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Forecasting Tricks for Irwin (February 28, 2014)

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Information about Forecasting Tricks for Irwin (February 28, 2014)
Sports

Published on March 4, 2014

Author: findOpensnow

Source: slideshare.net

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Forecasting tricks for Irwin Meteorologist Joel Gratz Photo: Connor Walberg ActionPhotoSchool.com

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.

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

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

Storm tracks for La Nina. Courtesy: Mike Baker, NWS Boulder

Storm tracks for El Nino. Courtesy: Mike Baker, NWS Boulder

This year is a La Nada.

Storm tracks for La Nada. Courtesy: Mike Baker, NWS Boulder

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. 160% 150% 140% 130% 120% 110% 100% Dec 1 Jan 1 Feb 1 Mar 1 April 1

Colorado SNOTEL Snow Water Equivalent (SWE) % of Normal Feb 27, 2014 UPPER GREEN 112 129 110 148 159 76 117 Steamboat Springs 111 Current SWE % of 1981-2010 Median WHITE-YAMPA 137 147 133 117 119 126 136 182 152 144 > 160% 130 98 188 126 Fort Collins 131 NORTH PLATTE 141 191 164 70 140-160% 162 90 117 105 120-139% 118 100-119% 60-79% 98 COLORADO HEADWATERS 80-99% 87 111 95 98 40-59% 128 Denver 123 147 110 144 152 149 132 150 141 70 Leadville 119 153 109 121 145 126 158 124 122 Grand Junction SMOKY HILL 148 Colorado Springs 116 1-39% 67 123 GUNNISON Gunnison 0% 136 76 Unavailable* Provisional Data Subject to Revision REPUBLICAN SOUTH PLATTE 130 123 UPPER ARKANSAS Pueblo UPPER COLORADO-DOLORES 140 25 76 73 101 82 LOWER SAN JUAN 67 58 81 106 85 99 70 89 114 97 122 87 79 72 138 95 88 95 RIO GRANDE HEADWATERS Alamosa 68 Durango UPPER SAN JUAN 72 47 39 94 10 UPPER CIMARRON 86 47 69 Prepared by the USDA/NRCS National Water and Climate Center Portland, Oregon http://www.wcc.nrcs.usda.gov/gis/ 0 10 20 40 60 80 Miles 100 * 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 2.5x Crested Butte

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? Less moisture (land source) Lots of moisture
 (ocean source) OK moisture (ocean + plants)

How to get air high? C L O U D onvection ow Pressure rographics ndercut ynamics

WEATHER 101: Five ways to get high C is for convection. cold air warm 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. Cold front moving left-to-right Cold Air Warm Air http://www.clker.com/cliparts/e/4/9/a/12401693261710228990Kliponius_Mountain_in_a_Cartoon_Style.svg.med.png

WEATHER 101: Five ways to get high D is for dynamic. This is complicated - it’s all physics. Jet Stream
 (river of fast air)
 30,000ft
 300mb 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.
 http://www.clker.com/cliparts/e/4/9/a/12401693261710228990Kliponius_Mountain_in_a_Cartoon_Style.svg.med.png

WEATHER 101: Five ways to get high D is for dynamic. This is complicated - it’s all physics. 18,000ft
 500mb Vorticity 
 counter-clockwise
 spin
 As vorticity centers (“vort max”) move, they induce upward motion in front and downward motion behind.
 http://www.clker.com/cliparts/e/4/9/a/12401693261710228990Kliponius_Mountain_in_a_Cartoon_Style.svg.med.png

SNOW in CO: What winds to watch? As a standard, winds are forecast (and measured) at 850mb, 700mb, 500mb, 300mb, and 250mb. JET STREAM 30,000ft
 300mb VORTICITY 18,000ft
 500mb OROGRAPHIC 10,000ft
 700mb 5,000ft
 850mb

Orographics get air high

Mountains = Precipitation Indian Peaks / RMNP Park Range Flattops Gore Ten Mile & Mosquito Grand Mesa Elk Mtns N&S San Juans Sawatch Sangre de
 Christo East San Juans

Favorable wind directions Steamboat RMNP Summit Co. Aspen Powderhorn Vail Crested Butte Telluride Silverton Wolf Creek

Crested Butte: West-southwest Irwin Crested Butte

Irwin: Almost any wind direction? Crested Butte

Vail: Northwest winds e or G Ra e ng Beaver Creek Vail Vail Pass

Beaver Creek: West winds e or G Ra e ng Beaver Creek Vail Vail Pass

Telluride: West & WNW winds

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

Moisture in the air 10F 0F Temperature >> colder

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

Denver Airport Grand Mesa Pueblo http://www.ncdc.noaa.gov/nexradinv/

Steamboat BC / Vail Aspen RMNP Summit Co. Crested Butte Telluride Wolf Creek http://www.ncdc.noaa.gov/nexradinv/

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 1 = a perfect score European = British = Canadian = American = 0.845 0.825 0.820 0.807

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)

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