Alternate Hurricane Classification Scheme
Currently, the National Hurricane Center (NHC) uses the Saffir-Simpson Hurricane Wind Scale (SSHWS) to gauge the severity of tropical cyclones (which includes tropical depressions, tropical storms, and hurricanes). One of the biggest criticisms of this approach is that it neglects the other impactful hazards within hurricanes: storm surge, flash flooding, and tornadoes. For example, Hurricane Harvey (2017) was a Category 4 hurricane, but most of the casualties and damage were caused when Harvey weakened to a tropical storm and dropped widespread 24"-48"+ rain totals over Southeast Texas where some locales picked up half a normal year's worth of rain in 1-2 days.
To address this shortcoming, I believe the NHC should develop a 0 to 5 scale for all hazards within a hurricane (wind, storm surge, flash flooding, and tornadoes). This would be consistent with what a lot of other National Weather Service offices use (e.g. the Storm Prediction Center), and it would concisely convey to the general public which hazards are expected to be most prominent and how impactful they will be. The "overall severity/impact" of a hurricane would then become the highest number among the individual hazards (I purposely used a term other than "category" to avoid confusion with the traditional SSHWS).
Here's a system (or something similar) that I would like to see the NHC formally use:
| Intensity | Wind | Storm Surge | Flash Flooding | Tornadoes |
|---|---|---|---|---|
| 0 (Minimal) |
Tree damage mainly restricted to small twigs and perhaps a few 1"-3" diameter branches. Isolated short-lived power outages possible. Very little to no property damage expected. Guideline: Winds under 58 mph Analog: Fernand (2019) |
Little to no coastal flooding. Standing water may transiently flow over coastal roadways, but depths should generally remain under 6". Very little to no property damage expected. Guideline: Maximum storm surge under 2' Analog: Danny (2021) |
Little to no flash flooding. Heavy rainfall may occur, but any flooding that occurs will be localized and low-end. Guideline: Widespread rain totals of 1"-2" with isolated totals of 3"-4" Analog: Melissa (2019) |
Tornadoes unlikely, and any tornadoes that do occur will be brief and EF0. Tornado watch not necessary. Analog: Dolly (2008) |
| 1 (Low) |
Several 1"-3" diameter branches downed, a few larger branches perhaps partially or completely broken off. Isolated short-lived power outages likely. Minor roof damage may occur, and some property damage may occur from falling tree debris. Guideline: Winds of 58-95 mph Analog: Barry (2019) |
Minor coastal flooding that will make travel along the immediate coastline potentially dangerous. Water may flow into coastal structures built at ground level. Guideline: Maximum storm surge of 2'-4' Analog: Nicholas (2021) |
Minor flash flooding likely. Heavy rainfall will occur, but flooding will primarily be confined to flood prone areas. Guideline: Widespread rain totals of 2"-4" with isolated totals of 6"-8" Analog: Claudette (2003) |
Tornadoes possible, and any tornadoes that do occur will mostly be EF0 intensity. Tornado watch may be necessary. Analog: Dennis (2005) |
| 2 (Moderate) |
Several 3"+ diameter branches broken off with a few large trees uprooted. Scattered power outages likely. Some property damage is likely. Guideline: Winds of 96-110 mph Analog: Sally (2020) |
Moderate coastal flooding that will make travel along the immediate coastline hazardous. Coastal structures situated at ground level could experience significant flood damage. Guideline: Maximum storm surge of 4'-6' Analog: Nate (2017) |
Moderate flash flooding likely. Heavy rainfall will cause flash flooding in flood-prone areas with isolated instances of life-threatening and significant flooding. Guideline: Widespread rain totals of 4"-6" with isolated totals of 9"-12" Analog: Arthur (2014) |
Tornadoes likely, but most tornadoes will be EF0-EF1. One or two EF2+ tornadoes possible. Tornado watch will be necessary. Analog: Hermine (2010) |
| 3 (Significant) |
Several large trees uprooted with a few snapped at the trunk. Widespread power outages likely. Significant roof loss on some homes. Extreme wind warning may be necessary. Guideline: Winds of 111-129 mph Analog: Otto (2016) |
Significant coastal flooding that will make travel along the immediate coastline impossible. Coastal structures situated at ground level will be heavily damaged. Dwellings elevated by posts may become structurally compromised. Guideline: Maximum storm surge of 6'-10' Analog: Hanna (2020) |
Significant flash flooding likely. Scattered instances of life-threatening and significant flooding, and flooding may occur in areas not normally susceptible to flooding. Guideline: Widespread rain totals of 6"-12" with isolated totals of 15"-18" Analog: Francine (2024) |
Tornadoes likely, a few tornadoes may be EF2+. Analog: Cindy (2005) |
| 4 (Devastating) |
Widespread long-lived power outages likely. Some homes severely damaged or nearly destroyed. Wind damage will isolate some neighborhoods for weeks. Extreme wind warning will be necessary. Guideline: Winds of 130-156 mph Analog: Delta (2020) |
Any coastal structure will be susceptible to severe damage or perhaps complete destruction. Guideline: Maximum storm surge of 10'-15' Analog: Laura (2020) |
Major flash flooding likely. Widespread life-threatening and significant flooding, and flooding will occur in areas not normally susceptible to flooding. Guideline: Widespread rain totals of 12"-24" with isolated totals of 30"+ Analog: Allison (2001) |
Tornadoes likely, several tornadoes will be EF2+. One or two EF3+ tornadoes possible. Analog: Ida (2021) |
| 5 (Catastrophic) |
Widespread long-lived power outages and utility disruptions expected. Several homes completely destroyed. Wind damage will isolate several neighborhoods for months. Guideline: Winds of 157+ mph Analog: Michael (2018) |
Coastal structures will be completely swept away and numerous inland structures will be heavily damaged or destroyed. Coastal flooding will make parts of the coastline completely unrecognizable. Guideline: Maximum storm surge of 15'+ Analog: Katrina (2005) |
Flooding will cause widespread and extremely crippling damage to infrastructure and topography. Severe flooding will occur in areas that don't normally see flooding. Guideline: Widespread rain totals of 24"+ with isolated totals of 48"+ Analog: Harvey (2017) |
Numerous tornadoes with several long-track EF2+ tornadoes expected. A few EF3+ tornadoes likely. One or two EF4+ tornadoes possible. Particularly Dangerous Situation (PDS) Tornado Watch will be necessary. Analog: Milton (2024) |
Interestingly enough, the NHC already does this to some extent in their advisory packages; each hazard can be assigned a descriptive label ("none", "limited", "significant", "extensive", "devastating", "catastrophic"), and each label could be assigned a numerical equivalent (0 for "none", 5 for "catastrophic"). Although the advisory packages are very detailed and thus probably not suitable for the general public, distilling the expected impacts down to a simple number should already be within the realm of possibility. And, media outlets can easily show a graphic that puts the numbers into perspective (like they do for the SPC's convective outlooks).
For those that are familiar with the SPC's convective outlooks, there was a time when the SPC's outlooks were just a category that attempted to cover all their hazards of interest (tornadoes, straight-line winds, and hail). Now, they have numbers (probabilities) assigned to each individual hazard to convey a more complete picture of which hazards are expected to be most (and least) impactful. And, it's the same idea with the SSHWS: trying to use a single number to cover multiple different hazards (the SSHWS category) just isn't effective at communicating the expected impacts. Like what the SPC did, my hope is that the NHC reworks their approach to tropical cyclones by explicitly assessing the severity of each individual hazard as opposed to gauging severity based on a single hazard.