☁️Meteorology Unit 13 – Weather Forecasting Methods and Tools

Basics of Weather Forecasting

• Weather forecasting predicts atmospheric conditions for a specific location and time based on current and historical data
• Involves analyzing various atmospheric variables such as temperature, humidity, air pressure, wind speed and direction
• Utilizes mathematical models, statistical techniques, and computer simulations to generate predictions
• Short-term forecasts cover a period of a few hours to a few days (nowcasting)
  • Rely heavily on current observations and short-term trends
• Medium-range forecasts extend from a few days to about two weeks
  • Incorporate numerical weather prediction models and statistical methods
• Long-range forecasts cover periods longer than two weeks (seasonal outlooks)
  • Consider global climate patterns, ocean currents, and long-term trends
• Accuracy of forecasts decreases with increasing lead time due to the chaotic nature of the atmosphere (butterfly effect)

Atmospheric Data Collection

• Weather data is collected from various sources to provide initial conditions for forecasting models
• Surface observations from weather stations measure temperature, humidity, air pressure, wind speed and direction, precipitation, and visibility
  • Automated weather stations (AWS) provide continuous, real-time data
• Upper-air observations are obtained using weather balloons (radiosondes) launched twice daily at specific locations worldwide
  • Measure vertical profiles of temperature, humidity, and wind speed and direction
• Aircraft-based observations (AMDAR) collect data during takeoff, landing, and en route
  • Provide valuable information on upper-air conditions and turbulence
• Marine observations from ships, buoys, and offshore platforms provide data over oceans and large water bodies
• Remote sensing techniques such as satellites and weather radar systems provide global coverage and high-resolution data
• Citizen weather observers and amateur radio operators (SKYWARN) contribute local observations during severe weather events
• Data quality control and assimilation techniques ensure the accuracy and consistency of collected data before use in forecasting models

Weather Maps and Charts

• Weather maps and charts are graphical representations of atmospheric conditions and forecasts
• Surface weather maps depict current conditions and observations at a specific time
  • Isobars represent lines of equal air pressure
  • Fronts indicate boundaries between air masses with different characteristics
• Upper-air charts show conditions at various pressure levels in the atmosphere (850 mb, 700 mb, 500 mb, 300 mb)
  • Contour lines represent geopotential height, which relates to the thickness of the atmospheric layer
• Skew-T diagrams display vertical profiles of temperature, dew point, and wind at a specific location
  • Used to assess atmospheric stability and potential for severe weather
• Prognostic charts (progs) show predicted atmospheric conditions at a specific time in the future
  • Generated by numerical weather prediction models
• Ensemble charts combine multiple model forecasts to assess uncertainty and probability of different outcomes
• Radar and satellite imagery provide real-time observations of precipitation, cloud cover, and atmospheric motion
• Streamline analysis charts depict wind flow patterns and help identify areas of convergence and divergence

Numerical Weather Prediction Models

• Numerical weather prediction (NWP) models are computer simulations of the atmosphere based on mathematical equations
• NWP models solve complex equations that describe atmospheric dynamics, thermodynamics, and physical processes
  • Equations include conservation of mass, momentum, and energy
• Models divide the atmosphere into a three-dimensional grid with specified horizontal and vertical resolution
  • Higher resolution models provide more detailed forecasts but require greater computational resources
• Initial conditions for NWP models are obtained from atmospheric data collection and assimilation techniques
• Models incorporate various physical parameterizations to represent sub-grid scale processes (convection, radiation, turbulence)
• Global models (GFS, ECMWF) provide forecasts for the entire Earth with a typical horizontal resolution of 10-50 km
• Regional models (WRF, NAM) focus on a specific area with higher resolution (1-10 km) and use global model output for boundary conditions
• Ensemble forecasting runs multiple model simulations with slightly different initial conditions to assess uncertainty and probability
• Post-processing techniques (model output statistics, bias correction) are applied to raw model output to improve forecast accuracy

Satellite and Radar Technology

• Satellites and weather radar systems provide critical data for weather forecasting and monitoring
• Geostationary satellites (GOES, Meteosat) orbit at an altitude of ~36,000 km and continuously monitor a fixed area of the Earth
  • Provide high-resolution visible and infrared imagery for tracking clouds, storms, and atmospheric motion
• Polar-orbiting satellites (NOAA, Suomi NPP) orbit at a lower altitude (~800 km) and provide global coverage by passing over the poles
  • Carry instruments for measuring temperature, humidity, and other atmospheric variables at various levels
• Weather radar systems emit microwave pulses and analyze the returned signal to detect precipitation, wind, and other phenomena
• Doppler radar measures the radial velocity of targets, allowing for the detection of wind speed and direction
  • Used for monitoring severe storms, tornadoes, and wind shear
• Dual-polarization radar emits and receives signals in both horizontal and vertical orientations
  • Improves the identification of precipitation type (rain, snow, hail) and reduces false echoes
• Radar data is processed and displayed in various formats (reflectivity, velocity, precipitation rate) for analysis and forecasting
• Satellite and radar data are assimilated into numerical weather prediction models to improve initial conditions and forecast accuracy

Forecasting Techniques and Methods

• Weather forecasters use a combination of techniques and methods to generate accurate and timely predictions
• Nowcasting involves short-term forecasting (0-6 hours) based on current observations and extrapolation of trends
  • Relies heavily on satellite and radar imagery, surface observations, and statistical techniques
• Synoptic forecasting analyzes the evolution of large-scale weather systems (high and low-pressure areas, fronts) using weather maps and charts
  • Considers the movement and interaction of air masses, jet streams, and other atmospheric features
• Model interpretation involves analyzing output from numerical weather prediction models and assessing their performance and reliability
  • Forecasters compare model results with observations and apply their knowledge of model strengths and weaknesses
• Ensemble forecasting uses multiple model runs with slightly different initial conditions to assess uncertainty and generate probabilistic forecasts
  • Helps quantify the likelihood of different weather scenarios and communicate forecast confidence
• Pattern recognition identifies recurring weather patterns and their associated impacts based on historical data and analogs
  • Assists in long-range forecasting and identifying potential extreme events
• Forecast verification and post-event analysis evaluate the accuracy of previous forecasts and identify areas for improvement
  • Helps refine forecasting techniques, models, and communication strategies

Specialized Forecasts and Warnings

• Specialized forecasts and warnings are issued for specific weather hazards and user groups
• Severe weather warnings (tornado, severe thunderstorm, flash flood) alert the public to imminent threats and provide guidance for protective actions
  • Based on radar observations, spotter reports, and forecaster expertise
• Aviation forecasts (TAFs, AIRMETs, SIGMETs) provide information on weather conditions relevant to aircraft operations
  • Include wind, visibility, cloud cover, turbulence, and icing
• Marine forecasts (coastal waters, offshore, high seas) address weather hazards and conditions affecting maritime activities
  • Include wind, waves, tides, and visibility
• Fire weather forecasts assess the risk of wildfire ignition and spread based on temperature, humidity, wind, and fuel conditions
  • Support fire management and suppression efforts
• Air quality forecasts predict the concentration of pollutants (ozone, particulate matter) and issue advisories for sensitive groups
• Hydrological forecasts (river levels, flood risk) are based on precipitation forecasts, soil moisture, and hydrological models
  • Support water resource management and flood mitigation efforts
• Specialized forecasts are tailored to the needs of specific industries (agriculture, energy, transportation) and user groups (emergency managers, media)

Challenges and Future Trends in Forecasting

• Weather forecasting faces ongoing challenges and opportunities for improvement
• Increasing model resolution and complexity requires significant computational resources and data storage capacity
  • Advancements in high-performance computing and cloud-based solutions help address these challenges
• Assimilating new data sources (private weather stations, smartphones, connected vehicles) can improve forecast accuracy but requires data quality control and privacy considerations
• Communicating forecast uncertainty and risk to diverse audiences is crucial for effective decision-making
  • Probabilistic forecasts, impact-based warnings, and user-friendly visualizations help convey uncertainty and potential consequences
• Improving forecasts for high-impact weather events (tropical cyclones, severe storms, heat waves) is a priority for protecting lives and property
  • Requires targeted research, enhanced observations, and improved model physics
• Subseasonal to seasonal (S2S) forecasting bridges the gap between weather and climate timescales
  • Relies on understanding and predicting large-scale climate patterns (El Niño, Madden-Julian Oscillation)
• Machine learning and artificial intelligence techniques show promise for improving forecast accuracy and efficiency
  • Can help identify complex patterns, optimize model parameters, and automate forecast production
• Collaborative research and international partnerships are essential for advancing weather forecasting science and services
  • Initiatives such as the World Meteorological Organization's High-Impact Weather Project foster global cooperation and knowledge sharing