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 “worst-case” scenario projections for a given tropical cyclone. Due to the inherent uncertainty in storm track and intensity, these estimates are intended 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.
Forecast Tropical Cyclone Wind
Arrival, Departure
and
Duration Information
|
Glossary of Wind Specific Time Arrival and Departure Periods |
Period | Time Range |
|---|---|---|
| "Post-Midnight" | 12:00 AM - 2:59 AM | |
| "Early Morning" | 3:00 AM - 5:59 AM | |
| "Mid-Morning" | 6:00 AM - 8:59 AM | |
| "Late Morning" | 9:00 AM - 11:59 AM | |
| "Early Afternoon" | 12:00 PM - 2:59 PM | |
| "Mid Afternoon" | 3:00 PM - 5:59 PM | |
| "Early Evening" | 6:00 PM - 8:59 PM | |
| "Late Evening" | 9:00 PM - 11:59 PM | |
| "CPA" |
Closest Point of Approach from the indicated locations to the center of the storm. |
|
Tropical Cyclone Risk Scoring |
Score | Threshold |
|---|---|---|
| 1 | 45-95 mph (TS to Cat 1) | |
| 2 | 96-110 mph (Cat 2) | |
| 3 | 111-129 mph (Cat 3) | |
| 4 | 130-156 mph (Cat 4) | |
| 5 | 157 mph or higher (Cat 5) |
Note: Tropical Cyclone Decision-Making for Protective Actions
All timeframes presented in this Windfield Table are based on the official National Hurricane Center (NHC) forecast and indicate the anticipated onset of sustained tropical-storm-force winds (set at 45 mph for the listed location. This guidance is generally aligned with local civil authorities, including Emergency Management, Law Enforcement, and Fire Rescue. It is strongly recommended that all protective actions be completed in advance of the expected arrival of tropical-storm-force winds. This report and its contents are intended solely for preparedness and planning purposes and should not be interpreted as exact timing or a precise expectation.