Weather Forecasting

An estimate of future weather conditions, including:
Temperature
Cloud cover
Humidity
Precipitation
Wind (speed and direction)

Weather Agencies

NOAA - National Oceanic and Atmospheric Administration:
Its mission is to understand and predict changes in Earth's environment, and conserve and manage coastal and marine resources to meet our nation's economic, social and environmental needs.
NWS - National Weather Service:
Provides weather, hydrological and climate forecasting and warnings.
Produces local forecasts upon which local TV and radio weather forecasts are based, with enhancements by local forecasters, graphics and simulations.

Severe Weather Services:
The Storm Prediction Center (Norman, OK)
National Hurricane Center (Miami, FL)

Weather Analysis

Current Conditions - based on observational data collected at:
Land based weather stations
Ships, data buoys, and oil platforms at sea
Airports and airplanes (in cooperation with the FAA)
ASOS: Automated Surface Observing Systems
Balloon-borne radiosondes
Radar
Weather satellites

Weather Satellites

Polar orbiting and Geosynchronous orbits (GOES: Geostationary Operational Environmental Satellite)
Provide multiple pieces of data:
Imagery:
Visible, Infrared, Water Vapor, Temperature at different elevations, Rainfall, Wind

Weather Maps

A map/graphical display of the current atmospheric conditions.
Simplified maps contain only some data
Plus:
Frontal boundaries
Isotherms
Isobars

Weather Forecasting

Traditionally based on analysis of:
Current conditions:
Comparison to known patterns and trends
Comparison to similar past conditions

Today's forecasting: uses sophisticated computer software.
Based on equations and numerical models which describe the behavior of gases and other factors in the atmosphere.
Programs attempt to mimic the real atmosphere.
Produce "prognostic charts" - future conditions.

Ensemble Forecasting: averaged multiple computer forecasts
Each forecast has slight variations in the starting data (within error range).
Multiple models allow for determination of the forecast's certainty or uncertainty.
f each forecast shows the same weather patterns, then there would be a high degree of confidence in the prediction.
Variations in the results would decrease the level of confidence.

The local Forecaster (TV or radio weatherperson) uses the computer predictions as a starting point.
Added to this prediction is:
Knowledge and experience with the local weather patterns.
Adjustments to the forecast.

Other Forecasting

Persistence Forecasting:
Analog Method:
Trend Forecasting:
Climatological Forecasting:

Upper-Air Analysis

Upper-air maps show similar data as surface analysis maps:
Isotherms, humidity, wind speed, wind direction
Typically 3 to 5 upper air maps are used:
850 (700), 500, 300 (200) mb
These maps use Height contours to show the elevation at which the designated pressure occurs.

850 mb Analysis Map

850 mb occurs at ~1500 m above the surface. Note specific height contours where it actually occurs.
Used to show cold and warm air advection
Areas where cold or warm air moves across isotherms
Are used to:
Winter: Predict areas of rain vs. snow.
Predict daytime high temperatures.
700 mb maps are used for areas in which the surface is above 1500 m.
700 mb used to predict formation and movement of T-storms.

500 mb Analysis Map

Occurs at ~5000 meters.
Used to predict:
Formation of storms
Movement of wave cyclones.
Clear and calm conditions.

300/200 mb Analysis Map

Occurs at ~10 km.
Uses Isotachs:
Shows the details of the jet stream.

Long Range Forecasting

30-day and 90-day Outlooks
Unlike the hourly to 2 week forecasts - not true weather forecasts.
Comparison of future temperature and precipitation as compared to normal conditions.
Defined as Above, Below or Equal Chance of Normal
Typically, not very reliable.

Forecast Accuracy

0-12 hr Predictions: very good for large and medium-sized weather systems.
Less accurate for small systems
Increasing accuracy for tornadoes, flash floods and hail, but still need improvement
Warning and Watch lead times have shown dramatic improvement in the past few decades.
12-72 hr Predictions: very good to good (generally).
3-7 day Predictions: fair to poor, but continuing to show improvement.
2 week Predictions: Poor, but continuing to show some improvement.

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