The art of weather forecasting Will it rain tomorrow? The art of weather forecasting

Agenda Measuring all of that air – current conditions Observing sites, Weather Buoys, Satellites, Radar, & Radiosondes (aka weather balloons) Using the past to predict the future –computer modeling Putting it all together – forecasting Sign me up! I want to be a meteorologist too.

Measuring all of that air

Measuring all of that air Knowing current atmospheric conditions is essential for weather forecasting This includes both surface conditions as well as the atmosphere aloft. The major means of making these measurements include: Surface observing stations Weather buoys Satellites Radar Radiosondes

Surface Observing Stations The oldest form of measuring the weather. Stations around the world measure & report current weather conditions (temperature, wind, rainfall, cloud cover, etc.). This includes staffed, volunteer, as well as remote reporting stations.

These measurements give us our surface maps

Now wait a minute! The earth is covered mostly in water. How do you know what’s going on in the oceans?

Surface conditions on water Weather buoys are uses to remotely report ocean surface conditions. Ship measurements are also used. Ocean measurements are spotty.

Weather Satellites Look at the entire globe

Weather Satellites Weather satellites allow for a view of the entire globe. Though not able to measure conditions directly, they provide a vast amount of information indirectly. Three major types of images: Infra-red Visible light Water vapor

Infra-red satellite images Measures the temperature of clouds The colder the cloud, the higher it is

Visible light satellite images Shows what the naked eye would see Only available from sunrise to sunset

Water vapor satellite images Shows amount of water vapor, not just clouds Good for following atmospheric circulation

Radar Seeing what’s going on in the clouds

Radar Radar shows where cloud & precipitation are Gives both horizontal and more importantly, vertical positions. Gives movement information as well as precipitation intensity. Helps in determining rain/ice/snow lines

Radiosondes (weather balloons) Note the attached parachute Measuring the actual conditions in the upper atmosphere

Radiosondes In manty cases, lifted by hydrogen filled (cheaper than helium) balloons Radiosondes measure: Temperature Relative humidity Pressure As they rise, wind speed and direction information is derived from the balloon’s movements.

Radiosondes Information gathered is radioed back. Movement determined by GPS. Directional radio antennas (old school method) are sometimes used more so outside of the U.S. Launched twice a day in the U.S.

Radiosonde launch network The nearest launch site is on Long Island

Radiosondes The balloon grows in size as the atmospheric pressure decreases. Eventually, the balloon bursts A small attached parachute helps slow the fall of the radiosonde. If found, radiosondes can be mailed back and are refurbished or salvaged. Less than 20% are returned.

Let’s see how a launch is done

Radiosondes don’t always come back in the best of shape.

Other times they do Radiosonde Balloon remnant Parachute

Using upper air data Radiosonde data is used to create the upper maps, like the 500mb map.

Using upper air data Provides temperature, moisture and wind changes at all levels of the atmosphere This data is also used to determine the stability of the atmosphere. Understanding atmospheric stability is extremely useful in determining the potentials for severe weather.

Source: National Center for Atmospheric Research Skew T, Log P diagrams Plots temperature and moisture (dew point) and wind data. A major tool in forecasting severe weather. Source: National Center for Atmospheric Research

Letting the machines do the work for us. Computer Forecasting Letting the machines do the work for us.

Computers in Forecasting Computers are a major component in modern weather forecasting. Quickly generate all of those maps and charts of current conditions. With historical weather data, used to model the atmosphere which allows for the forecast models forecasters rely on heavily.

Computer Forecast Models Modern superfast computers have made for the rapid growth in forecast modeling possible Short term (looking ahead 6 hours) forecast modeling is used to help predict severe weather, snow storms, etc. No single forecast model is “best”.

Weather Forecast Models Often forecasters compare a few models to develop their forecast. Forecast models include: Long term (days) Global Forecast System (GFS) – North American European Centre for Medium-Range Weather Forecasts (ECMWF) - European Short term (hours) North American Mesoscale Forecast (NAM) Rapid Refresh Model (RAP)

“The computer does not understand these things.” -- Tetsuya “Ted” Fujita tornado expert developer of the F-scale for tornadoes

Forecasting is really an art Forecasters use all of the available data to generate their forecasts. Computer forecast models can not do it all… yet. Past experience is relied upon. Sometimes you just need to look out of the window and see what the weather is like.

How do I become a weather forecaster?

Becoming a meteorologist Meteorology uses a lot of physics & math. A minimum of a bachelors degree is needed. An advanced degree is really needed to move up in the field. Meteorology is not just forecasting: Broadcasting Climate Research Forensics

Thank you for your attention. Does anyone have any questions?