Post on 14-Jan-2015
description
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