Weather Prediction 2004 5

Weather Prediction:: 

Weather Prediction: And I care because … ?

Slide2: 

VERSUS THIS

Slide3: 

THIS!

I care because …: 

I care because … I want to stay warm I want to stay dry I want to be SAFE

Slide5: 

“Weather-related accidents in the mountains rarely occur without warning.”

Pearls of wisdom: 

Pearls of wisdom Always be prepared for the worst A dry pair of socks. Priceless. Know the risks associated with incoming weather

Three simple tasks: 

Three simple tasks Check the area forecast beginning one week in advance and continue to monitor changes as close to trip departure as possible Check old and recent trip reports from the area. Learn a few basics, i.e. the good, the bad, and the ugly signs of weather.

Fronts: 

Fronts Cold fronts Associated with high pressure systems Warm fronts Associated with low pressure systems Occluded fronts Involves both cold and warm fronts

Cold fronts: 

Cold fronts Unstable  Active! High ceilings & good visibility severe & violent weather Short lived Tend to originate from N or W (N hemisphere) Altostratus  Nimbostratus & Cumulonimbus rain clouds

Warm fronts: 

Warm fronts Relatively stable Low ceilings & poor visibility Less severe weather Long lived Rises above cooler air Slowly cools When the dew point is reached  rain

Occluded fronts: 

Occluded fronts When one air mass is completely displaced from the ground by two other air masses Result temp dependent Pursing front is COLD: Squalls Thunder & Lightning Pursuing front is WARM: Heavy precipitation

How to track fronts: 

How to track fronts On a weather map fronts are drawn where there is large change in temperature and a shift in wind direction. Fair weather is generally associated with Highs while stormy weather is associated with Lows and with the portions of fronts that extend from them.

What is …: 

What is … Rain: water droplets coalesce until large enough to be pulled by gravity to the earth Snow: repeated layers of water condense on ice crystals until large enough to fall Dew & frost: not precipitation; moisture that will collect on objects below the condensation point of the surrounding air

¡Lightning!: 

¡Lightning! Friction – rapidly moving air particles 30 Million volts!  holy crap! 5 second rule 5 seconds = 1 mile

¡Lightning! - precautions: 

¡Lightning! - precautions High ground = Bad Metal (backpack stays) = Bad Wet = Bad Depressions / caves = Bad Single trees = Bad Keeping the group close together = Bad Crouch; DO NOT lie down or sit

Jesus actor struck by lightning: 

Jesus actor struck by lightning It was the second time Michelini had been hit by lightning during the shoot.

How to use the clouds: 

How to use the clouds Consistent observation … practice! Storms may be incoming if Clouds are massing & increasing in size Clouds begin to move faster across the sky Wind velocity Change in barometric pressure

But what ARE clouds?: 

But what ARE clouds? Water droplets & ice crystals Held aloft by turbulent air movements Buckets o’ precipitation As the number and size of water droplets or crystals increase, they become too heavy and fall to the earth It’s all about the saturation point Think rock candy

Cloud vocab: 

Cloud vocab Cirri – High level Alto – Medium level Nimbus – Low Level Stratus – Layered or Layers Cumulus – Heap or Accumulation

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Cirrus - predominantly ice crystals - associated with other cloud types

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Cumulus - heap clouds -associated with fair weather

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Cirrocumulus - high level heap clouds - indicate instability & ensuing poor weather

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Altocumulus - medium level heap clouds; fleecy or puffy - early morning = thunder storms w/in 24 h

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Cumulonimbus - large, towering, “anvil” clouds - hail, lightning, downpours & other acts of wrath by Mother Nature

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Stratus (Fog) - layered, formless, undefined - won’t let sunlight through

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Cirrostratus - spread out, high level, vein-like halos common commonly a lowering of the ceiling  precipitation

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Altostratus - medium level flat, striated, and dark grey darkening indicates possible precipitation

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Nimbostratus - low level, dark, & thick scud (ragged edges) produce constant precipitation

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Lenticular - Produced by waves in the airstream commonly found at mountain peaks due to cresting

“The sun’ll come out, tomorrow …”: 

“The sun’ll come out, tomorrow …” But will it? Little orphan Annie says,

Predictors of fair weatherWhen one or more of the following are true …: 

Predictors of fair weather When one or more of the following are true … Wind is blowing from the west or northwest Barometric pressure remains steady or rises slowly Fair weather cumulus dot the sky Early morning fog dissipates by noon

Things are getting betterWhen one or more of the following are true …: 

Things are getting better When one or more of the following are true … Barometric pressure rises quickly South winds shift to the West Cloud ceiling lifts 

Predictors of poor weatherWhen one or more of the following are true …: 

Predictors of poor weather When one or more of the following are true … Barometric pressure drops Cumulus clouds develop vertical columns Clouds lower & thicken Skies darken South winds increase velocity “Wind from the South brings rain in its mouth.” Winds turn in a counterclockwise direction (indicative of low pressure)

Its going to get colderWhen one or more of the following are true …: 

Its going to get colder When one or more of the following are true … (hint: this might be good to know) The night is clear with no cloud cover and little/no wind The barometric pressure rises in winter The barometric pressure rises in front of an oncoming system of clouds or a cold front

Four major indicators of an incoming storm: 

Four major indicators of an incoming storm Changes in cloud cover Changes in air pressure Changes in wind speed Changes in wind direction

Just remember …: 

Just remember … Fair does not always mean better Mt. Rainier clear, beautiful weather; first warm day of the climbing season on the upper slopes Two experienced climbers attempting Liberty Ridge One man fell 200 ft and died of his injuries The second fell 40 – 60 ft sustaining injuries that did not allow him to aid his partner Both were EMTs

Air movements during the day: 

Air movements during the day Warm air ascends land forms during the day Cold air descends land forms during the night

What geography does to winds: 

What geography does to winds Upslope winds while sun warms the hillsides and warm air rushes upward Downslope winds occur during the night or in the shade when warm air cools and sinks

Foehn or Chinook winds: 

Foehn or Chinook winds Descend slopes increase temperatures dramatically Can warm as much as 6 degrees / 1000 ft Can melt up to 1 ft snow in 2-3 hrs

Chinook winds occur when …: 

Chinook winds occur when … Downwind of a major ridge or crest Primarily to the East of mountains Winds across crest exceed 30 mph Precipitation observed over the crest

The effects of wind chill: 

The effects of wind chill

What geography does to temperature: 

What geography does to temperature 5.5 degree change with every 1000 feet. Remember this is with NO moisture

What geography does to temperature: 

What geography does to temperature WITH moisture: 5.5 degree change with every 1000 feet while ascending 3.5 degree per 1000 feet while descending

Is the old saying true?: 

Is the old saying true? “Red sky in morning, sailors give warning. Red sky at night, sailors delight.” Yes! The saying often holds true in the United States. The weather patterns in North America generally move from west to east, thus, when clouds arrive overhead at sunrise the sky will appear red, signaling a storm "moving in". When the storm eventually passes, the sky will clear in the western sky. If sunset occurs simultaneously, the light will cast a red glow on the clouds above, now moving towards the east.

Weather proverbs: #1 : 

Weather proverbs: #1 Geese (and other migrating birds) fly higher in fair weather than in foul. True Because pressure lowers as you ascend, the higher you go, the less pressure you will find. Birds seek height in migration to make use of their ceiling (or altitude limit) is lifted in good-weather, high-pressure air, and lowered in low-pressure, stormy air.

Weather proverbs: #2 : 

Weather proverbs: #2 A cow with its tail to the west, makes weather the best; A cow with its tail to the east, makes weather the least. True This is a natural instinct, so the animal may face and see an invader; the wind would carry the scent of an invader from the opposite side. In general, an east wind is a “rain wind” and a west wind is a “fair wind,” the grazing animal's tail becomes a weather vein of sorts.

Weather proverbs: #3 : 

Weather proverbs: #3 The higher the clouds, the better the weather. True Higher clouds indicate both dryness of air and higher atmospheric pressure. Both these qualities are present with fair weather.

Weather proverbs: #4 : 

Weather proverbs: #4 Sun or moon halos indicate a coming rain (or snow): the larger the halo, the nearer the precipitation. True This is more likely to be true during warm weather than during midwinter. You are seeing the sun (or moon) through the high crystals of cirriform clouds. When these cover the whole sky, it is a sign of an approaching warm front when a long, slow rain will occur.

Weather proverbs: #5 : 

Weather proverbs: #5 When leaves show their backs, it will rain. True When trees grow, their leaves fall into a pattern according to the prevailing wind. Therefore, when a storm wind (which is naturally a non-prevailing one) occurs, the leaves will be ruffled backwards and show their light undersides.

And pay attention to your hair! : 

And pay attention to your hair! Straighter hair means drier weather Wavy, curly, or frizzy hair means humidity, a.k.a., wet weather Some instruments, such as hygrometers, use hair as the primary working element because it contracts and expands with changes in humidity

Resources: 

Resources http://www.crh.noaa.gov/ http://www.neice.com/ http://www.mountwashington.org/ http://www.theweatherprediction.com/

Resources: 

Resources Basic Essentials: Weather Essentials Michael Hodgson Freedom of the Hills Chapter 23, Mountain Weather

Tips for this weekend: 

Tips for this weekend Keep track of: Weekend forecast Cloud type Cloud movement (speed & height) Discuss alternative routes/plans to compensate for bad weather and still get to the summit

Plan your gear accordingly: 

Plan your gear accordingly keep warm & dry! Water bottle cozies Pack covers Extra plastic bags

What can we expect: 

What can we expect Remember, these are predictions for Elkins, so we should expect colder temps Friday: High of 35; rain Saturday: High of 44, low of 31; wind and snow Sunday: High of 50; mostly cloudy