWS&issuedby=LWX&product=PNS&format=CI&version=21&glossary=0&highlight=off

[Always in Zugzwang]

That is strange.  As you say, the total they reported may be accurate but the manner in which they measured it does sound odd.  Certainly a pretty good gradient did exist.  I was at the Kennedy Center yesterday afternoon for a performance, and when I got out (around 4PM or so), walked out onto that deck area overlooking the river.  I'd estimate there were ~4" there at that time.  Of course, that's considered more "northwest" DC I believe.  And the snow was still coming down pretty hard.

 

At any rate, there has been a lot of question on DCA's snow measurements over the years.  I recall the same kind of thing being discussed after Feb. 5-6, 2010 (Snowmageddon) when they "only" got 17.8 or something, whereas other measurements within DC were 20"+.  When I lived in the Capitol Hill neighborhood a few years back, I almost always measured a noticeable amount more than what DCA got (and no, not slant-sticking or the like!).  They've had some better measurements and years, and others that were seemingly bad.  I don't know what to make of it, if it's really that bad overall or if that's all anecdotal.  My feeling is that they either tend to get awful measurements, or that particular location is just simply unrepresentative of the District as a whole (by that I mean the city itself).  I guess there's more scrutiny because DCA is used as "the" official measurement for DC.

 

Personally, I think it's a bit of a stretch that they've lumped together the records since moving to the current location of DCA with the previous records before that (I think the location was around Georgetown?).  Those seem to have a significant enough difference in climatology.

[Inverted_Trough]

I noticed this too.  They reported 2.6" of snow at 3:55 PM.  They had another hour-and-a-half of snow - some of it moderate - before it changed to IP/ZR.  Yet their measurement remained 2.6" at 7:00 pm.  I don't get it.

[WVclimo]

Though they are not first-order stations and don't report snowfall, the precip records from MRB and HGR are skewed as well. Not sure if this will be corrected in quality control within NCDC or not.

On Monday's storm, MRB reported a trace of precip and HGR reported 0.09". I am between the two and had 0.25". Yesterday, MRB did not report, and HGR reported 0.16". As a result of this under reporting of the two biggest precip events this month, MRB is still at 0.23" for the month and HGR is at 0.38". If no more falls this week, MRB will record its 5th driest month on record, which is not how I will remember the month, since I have had double-digit snowfall.

[Deck Pic]

Yes....you're right. It was a 3:55 report.

[Ian]

Looks like they picked up about 0.08" liquid as snow after that report with temps in mid-20s.. so their number seems sketchy. :<

[Deck Pic]

Still haven't figured out how you have 2.6" at 3:55pm, it snows until 5:19 and during the 3:55 - 5:19 period you pick up 0.08" liquid...during that hour+ period you have an OB of 0.5 viz snow....and you pick up NO additional snow.....what a joke...I don't understand how the NWS certifies this nonsense.

[donsutherland1]

And they have been so good this winter and last.

Timeline -

4:40: They report 2.6" in the afternoon CLI. Not sure when this measurement is taken and conveyed to LWX, but certainly can't be any later than 4:40

4:42: I make a post with the numbers in the OBS thread

4:52: DCA reports snow at 27 degrees, with 0.5 visibility. We all are getting yellow banded before the flip. I pick up roughly 0.5-0.6 between 4:40 and when I flip close to 5:30

12:47: CLI indicates DCA's storm total is 2.6" which is exactly what they measured no later than 4:40 (and likely before that)

So you are telling me that DCA did not pick up even 0.1" after the 4:40 CLI?

Is there an explanation for this? Observer waited until after the flip to measure again and there was compaction? Someone accidentally dropped a piece of luggage on the snowboard? (which we all know is outside terminal A).

I don't have a problem with the measurement itself per se. It might be a tad low, but I imagine they had to do a bit worse than me (3.5") near downtown. Though an Alexandria spotter reported 3.1" at 5:13 which doesn't mean much but is probably closest measurement to DCA. But the timeline makes no sense. Hopefully we aren't going back to the days when DCA's measurements were suspect.

ETA: it was 3:55 when they reported 2.6"

http://forecast.weather.gov/product.php?site=NWS&issuedby=LWX&product=PNS&format=CI&version=21&glossary=0&highlight=off

What might have happened is:

 

1. The earlier measurement was taken with 2.6".

2. Some additional snow fell, but no measurement was made at the time the snow stopped falling.

3. The freezing rain/rain then washed away the additional snow.

 

Hopefully, the issue will be addressed in quality control given that the observations clearly showed additional snow had fallen.

[MDstorm]

Still haven't figured out how you have 2.6" at 3:55pm, it snows until 5:19 and during the 3:55 - 5:19 period you pick up 0.08" liquid...during that hour+ period you have an OB of 0.5 viz snow....and you pick up NO additional snow.....what a joke...I don't understand how the NWS certifies this nonsense.

You are right.....this makes no sense. Well, at least their temperature measurements are accurate and representative of the area.

MDstorm

[Deck Pic]

What might have happened is:

 

1. The earlier measurement was taken with 2.6".

2. Some additional snow fell, but no measurement was made at the time the snow stopped falling.

3. The freezing rain/rain then washed away the additional snow.

 

Hopefully, the issue will be addressed in quality control given that the observations clearly showed additional snow had fallen.

 

I think that is definitely a possibility....not sure what QC measures  they have in place.  I had 2.6" at 4pm, so was a little surprised they were doing as well as me.  But it is certainly possible.  H20 in Rose Hill got 4".  It wasn't a perfectly latitudinal storm...

[DCAWx]

And they have been so good this winter and last.

Timeline -

4:40: They report 2.6" in the afternoon CLI. Not sure when this measurement is taken and conveyed to LWX, but certainly can't be any later than 4:40

4:42: I make a post with the numbers in the OBS thread

4:52: DCA reports snow at 27 degrees, with 0.5 visibility. We all are getting yellow banded before the flip. I pick up roughly 0.5-0.6 between 4:40 and when I flip close to 5:30

12:47: CLI indicates DCA's storm total is 2.6" which is exactly what they measured no later than 4:40 (and likely before that)

So you are telling me that DCA did not pick up even 0.1" after the 4:40 CLI?

Is there an explanation for this? Observer waited until after the flip to measure again and there was compaction? Someone accidentally dropped a piece of luggage on the snowboard? (which we all know is outside terminal A).

I don't have a problem with the measurement itself per se. It might be a tad low, but I imagine they had to do a bit worse than me (3.5") near downtown. Though an Alexandria spotter reported 3.1" at 5:13 which doesn't mean much but is probably closest measurement to DCA. But the timeline makes no sense. Hopefully we aren't going back to the days when DCA's measurements were suspect.

ETA: it was 3:55 when they reported 2.6"

http://forecast.weather.gov/product.php?site=NWS&issuedby=LWX&product=PNS&format=CI&version=21&glossary=0&highlight=off

 

The total snowfall is correct for the 21st. The problem is people make assumptions for things they don't understand and think they know more than people who have been Meteorologists and Meteorologist Technicians for over 30+ years. The 2.6 is the total snowfall for the whole day and it's reported about a minute after midnight on the 22nd. At 3:52pm the total up to that time was 1.8 inches. Between 3:52pm & 4:52pm another 0.5 inches of snow occurred making the total snowfall up to 4:52pm 2.3 inches. At 5:52pm another 0.3 inches of snow/ice pellets fell making the total snowfall for the day 2.6 inches. A trace of snowfall occurred both at 6:52pm and 7:52pm but traces aren't added to the total.

 

Also, there were two SNINCR remarks on the 3:52pm and 4:52pm observations which validates the lower visibility due to increased snowfall rates in the observations themselves. There is your explanation....

[StudentOfClimatology]

The total snowfall is correct for the 21st. The problem is people make assumptions for things they don't understand and think they know more than people who have been Meteorologists and Meteorologist Technicians for over 30+ years. The 2.6 is the total snowfall for the whole day and it's reported about a minute after midnight on the 22nd. At 3:52pm the total up to that time was 1.8 inches. Between 3:52pm & 4:52pm another 0.5 inches of snow occurred making the total snowfall up to 4:52pm 2.3 inches. At 5:52pm another 0.3 inches of snow/ice pellets fell making the total snowfall for the day 2.6 inches. A trace of snowfall occurred both at 6:52pm and 7:52pm but traces aren't added to the total.

Also, there were two SNINCR remarks on the 3:52pm and 4:52pm observations which validates the lower visibility due to increased snowfall rates in the observations themselves. There is your explanation....

I can't find that..do you have link on you by chance? Thanks.

[DCAWx]

I can't find that..do you have link on you by chance? Thanks.

 

 

You can't find it because it's on the DCA Snowfall/Snow depth Worksheet for Feb 21 2015 that I'm holding in my hand. 

[arlwx]

The confusion exists because the PNS table shows DCA reporting 2.6 inches around 4 pm and again at 7 pm.

 

The original report may have been in error.

 

Ballston got 2.6 inches in mid-afternoon and another inch by 6 pm.

[Ellinwood]

I have been waiting years for this moment.

[DCAWx]

The confusion exists because the PNS table shows DCA reporting 2.6 inches around 4 pm and again at 7 pm.

 

The original report may have been in error.

 

Ballston got 2.6 inches in mid-afternoon and another inch by 6 pm.

 

It was either an error or someone at NWS Sterling pulled that total out of the sky because DCA doesn't enter the daily snowfall total into ASOS to be transmitted longline until 0000LST of the next day.

[MN Transplant]

Thanks, DCAWx.  Good to hear from someone who really knows this.  Hope you stick around to correct us all when we complain about snowfall reports

 

So, basically, the Public Info Statement in the afternoon was wrong. 

 

One question about reporting, you guys must do some intermediate reports to LWX because we do see amounts listed during the off hours.  Is that them calling you guys up to ask what has fallen so far, or is that you sending them an "offline" report?

[RodneyS]

It was either an error or someone at NWS Sterling pulled that total out of the sky because DCA doesn't enter the daily snowfall total into ASOS to be transmitted longline until 0000LST of the next day.

I'm not sure what happened in this case, but errors sometimes do creep in.  Most here will recall that last year on February 13th there was a major snowstorm in this area, and somehow the preliminary minimum temperature report at Dulles was way off.  I pointed this out in an e-mail to Steve Zubrick of NOAA, and on February 25th (by coincidence, exactly one year ago today), he sent me the following response:

 

Here's the changes we made to Feb 13, 2014 Dulles Climate data:

 

1)  Min temp is corrected to 20F (441 AM) from erroneous value of 4F

2)  Precip changed slightly from 1.26" to 1.24"

3)  The corresponding values were adjusted for the departures from normal for HDD/monthly precip/temperatures.

 

An corrected daily climate summary (CLIIAD) was sent at 957 AM today for the Feb 13 KIAD data, as well as a corrected preliminary F-6 form (CF6IAD) sent at 944 AM.

 

As you point out, these data are considered preliminary, and changes can come at anytime.

[Ian]

Wasn't really an assumption based on NWS reporting. Thanks for response tho.

[WEATHER53]

So in essence some other entity made a mistake and thus the appearance of DCA underreporting again.

[Deck Pic]

The total snowfall is correct for the 21st. The problem is people make assumptions for things they don't understand and think they know more than people who have been Meteorologists and Meteorologist Technicians for over 30+ years. The 2.6 is the total snowfall for the whole day and it's reported about a minute after midnight on the 22nd. At 3:52pm the total up to that time was 1.8 inches. Between 3:52pm & 4:52pm another 0.5 inches of snow occurred making the total snowfall up to 4:52pm 2.3 inches. At 5:52pm another 0.3 inches of snow/ice pellets fell making the total snowfall for the day 2.6 inches. A trace of snowfall occurred both at 6:52pm and 7:52pm but traces aren't added to the total.

 

Also, there were two SNINCR remarks on the 3:52pm and 4:52pm observations which validates the lower visibility due to increased snowfall rates in the observations themselves. There is your explanation....

 

Thanks for the explanation.  Appreciate it. And the total seemed reasonable to me.  It was the evolution that didn't make sense.  Sterling reported 2.6" at 3:55 (sounds like they were in error). Based on that do you think it was unreasonable of me to Question the total, given what occurred between 3:55 and 5:30?

[WEATHER53]

It was either an error or someone at NWS Sterling pulled that total out of the sky because DCA doesn't enter the daily snowfall total into ASOS to be transmitted longline until 0000LST of the next day.

 

It was either an error or someone at NWS Sterling pulled that total out of the sky because DCA doesn't enter the daily snowfall total into ASOS to be transmitted longline until 0000LST of the next day.

Where is the temperature measurement device located. Out on the tarmack in a properly unencumbered and uninfluenced location or up on the roof not too far from the office? Thanks.

[Inverted_Trough]

While you're here, any idea why buoy WASD2, located about a mile northeast of DCA, right on the water, is nearly always about 2 degrees colder than DCA?  (in fact, I've never seen it read warmer than DCA).  It seems that during the winter the moderating effect of the water should at least cause its readings to be much more similar, if anything the buoy should occasionally run warmer (which, again, seems to never happen).  Just curious is all.

[Ellinwood]

Can I have your autograph?

[WEATHER53]

So a brief appearence to chastize us and then disappear. That attitude is the same attitude that allows DCA to continue to be so messed up.

[uncle W]

it would be worse if the measurements were taken by a zoo keeper...

[eurojosh]

Even with the pending best snow of the winter, I would still vote this for best thread of the winter.

[Inverted_Trough]

Let's add 1/23/16 to the docket of evidence!