Weather and Risk Management(For hiking, climbing, and generally enjoying oneself in the mountains without being completely miserable… or dangerous)

Sean MackayAMC SHP 2014

“Good judgment comes from experience. Experience comes from bad judgment.”

- Evan Hardin“Early up …. early down.” But why?

“The mountains will always be there, the trick is to make sure you are too.”

- Hervey Voge

A few facts to make you think….

• Hypothermia ( 33 )• Drowning ( 6 )• Avalanche ( 13 )• Falling ice ( 6 )

• Falls ( 43 )• Natural Causes ( 19 )• Causes unknown ( 3 )• Other ( 25 )

135 recorded fatalities in the Presidential Range of NH

Of the deaths from hypothermia, 15 occurred during the summer (June-Sept)

Mt .Washington• Average annual temperature = 27.2 ° F• Average wind = 35 mph (gusts >100 mph occur several times each month)• Annual precip. = 102 in of water equivalent (including 26ft of snow)• Snows every month of the year (including August)• Summit temperatures are typically 20-30 ° F colder than valley temps• Summit winds are 20-100 mhp higher than valley winds

Energy dissipation and redistribution is the ultimate source of all weather

The earth (in case you were confused already)

The sun: Where it all begins

(not drawn to scale)

Complicated by…• Earth’s rotation (Coriolis effect – imparts

spin)• Surface materials (differential heating /

differential drag)• Ocean / Land• Unique properties of H2O• Topography

Meteorology 101

In the mountains, we experience “weather” associated with both:• Large scale / regional factors

• Pressure systems• Fronts

• Local factors• Topography• Daily heating cycles

Meteorology 101

Just a few more basics…• As air heats it expands and rises• As air rises it cools• As it cools to or beyond the

dewpoint – it produces clouds and/or precipitation

Meteorology 101Large scale / regional factors

Low

High

Meteorology 101

Local topographic and orographic factors

Impacts on the hiker/climber

Learn to use basic concepts of meteorology and forecasting to know when to avoid or expect/prepare for common mountain weather hazards such as:

• Lightning• Heavy precipitation• High winds• Sun exposure

• Excessive Heat• Excessive Cold• Poor visibility

• Associated with:• Frontal boundaries (esp. cold fronts)• Daily differential heating of the landscape under warm humid

conditions (typically in the afternoon)• High mountains receive 5 times as many thunderstorms each year as

coastal environments

Thunderstorms / Rain

Lightening• Origen: Collisions between water and ice in the cloud induce charge

separation; upper part of the cloud positively charged / lower negatively charged. The negative charge at the base induces a positive charge on the ground. Lightning occurs once the charge difference overcomes air resistance.

• Located several miles ahead of the storm in addition to directly beneath it.

• 200ppl/year die of lightning strikes in the US.Rain (up to ~125M gallons)• Flooding• Trail instability

Annual lightning incidence map

Thunderstorms / Rain

If thunderstorms are forecast

• Get away from water

• Seek low ground • Do not stand/sit

under a tree (good luck with this in NE)

• Crotch, but do not lay down

If you see a thunderstorm…

• Do not hike or camp in narrow valleys / gullies• Do not hike / climb in exposed areas (esp. above tree line)• Watch small cumulus clouds for vertical growth – this is a sign for

developing thunderstorms

Gauge the movement of the storm by watching and listening….• [Strike time – thunder (s) ] / 5 = distance to storm (miles). • Do this several times to see which direction it is moving

Thunderstorms / Rain

Low

Moderate

High

wind

wind

Wind

Use topography / landscape to your advantage if possible• Tree line• Boulders, etc.

Mountains both cause and alter winds considerably • Valley winds / gravity winds

• I.E. Camping right at the base of the valley wall can be a bit breezy

• Gap winds• Occur at breaks in the topography

(passes, between two peaks, etc.)• Wind speeds can double

• Foehn winds• Cool air descends and adiabatically

warms - acceleration and rapid warming

• Katabatic winds• Elevation exposure to upper atmosphere

winds

Wind Chill

Non-linear decrease in “apparent” temp.

What about being too hot..?

Heat Index• How hot a combination of temperature and humidity feels• Based on the body’s capability to utilize evaporative cooling

Mountain weather forecastingWhat if forecasts are either limited or unavailable?

Use valley temperature to estimate temps at elevation:• Temperature decreases 3.5 to

5.5 ° F for every 1000ft of elevation

Learn how to read the wind, clouds, and air pressure changes….

Mountain weather forecasting

Halo

Altocumulus

Cumulonimbus

Stratocumulus

Cold front associated

24-48 hr. before precipitation

Potential for thunderstorms/ showers

Isolated but heavy rain, lightning, wind

Often follows cold front, possible light showers

Warm front associated

Cirrostratus

Nimbostratus

No worries – have fun!!

Widespread steady precipitation

Other

Lenticular

High winds!!

Mountain weather forecasting

Mountain weather forecasting

Pressure changes over ~3 hrs. (altimeter/barometer?)• Increasing pressure/decreasing ‘altitude’

Fair weather ahead – go play!!!!• Decreasing pressure / increasing ‘altitude’

0.06 inch or more…… high winds (definitely) / precipitation (possibly) on the way

Wind direction / speed (Northern Hemisphere)• Shift E or SE low

front approaching / precip. Possible

• Shift SW or NW cold front passage / drying likely

• Increasing from SW to W High pressure approaching / gusty winds decreasing

Risk Management

Risk ManagementObjective Hazards

(environment)Subjective Hazards

(you!)Accident Potentialx =

Environment (objective) hazardsTerrain

- rocky trail, exposed ledges, etc., falling rock, falling iceWeather

- cold, wind, precip, etc.Other

- Beestings, poison ivy, overexposure to the sun, darknessEquipment

- broken stove, improper clothing, boots not broken in, etc.

Risk ManagementObjective Hazards

(environment)Subjective Hazards

(you!)Accident Potentialx =

You (subjective) hazardsPoor Planning

Weather, route, terrain knowledge, equipmentIndividuals

lack of awareness, insufficient skills, poor conditioning, fear / anxiety, careless attitude, ‘summit fever’, not maintaining hydration/eating

GroupLack of leadership, splintering into sub-groups, scapegoating, poor communication, interpersonal friction“New Guy syndrome” “Old Guy Syndrome”

Risk Management

Risk rating = likelihood x consequence severity

Thank youHappy hiking!

Sean MackayAMC SHP 2014