Weather forecastingfor mountaineers

Photo: Joel Gratz

Meteorologist Joel Gratz

1960

2005

1) Know when totrust the forecast

How this presentation will help you:

2) Identify the mosthazardous conditions.

Hi, I’m Joel Gratz.

I grew up in Pennsylvania,ski raced and instructed, then moved to Colorado after studying meteorology at Penn State.

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

And it made me mad!

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

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

Big Weather(primary care doctor)

(knee surgeon)

Denali x3

Everest

Aconcagua

50 statehigh points

1) Know when totrust the forecast

How this presentation will help you:

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 is not magic. It’s physics.

Forecasts are rarely perfect, but they are getting better every year. Study them, don’t dismiss them.

When to trust the forecast

10 days+ storm or no storm+ cold, hot, dry, moist

3-5 days+ details becoming clearer

1-2 days+ details are as clear as possible

How to plan

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

1) Know when totrust the forecast

How this presentation will help you:

2) Identify the mosthazardous conditions.

Hazards to Mountaineers

Precipitation

Temperature

Wind

Lightning

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)

Five ways to get high

C is for convection

L is for low pressure

O is for orographics

U is for undercut

D is for dynamics

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

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

Bonus:How to forecast hazards

How this presentation will help you:

1,00

0ft

5.5

degr

ees

3.3

degr

ees

Dry Moist

SNOTEL

Weather Stations

MesoWest Weather Stationsmesowest.utah.edu

CAIC Weather Stationshttps://avalanche.state.co.us/obs_stns/

stns.php

Jamming the Radar

Overshooting the Snow

0.5 deg

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

Denver Airport

PuebloGrandMesa

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

RMNP

Steamboat

Telluride

Wolf Creek

Aspen

Vail

Summit Co.

Crested Butte

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

Weather models

www.TwisterData.comwxweb.meteostar.com/models/

NAM: 84hrs (3.5 days)GFS: 384hrs (16 days)

Wind Speed (mb level)Temperature (mb level)

Precipitation

700mb = 10,000ft

850mb = 5,000ft

1000mb = 0ft

500mb = 18,000ft

300mb = 30,000ft

Stay away from Arnold

Thick clouds withwell defined “muscles” are a sign of strong convection. This could mean lightning is imminent.

Stay away from ArnoldWell defined, bulging muscles.

Cloud is darkunderneath, whichmeans it’s thickenough to blocksunlight. I was nervous, but lackof well definedmuscles showedweak convection,and we were OK.

Joel Gratzjoel@opensnow.com

that’s not me,but I did take the picture