Less Confusing Saffir-Simpson Scale Released
Hurricane Ike, Image: NOAA
When Hurricane Ike slammed into the Texas coastline in September 2008, hurricane forecasters rated it a category 2 hurricane on the Saffir-Simpson scale with maximum sustained winds of 110 miles per hour. The storm surge associated with Ike topped 15-20 feet. If you used the Saffir-Simpson scale as a guide, the storm surge associated with Ike should have been about 6′. (See the graphic below.) The mismatch between the wind speeds generated by the storm and the associated storm surge have led the National Hurricane Center to drop storm surge from the widely used scale.
Old Saffir-Simpson Scale, Image: NOAA
The Saffir-Simpson scale was developed in 1971 by engineer Herbert Saffir and National Hurricane Center Director Bob Simpson to help forecasters explain the potential damage from a hurricane to the public. It was mainly designed as a way to explain what damage would occur to structures if a hurricane hit with 75 mile per hour winds, 95 mile per hour winds, 110 mile per hour winds, etc. After the scale was developed, forecasters realized storm surge was a significant part of the damage from a hurricane, and they tried to come up with the height of the storm surge associated with different wind speeds. Unfortunately, it has led to errors in forecasting and misleading the public. The effect of storm surge on a coastline depends on the strength of the winds, the direction of the storm, the topography of the coastline, and the bathymetry (or topography of the coastline under the water.) Now, individual weather service offices, as well as universities, produce individual storm surge forecasts for each storm depending on the strength of the storm and its track. Here are the guidelines given today by the National Hurricane Center for the now called Saffir-Simpson Hurricane Wind Scale:
| Category | Winds | Effects |
|---|---|---|
| One | 74-95 mph | No real damage to building structures. Damage primarly to unanchored mobile homes, shrubbery, and trees. Also, some coastal road flooding and minor pier damage |
| Two | 96-110 mph | Some roofing material, door, and window damage to buildings. Considerable damage to vegetation, mobile homes, and piers. Coastal and low-lying escape routes flood 2-4 hours before arrival of center. Small craft in unprotected anchorages break moorings. |
| Three | 111-130 mph | Some structural damage to small residences and utility buildings with a minor amount of curtainwall failures. Mobile homes are destroyed. Flooding near the coast destroys smaller structures with larger structures damaged by floating debris. Terrain continuously lower than 5 feet ASL may be flooded inland 8 miles or more. |
| Four | 131-155 mph | More extensive curtainwall failures with some complete roof strucutre failure on small residences. Major erosion of beach. Major damage to lower floors of structures near the shore. Terrain continuously lower than 10 feet ASL may be flooded requiring massive evacuation of residential areas inland as far as 6 miles. |
| Five | greater than 155 mph | Complete roof failure on many residences and industrial buildings. Some complete building failures with small utility buildings blown over or away. Major damage to lower floors of all structures located less than 15 feet ASL and within 500 yards of the shoreline. Massive evacuation of residential areas on low ground within 5 to 10 miles of the shoreline may be required. |
The Pacific is Getting All the Action!
Tropical Storm Marty (courtesy NOAA)
Tropical Storm Marty formed off the Mexican coast last night, and Baja California could once again be affected by a tropical system in the few days. It’s expected to weaken once it gets close to Baja, and it doesn’t look like it will be close enough for Baja to even experience tropical storm force winds. However, wave action from the system could affect swells off the Pacific coast, check out Surfline’s Hurricane Tracker forecast for the latest on the swells from this tropical system.
Remnants of Fred (courtesy NOAA)
On the left hand side of the page, I have the latest satellite imagery from the Atlantic Ocean, which shows the remnants of Hurricane Fred. Fred was the second major hurricane of the season after Hurricane Bill. In this satellite picture, the remnants of Fred are an area of showers and thunderstorms on the far right. At least one reliable computer model has Fred regenerating close to the Bahamas. But I have to remind readers once again that these computer models have trouble forecasting the intensity of a storm. If Fred did regenerate close the Bahamas, another upper level trough sweeping across the continental United States would carry Fred on a more northerly track once it moved close to the Bahamas. Keep in mind, though, the National Hurricane Center is giving the remnants of Fred a low (less than 30%) chance of redeveloping.
Meanwhile, rain from a STUBBORN area of low pressure continues to plague the Midwest. The US Radar Map shows stormy conditions over Arkansas, Tennessee, Alabama and Mississippi from that area of low pressure that dumped heavy rain over Texas and Louisiana this past weekend. Forecast maps show that low persisting over the central United States through next week, when that large upper level trough finally moves through, changing the weather pattern. Remember, you can watch any TV broadcast anywhere across the US by clicking on my link, GET YOUR LOCAL TV FORECAST!. The link is in the right hand column, scroll down to the bottom. Today, a lot of the weather action is in Nashville, Tennessee. You can look at the local radar, and watch the ABC Nashville TV Weather for more information.
Hurricane Ike’s Anniversary was a couple of days ago. A friend sent me this link. It’s pretty cool to see the before and after pictures compiled. I remember watching KHOU, the CBS affiliate in Houston’s, broadcast online all night.
-Dawn Brown