forecasting tricks for irwin (february 28, 2014)

Forecasting tricks for Irwin

Photo: Connor Walberg ActionPhotoSchool.com

Meteorologist Joel Gratz

1960

2005

I want to remove the mystery of Colorado weather.

Hi, I’m Joel Gratz.I grew up in Pennsylvania, ski raced and instructed, then moved to Colorado after college.

And I started to miss powder days due to inaccurate forecasts.

Dec 2007 28 people email list

2008-2009 500 people email list

2009-2010 245,000 pageviews

2010-2011 1,315,000 pageviews

2011-2012 3,330,000 pageviews

2012-2013 12,000,000 pageviews

2013-2014 ~18,000,000 pageviews

So I learned how to forecast in Colorado, and started to share.

This is where we look for El Nino or La Nina.

Courtesy: Mike Baker, NWS Boulder

Storm tracks for La Nina.

Courtesy: Mike Baker, NWS Boulder

Storm tracks for El Nino.

This year is a La Nada.

Courtesy: Mike Baker, NWS Boulder

Storm tracks for La Nada.

It snowed in Aspen during September.

Of the past 22 Septembers with snow, 19 of the

ensuing winters have been average or above.

- Cory Gates, AspenWeather.net

Perhaps there’s another clue. !

We set a snowfall record in April and a rainfall record in September for Boulder. Does this tell us anything about winter snow in the mountains?

Each line shows amount of snow on the ground for various weather stations, during winters after heavy precipitation in Boulder.

100%

110%

120%

130%

140%

150%

160%

Dec 1 Jan 1 Feb 1 Mar 1 April 1

Pueblo

Durango

Alamosa

Gunnison

Leadville

Fort Collins

Grand Junction

Colorado Springs

Steamboat Springs

UPPER ARKANSAS

SOUTH PLATTE

GUNNISON

WHITE-YAMPA

REPUBLICAN

COLORADO HEADWATERS

RIO GRANDE HEADWATERS

UPPER SAN JUAN UPPER CIMARRON

UPPER COLORADO-DOLORES

NORTH PLATTE

SMOKY HILL

LOWER SAN JUAN

UPPER GREEN

Denver

47

79

72

68

94

70

88

89

95

67

82

99

9895

95

87

72

98

58

76

39

98

97

47

67

73

69

86

81

76

85

70

90

87

10

148

136

117

141

126

138

117

118

152

114

121 148

129

126

131

137

136

126

123

109

164

119

122

122

106

117

149

111

130

128

110

101

130

162

124

145

144

141

119

150

147

132

112

110

111

159

144

158

191

147

140

116

188

152

153

105 123

123

182133

76

25

ColoradoSNOTEL Snow Water Equivalent (SWE)

% of Normal

70

0 20 40 60 80 10010Miles

Prepared by theUSDA/NRCS National Water and Climate CenterPortland, Oregonhttp://www.wcc.nrcs.usda.gov/gis/

Provisional Data Subject to Revision

Current SWE % of 1981-2010Median

> 160%

140-160%

120-139%

100-119%

80-99%

60-79%

40-59%

1-39%

0%

Unavailable*

Feb 27, 2014

* Data unavailable at time of posting or unavailable long-term normal.

This year

Average

2010-2011

Average

Schofield Pass

2010 - 2011 Season:

2 of 60 storms created

25% of the total season snow

2010-2011

2013-2014

Schofield Pass

Crested Butte

2.5x

Long range forecasts stink! !

We cannot reliably predict snow accumulations beyond about two weeks. Seasonal outlooks are even worse.

Actual Storm Track

16 Day Forecast

15 Day Forecast

14 Day Forecast

13 Day Forecast

12 Day Forecast

11 Day Forecast

10 Day Forecast

9 Day Forecast

8 Day Forecast

7 Day Forecast

6 Day Forecast

5 Day Forecast

4 Day Forecast

3 Day Forecast

2 Day Forecast

1 Day Forecast

Actual Storm Track

Weather happens when moist air

gets high

1 2 3

Where’s the moisture?

Lots of moisture(ocean source)

Less moisture (land source)

OK moisture (ocean + plants)

C onvection L ow Pressure O rographics U ndercut D ynamics

How to get air high?

WEATHER 101: Five ways to get high

C is for convection.

warm air

cold air

WEATHER 101: Five ways to get high

L is for low pressure.

Low Pressure

Orographics!

O is for orographic.

WEATHER 101: Five ways to get high

U is for undercut.

http://www.clker.com/cliparts/e/4/9/a/12401693261710228990Kliponius_Mountain_in_a_Cartoon_Style.svg.med.png

Cold Air Warm Air

Cold front moving left-to-right

WEATHER 101: Five ways to get high

D is for dynamic.

http://www.clker.com/cliparts/e/4/9/a/12401693261710228990Kliponius_Mountain_in_a_Cartoon_Style.svg.med.png

This is complicated - it’s all physics.

30,000ft300mb

Jet Stream(river of fast air)

Induces upward motion by “pulling” surface air upward into the void left by the fast-moving air above. Similar to opening a car window while moving and having a piece of paper “sucked” out.

WEATHER 101: Five ways to get high

D is for dynamic.

http://www.clker.com/cliparts/e/4/9/a/12401693261710228990Kliponius_Mountain_in_a_Cartoon_Style.svg.med.png

This is complicated - it’s all physics.

Vorticity counter-clockwise

spin

As vorticity centers (“vort max”) move, they induce upward motion in front and downward motion behind.

18,000ft500mb

SNOW in CO: What winds to watch?

5,000ft850mb

10,000ft700mb

18,000ft500mb

30,000ft300mb

As a standard, winds are forecast (and measured) at 850mb, 700mb, 500mb, 300mb, and 250mb.

JET STREAM

VORTICITY

OROGRAPHIC

Orographics get air high

Mountains = Precipitation

Indian Peaks / RMNP

Sangre deChristo

Park Range

Flattops

Grand Mesa

Elk Mtns

East San Juans

N&S San Juans

Sawatch

Gore

Ten Mile & Mosquito

Favorable wind directions

Wolf Creek

Silverton

Telluride

Powderhorn Crested Butte

AspenVail

Summit Co.

SteamboatRMNP

Crested Butte: West-southwest

Irwin Crested Butte

Irwin: Almost any wind direction?

Crested Butte

Vail: Northwest winds

BeaverCreek

Vail

Gore Range

VailPass

Beaver Creek: West winds

Vail

Gore Range

VailPass

BeaverCreek

Telluride: West & WNW winds

http://www.its.caltech.edu/~atomic/snowcrystals/primer/primer.htm

Moi

stur

e in

the

air

Temperature >> colder

10F 0F

The best snow requires... • Lots of moisture

• Temperatures between about 0-10F where the lift is taking place (usually mountain top, but sometimes higher)

• Best wind for Crested Butte = West-southwest Irwin = SW through NW

Wind directions? Complicated. What about radar? !

Nope. There’s a problem...

Radar

Jamming the Radar

Overshooting the Snow

0.5 deg

http://www.ncdc.noaa.gov/nexradinv/

Denver Airport

PuebloGrand Mesa

http://www.ncdc.noaa.gov/nexradinv/

RMNP

Steamboat

Telluride

Wolf Creek

Aspen

BC / Vail

Summit Co.

Crested Butte

http://www.ncdc.noaa.gov/nexradinv/

4.8 mile resolution

2.4 mile resolution

4.8 mile resolution

2.4 mile resolution

4.8 mile resolution

2.4 mile resolution

Model Accuracy at 6-day forecast

European = British = Canadian = American =

0.845 0.825 0.820 0.807

1 = a perfect score

How to plan

7-10 days 4-5 days 2-3 days

Joel Gratz joel@opensnow.com

What’s the forecast?

To the internet!

Forecast process!Forecast sites!Model biases!Downslope wind (Foehn)