Rita Downgraded?

[Ivanhater]

those waves from Ivan were in deep water, not near the shelf

I know about the waves out in the ocean, im talking about the ones in Pensacola Bay

[f5]

Pensacola isn't going to have the kind of surge Mississippi&Louisiana got beacuse that water isn't shallow.they get higher waves but its alot better than walls of water eating structures in its path

[Derek Ortt]

that area is more wave prone due to the deeper water offshore

That said, when Ivan hit Cayman, it was producing 50 foot waves onshore

[Ivanhater]

Pensacola isn't going to have the kind of surge Mississippi&Louisiana got beacuse that water isn't shallow.they get higher waves but its alot better than walls of water eating structures in its path

Im not talking about surge, im talking about waves, and im not talking about what is worse, im asking what made ivan produce such high waves

[Ivanhater]

that area is more wave prone due to the deeper water offshore

That said, when Ivan hit Cayman, it was producing 50 foot waves onshore

thanks for helping

[Derek Ortt]

the waves are worse for structures right on the beach that is the storm surge

[Pearl River]

wxman57 wrote

That's not too different from what I was saying - a LARGE Cat 3. However, the NHC statement is incorrect concerning the "Cat 5 waves". I've been a marine meteorologist since 1980, so I do know about wave generation. That Cat 5 wind was over such a small area of the ocean that it would not have generated much of an increase in wave heights. Wave height is a function of wind speed, duration, and fetch. Wind speed with no duration or fetch won't build big waves. On the other hand, the large area of 60-100 mph winds had a much longer fetch and duration - so that's where the big waves came from. And such waves were still being generated up to landfall.

Thanks for clearing that up.

[dhweather]

wasnt ivan's waves the largest waves ever recorded during a hurricane? was it the storm itself or was it the shape of the coastline that caused it?

Those waves were recorded well offshore by Dr. Bill Teague and crew of the Naval Research Laboratory, Stennis Space Center.

Here's a nice article on that:

http://news.nationalgeographic.com/news ... ewave.html

[Ivanhater]

NOAA BUOY REPORTS RECORD WAVE HEIGHT
DURING HURRICANE IVAN

Oct. 13 — A 52-foot wave produced by Hurricane Ivan in the Gulf of Mexico last month was the highest wave reported in a hurricane according to records from NOAA's National Data Buoy Center (NDBC).

Buoy station 42040, operated by NDBC, was located about 75 miles south-southwest of Dauphin Island, Ala., when it reported the 52-foot wave at 6:50 p.m. CT on September 15. Hurricane Ivan later crossed the Alabama coast just west of Gulf Shores in the early morning hours of September 16 as a major Category 3 hurricane.

Undoubtedly, Hurricane Ivan produced unmeasured waves higher than 52 feet, according to NDBC scientists. Wave heights that buoys measure are the average of the highest third of the waves sampled during a 20-minute period. The single highest wave is typically 50 to 80 percent higher. Also, Ivan's eye passed east of the buoy, keeping the highest waves and winds to the east. Sustained winds at the buoy reached only 63 mph with gusts to 85 mph.

Ivan's towering wave exceeds those measured in other infamous storms. In 1969, Hurricane Camille produced a 44-foot wave by an oil rig near the storm's center.

Only two other buoy reports exceed the 52-foot mark set by Ivan, both of which occurred in the North Pacific where winter storms are larger than hurricanes and winds blowing across a longer distance create larger waves. The highest wave ever reported by an NDBC buoy was 55 feet and was measured south of Alaska's Aleutian Islands in 1991.

[Ixolib]

the waves are worse for structures right on the beach that is the storm surge

...and bridges over Escambia Bay.

[f5]

will NHC continue their downgrade parade with Rita?

[Javlin]

Thanks alot guys now I understand what happened a little clearer.

[wxman57]

Im not talking about surge, im talking about waves, and im not talking about what is worse, im asking what made ivan produce such high waves

Wave heights are a funciton of:

1. Wind speed
2. Fetch -- the distance across the water over which the wind blows
3. Duration of the wind - the time it blows over a given fetch
4. Ocean depth
5. To a lesser degree air temperature vs. SST. Cold air over warm water produces larger waves than the reverse.

To calculate wind waves, we use the Bretschneider equation. Basically, we plug in the wind speed, fetch, and duration and get the wave height and wave period. To generate maximum wave heights you need a strong wind blowing for a long time over a long fetch of water. That won't happen near the core of a hurricane (stronger wind but very short fetch and duration). The bigger waves are generated by the wind field that blows over the longer fetch, basically toward the middle parts of the hurricane, in the range between the hurricane force winds and the tropical storm force winds. These winds aren't as strong as core winds, but they cover a much larger area for a longer period of time. Hence, they can generate very large waves in a large hurricane like Ivan.

Ivan's wind field was actually a little larger than Katrina, in the top 10% of all hurricanes in terms of size of 58, 74, and 100 mph wind radii. That's the reason it produced such huge waves.

Now, I also mentioned water depth. A wave will break when the height reaches 2/3 the water depth. So the maximum wave height in, say, 60 feet of water is 40 feet. Anthing bigger breaks. As you know, the water well offshore Pensacola is much shallower than 60 feet in many areas, so most of Ivan's wave energy was lost as those big waves broke way offshore. In the relatively shallow bays, waves were much, much lower (2/3 water depth rule applies).

[Ivanhater]

Im not talking about surge, im talking about waves, and im not talking about what is worse, im asking what made ivan produce such high waves

Wave heights are a funciton of:

1. Wind speed
2. Fetch -- the distance across the water over which the wind blows
3. Duration of the wind - the time it blows over a given fetch
4. Ocean depth
5. To a lesser degree air temperature vs. SST. Cold air over warm water produces larger waves than the reverse.

To calculate wind waves, we use the Bretschneider equation. Basically, we plug in the wind speed, fetch, and duration and get the wave height and wave period. To generate maximum wave heights you need a strong wind blowing for a long time over a long fetch of water. That won't happen near the core of a hurricane (stronger wind but very short fetch and duration). The bigger waves are generated by the wind field that blows over the longer fetch, basically toward the middle parts of the hurricane, in the range between the hurricane force winds and the tropical storm force winds. These winds aren't as strong as core winds, but they cover a much larger area for a longer period of time. Hence, they can generate very large waves in a large hurricane like Ivan.

Ivan's wind field was actually a little larger than Katrina, in the top 10% of all hurricanes in terms of size of 58, 74, and 100 mph wind radii. That's the reason it produced such huge waves.

Now, I also mentioned water depth. A wave will break when the height reaches 2/3 the water depth. So the maximum wave height in, say, 60 feet of water is 40 feet. Anthing bigger breaks. As you know, the water well offshore Pensacola is much shallower than 60 feet in many areas, so most of Ivan's wave energy was lost as those big waves broke way offshore. In the relatively shallow bays, waves were much, much lower (2/3 water depth rule applies).

very good info, thanks

[Hybridstorm_November2001]

Yes the Bretschneider Equation's principles say something like an Intense Nor'Easter type storm raging for a week in the North Atlantic can, at least in theory, build up a maximum wave height of something like 104 ft, not counting surge! Simply because it remains in the same general area, and the seas just keep building and building and building. Fun stuff

[MGC]

The Grand Casino in Gulfport had waves break on the third floor of the water front hotel. The Grand is build atop pilings and the first floor is about 20 feet about the beach. I can only guess but I would estimate that wave crest on the beach in Gulfport at about 35-40 feet. I was at the Harrison County Courthouse yesterday and I discovered why some of the wind instruments failed. It was not due to power but one of the cups got ripped off. I guess it was spinning too fast....MGC

[Ixolib]

The Grand Casino in Gulfport had waves break on the third floor of the water front hotel. The Grand is build atop pilings and the first floor is about 20 feet about the beach. I can only guess but I would estimate that wave crest on the beach in Gulfport at about 35-40 feet. I was at the Harrison County Courthouse yesterday and I discovered why some of the wind instruments failed. It was not due to power but one of the cups got ripped off. I guess it was spinning too fast....MGC

And, interestingly enough, the primary reason for building it on pilings - with the first floor about 20" feet up - was so that when the hurricanes came, the surge would simply wash out the "downstairs" area which housed only the Bell Stand and Valet.

Guess that theory, too, was blown out the window...

[Audrey2Katrina]

Just out of curiosity; wasn't there a reference in the NHC report to a buoy that measured a 55 ft. wave in Katrina (undoubtedly when still a 5)? If so, this would be yet another example of how these two storms compared while having different effects due to the landfall area and water depths offshore?

Rita may well be downgraded to a 2 "at" landfall;" but I guess it'll be another hard sell to the folks of E. Texas and Cameron that went through it--just speaking from experience. Any data on the max waves she produced? I mean her intensity was even greater than that of Katrina and the lowest pressure since Gilbert, until Wilma came along.



A2K

[Pearl River]

From the NWS Lake Charles Post Storm Report on Rita

STORM SURGE...

CALCASIEU PASS LA (NOS)...... 5.50 FT MLLW AT 0200 UTC SEP 24 2005
(GAGE BECAME DISABLED AT THAT TIME)
RAINBOW BRIDGE TX (NOS)...... 3.85 FT MLLW AT 1530 UTC SEP 24 2005
............................. 3.88 FT MLLW AT 0948-1042 UTC SEP 25 2005
SABINE PASS NORTH TX (NOS)... 6.37 FT MLLW AT 0554 UTC SEP 24 2005
(GAGE BECAME DISABLED AT THAT TIME)
PORT ARTHUR TX (TCOON)....... 4.59 FT MLLW AT 0800 UTC SEP 24 2005
............................. 4.11 FT MLLW AT 0700 UTC SEP 25 2005


BASED ON NWS STORM SURVEY...ESTIMATED MAXIMUM STORM SURGES...

CALCASIEU PARISH...

STORM SURGE ESTIMATED UNDER THE I-10 BRIDGE IN LAKE CHARLES...6
FT MSL...WATER REACHED THE YACHT CLUB...AND PUSHED THE BOATS INTO
THE RAILROAD BRIDGE JUST NORTH OF I-10.

DOWNTOWN LAKE CHARLES FLOODED ON THE EXIT RAMP FOR RYAN STREET ON
I-10...REACHING A DEPTH OVER 6 FEET. WATER CAME OVER AND AROUND
THE PITHON PUMP STATION ON LAKESHORE DRIVE...AND FLOODED PORTIONS
OF DOWNTOWN LAKE CHARLES WITH UP TO 3 TO 6 FEET OF WATER.

STORM SURGE REACHED SOUTHWESTERN SIDES OF LAKE CHARLES...WHERE
THE STORM SURGE BACKED UP THE SHIP CHANNEL. GAUTHIER ROAD WAS
COVERED WITH WATER BETWEEN ELLIOTT ROAD AND THE SHIP CHANNEL.
WATER ALSO REACHED NORTH OF TANK FARM ROAD BETWEEN ELLIOTT AND
NELSON ROADS...FLOODING A MOBILE HOME PARK.

BLACK BAYOU SOUTH OF LAKE CHARLES REGIONAL AIRPORT...10 TO 15 FT
MSL...BASED ON DEBRIS LINE AT NWS EMPLOYEE HOME (2 TO 4 FT ABOVE
GROUND LEVEL). THE STORM SURGE ALSO REACHED PORTIONS OF LINCOLN
ROAD ALONG SOUTH SIDE OF THE AIRPORT (ESTIMATED 1 TO 2 FEET
ABOVE THE ROAD).

CAMERON PARISH...

CAMERON...15 TO 20 FEET MSL...BASED ON DEBRIS LINE REACHING
SECOND FLOOR OF INSIDE STAIRWELL AT COURTHOUSE AND DEBRIS LINE
AT AMBULANCE BARN AT THE HOSPITAL. NEARLY EVERY HOME AND
BUSINESS BETWEEN CREOLE AND DOWNTOWN CAMERON WAS DESTROYED. MANY
WERE COMPLETELY WASHED AWAY.

HEBERT`S MARINA & GRAND LAKE...10 TO 15 FEET MSL...BASED ON
DEBRIS LINE AT THE NWS GAUGE AT HEBERT`S MARINA AND AT THE HARBOR
LIGHTS RESTAURANT. NUMEROUS HOMES WERE DAMAGED OR DESTROYED.

[Audrey2Katrina]

Thanks for the info, Pearl River; but with all that info of the water depths in Lake Charles, while I've been through the town many times, I have no idea what elevation some of those places would be above sea-level, so it doesn't make it clear to me what the surge actually was that hit the Lake Charles area.

The Cameron data, is clear enough 15-20 foot surge... That's impressive, and scary.

Well, I'm sure I don't have to tell YOU about that!

A2K