Understanding Hail Forecasts: A Quick Guide

Hailstorms can cause significant damage to property and crops, making it essential to understand hail forecasts. This guide provides a concise overview of hail forecasting, including key indicators, forecast categories, and safety measures.

What Is Hail and How Does It Form?

Hail consists of ice balls or pieces ranging from 0.25 inches (6.35 mm) to over 6 inches (152.4 mm) in diameter. It forms within strong thunderstorms when updrafts carry raindrops into extremely cold areas of the atmosphere, causing them to freeze and accumulate layers of ice. The size of hailstones depends on the strength of the updrafts and the amount of supercooled water available. (earthnetworks.com)

Key Indicators for Hail Forecasting

Meteorologists assess several factors to predict hail formation:

• Updraft Strength: Strong updrafts keep hailstones aloft longer, allowing them to grow larger.

• Atmospheric Instability: A significant temperature difference between the surface and the upper atmosphere can lead to severe thunderstorms capable of producing hail.

• Moisture Content: Adequate moisture provides the necessary supercooled water for hailstone growth.

• Wind Shear: Changes in wind speed and direction with altitude can influence storm rotation, affecting hail development. (nssl.noaa.gov)

Understanding Hail Forecast Categories

The National Weather Service (NWS) issues hail forecasts with specific probability percentages:

• 5% Probability: Low chance of hail.

• 15% Probability: Moderate chance of hail.

• 30% Probability: High chance of hail.

These percentages indicate the likelihood of hail occurring within a 25-mile radius. (hailstormlocator.com)

Hail Size Classification

The NWS classifies hail sizes as follows:

• Severe Hail: 1 inch (2.54 cm) or larger in diameter.

• Destructive Hail: 2 inches (5.08 cm) or larger in diameter.

Larger hailstones can cause significant damage to vehicles, roofs, and crops. (earthnetworks.com)

Safety Measures During Hailstorms

To protect yourself during a hailstorm:

• Seek Shelter: Stay indoors or in a sturdy building.

• Protect Vehicles: Move cars into garages or covered areas if possible.

• Stay Informed: Monitor local weather updates and heed any warnings or advisories.

Understanding hail forecasts and taking appropriate precautions can help minimize the risks associated with hailstorms.

Highlights:

• Cheat Sheet: How NOAA’s Storm Prediction Center’s New Intensity Levels Make Severe Weather Outlooks Clearer Across the U.S., Published on Wednesday, March 04
• Before the hail hits, these are the warning signs, Published on Tuesday, March 10