Windfield Report – Questions & Answers

Q1: How should wind estimates provided by Early Alert be interpreted?

The wind estimates in Early Alert’s Windfield Report represent “worst-case” scenario projections for a given tropical cyclone. Due to the inherent uncertainty in storm track and intensity, these estimates are intended for planning purposes only and should not be viewed as exact predictions.

Q2: Why are “worst-case” wind estimates used?

Worst-case estimates help decision-makers account for potential forecasting errors. Specifically, they reflect the typical one-category margin of error in Saffir-Simpson scale intensity forecasts, allowing users to plan for a storm that may be stronger than predicted.

Q3: What are the “worst-case” wind estimates based on?

These estimates incorporate conservative assumptions designed to err on the high side. They are based on National Hurricane Center (NHC) projections for maximum sustained winds (e.g., ≥74 mph) and the spatial extent of those winds in all four storm quadrants (northeast, southeast, southwest, northwest).

Q4: If the NHC forecast is accurate, how do “worst-case” estimates compare to actual observed winds?

In such cases, worst-case estimates will likely exceed observed wind speeds. This is expected for two reasons:
•  Maximum winds represent a brief, localized peak, not the norm across an area.
•  The NHC’s wind estimates are adjusted for landfall but do not fully account for terrain roughness, buildings, or vegetation, all of which reduce wind speeds.

Q5: How should decision-makers use the Windfield Report for protective actions?

The timing guidance in the Windfield Report is based on the anticipated onset of sustained tropical-storm-force winds (≥45 mph) in coordination with local civil authorities (e.g., Emergency Management, Law Enforcement, Fire Rescue). It is strongly recommended that all protective actions be completed prior to the onset of these wind conditions.