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How Do We Predict Weather? General Weather Information Clouds, rain, thunderstorms, etc. What is the National Weather Service??. Organizational Structure…. U. S. Department of Commerce (International Trade, US Business Growth, Aid in Technological Advancement)

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How do we predict weather general weather information clouds rain thunderstorms etc l.jpg

How Do We Predict Weather?

General Weather Information

Clouds, rain, thunderstorms, etc.



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Organizational Structure…

U. S. Department of Commerce

(International Trade, US Business Growth, Aid in Technological Advancement)

National Oceanic and Atmospheric

Administration (NOAA)

(Climate, Ocean Life, Satellites, Research)

National Weather Service

(Forecasts, Warnings, River Data, Weather Safety)


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What We Do

Produce Weather, Water and

Climate Forecasts and Warnings

-For All Americans

-To Protect Life and Property

-To Enhance the National Economy

Data and Products:

-Government Agencies

-Private Sector

-The Public

-Global Communities

Weather and data are becoming more important to the economy and business decisions


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National Weather Service

Our Primary Mission:

The protection of lives and property

Watches, warnings, and advisories for:

-Severe Thunderstorms

-Floods

-Winter Storms

-Tornados

-Flash Floods


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Advisory: Just so you know…

Watch: Stay Alert!

Warning: Take Cover NOW!


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National Weather Service

  • 122 Weather Forecast Offices (CONUS, AK, HI, Guam and Puerto Rico)



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WEATHER FORECASTING

This problem has two parts . . .

Analyze: What’s going on right now?

Forecast: What’s going to happen?


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Analyzing the Weather

Surface Observations . . .

mostly at airports . . .

can be taken by people

Or by machines such as the ASOS -

Automated

Surface

Observing

System


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COOPERATIVE OBSERVERS

  • Volunteer weather observers

  • Daily temperature and precipitation reports

  • River level reports

  • Important for ground truth


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Of course, we can’t forget radar!

It can see father - with greater detail and more power than any other weather radar in the world!!

So sensitive . . . it can detect birds . . . bats . . . bugs and pollen in the air . . . and leaves rustling on nearby trees.


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But observations are not limited to surface conditions. Aircraft reports of winds and weather are important.

And observations from upper air balloons launched twice a day at around 120 sites are the basis of upper air analysis.


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Dozens of satellites keep a constant watch over the earth each day. Some are geosynchronous (stay in the same position over the earth) while others orbit around the earth.


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FORECASTING each day. Some are geosynchronous (stay in the same position over the earth) while others orbit around the earth.

There are 3 basic methods of forecasting:

  • Persistence

  • Experience

  • Computer Modeling


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PERSISTENCE: each day. Some are geosynchronous (stay in the same position over the earth) while others orbit around the earth.

  • Not much is going to change.

  • Tomorrow will be like today.

  • Works great in summer.

  • Not so good the rest of the year.


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EXPERIENCE: each day. Some are geosynchronous (stay in the same position over the earth) while others orbit around the earth.

  • Forecast what was seen before to repeat.

  • This is good for 1 to 2 day forecasts.

  • Works great a lot of the time.

  • Problem when something new happens.


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MODELS: each day. Some are geosynchronous (stay in the same position over the earth) while others orbit around the earth.

  • They are better than people past 3 days.

  • Works great most of the time.

  • Problem when bad data gets put in or if something really new occurs.


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Let’s start with a question. . . Why do we have weather?

The Earth rotates on a tilted axis.

Due to the tilt, the equator is always heated more than either pole.


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The Result . . . weather?

Part of Earth’s atmosphere is too cold and dense and part of the atmosphere is much too warm and light

Somehow . . . this must all be balanced out.


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Not just temperature differences… weather?

Air which stays over water for long periods of time absorbs some of the moisture through evaporation.



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CLOUDS weather?

  • Cirrus

  • Stratus

  • Cumulus

  • Nimbus


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Cirrus Clouds weather?

  • High-level clouds

  • Usually only ice crystals

  • Generally in fair weather


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Stratus Clouds weather?

  • Base is usually only a few hundred feet above the ground

  • Little to no vertical development

  • Can cover entire sky


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Cumulus Clouds weather?

  • Base is at low level, but tops can reach 60,000 feet (11 miles) high

  • Made of both ice and water droplets

  • Puffy like cotton balls


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Nimbus Clouds weather?

  • Generally form 7,000 to 15,000 feet (1 to 3 miles) above ground

  • Steady precipitation


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PRECIPITATION weather?

Two basic ways precipitation forms:

  • “Collision” process (warm clouds)

  • “Ice Crystal” process (cold clouds)



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“Ice Crystal” Process weather?

Easier for water vapor to deposit directly onto ice crystals. Crystals then grow heavy enough to start falling.


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Rain or Snow?? weather?


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THUNDERSTORMS weather?

  • Moisture

  • Instability

  • Lifting

In order to form, thunderstorms need:


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Mid and upper-level moisture can arrive from the Pacific. weather?

Low-level moisture comes from the Gulf of Mexico.


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INSTABILITY weather?

  • If air is stable, it will try to go back to where it was

  • If air is unstable, it will continue in the direction it was pushed


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LIFT weather?

  • Differences in heating

  • Terrain

  • Fronts, boundaries, drylines



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Thunderstorm Hazards weather?

  • Hail

  • Damaging Winds

  • Tornados

  • Flash Floods


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HAIL weather?


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DAMAGING WINDS weather?

Damage from

a tornado

Damage from

a downburst


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TORNADOS weather?

F-Scale

  • Named after its creator, Dr. Fujita

  • Used to describe how fast winds in a tornado are

  • Actually goes all the way to F12, which is the speed of sound


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Minimal Tornado weather?

- F0, F1

- 67% of S.C. TX Tornadoes

- Causes 5% of all deaths

- Life span 1 to 2 minutes

- Path length less than 1 mile

- Path width less than 100 yards

- Wind speeds up to 110 mph


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Strong Tornado weather?

  • - F2, F3

  • - 30% of S.C. TX Tornadoes

  • - Causes 30% of all deaths

  • Life span 15 to 20 minutes

  • Path up to 15 miles

  • - Path width up to 500 yards

  • - Wind speeds up to 200 mph


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Violent Tornado weather?

- F4, F5

- 3% of S.C. TX Tornadoes

- Causes 65% of all deaths

- Life span to several hours

- Path length dozens of miles

- Path width to 1 1/ 2 miles

- Wind speeds over 300 mph



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FLASH FLOODING weather?


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For each foot of rising water, a car weighs weather?1500 pounds less!

As little as 18 inches of water can float a truck! It takes only 12 to 14 inches of water to float a car!


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Tire 8” wide, weather?

30” diameter

floats 816 lbs

of car weight

Tire 12” wide,

30” diameter

floats 1225 lbs of car weight


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For Current Weather Information: weather?

NOAA Weather Radio

Or:

www.weather.gov

Clickable map of the entire U.S.

www.srh.noaa.gov/ewx

NWS Austin/San Antonio’s Homepage


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QUESTIONS? weather?

Marianne Sutton@noaa.gov

National Weather Service

Austin/San Antonio

2090 Airport Road

New Braunfels, TX 78130