CONTEST STATUS - Updated: SUN ... 07-DEC-14 @ 6:30 PM EST

Winter '14 / '15 - Snowfall Forecast Contests

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16th Annual 'Regular Season'
STORM #2
Synoptiscope in VCP32

STORM #1 (26/27-NOV-14):
FINAL results here

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14th Annual 'Season-total'
Forecasts here.
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Thursday, February 11, 2010

Winter '09 / '10 - BWI/s Historic Snowfall Season

History in the making....with several more weeks of winter left on the clock.

Baltimore / Washington International airport (BWI) has measured 79.9" of snow as of 10-FEB...the most ever observed since record-keeping began in 1883.

How unusual is it for BWI to see this much snow in one winter?

This amount of snow would be considered a statistical outlier...more than four standard deviations (4.322) above the period-of-record mean of 21.9".

It's more snow than 99.994% of all other winters.

Other notable seasons at BWI were 2002/3 (58.1")...1995/6 (62.5")...1963/4 (51.8")... and 1898 (51.1")....all of which were more that two standard deviations above the mean (more snow than 95% of all other winters).
Interesting to note...three of the largest season-total snowfalls have occurred in the last 15 years...during a time when NHEMI areal snowfall has been generally well below average...especially during summer.
How rare is this winter/s snowfall?
How often can an extreme season such as this be expected?

Since it/s never happened during the period-of-record...a statistical technique using a Gumbel distribution can be applied to determine the 'return-period' for BWI receiving this amount of snow in one winter. The distribution and return-period are calculated using the 126-year historical season-total snowfall data from LWX.


The 126-year Gumbel distribution for BWI season-total snowfall is shown above.

The calculation...based on the line's slope...intercept...and a crisp double-inverse natural log function...shows the return-period as once every 675 years! The return-period for the runner-up 'Winter of 1995/96' is only 115 years.

Image: Baltimore...MD FEB-1899 (credit:  Baltimore Sun)

4 comments:

Anonymous said...

If they get another 20 or 30 inches, then the return period will rise to the order of a thousand years or maybe more. Of course at some point, snowfall from a given winter would not melt and an ice age would begin. But most of us figured that would originate around Quebec City or north, not in the Mid Atlantic!

-- Roger Smith

TQ said...

Quebec? D'accord!

If BWI measures 100"...its winter/s season-total snowfall will have a return-period of 5,250years.

Looking at PHL...too. Their 100" return-period is 7,760.

Anonymous said...

Hmm, that's almost back to the Younger Dryas (end of the last glacial period, ice age, what have you == Wisconsin glacial) ... I suppose when it's sunny and 80 degrees in April most of this snow will be gone, except around mall parking lots.

Or will it? (tick tock) -- RS

TQ said...

The return period will be less now that there's a data point for at least 80".

A few thousands years less...but still quite long.