Air Masses and Fronts

Introduction

If you have access to weather information, the simplest way of forecasting is called "persistence": whatever happened today will happen tomorrow. This works well for many locations, such as Hawaii, San Diego, and San Juan. However, most midlatitude locations (roughly, 30 degrees or more from the equator and poles) experience weather which frequently changes a lot from day to day. This module discusses how to use knowledge of weather patterns and forecasts to make the equivalent of persistence forecasts, both simple and advanced. These techniques are the best available when no computer forecasts are around, and are essential for modifying or correcting computer forecasts.

Learning Objectives

• To understand the distribution of temperature in air masses and fronts.
• To understand the difference between the movement of air and the movement of weather patterns.
• To be able to identify the location whose weather today will be like the forecast site's weather tomorrow.

Table of Contents

1. Air Masses and Fronts: An Introduction
2. Advection
3. Air Mass Motion Forecasting Technique
4. Winds and Source Regions
5. Winds and Source Regions Example
6. The Motion of Air vs. The Motion of Weather Patterns
7. Weather Pattern Extrapolation Forecasting Technique
8. Air Mass Changes Due to Elevation
9. Summary

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