Ida weakens to a tropical storm; tropical disturbance 96E kills 124 in El Salvador

By: Dr. Jeff Masters , 3:20 PM GMT on November 09, 2009

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Tropical Storm Ida is steadily weakening as it hurtles northwards towards the Gulf of Mexico coast. Rains from Ida have already pushed into south-central Louisiana, where radar estimates indicate up to an inch of rain has fallen. Winds along the Gulf Coast of Mississippi, Alabama, and the Florida Panhandle were 20 - 25 mph this morning, and will steadily increase today as Ida draws near. Winds at the Mississippi Canyon buoy 150 miles south of Gulfport, MS were sustained at 45 mph at 8 am EST this morning, with 19 foot waves.


Figure 1. Microwave "radar in space" image of Ida taken at 7:15 am EST on Monday, 11/9/09. The eye is visible as a dark spot, but the eyewall has partially collapsed. The strongest echoes are on the north side of the storm, and Ida's heaviest rains and highest winds will hit the coast tonight, well in advance of the arrival of the center. Image credit: Navy Research Lab, Monterey.

Infrared and visible satellite loops show that wind shear has substantially degraded the appearance of Ida, and there is very little heavy thunderstorm activity in the storm's eyewall. Most of Ida's heavy thunderstorms have been displaced to the north of the storm, due to strong upper-level winds out of the southwest creating 30 knots of wind shear. Water vapor satellite imagery reveals a large area of dry air to the southwest of Ida, and the shear has now driven this dry air deep into the core of the storm, significantly disrupting it. The latest 6:30am EST vortex report from the Hurricane Hunters reported that the eyewall was ragged, and the pressure had risen to 997 mb. A recent microwave satellite image of Ida (Figure 1) shows that the eyewall is weak and has partially collapsed. Ida's most intense thunderstorms are on the north side of the storm, and the heaviest rains and highest winds will hit the coast tonight, well in advance of the arrival of the center.

The intensity forecast for Ida
The intensity forecast models predict that Ida's winds will range between 50 - 65 knots (58 - 74 mph) at landfall. The high wind shear of 30 knots currently affecting Ida is forecast to increase to 40 knots by late afternoon, and 55 knots by midnight. With Ida now over waters near 26°C, which is barely enough to support a hurricane, and with water temperatures decreasing to 23°C near the coast, the combination of high wind shear and cold waters will act to significantly weaken Ida. However, Ida is beginning to transition to an extratropical storm, and it is often the case that during such a transition the winds will gain energy from the process, though that's looking unlikely in this case. I expect Ida's top winds will be in the 50 - 60 mph range along the coast tonight and Tuesday morning. Regardless of Ida's strength at landfall, the storm will be able to dump 4 - 8 inches of rain along the Gulf Coast and well inland. We can't rule out the possibility of an isolated tornado when Ida makes landfall, but the Storm Prediction Center Discussion maintains that the airmass in place over the Gulf Coast is relatively stable, and prospects for an appreciable severe weather threat appear low.


Figure 2. Maximum storm surge (depth of water above ground) for a Category 1 hurricane with 85 mph winds moving north-northeast at 15 mph. Ida is expected to be moving at this speed and direction at landfall, but will be much weaker, so surges will not be this high. Furthermore, the storm will not create this level of surge along the entire coast--the image above is a composite worst-case scenario for all the storms shown by the black tracks with arrows. Image credit: NOAA SLOSH model run for Mobile Bay, 2008 version. Heights are given relative to the NAVD88 datum.

The storm surge forecast for Ida
Storm surge is the other major concern for Ida. With a strong high pressure system anchored over the U.S. today, the pressure difference between this high and Ida is creating a strong pressure gradient that was driving tides 2.5 feet above normal at Shell Beach, LA (on the east side of New Orleans) this morning, one foot above normal at Dauphin Island, AL, and one foot at Pensacola, FL (Figure 3). NHC is now calling for a storm surge of 3 - 5 feet above ground level, which is a reasonable forecast even if Ida weakens further. A large stretch of coast will be subject to very high water levels for an extended period of time today and tomorrow, with battering waves on top of the surge likely to cause a significant coastal erosion event. A particular concern is the western end of Alabama's Dauphin Island, when even a strong tropical storm can cause significant damage to the low-lying, heavily developed barrier island. The tidal range along the Gulf Coast varies by about 1.5 feet between low and high tide, and high tide is near 2 am EST on Tuesday.




Figure 3. Observed vs. predicted water levels at three coastal stations. Top: Shell Beach, LA (just east of New Orleans); middle: Dauphin Island, Alabama; bottom: Pensacola, FL. The green line shows how high above normal the water is. For Shell Beach, it was 2.5 feet above normal at 9am CST, while it was just over 1.0 feet above normal at the other two locations. Image credit: NOAA Tides and Currents.

Comparing to Hurricane Kate
The last November hurricane in the Gulf of Mexico was Hurricane Kate. Kate struck the Florida Panhandle near Mexico Beach on November 21, 1985 as a Category 2 storm with 105 mph winds. According to Wikipedia, Kate killed five people in Florida and did $300 million (1985 dollars) in damage. Ida will cause relatively minor damage compared to Kate.

Links to follow:
U.S. Severe Weather Page
Wundermap for the Gulf Coast of Alabama.
Long-range radar out of New Orleans, LA.
Navarre Beach, FL webcam.
Coastal observations from the University of South Alabama.
Coastal observations from LSU.

El Salvador floods kill 124
Heavy rains that began on Thursday due to tropical disturbance 96E have killed at least 124 people in El Salvador, with 60 people still missing. The flooding hit the capital of San Salvador and rural areas to the east. The heavy rains were due to tropical disturbance 96E (Figure 4), which formed off the coast of El Salvador on Wednesday, November 4. The counter-clockwise flow of air around the disturbance pulled large quantities of moist, Pacific air over the coastal mountains in El Salvador, dumping heavy rains of up to five inches, according to satellite estimates. The rains must have been much heavier over a small area that the satellite could not resolve. The terrible devastation I'm seeing in news photos indicates much higher rains of perhaps 10 - 15 inches must have fallen in a concentrated area in the mountains.


Figure 4. Satellite image of tropical disturbance 96E, which moved over El Salvador Thursday through Saturday, bringing heavy rains. Also pictured is Tropical Depression Eleven, which intensified into Tropical Storm Ida later that day. Ida was not responsible for the flooding in El Salvador, though it may have helped pull 96E into El Salvador. NASA has a nice zoom image> of 96E from November 5.

I'll have an update on Ida this afternoon.

Jeff Masters

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627. Mikla
Buoy Data... NOte the 25ft wave height...
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Quoting druseljic:


I think it was a pun - you have a home in Mobile, hence a "Mobile home".


Sorry having a Blond Male Moment.... just did not get it....

Taco :0)
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Cloudy and dreary here in Prairieville, La.. Ida is makin' me wanna nap
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Ida is persistent. Core has good precipitation and windfield, albeit small. Anybody want to D.I. west end tonight?
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623. xcool
she back cat 1 ohhh wow
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Quoting HurricaneSwirl:


Can't tell if you're being sarcastic or not, but it's been going on for months and it's TERRIBLE. Worst show ive seen hands down.

Ever since NBC bought The Weather Channel, a lot of interesting things have been happening with it...
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"Terrible" would be an upgrade to WUWA on TWC...
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Quoting druseljic:


I think it was a pun - you have a home in Mobile, hence a "Mobile home".

Somebody "got it". ;)
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Quoting TheCaneWhisperer:
I swear IDA looks like it's making a B line for NOLA.

Im trying to patiently await this turn east but umm yea so far the satelite makes me nervous.

Pat whats your thinking?
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618. IKE
Ida's coc coming into view on the 124NM Mobile radar....

Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting atmoaggie:

Hope you are "back" to being spry soon ,darlin.


What a really funny guy you are, darlin;'...LOL
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Al Roker cooks BBQ and predicts weather
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Quoting DestinJeff:
i just saw on TWC that Al Roker has new morning show! It's called "Wake Up With Al" ... they sure aren't getting the word out very much!


Can't tell if you're being sarcastic or not, but it's been going on for months and it's TERRIBLE. Worst show ive seen hands down.
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Thanks for the mail DrNo...now I guess "we" have a special relationship...so I will give you a nickname...as I do all my "special" buddies...I will dub you Corky...welcome to the Conch fan club, your membership card will be mailed in 4 to 6 weeks :)
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("Going to Biloxi" deja vu, just smaller.)
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Quoting DestinJeff:
i just saw on TWC that Al Roker has new morning show! It's called "Wake Up With Al" ... they sure aren't getting the word out very much!
No, it has been changed to "Another Morning of Anoying Al"
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FLOODMAN.. You called darlin'?

Reminds me of the Coe song......You don't hane to call me darlin', darlin.
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Quoting taco2me61:


Hey There HIEXPRESS I want you to know I have a 4 bedroom House and Love it.....

Taco :0)


I think it was a pun - you have a home in Mobile, hence a "Mobile home".
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Quoting Halyn:


Ike .. is Oz on live like he said he was going to try last night .. I finally gave up and went to bed .. :)



Technical difficulties with the live webcam has prevented him from broadcasting live during the storm but he will be shooting HD video for the youtube video to come later. Sounds like he's getting pretty good squalls from the initial feeder bands.
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Just got word, most of the west end of Dauphin Island is under water, as well as some beach roads in Gulf Shores.
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Quoting Floodman:


Good seeing you...WUMail for you, sir

Hope you are "back" to being spry soon ,darlin.
Member Since: August 16, 2007 Posts: 6 Comments: 12461
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Quoting BurnedAfterPosting:


True it would lol


Wouldn't that be an "Oh Crap"
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Sounding from Fort Walton Beach from 10 AM CST...lotsa shear (directional, that is).
Good thing the CAPE isn't there, but could be a foretelling thing for the severe stuff in the event of on-shore convection.


(full size, click!)
Member Since: August 16, 2007 Posts: 6 Comments: 12461
Thank you also eyes
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NHC would never upgrade her back to hurricane strength. Too late for that. That ship sailed when she was downgraded.
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Quoting eyesontheweather:
You lucky DOG, that's 2 "darlin"s" in 3 posts. Good to see ya, sorry to hear the back is not getting better.


Good seeing you...WUMail for you, sir
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Quoting stormsurge39:
Wheres the trough to turn Ida, or is she going too fast?


she is suppose to slow down a little bit as she starts to approach the coast and once she is onshore.
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Quoting TheCaneWhisperer:
'

Yeah, I know but, looking at P451's image sure would fool many.


True it would lol
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Quoting BurnedAfterPosting:


looks are deceiving

she is headed north right now, she will miss NO
'

Yeah, I know but, looking at P451's image sure would fool many.
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Afternoon,all,so I gather from reading back,recon is reporting hurr. force winds.
She's a tough old lady,she's not going out without a fight.sure hope people along the coast haven't let their guard down.
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Quoting atmoaggie:

SW Quad? Could be downburst winds...


It was at a time when they were coming out of rain, which is known to cause an increase in readings. However the report in the Vortex message was one not included in the HDOB obs which report 10 sec avg every 30 sec so there is 20 sec of data not reported by HDOB. I believe the flight met does see that data so it must be.
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Quoting Patrap:
Ida looks a lot like Hurricane Cindy from July 05 and I expect her impacts to be about the same where and to the right of where Landfall occurs

Mobile Medium Range Radar



Cindy 2005



Patrap thanks for posting this map, its more than easy to tell Idas going NNW!
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Quoting ConchHondros:


Sweet...I got an Honorable mention ;-)...Flood is worn out I would imagine...


LOL...Mrs. Flood is more worn out than I am...
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Quoting Hurricane1956:
I think that all the west coast of Florida is going to have a big suprise!! all the way down to the Florida Keys,just look at the band of rain and thunderstorms approaching the West Coast amazing!! picture.


link please?
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Quoting Floodman:


Bad, as is very much not good...I'm into the heavy hitters now : (

I see the surgeon on Friday...

Thanks for asking darlin'!
You lucky DOG, that's 2 "darlin"s" in 3 posts. Good to see ya, sorry to hear the back is not getting better.
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Quoting TheCaneWhisperer:
I swear IDA looks like it's making a B line for NOLA.


looks are deceiving

she is headed north right now, she will miss NO
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Quoting HIEXPRESS:

Everybody there lives in a Mobile home.


Hey There HIEXPRESS I want you to know I have a 4 bedroom House and Love it.....

Taco :0)
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Ida looks a lot like Hurricane Cindy from July 05 and I expect her impacts to be about the same where and to the right of where Landfall occurs

Mobile Medium Range Radar



Cindy 2005



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LOL, Ida will turn more E when she gets darn good and ready! Ive seen more E of N than anything else and she still gets fartherN and farther W on the Map. whew
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Good afternoon all,

Can someone explain to me the nature of the line of storms extending from Ida into the Yucatan channel? I've seen this often in November/October GOM storms. Is it related to a front/trough? It looks as though it will be dragging slowly across the FL peninsula if Ida turns to the east as forecast. Does this band contain severe weather (tornadoes, high winds, etc) or is it just a rain/flooding event? Is there a technical name for it or is it just a feeder band? If anyone can answer some of these questions, I would be grateful. Thanks.
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I swear IDA looks like it's making a B line for NOLA.
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Quoting P451:
Incredible....




The whole peninsula of Florida is going to get whacked by that band trailing down on her east side
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Quoting stormsurge39:
Ive never seen Mobile County Emergency Management wait and see like this! If it comes W of Dauphin Island, those folks are in for a bad ride!


West end is clear of people, Bienville is flooded. Be a few days before we can get down there and check things out. We know the drill.
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IKE, check your mail....
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Hmmmmmmmmmmmmmmmm, latest report from the Shell/MARS platform has no wind speed. Leaves all sorts of room for speculation...
http://www.ndbc.noaa.gov/station_page.php?station=42363
Member Since: August 16, 2007 Posts: 6 Comments: 12461

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About JeffMasters

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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