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

By: Dr. Jeff Masters , 9. marraskuuta 2009 klo 15:20 (GMT)

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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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678. Halyn
9. marraskuuta 2009 klo 23:08 (GMT)
Had to leave for a while .. where has everyone gone ? What did I miss that silenced this blog?
Member Since: 7.08.2008 Posts: 0 Comments: 98
677. 850Realtor
9. marraskuuta 2009 klo 21:54 (GMT)
Hey All,

Just wanted to pass on a Pensacola Doug and CycloneOz sighting. They were in the hood a little while ago gathering data!
Member Since: 14.09.2009 Posts: 0 Comments: 283
676. 996tt
9. marraskuuta 2009 klo 21:18 (GMT)
Quoting BurnedAfterPosting:


maybe he is related to the Kite flying idiot who became the dunce of the world during Fay last year lol


Dude, that is cold.
Member Since: 5.09.2008 Posts: 0 Comments: 308
675. drj27
9. marraskuuta 2009 klo 21:03 (GMT)
Quoting mattkenton:
So is Ida a hurricane again or no? If so where is the data that supports this. I'd like to check it out.
no still 70 mph tropical storm
Member Since: 25.08.2006 Posts: 0 Comments: 98
674. portraitrick
9. marraskuuta 2009 klo 21:02 (GMT)
28.4n 88.5w moving north
Member Since: 1.09.2008 Posts: 0 Comments: 3
673. mattkenton
9. marraskuuta 2009 klo 20:54 (GMT)
So is Ida a hurricane again or no? If so where is the data that supports this. I'd like to check it out.
672. nolacane2009
9. marraskuuta 2009 klo 20:53 (GMT)
Winds picking up here pretty good in NOLA..
Member Since: 19.08.2009 Posts: 0 Comments: 248
671. MTWX
9. marraskuuta 2009 klo 20:48 (GMT)
Afternoon all!! Just waiting on the rain we don't need!
Member Since: 20.07.2009 Posts: 23 Comments: 1391
670. portraitrick
9. marraskuuta 2009 klo 20:45 (GMT)
Just got back from the beach in Biloxi, and the water is creeping up the beach. One of the few times we have surf.
Member Since: 1.09.2008 Posts: 0 Comments: 3
668. Marlinzfan
9. marraskuuta 2009 klo 20:40 (GMT)
Quoting eyesontheweather:
is there high winds associated with this line?


No just some light rain it looks like on radar.
667. Halyn
9. marraskuuta 2009 klo 20:39 (GMT)
Quoting hurricanejunky:


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.


Thank you .. :) Although I seldom post (don't know enough to sound halfway intelligent) I have been here long enough to feel "at home" .. and often I worry about the ones in harm's way .. from the safety of my Illinois home. Flood .. hang in there .. btdt and have the t-shirt to prove it .. will be thinking about you .. :)
Member Since: 7.08.2008 Posts: 0 Comments: 98
666. Marlinzfan
9. marraskuuta 2009 klo 20:39 (GMT)
Quoting P451:


If she pulls Easterly then that could be a problem. I think we were discussing that potential scenario last night.



But there doesn't appear to be much heavy rain in it. I think some folks here are wishcasting again. It looks to be some nice NEEDED rain.
665. msjayhawk
9. marraskuuta 2009 klo 20:38 (GMT)
Ready for that turn to the east.... Anytime now.

Diamondhead, MS
Member Since: 10.06.2008 Posts: 0 Comments: 13
664. PalmBeachWeather
9. marraskuuta 2009 klo 20:38 (GMT)
Sorry, Bad finger
Member Since: 3.10.2008 Posts: 0 Comments: 5750
663. PcolaDan
9. marraskuuta 2009 klo 20:37 (GMT)
NEW BLOG
Member Since: 22.08.2008 Posts: 12 Comments: 6010
662. PalmBeachWeather
9. marraskuuta 2009 klo 20:37 (GMT)
STORMsURGEON.bE CAREFUL, SOME PEOPLE HERE DON'T KNOW.tHEY HAVE BEEN THROUGH A FEW BAD ONES
Member Since: 3.10.2008 Posts: 0 Comments: 5750
661. JUSTCOASTING
9. marraskuuta 2009 klo 20:37 (GMT)
So is Ida back to hurricane strenght or not ?
Member Since: 15.08.2006 Posts: 2 Comments: 666
660. SQUAWK
9. marraskuuta 2009 klo 20:37 (GMT)
3D RADAR across the eye of Ida

Member Since: 9.12.2008 Posts: 0 Comments: 2498
659. eyesontheweather
9. marraskuuta 2009 klo 20:36 (GMT)
Quoting Hurricane1956:
That is exactly what I mention quoting a patrap picture a few entries ago,that line coming from east to west looks very scary for all the east coast of Florida from the FLorida keys up North,we'll see what happens??.
is there high winds associated with this line?
Member Since: 25.08.2008 Posts: 0 Comments: 633
658. atmoaggie
9. marraskuuta 2009 klo 20:36 (GMT)
Ida is about to dip her to toes in cold water.

Member Since: 16.08.2007 Posts: 6 Comments: 12461
657. PcolaDan
9. marraskuuta 2009 klo 20:36 (GMT)
Member Since: 22.08.2008 Posts: 12 Comments: 6010
656. StormSurgeon
9. marraskuuta 2009 klo 20:35 (GMT)
175 mph wind in Mobile! Kidding of course. Starting to get a little windy.....lots of rain.
Member Since: 1.09.2007 Posts: 0 Comments: 1793
655. K8tina
9. marraskuuta 2009 klo 20:35 (GMT)
Just got back from a quick drive to check out the waves on Okaloosa Island. A little rainy and breezy out there. The waves look like a washing machine. No flooding on Hwy 98 but all the parks are closed (the pier was still open though not many ppl out on it). Took some pics w/my new camera and came home. Roads are pretty clear here in FWB but I'm sure that'll change as the afternoon & evening wear on and the heavy rains come ashore! ;)
654. mobilehurricane
9. marraskuuta 2009 klo 20:35 (GMT)
5-day plot - Wind Direction Wind Direction (WDIR): E ( 90 deg true )
5-day plot - Wind Speed Wind Speed (WSPD): 50.5 kts
5-day plot - Wave Height Wave Height (WVHT): 27.9 ft
5-day plot - Dominant Wave Period Dominant Wave Period (DPD): 9 sec
5-day plot - Air Temperature Air Temperature (ATMP): 73.2 °F
5-day plot - Dew Point Dew Point (DEWP): 71.6 °F still an easterly wind shows that the center has not passed this point
653. alaina1085
9. marraskuuta 2009 klo 20:35 (GMT)
Quoting Patrap:
Ida is VERY west Loaded with Wind,all the stronger Gusts seems to be in the LEFT semi Circle..
She is accelerating to the NNW really fast now

So you think shes going to come closer to home then expected?
Member Since: 2.08.2006 Posts: 0 Comments: 1240
652. PalmBeachWeather
9. marraskuuta 2009 klo 20:35 (GMT)
One says "East" one says "West" reminds me of Sunny Anderson one year ago, and now...East meets west and spreads out
Member Since: 3.10.2008 Posts: 0 Comments: 5750
651. HurricaneSwirl
9. marraskuuta 2009 klo 20:34 (GMT)
Quoting heavyweatherwatcher:
"Terrible" would be an upgrade to WUWA on TWC...


Even in all caps? Yeah, your right.

WUWA was the final straw for me hating TWC and I refuse to watch WeatherScan because it is TWC-powered. I come here for all of my weather needs.

So Ida's a Cat 1 again? 25 ft seas in a Cat 1? Could the energy from the merge do that?
Looks like im gonna get smacked by this. Actually, it looks like everybody in SE LA, Alabama, Mississippi, Georgia, Florida, Tennessee, and maybe South Carolina are gonna get smacked by this.
Member Since: 7.07.2008 Posts: 2 Comments: 3237
649. stormsurge39
9. marraskuuta 2009 klo 20:34 (GMT)
Quoting taco2me61:
Now the EMA just caaled my home phone and are setting up shelters for mobile....
Are you in the city limits or county?
648. IKE
9. marraskuuta 2009 klo 20:33 (GMT)
Quoting hurricanejunky:
The clear spot on the radar loop that looks like the COC isn't the COC, right? It's deceiving. Looking at it for a bit I gather it's moving due north maybe slightly east of north. Anyone else seeing this movement?


It may be nudging just a touch east of north or due north, for now.

Looks like Mobile to Pensacola is ground zero.
Member Since: 9.06.2005 Posts: 23 Comments: 37858
646. Patrap
9. marraskuuta 2009 klo 20:33 (GMT)
Ida is VERY west Loaded with Wind,all the stronger Gusts seems to be in the LEFT semi Circle..
She is accelerating to the NNW really fast now
Member Since: 3.07.2005 Posts: 414 Comments: 125613
645. StormSurgeon
9. marraskuuta 2009 klo 20:32 (GMT)
Quoting IKE:
Ida's coc coming into view on the 124NM Mobile radar....



She ain't done yet is she?
Member Since: 1.09.2007 Posts: 0 Comments: 1793
643. atmoaggie
9. marraskuuta 2009 klo 20:32 (GMT)
Tough to imagine Ida really maintain a hurricane structure given the appearance, open eyewall, lowering SSTs, and...
...no lightning. Only in the band stretching down the FL west coast.

Member Since: 16.08.2007 Posts: 6 Comments: 12461
642. Hurricane1956
9. marraskuuta 2009 klo 20:31 (GMT)
Quoting P451:


If she pulls Easterly then that could be a problem. I think we were discussing that potential scenario last night.

Quoting P451:


If she pulls Easterly then that could be a problem. I think we were discussing that potential scenario last night.

That is exactly what I mention quoting a patrap picture a few entries ago,that line coming from east to west looks very scary for all the east coast of Florida from the FLorida keys up North,we'll see what happens??.
Member Since: 28.08.2006 Posts: 0 Comments: 591
641. taco2me61
9. marraskuuta 2009 klo 20:31 (GMT)
Now the EMA just caaled my home phone and are setting up shelters for mobile....
Member Since: 7.07.2005 Posts: 6 Comments: 3173
639. stormsurge39
9. marraskuuta 2009 klo 20:30 (GMT)
Quoting IKE:
Ida's coc coming into view on the 124NM Mobile radar....

Ike have you heard that Ida is suppossed to slow down when it is closer to landfall?
638. Patrap
9. marraskuuta 2009 klo 20:30 (GMT)
Member Since: 3.07.2005 Posts: 414 Comments: 125613
637. dsenecal2009
9. marraskuuta 2009 klo 20:29 (GMT)
Quoting alaina1085:


Im in Pville as well and DITTO!


Over in Gonzales and the wind is picking up
Member Since: 25.09.2009 Posts: 0 Comments: 119
636. MakeAWishCast
9. marraskuuta 2009 klo 20:28 (GMT)
Quoting alaina1085:


Im in Pville as well and DITTO!


You look familiar!!

An attrative weather junkie... This girl is after my heart! Haha
635. Patrap
9. marraskuuta 2009 klo 20:28 (GMT)



Current Conditions

Boothville, Louisiana (Airport)

Updated: 36 min 15 sec ago
Light Rain
68 °F
Light Rain Mist
Humidity: 87%
Dew Point: 64 °F
Wind: 31 mph from the ENE

Wind Gust: 46 mph

Pressure: 29.86 in (Falling)

Visibility: 5.0 miles
UV: 1 out of 16
Clouds:
Mostly Cloudy 1900 ft
Mostly Cloudy 2400 ft
Overcast 2800 ft
(Above Ground Level)
Member Since: 3.07.2005 Posts: 414 Comments: 125613
634. hurricanejunky
9. marraskuuta 2009 klo 20:27 (GMT)
The clear spot on the radar loop that looks like the COC isn't the COC, right? It's deceiving. Looking at it for a bit I gather it's moving due north maybe slightly east of north. Anyone else seeing this movement?
Member Since: 28.08.2006 Posts: 6 Comments: 2895
633. LAnovice
9. marraskuuta 2009 klo 20:27 (GMT)
Can somebody please tell Ida - this is NOT a football game and she doesn't need to be a line-backer - Don't like how she fakes to the east - and then pops up a few steps west....
Member Since: 7.09.2007 Posts: 0 Comments: 361
632. TampaSpin
9. marraskuuta 2009 klo 20:27 (GMT)
I just posted an update on my blog at comment 29! I will be on my blog for now.
Member Since: 2.09.2007 Posts: 177 Comments: 20430
631. alaina1085
9. marraskuuta 2009 klo 20:26 (GMT)
Quoting MakeAWishCast:
Cloudy and dreary here in Prairieville, La.. Ida is makin' me wanna nap


Im in Pville as well and DITTO!
Member Since: 2.08.2006 Posts: 0 Comments: 1240
630. xcool
9. marraskuuta 2009 klo 20:26 (GMT)
Grand Isle Rushes To Repair Collapsed Levee
Member Since: 26.09.2009 Posts: 2 Comments: 15603
629. presslord
9. marraskuuta 2009 klo 20:26 (GMT)
Dauphin Island after Katrina
Link
Member Since: 13.08.2007 Posts: 0 Comments: 10458

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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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