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. |
Better Hurricane Forecasting-More Time to Get Out
When a hurricane approaches, all the public wants to know is: Where is it going? And, do I need to evacuate?
The National Hurricane Center says better track forecasts will allow them to give you more warning if a hurricane is headed toward your city. Instead of just 24-hours notice, hurricane forecasters say the track forecasts have improved so much, they can now issued a hurricane warning 36-hours in advance of a storm. That gives residents 12 more hours to board up their house, and make preparations for the advance of the storm, including evacuating if need be. Hurricane watches will be posted along coastlines 48-hours in advance of the storm’s landfall. “With increases in population and infrastructure along vulnerable U.S. coastlines, emergency managers need more lead time in order to make life-saving decisions regarding evacuations,” said Bill Read, director of NOAA’s National Hurricane Center. (Source: NOAA)
Forecast Track: Hurricane Ida, Image: NHC, NOAA
(This is a forecast graphic. Click here for the actual track of Hurricane Ida.)
The image above is a forecast track advisory from Hurricane Ida on Sunday, November 8th when it was between Cuba and Cancun, Mexico. I’ve circled Ida’s position on the map at 12PM on that Sunday. In 24 hours, the storm was expected to still be a hurricane as it approached Southeast Louisiana, Mississippi, Alabama and the panhandle of Florida. The National Hurricane Center was giving the coastlines a 36-hour advance notice that the storm could be a hurricane or extra-tropical hurricane as it approached the coast. Now, this watch will be issued 12-hours earlier.
Will this advanced lead time in the track forecast give TV meteorologists better tools to warn the public? Yes and no. Yes, we will be able to tell the public “… We are under a hurricane watch this evening. That means National Hurricane Center forecasters believe the hurricane is going to make landfall along our coastline in the next 48 hours.”
But, we still won’t be able to tell the public with complete confidence how strong the storm will be once it approaches. We’ve said this over and over, that despite advances in forecasting the path of the storm, the intensity forecast is still far from perfect.
For example, let’s just take a look at the graphic above, when the storm was 2 days away from hitting the northern Gulf Coast.
Comparing Forecast to Actual Track, Image: NOAA
24 hours after this advisory was issued, Ida had actually weakened to a tropical storm. Thus all the hurricane watches and warnings became tropical storm watches and warnings for the northern Gulf Coast. Ida made landfall in Dauphin Island, Alabama at about 7am on November 10th as a tropical storm with 45 mile per hour winds. A substantial difference from what was forecast just 24 hours earlier.
However, the track forecast was spot on! That’s why the NHC has become more and more confident that they can tell you where the storm is headed.
And, despite the pitfalls I’ve shown you in this blog when it comes to the intensity forecast, more and more hurricane research is aiming to improve that forecast as well.
-Dawn Brown
Gulf Low Will Dump Rain, Snow
Computer Forecast, Tonight, Image: Unisys Weather
Computer Forecast, Thursday, Image: Unisys Weather
A storm system setting up over Texas and drawing moisture from the Gulf of Mexico is creating the possibility of snow over West Texas and heavy rain over Southern Texas, Louisiana, Mississippi and Alabama. (Click here for your local TV forecast.)
This same system will ride up the Appalachians Thursday, becoming a snow-maker for parts of the Great Lakes and a rain-maker for much of the Northeast.
Yesterday was November 30th, the last official day of the 2009 hurricane season. The National Oceanic and Atmospheric Administration has a full report on the less-than-average season.
-Dawn Brown
October’s Climate Report
Northeast Radar, Image: NOAA (Old)
Click for the latest Northeast Radar image.
New England is being pummeled by Ida’s rains this Friday. Marine storm warnings are in effect from Delaware and South Jersey to off the coast of Long Island to northern New England. Click on the foregoing links for the latest watches and warnings from local TV forecasters.
NOAA, the National Oceanic and Atmospheric Administration has released its climate report card for the United States. According to NOAA, the United States had the third coolest October this year and the highest precipitation totals on record.
Climate State Ranks, Image: NOAA
Precipitation State Ranks, Image: NOAA
According to NOAA, “The average October temperature of 50.8 degrees F was 4.0 degrees F below the 20th Century average. Preliminary data also reveals this was the wettest October on record with average precipitation across the contiguous United States reaching 4.15 inches, 2.04 inches above the 1901-2000 average.” (Source: NOAA)
-Dawn Brown
Remnants of Ida Flooding East Coast
National Forecast, Image: NOAA
Heavy rain continues to pound the Northeast as the remnants of Ida continue to drench Virginia, Maryland, D.C., Delaware and New Jersey. It doesn’t look like it’s going to let up until late Friday into Saturday.
Northeast Radar, Image: NOAA (Old)
Click here for the latest radar image.
Precipitation Forecast, Image: NOAA
The Hydrometeorological Prediction Center is predicting at least 5 inches of rain through Sunday for coastal areas from North Carolina to Northern New Jersey. Here’s a complete list of rainfall totals from the remnants of Ida:
...ALABAMA... OPELIKA 11.0 S 9.83 CENTREVILLE 6SW 6.35 WARRIOR LOCK AND DAM 6.15 CLANTON 5.69 SMITHS 5NW 5.54 BREWTON 3SSE 5.50 DEMOPOLIS LOCK & DAM 5.46 ATMORE 12N 5.41 WADLEY 1WNW 5.33 BREWTON 3ENE 5.20 LAFAYETTE 2W 5.10 USFS TALLADEGA 5.01 ...DELAWARE... GEORGETOWN 5.8 W 1.72 DOVER 6.4 WNW 1.65 MARYDEL 2.4 SE 1.47 SMYRNA 2.7 SSE 1.39 MIDDLETOWN 0.9 SSE 1.00 ...FLORIDA... GONZALEZ 2.5 NNW 6.78 PORT ST. JOE 0.6 SE 6.32 LAKELAND 1.5 W 5.75 CRESTVIEW/BOB SIKES 4.53 PENSACOLA RGNL ARPT 4.07 DE FUNIAK SPRINGS 12WNW 4.02 MOSSY HEAD 4.00 ...GEORGIA... COLUMBUS 15NW (GA POWER CO) 7.25 MANCHESTER 3.6 ENE 7.00 FORSYTH 6.0 NNW 6.86 WOODBURY 6.85 BERNER 0.4 ENE 6.62 DOUGLASVILLE 0.2 N 6.11 BOGART 4.2 SE 6.00 LA GRANGE 2.5 NE 5.96 WEST POINT 5.84 ATLANTA 5.67 ...MARYLAND... PARK HALL 0.2 SW 2.86 PATUXENT NAS 2.85 LEONARDTOWN 0.6 NE 2.71 RIDGE 1.0 N 2.47 HOLLYWOOD 1.5 NW 2.28 SALISBURY 3.7 SSE 2.20 BISHOPVILLE 3.1 E 2.07 PRINCESS ANNE 2.1 SSW 1.86 WALDORF 3.6 SSE 1.77 CAMP SPRINGS 0.1 ESE 1.68 ...MISSISSIPPI... WAYNESBORO 2W 4.13 WIGGINS 6E 4.11 ...NORTH CAROLINA ... SWANSBORO 3.3 NW 9.26 SNEADS FERRY 1.5 S 8.57 NEWPORT 0.2 SW 8.15 HAVELOCK 1.8 W 7.12 MOREHEAD CITY 6.0 WNW 6.96 ELIZABETHTOWN 6.2 NW 6.85 TRENT WOODS 1.3 SSE 6.57 MIDDLESEX 5.5 SSW 6.55 JAMES CITY 2.5 S 6.36 RALEIGH 4.5 NNE 5.10 ...NEW JERSEY... LOWER TWP 2.2 NE 1.18 LINWOOD 0.7 SSW 1.14 UPPER TWP 3.2 SE 1.08 MIDDLE TWP 4.4 SW 1.04 ESTELL MANOR 4.0 WNW 1.04 ...SOUTH CAROLINA... CLARKS HILL 2W 5.69 WALHALLA 1.5 NW 5.45 POMARIA 4.0 N 5.32 WEST UNION 1.5 ESE 5.14 SENECA 4.9 N 5.09 CLEVELAND 4S 5.08 GREENWOOD 0.5 SSE 4.91 NORTH MYRTLE BEACH 4.88 MARIETTA 1.8 SW 4.81 JACKSON 3.4 ENE 4.75 GREENVILLE/SPARTANBURG AP 4.24 ...TENNESSEE... MOUNT LECONTE 4.11 NEWPORT - FRENCH BROAD RVR (TVA) 3.62 COPPERHILL (TVA) 3.62 COSBY 3.44 GATLINBURG 2SW/PARK HQ (IFLOWS) 3.34 SEVIERVILLE/LITTLE PIGEON RIVER 3.33 DOUGLAS DAM (TVA) 3.31 GATLINBURG (TVA) 3.17 TELLICO PLAINS (TVA) 3.10 WILDWOOD (TVA) 3.06 OAK GROVE (TVA) 3.01 ...VIRGINIA... CHESAPEAKE 3.5 NE 6.60 VIRGINIA BEACH 1.2 SW 6.45 ROCKY MOUNT 3.6 W 6.25 BOONES MILL 12.6 E 5.80 MONETA 3.6 SW 5.79 ROCKY MOUNT 6.4 NE 5.72 COPPER HILL 6.2 S 5.55 JONES CREEK 5.52 MARROWBONE RESERVOIR 5.44 LYNCHBURG 2.5 NNW 3.75
-Dawn Brown
Ida Could Bring Flooding Rain
National Radar, (Old) Image; NOAA
Ida has finally made the transition to an extratropical cyclone (winter-type storm) this morning. Click here for the latest national radar imagery. Forecasters in Huntsville, Alabama, Atlanta, Georgia, and the Carolinas are following the storm. These areas could suffer from flooding rains over the next few days. Watch your local TV forecaster for the latest watches and warnings.
-Dawn Brown
High Winds, Heavy Rain… Ahead of IDA
Gulf Coast Radar, Image: NOAA Image is Old!
Click on the following link for the latest radar image of Ida. Ida continues to plow toward the Gulf Coast, creating high winds, and dumping heavy rain on Panama City, Florida, Mobile, Alabama and coastal areas outside of New Orleans, Louisiana. TV forecasters in those areas can give you the latest watches and warnings, and current position of Tropical Storm Ida. It appears the worst of the heavy rain is out ahead of the storm.
Ida Track, Image: NOAA click to enlarge
-Dawn Brown
Ida Weakens In Hostile Environment
Ida weakens due to wind shear, cold sea surface temps, and dry air. All hurricane warnings have been dropped. Tropical storm warnings from Louisiana to Florida. Isolated heavy rainfall along the northern Gulf Coast expected. It looks like Ida is transitioning from a tropical to an extra-tropical or winter-type low pressure system. High winds and isolated heavy rain will still be a problem.
9AM Update from National Hurricane Center:
The center of tropical storm Ida was located near latitude 26.5 North, longitude 88.3 West, or about 185 miles south-southeast of the mouth of the Mississippi river and about 285 miles south-southwest of Pensacola, Florida
Ida is moving toward the north-northwest near 17 mph. A turn toward the north and then to the north-northeast is expected over the next 24 hours. On the forecast track, the center of Ida is expected to make landfall along the northern Gulf Coast Tuesday morning. After landfall, a turn to the east is expected on Tuesday.
Maximum sustained winds continue to decrease and area now near 70 mph with higher gusts. Some additional weakening is expected today as Ida approaches the coast.
-Dawn Brown
Wind Shear is Ripping Ida Apart
Ida Weakens, Image: NOAA click to enlarge
Ida is looking pretty ragged this morning as wind shear over the Gulf Coast is starting to tear the storm apart.
Hurricane Ida’s winds are down to 80 miles an hour. 30 knots or 35 mile per hour wind shear is tearing the storm apart. National Hurricane Center forecasters still forecast a hurricane at landfall, but I think that’s generous to say the storm will maintain these winds over the next 24 hours. I think heavy rain and possibly up to 60 mile per hour winds at landfall are what Gulf Coast residents can expect out of this storm. The tropical storm force winds will be relegated to the Alabama/Florida border.
Hurricane watches and warnings remain for the northern Gulf Coast. For the latest watches and warnings, go to GET YOUR LOCAL TV FORECAST! on the right hand side of this page. It is the last green tab on the right. You can watch forecasters from New Orleans, Louisiana to Tampa, Florida forecasting this storm!
Ida Track, Image: NOAA click to enlarge
-Dawn Brown
Ida Advances as a Cat 2 Hurricane
Hurricane Ida 5-Day Track, Image: NOAA click to enlarge
- Hurricane Ida, Infrared Satellite, Image: NOAA click to enlarge
Hurricane Ida is advancing toward the northern Gulf Coast as a category 2 hurricane this Sunday with maximum winds up to 105 miles per hour. In their discussion National Hurricane Center forecasters indicate the satellite presentation of the eye is looking a little more ragged this Sunday evening. The wind shear in this part of the Gulf of Mexico is about 30 knots, or about 35 miles per hour.
The southwesterly shear is expected to slightly weaken the storm as it continues its northerly course. Click here for the latest wind shear image.
The National Hurricane Center is currently forecasting Ida to remain a hurricane for the next 36 hours, making landfall as a possibly category 1 hurricane near the Alabama/Florida border. It is expected to make a transition to a winter-type cyclone when it collides with a cold front that is currently crossing the central United States. Current computer model forecasts suggest Ida may be forced on a more easterly track because of this oncoming front. (Go to the Hurricane Tracking link to your left.) By Monday morning, Ida’s fate and its impact on the Gulf Coast will become more apparent. Overnight, we’ll know how Ida is handling the increased wind shear and the cooler waters of the northern Gulf of Mexico. As I say this, the computer models have done a pretty good job of forecasting Ida’s re-strengthening in the Caribbean and Gulf, and they continue to forecast a storm with hurricane force winds at landfall.
Storm Surge Modeling from the National Hurricane Center gives coastal residents an idea of the probability of being affected by storm surge and higher than average tides. When you are looking at the map, zoom into your area. Then, choose probability of storm surge either above 2′, 3′, 4′… etc. Then click on the button, “Load Data”.
Currently, there is a 5-10 % probability of storm surge above 6′ affecting coastal areas of Louisiana and Mississippi. The probabilities change based on the strength and path of the storm. Watch your local TV forecasts in Louisiana, Mississippi, Alabama and Florida for the latest watches and warnings.
-Dawn Brown