Winter '11 / '12 - October Snow Cover

Too bad this classic benchmark storm didn't show its hand early enough to kick-off the 13th Annual NEWxSFC.

UPDATE:  ABE - 6.8

Image courtesy NOHRSC

Winter '11 / '12 - Trending: The North Atlantic Oscillation

The North Atlantic Oscillation (NAO) often plays an important role in defining the character of sensible weather during east coast winters.  It and its godfather the Arctic Oscillation (AO) are also two of the harder features to forecast beyond a week or ten days which leaves seasonal forecasts vulnerable to considerable error.

The developing consensus for Winter '11 / '12 leans heavily on a strengthening la Nina fortified by the trending cool phase of the Pacific Decadal Oscillation (PDO).  These conditions in the eastern Pacific ocean favor a predominantly northern stream storm track passing west of the Appalachian Mountains into northern New England, the result of a blocking ridge axis over the SE CONUS...especially during a positive phase of the Northern Annular oscillations (NAO and AO).

Given the recent trend shown below...how probable is it the phase of NHEMI annular oscillations will be positive this winter?

The time-series above shows the total number of months the NAO was positive or negative during each year.  These data are quite noisy but do show most years during the '50s had greater than or equal number of negative months than positive months and the late '80s to the mid-'90s were dominated by years with more positive months than negative.

Summing the positive and negative months over five years produces a smoother plot and reveals clearly the negative dominance during most of the '50s...the mid-'60s to early '70s...and ever since 2000.  The 'even' line for the period is 30 months.

Positive months held sway between the mid-'80s and much of the '90s during the peak of the AGW war.

Summing the positive and negative months over a decade removes all the noise and shows the positive phase has been the dominant state of the NAO for thirty years (1970 - 2000).  The 'even' line for this period is 60 months.

Coupled with conditions in the Pacific -- evidenced by the initial years of the PDO's cool phase -- the NAO's trending decadal data could be signaling an impending era of colder than 'normal' winters.

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More later about the correlation between NAO and west Atlantic ocean SST anomalies along with how a la Nina winter can be affected by negative NH annular oscillations..

Winter '11 / '12 - 1st Contact

Up to 9" of snow was observed earlier this week INVOF this picture taken in Snowshoe...W. Va. (map).

Right next door at Hot Springs...VA (KHSP)...winter's preview was observed Monday evening...

020255Z AUTO 28016G22KT 1/4SM -SN OVC003 02/02 A2990 RMK AO2 =

020235Z AUTO 27016G22KT M1/4SM SN OVC001 02/02 A2990 RMK AO2 =
020215Z AUTO 28016G21KT M1/4SM -SN OVC001 02/02 A2990 RMK AO2 =
020158Z AUTO 28017G24KT 1/4SM -SN OVC001 02/02 A2991 RMK AO2 =
020136Z AUTO 27017G21KT M1/4SM -SN OVC001 02/02 A2990 RMK AO2 P0003 =
020115Z AUTO 27018G21KT M1/4SM RA OVC001 02/02 A2991 RMK AO2 P0002 =
020056Z AUTO 27017KT M1/4SM -RA OVC001 01/01 A2991 RMK AO2 P0001 =
020035Z AUTO 28016G20KT M1/4SM SN OVC001 01/01 A2991 RMK AO2 P0001 =
020016Z AUTO 28015G21KT M1/4SM SN OVC001 01/01 A2992 RMK AO2 =
012355Z AUTO 28018G21KT M1/4SM SN OVC001 01/01 A2992 RMK AO2 =
012335Z AUTO 28014KT M1/4SM SN OVC001 01/01 A2992 RMK AO2 =
012315Z AUTO 28015G20KT M1/4SM SN OVC001 01/01 A2992 RMK AO2 =
012255Z AUTO 29017G20KT 1/4SM SN OVC001 01/01 A2992 RMK AO2 =
012235Z AUTO 28016G21KT M1/4SM SN OVC001 01/01 A2992 RMK AO2 =

For more than three hours...HSP vsby met or exceeded blizzard criteria.  Too bad the pressure gradient force was not up to the task.

Winter '11 / '12 - Quasi-Biennial Oscillation : ENSO

- QBO...having begun its negative phase in August...stands at -2.30 in September.  QBO will remain negative and intensify throughout the upcoming winter.

- ENSO consensus forecast (see Table 1) for D-J-F from the latest numerical and statistical model runs expects a neutral ENSO to 'weak' la Nina.

Forecast SST Anomalies (deg C) in the Niño 3.4 Region

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Easterly QBO during la Nina favors 1) a cold central US and 2) negative NAO and hi-latitude blocking.
- D'Aleo

Note the negative correlation between the QBO state and geo-potential heights over the Pole and the SE CONUS where a negative / east (positive / west) QBO means heights are positive (negative).  The former implies hi-latitude blocking and the latter suggests la Nina-like ridging.

The polar vortex is weaker and more easily disturbed during easterly QBO and low solar activity.  The current solar cycle is comparatively weak.

"...QBO determines the character of the early winter, leading to a colder and more stable polar vortex in December and January during the west phase of the QBO and a more disturbed and warmer Arctic during the east phase of the QBO."
- SPARC

"Major winter stratospheric warmings preferentially occur during the easterly phase of the QBO..."
- Holton and Tan (1980)

Major warmings can produce deep-layer anti-cyclonic circulations that descend into the troposphere resulting in blocking flow regimes over hi-latitudes.  Blocking is implicated when moderate to strongly negative NAO and AO indexes are observed.

"Pronounced weakenings of the NH wintertime stratospheric polar vortex tend to be followed by episodes of anomalously low surface air temperatures and increased frequency of occurrence of extreme cold events..."
Thompson, et. al. (.pdf)

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QBO analog year of 'least regret' is 93/94, the bride's maid is 76/77...then it's 83/84...88/89....and finally 64/65.  Some winters can be eliminated when the ENSO is considered.

ENSO state for QBO analog winters are...
93/94:  neutral (+0.2)
76/77:  weakly positive (+0.6)
83/84:  neutral (-0.4)
88/89:  strongly negative (-1.7)
64/65:  weakly negative (-0.8)

Given the currently modeled ENSO forecasts...this winter's best QBO : ENSO analogs appear to favor 83/84...possibly 64/65 if there's strengthening.

More about the analog years and the current state of other analogs NAO/AO/PNA/PDO later...

The North Atlantic Oscillation: New Monograph from American Geophysical Union

"The Monograph is thematically organized and provides a comprehensive (multidisciplinary) overview of material (theory, observations and models) related to the NAO. There are 12 chapters, each presenting a thorough overview of a topic, and most contain new research as well.

"The NAO is one of the oldest known world weather patterns, as some of the earliest descriptions of it were from seafaring Scandinavians several centuries ago.

"Surface temperatures over the NH are likely to be warmer now than at any other time over the past millennium, and a substantial fraction of this most recent warming is linked to the behavior of the NAO, in particular a trend in its winter index from large amplitude anomalies of one phase in the 1960s to large amplitude anomalies of the opposite phase since the early 1980s.

"That the ocean may play an active role in determining the evolution of the NAO is also one pathway by which some limited predictability might exist. New statistical analyses have revealed patterns in North Atlantic SSTs that precede specific phases of the NAO by 6-9 months, a link that likely involves the remarkable tendency of the extratropical ocean to preserve its thermal state throughout the year."

Expected release date:  early DEC

Overview (.pdf) here.

Winter '10 / '11 - Season-total Snowfall Forecast Contest - Final Results

Forecasts have been verified and posted at the web site here.

Congratulations to rookie forecaster Roger Smith for placing 1st this year.

Hope to see y'all back again next winter!

Winter '10 / '11 - Season-total Snowfall Forecast Contest - Preliminary Verification

Green >= 75th percentile
Red <= 25th percentile

Eighteen of the 24 forecast stations measured more snow than their period of record normal (PORN).  All told...1,403" of snow were measured...55% more than PORN (909.8") for the months of DEC through MAR.

The winter/s big winner as a percent of normal was ORF with almost three times their PORN snowfall...the bulk of which came in DEC.  Other over-achieving stations in the upper 75th percentile of all forecast stations were EWR...BGR...BDR...ACY...and NYC. 

New monthly records
BTV:  Feb 43.1"
BDR:  Jan 42"
BDL:  Dec 14.2"  + Jan 57"
EWR:  Jan 37.4"
NYC:  Jan 36"
RDU:  Dec 8.3"

Top honors for 'most inches above PORN' went to BGR...BTV...BGM...BDL...EWR...and BOS.

Biggest losers were CAR...RIC...MDT...BWI...DCA...and IAD which all measured less than 100% PORN.

SBY has been removed from the station list b/c of missing data for all months again this year.  All SBY forecasts will be set to zero.

Please note any errors in Comments and include a link to the correct data.

Final results coming in a few days.

Winter '10 / '11 - FINAL Standings

After eight snow storms...the snowfall forecasting season for the Winter of '10 / '11 comes to a close.

Under the 'two-thirds' rule...the best 'two out of three' Z-scores are used to compute the final standings. After Snow Storm #8...your top six Z-scores were used to calculate these standings. Data used to compute the standings are posted at the Contest web site here.

Z-scores are used to standardize / normalize forecast errors for each snow storm so at the end of the season...the 'equalized' scores can be averaged.

An expanded data table with higher resolution graphics and additional measures of forecaster skill at the Contest's home page.

Winter '10 / '11 - Snow Storm #8 - Final Results

1st - donsutherland1
SUMSQ: 49.62
SUMSQ Z: -0.638
STP: 13.76 (4)
TAE: 21.64 (1)
AAE: 1.08 (1)

2nd - TQ
SUMSQ: 58.45
SUMSQ Z: -0.605
STP: 13.05 (2)
TAE: 22.25 (2)
AAE: 1.11 (2)

3rd - Donald Rosenfeld
SUMSQ: 91.14
SUMSQ Z: -0.483
STP: 12.76 (1)
TAE: 28.85 (3)
AAE: 1.44 (3)

Honorable Mention - Brad Yehl
SUMSQ: 106.75
SUMSQ Z: -0.425
STP: 21.25 (5)
TAE: 31.15 (4)
AAE: 1.56 (4

SUMSQ: sum of square errors
STP: storm-total precipitation error
TAE: total absolute error
AAE: average absolute error
(rank)

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Full forecast verification and summary at the Contest/s home page.

Winter '10 / '11 - Snow Storm #8 - Preliminary Verification

Preliminary storm-total snowfalls for Friday and Saturday from CDUS41 and CXUS51...as of 9 AM Sunday.

Some stations in the data table do not have SN:H2O reported b/c their totals included mixed precipitation.

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Two daily records.

SAT...01-Mar-11
BGR - 14.4" (8.5"; 1993)
CAR - 7.5" (3.6"; 1978)

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Please report any errors and drop a link to the correct data in Comments.

Final results and storm summary Monday evening.