Understanding Violent Weather II: Winter Storms

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UnderstandingViolent Weather IIWinter Storms
Paul Kocin
National Press FoundationNorman, OklahomaMarch
14, 2007
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AGENDA
(1) Winter Weather is Pretty How serious is
winter weather? So why should journalists care?
(2) Winter forecast issues You should know
(3) How have winters been affected By Global
Warming
(4) Northeast Snowfall Impact Scale (NESIS)
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(1) Winter Weather is Pretty How serious is
winter weather? So why should journalists care?
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This is why
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• Each year, automobile accidents claim an
  incredible amount of lives, cause injuries and
  property damage.

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• The average/year
• 41,000 deaths,
• 3 million injuries,
• billions in damage.

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• Most of the above is NOT weather related, BUT
  about 15 is!

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• Although 15 sounds like a small percentage, that
  still leaves approximately

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• 7,000 deaths
• 800,000 injuries
• and billions of dollars in damage per year!

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• Lets put these numbers in perspective
• Deaths (10-year average)
• Hurricanes are responsible for about 18 deaths
  /yr (that will change)
• Tornadoes are responsible for about 58 deaths /yr
• Floods are responsible for about
• 84 deaths /yr
• Heat Waves are responsible for about 237 deaths
  /yr

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• Adverse weather is associated with over 1.5
  million crashes per year.
• The adverse weather is typically rain, snow/ice
  and fog.

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• Examples In 2001
• 5400 deaths linked to rain-slicked roads
• 1100 deaths linked to snow and ice
• 670 deaths linked to fog
• Cost estimates
• Injuries, loss of life, and property damage cost
  an average of 42 billion dollars annually just
  for snow and ice!

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LETS PUT ALL THIS IN PERSPECTIVE

• Most of us are more likely to be affected through
  injury, death, or property damage from road
  weather than from more well-known weather issues
  such as hurricanes, tornadoes, and flash floods
  combined.

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AND FINALLY

• And snow and ice make up a significant component
  of the dangers posed to transportation nationwide

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So why should journalists care?

• While events make the news, there are less
  sexy weather hazards that impact far more people

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Agenda
(2) Winter forecast issues You should know
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Winter vs Severe Storm vs Hurricane
forecasting 3 very different kinds of
problems 0 Hurricanes involve assessing track,
intensity and size of circulation, storm surge,
flooding rains and timing 0 Severe Storms
involve pinpointing areas when and where
tornadoes, hail and strong winds will occur 0
Winter storms involve determining
precipitation type, amount, location and timing
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Winter forecast issues O The main issue Rain
vs freezing rain vs sleet vs snow O
Predictability Uncertainty O Winter
climatology-means and extremes (how common vs
how rare)
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So how do we forecast a winter storm? O Depends
on how far out from the event O Long range and
short range models O Data!
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When do we see something coming? O Right now,
there are patterns that sometimes foretell that
winter storms may be affecting our area O Its
often not El Nino (although sometimes that has a
big role) O
NAO
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When do we see something coming? O Sometimes we
see signals that suggest a major snow is possible
as much as 10 days in advance O a lot of these
signals are false alarms O As we get to 3 to 5
days in advance, we start getting excited (so do
you!)
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The tools we use O A magic wand? O The farmers
almanac? O Uncle Freds bunions? O Models
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(No Transcript)
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What are models? O Very complex computer programs
based on basic physics and physical
parameterizations run on some of the worlds most
powerful computers O these models compute
trillions of numbers that predict the future
state of the atmosphere and can be plotted on
maps O meteorologists love to look at model data
on maps!!!!!
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Current models

• Long range
• The GFS up to 15 days
• Short range
• NAM others (MM5, RUC, GFS good too)
• every 3hrs thru 84 hours (3 1/2 days)
• Foreign models
• ECMWF
• UKMET
• Canadian Model
• and there are others, ensembles, etc.

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When the !!! is hitting the fan

• Radar much better with snow than only 15 years
  ago
• Surface weather charts
• My secret weapon try to plot every hour
• allows me to see if storm is going according to
  plan or not
• Satellite data, model updates, coop observers
• webcams, colleague consultation

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Winter forecast issues O During winter, people
expect us to accurately predict precipitation
amounts (in terms of snow depth) need to
express uncertainty O Turns out that we have
little skill in this area, especially more than
36 hours out - few mind if 1 inch of rain versus
.25 inches falls
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SNOWFALL MEASUREMENTS O snowfall is
surprisingly tough to measure accurately O
Unfortunately, the official measurements often
do not capture real variations in snowfall that
can and do occur over small distances
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Measuring snow

• Snowfall vs snow depth
• Measuring at differing intervals may get you
  different amounts
• Snow melts, compacts, sublimates, drifts,
  refreezes
• It accumulates differently on different surfaces
• Its a messy substance to measure
• Therefore, its even more messy to forecast

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Winter forecast Reality O Precipitation (and
that means snow) remains a meteorological issue
that is still not well resolved O Meteorologists
have been providing forecasts of precipitation
amounts for years (in terms of snowfall
forecasts) it has almost been a crapshoot O
does it make a difference whether it is a 1- day,
2-day, 3- day or 7-day forecast!
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Winter forecast issue Reality O That said,
precipitation forecasting has improved to a point
where forecasts are skillful 24 to 48 hours out
(there are, of course, exceptions!!)
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Winter forecast issue Reality O Not all weather
situations are equally predictable O And
forecasters dont necessarily know when a
situation is more predictable than not (we
usually find out when you do - after the stuff
happens)
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Winter forecast issue Reality O Sometimes all the
models are in agreement! O Problem is, model
agreement doesnt mean accurate forecast thats
where the science is
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The main issue Rain vs freezing rain vs sleet
vs snow o Winter storms are usually more
complicated than this!!!!!!!
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The problem with forecasting heavy snow

• It often occurs close to the rain/snow line
• It sometimes occurs close to the northwestern
  edge of the snow
• 50-mile errors in location produce big problems!
• The dreaded dry slot
• Forecast amounts depend on how its measured and
  measuring snow is not as easy as it sounds

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Example Look at this narrow band of snow!
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Another example One of the craziest snows in
recent memory!!
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Winter forecast issues
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Predictability Some storms are easy. ?
Affect one small region its well
forecast Life is GREAT ? Most storms are
widespread, multi- day, multi-form
events.. forecasts can be good one place,
lousy others..lots of areas for major
errors!
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More predictability 0 Whether big or small,
winter storm predictability is very
variable!!! 0 Some winter storms are amenable
to prediction even several days in advance 0
Other winter storms seem to be unpredictable
even up to the day of the event
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Uncertainty 0 There is always uncertainty when
predicting snowfall amounts 0 Uncertainty can
be expressed probabilistically 0 Uncertainly
doesnt mean we dont know, but represents a
continuum from what we do know versus what we
dont
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Mean Annual Snowfall
Winter climatology-means and extremes (how
common vs how rare)
o
Bismarck
Boston
50
o
40
o
o
New York
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o
o
Chicago
o
Denver
Washington
San Francisco
20
o
10
o
5
Atlanta
Los Angeles
o
2
Dallas
o
Miami
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Winter Climatology
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Winter Climatology
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Agenda
(3) How have winters been Affected By Global
Warming?
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How cold was this winter? (December thru
February)
45th warmest in 112 seasons
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How did it break down month to month?
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Past 8 winters Warm or cold? Nationwide Ranking
2006/2007 45th Warmest 2005/2006 3rd
Warmest 2004/2005 10th Warmest 2003/2004 42nd
Warmest 2002/2003 31st Warmest 2001/2002 5th
Warmest 2000/2001 26th Coldest 1999/2000
Warmest
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No shortage of major winter storms During the
same period
January 25, 2000 December 30, 2000 February 5,
2001 March 5-7, 2001 December 25, 2002 January
3-4, 2003 February 15-17, 2003 December 5-7, 2003
January 27-28, 2004 January 22-23, 2005 December
9, 2005 February 11-12, 2006 February 13-14, 2007
And these are just major Northeast Winter Storms
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Regional Temperature Comparison 6 previous
winters
2005/ 2006
2002/ 2003
2004/ 2005
2001/ 2002
2003/ 2004
2000/ 2001
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When its been warm, its very warm And persistent
For example, January 2006
By far Warmest January on record 20o
departures North-central
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And this winter began very mild
December 2006
4th warmest December on record
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But ended on a very cold note
February 2007
34th coldest February
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So, how have winters been doing in the Global
Warming era?

• Most have been warm - s 1,3 and 5
• warmest have occurred in last 8 winters
• persistent warm regimes punctuated
• but not offset by significant cold periods
• Still have tendency for some very crippling
• winter storms despite warmth
• (NE storms, lake-effect, Denver 2003, etc.)

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Weve come up with a scale that estimates winter
storm impact For Northeast Winter Storms

• which brings us to the last topic of
• the presentation..

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Agenda
(4) Northeast Snowfall Impact Scale (NESIS)
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Fujita and Saffir-Simpson Scales

• Measure potential for
• DESTRUCTION
• to property and
• loss of life from
• tornadoes and hurricanes
• Categories (0 or 1 thru 5)
• Scale used during (Saffir-
• Simpson) or after (Fujita)
• the event

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NESIS

• Measures potential for human and economic
  DISRUPTION
• Categories (1 thru 5)
• Use during and after
• storm

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SNOWSTORM IMPACT DUE TO

• SNOWFALL
• WIND SPEED
• TEMPERATURE
• DURATION
• INTENSITY
• STORM INTENSITY
• GROUND TEMPERATURES
• SUN ANGLE
• TIME OF DAY, ETC., ETC. ETC.
• ETC!

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TOO COMPLICATED!!!!!

• LOOKED AT 30 CASES
• 1950-2000
• CONTOURED SNOWFALL
• at 4, 10 and at
• 10 intervals
• THOSE CONTOURS
• REPRESENT
• (1) an AREA
• (2) an AFFECTED POPULATION

Feb 1978
Mar 1993
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What NESIS is

• A measure that is based on the integrated effects
  of storm snowfall in the Northeast United States

• thru areal coverage of snowfall amounts and
  population affected

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How to get estimates of area and population?

• GIS Systems
• Initially done for 30 cases for 4, 10,
  20....Etc.
• A mean Area and mean Population were computed for
  30
• cases

FEB 1978
MAR 1993
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Northeast Snowfall Impact Scale (NESIS) Sxn
n (An/Amean Pn/Pmean) SUM (AREAS
POPULATIONS) CONTAINED IN EACH SNOWFALL
INTERVAL A Area of snowfall within a
given contour interval Amean mean area
of 30 cases P Population of area
within a given contour interval Pmean
mean population for 30 cases n
Interval number (gt4N0.4 10 N1 gt20, N2
gt30, N3..) And applied the equation to all 30
cases
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How was NESIS applied?

• Applied to the total snowfall distribution
• (Northeast and area east of Rockies)

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Examples
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Mostly 4-10, small 10
NESIS VALUES Close to 1
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Larger area of mostly 4-10
NESIS VALUES Close to 2
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Small 4, Larger area of 10, small 20
NESIS VALUES Close to 3
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Larger 4, Larger area of 10, small 20
10
4
NESIS VALUES Greater than 4
20
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Even larger area of 4, 10, 20
NESIS VALUES Greater than 8!
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Mean 4.80
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Tested the scale on 70 cases

• 30 Major Snowstorms
• 15 Interior Snowstorms
• 15 Moderate Snowstorms
• 4 Historic Snowstorms
• Recent Snowstorms
• incl Winter of 2002/2003
• Then came up with Categories

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NESIS CATEGORIES

• CATEGORY NESIS VALUES of CASES DESCRIPTION
• 1 1 2.499 23 NOTABLE
• 2 2.5 - 3.99 22 SIGNIFICANT
• 3 4 5.99 16 MAJOR
• 4 6 - 9.99 7 CRIPPLING
• 5 10.0 2 EXTREME

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The Blizzard of 05
NESIS6.10 CAT 4
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The Blizzard of 06
NESIS6.10 CAT 4
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The Valentines Day Storm of 2007
NESIS6.10 CAT 4
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Northeast Snowfall Impact
Scale
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5 Top Ranked Snowfalls for 70 major snows

• Rank DATE NESIS CATEGORY
• 1 12-14 MAR 1993 12.52 5
• 2 6-8 JAN 1996 11.54 5
• 3 15-18 FEB 2003 8.91 4
• 4 11-14 MAR 1888 8.34 4
• 5 11-14 FEB 1899 8.11 4

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SUMMARY

• NESIS is an Objective Scale that measures the
  impact of Northeast snowstorms on the densely
  populated Urban Corridor
• A Scale Derived from 30 Historical Cases
  (1950-2000)
• Computed Values mapped to Specific Categories
  (1-5)

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SUMMARY (Contd)

• Application appears to separate the most
  memorable storms from others with subjectively
  smaller impacts
• The scale provides an objective number for total
  snowfall distribution and relates impact that
  matches a subjective view of the snowfall maps

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• THE END

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Go stormchasing!
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Winter Climatology Noreasters
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Winter Climatology Clippers
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Winter Climatology Panhandle
Hooker
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• Winter Climatology
• Storms vs lake-effect snow

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Mean Annual Snowfall
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40
30
20
10
5
2
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Winter Climatology
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Winter Climatology
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Winter Climatology
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Winter Climatology