Mount Rainier Paradise reaches 200" snow depth

Amar,

You are the expert so I am asking this question to you.

How come when I read snotel data for Year-to-Date Precipitation, the accumulated precipitation amount will go down as well as up? I understand going up...but whay does the Year-to-Date Precipitation go down from one reading to the next over several hours?

Here is an example:
www3.wcc.nrcs.usda.gov/nwcc/sntl-datarpt...s=7&state=washington

Thanks for helping me understand the data!

Stefan

How come when I read snotel data for Year-to-Date Precipitation, the accumulated precipitation amount will go down as well as up?  I understand going up...but why does the Year-to-Date Precipitation go down from one reading to the next over several hours?

This FAQ from the Idaho SNOTEL site has info about precip gauge errors, see question #2: www.id.nrcs.usda.gov/snow/faq/snow_prec_faq.html

Q2. How can year-to-date precipitation decrease? For example, Trinity Mountain SNOTEL’s precipitation was 7.8 inches then the next reading shows 7.7 inches. Shouldn’t cumulative precipitation always be increasing?

Cumulative precipitation should only increase through a water year, however we allow small decreases in raw precipitation data (less than -0.5 inches) so that it passes through our automatic quality checks. This allows the data to be included in our data reports. For large decreases (greater than -0.5) the data is flagged suspect and will show up as a -99.9, those values are kept out of data reports. The reasons you might observe decreases include...

1. The voltages that our electronic pressure transducers use to measure precipitation and snow water can flutter up and down with temperature changes. This is particularly evident in hourly data, since diurnal temperature changes cause greater fluctuations than readings taken on consecutive midnights, when we measure daily data.

2. There might be an air bubble in the plumbing line leading to the transducer. Temperature changes cause the air bubble to expand and contract and this is another reason for measurement flutter. Bleeding the air out of all plumbing lines is one of our common field maintenance practices.

3. The data you are looking at hasn't been manually quality checked yet. We do weekly edits each Monday to smooth these kinds of flutter out of the daily data. Generally in a day or two the data will rebound to where it was and we'll edit out the low value the following Monday. The hourly data is raw and it does not undergo this weekly quality checking process so decreases remain in those data sets. If a precipitation decrease is observed in daily data that is more one water year old, it should be brought to the attention of the snow survey as it should be corrected.

4. The final case is there is something wrong at the site. There are various problems that can cause a precipitation gage to decrease. These include leaks caused by an animal such as a bear or mouse chewing a hole in the plastic plumbing, or a human vandalizing the gage with bullet holes. When a leak is suspected we schedule a repair trip to the SNOTEL site to fix it. Until the repair is made we edit the data using nearby sites or during the winter we'll estimate precipitation using the snow pillow.

Regarding the Hozomeen Camp site that you linked to, the answer is that the precip gauge at that SNOTEL site appears to be malfunctioning, and the NRCS SNOTEL staff is aware of the issue. If you look at the midnight (0000) values of the data, you'll notice that they are all exactly 38.7", regardless of what the adjacent values at 2300 or 0100 might be. The midnight values are checked and quality controlled by NRCS staff, and in this case they've clearly been manually edited to all be equal to 38.7".

This shows the last 30 days of midnight values only ( www3.wcc.nrcs.usda.gov/nwcc/sntl-data000...=30&state=washington ), and it looks like the problem began just before April 17, since all midnight values have been constant at 38.7" since then, despite continuing precipitation.

That 65" snowfall was partly responsible for me moving out to Seattle -- iI wanted to move someplace with real mountains and big snowfall. Choosing the UW and moving to Seattle remains the single best decision I've ever made in my life (my mom disagrees, she nearly went apoplectic at my decision, and still can not believe that I chose the UW over Yale).

Wise move! I did a post-doc at Yale, then joined the faculty (School of Medicine). I loved the diversity of visiting seminar speakers in my field (ecology), but that was it; very limited in access to mountains :'( but I ended up in WA almost by accident (was strongly urged to come here by my employer) and once here for nearly a decade, I began skiing for the first time in my life. 20 years later, bc skiing remains my passion as does hiking the subalpine and alpine in Mt. Rainier.

Thanks Amar!

With the next storm likely to dump another 2-3 ft on Wednesday-Thursday, and given its average snowfall of 23" in May and 6" in June, it is very likely that Paradise will break the 900" mark this season, something which it has done only 7 times before (last time was 947" in 2007-. That was my pre-season prediction, that Paradise would break 900" this year, based on its average snowfall in strong La Niña years of 915". A prediction that looked to be highly erroneous by the time mid-February rolled around and the snowfall total was still hovering near 450", but now looking much closer to the mark.

Well, that happened very quickly: Paradise has already broken 900" of snowfall for the season, with the park phone recording reporting 902" as of this morning. This is now the 8th highest seasonal snowfall on record at Paradise in 85 years of snowfall data. There has been 23" of new snow at Paradise so far in May, which equals the normal amount for the entire month of May.

The maximum snowdepth at the NPS snow stake this year was 253" on April 28, which is the 13th greatest seasonal maximum out of 93 years that have data for seasonal maxima. It's also 1" more than the seasonal maximum from 2007-2008 (252" on March 29, 2008), which was the most recent strong La Niña year with 947" of snowfall.

However, the late season values are even more impressive this year, as the May 1st snowdepth is the 6th greatest on record. As of today (May 9), the current snowdepth is 242", and the only other seasons which have had snowdepths over 240" this late are 1916-17, 1955-56, 1971-72, 1973-74, and 1998-99, which were all HUGE snow years with over 1000" of snowfall.

[hr]Here's the final CLISNO data for this season for May 1, looking very impressive across the board as a percent of normal:

[tt]CLIMATOLOGICAL SNOWDEPTH INFORMATION
NORTHWEST WEATHER AND AVALANCHE CENTER SEATTLE WASHINGTON
DAY  1  MONTH  5  YEAR  2011

DATA IN INCHES, -99 DENOTES MISSING DATA

            CURRENT  CLIMATE  PER CENT   LAST  THRU 2010  THRU 2010
            DEPTH    AVERAGE  OF NORMAL  YEAR  MAX/YEAR   MIN/YEAR

HURRICANE   169       91      186         89   145/1982    25/2005
MT BAKER    241      138      175        166   270/1999    20/1934
STEVENS     113       81      140         72   141/1964    13/2005
SNOQUALMIE   87       59      147         33   131/1974     0/2005
STAMPEDE     98       80      122         57   176/1964     0/2005
MISSION      52       33      158         33    56/1999     0/2005
CRYSTAL     107       72      149         76   115/1999    17/2005
PARADISE    244      159      153        158   295/1972    36/1941
WHITE PASS   66       29      228         29    76/2008     0/2005
TIMBERLINE  211      153      138        159   270/1999    43/1977
MEADOWS     156      114      137        118   189/2008    30/2005
[/tt]

Great data Amar!

Do you (or anyone else) know if there's a direct correlation between record snow years, and summer weather trends?