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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428. srada
Good Afternoon everyone..Just watched that Bastardi video posted in the blog and I of course live on the coast of NC in Wilm..usually he is hyped up about noreasterns but he is really calling for a bad storm our way if the low of IDA vamps up according to the UKMET model..I just hope everyone keeps safe along this storms path
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what a difference looking at the water vapor and the radar, almost looks like different storms.
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just saw some footage of a pier on TWC...waves all the way to the bottom of the top if that makes sense...overspray is over the pier...no roller coaster on earth would be near what that ride would be today...
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Clearly a defined eye on radar.
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Quoting MahFL:
StormW you have a spelling mistake in your forcast, we are all doomed !!!!!
LOL
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Mississippi canyons buoy 52.4 kts sustained (60.3 mph for you math challeged) with waves at 24.6ft. I think the COC is already past that bouy???
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Quoting rareaire:
About half the folks on this site are in that business!!


Yes they are. I wonder where my friend Ron is Floodman. I figured he would be on today. Well he was earlier for a minute or two.

Sheri
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Quoting IKE:


Moving northward for now.
Member Since: September 6, 2009 Posts: 2 Comments: 3759
Quoting catastropheadjuster:


LMAO I about choked on my M&M when I read this. You made a funny. LOL

They just said on the news Mobile County Just declared State of Emergency.


My puter screen just got a shot of Mt. Dew...roflmao
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Look, a pinhole eye...LOL

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Quoting catastropheadjuster:


me to.

Sheri
About half the folks on this site are in that business!!
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417. IKE
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting JUSTCOASTING:


Central I have the same type of job..


me to.

Sheri
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I think Ida is running our of real estate and high SST to get much stronger.
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Quoting rareaire:
So if you live on the south coast 60 to 75 mph winds sustained are no big deal? No being trite just thats the 3rd time someone has said that. I see that headed my way im taking it serious but then i dont live on the coast!


Steady light rain in Mobile. Blustery and rainy tonight....ho hum. Just don't drive through any rain swollen creeks and all will be fine.
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I went by my house for lunch and noticed that Tampa Bay is higher than usual. I don't think anything will flood, but still an interesting observation.
Member Since: April 26, 2009 Posts: 3 Comments: 3667
Quoting atmoaggie:

Yeah. Tough to describe...and don't have the time at the moment to figure out how to draw an arrow on an animated gif...


Or you could just move your cursor over the vortex message coordinates using the NWS radar to determine the position :)
Member Since: October 28, 2006 Posts: 57 Comments: 30562


AOI

AOI

AOI

AOI

TS BUSTED FORECAST, to be used in the event you make a minor discrepancy in your forecast.
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Quoting ConchHondros:


LMAO...DrNo couldnt hold Floods jockstrap..that would be like..well...poking a bear with a toothpick...what a maroon (with a bugs accent)


LMAO I about choked on my M&M when I read this. You made a funny. LOL

They just said on the news Mobile County Just declared State of Emergency.
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409. MahFL
StormW you have a spelling mistake in your forcast, we are all doomed !!!!!
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Quoting rareaire:
So if you live on the south coast 60 to 75 mph winds sustained are no big deal? No being trite just thats the 3rd time someone has said that. I see that headed my way im taking it serious but then i dont live on the coast!


Its those new 100 foot pine tree proof houses they are building now...
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Just want a little rain here in Tallahassee... Been dry lately so a little rain and wind wouldn't be so bad. Rain shield is off to our west by a county or two and slowly moving our way.
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Quoting centralflaman:
Well this was the last chance for all the insurance adjusters and roofers to make some money this year. My brother is an insurance adjuster and has one of those jobs that needs mother nature to make money. I told him his job was like the guy who bets the dont pass line on the craps table. Going against everyone else. lol


Central I have the same type of job..
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come in around Mobile Bay
That's where the NHC track puts it now.
Member Since: August 18, 2006 Posts: 0 Comments: 188
Quoting Joshfsu123:


I just looked again and it looks like you were right... seems to be the center and there was a smaller vortex rotating around the bigger center.

If it moved due north the rest of the way, it would come in around Mobile Bay..


but I could also be wrong.
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So if you live on the south coast 60 to 75 mph winds sustained are no big deal? No being trite just thats the 3rd time someone has said that. I see that headed my way im taking it serious but then i dont live on the coast!
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Bastardi video from today
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401. IKE
Quoting Joshfsu123:


I just looked again and it looks like you were right... seems to be the center and there was a smaller vortex rotating around the bigger center.

If it moved due north the rest of the way, it would come in around Mobile Bay..


We'll be able to tell better as the afternoon moves along...
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting IKE:


After looking at the radar again, I'm not convinced I'm not right, but I definitely could be wrong.


I just looked again and it looks like you were right... seems to be the center and there was a smaller vortex rotating around the bigger center.

If it moved due north the rest of the way, it would come in around Mobile Bay..
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Quoting BurnedAfterPosting:


Center is on the very southern end of the radar. As Drak said it is not the clear spot north of it

Yeah. Tough to describe...and don't have the time at the moment to figure out how to draw an arrow on an animated gif...
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Quoting catastropheadjuster:


you was here trying to start trouble with Floodman earlier BR>
Sheri


LMAO...DrNo couldnt hold Floods jockstrap..that would be like..well...poking a bear with a toothpick...what a maroon (with a bugs accent)
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Dauphin Island, AL impact head on.....stinks because the west end has in no way recovered from Katrina. Overwash is certain with 6' surge and T.S. winds. Glad we went down and took care of our property yesterday. Rainy, blustery night in Mobile, but nothing serious.....just entertaining....I hate raking!
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tide starting to go up here, normally would be on the downswing at this time
Link
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Quoting atmoaggie:
I think whomever that was is correct. This is the eye at the south end of the radar. Still clear (by radar) though it has never (?) been fully cleared by satellite.



Center is on the very southern end of the radar. As Drak said it is not the clear spot north of it
Quoting IKE:
Buoy at 28.8N and 86W.....

Wind Direction (WDIR): E ( 100 deg true )
5-day plot - Wind Speed Wind Speed (WSPD): 36.9 kts
5-day plot - Wind Gust Wind Gust (GST): 46.6 kts

5-day plot - Wave Height Wave Height (WVHT): 18.0 ft
5-day plot - Dominant Wave Period Dominant Wave Period (DPD): 11 sec
5-day plot - Average Period Average Period (APD): 7.2 sec
5-day plot - Atmospheric Pressure Atmospheric Pressure (PRES): 29.90 in
5-day plot - Pressure Tendency Pressure Tendency (PTDY): -0.11 in ( Falling Rapidly )

5-day plot - Air Temperature Air Temperature (ATMP): 70.7 °F
5-day plot - Water Temperature Water Temperature (WTMP): 77.7 °F
5-day plot - Dew Point Dew Point (DEWP): 70.0 °F


That buoy must be surprised.
Member Since: September 6, 2009 Posts: 2 Comments: 3759
I think whomever that was is correct. This is the eye at the south end of the radar. Still clear (by radar) though it has never (?) been fully cleared by satellite.

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392. IKE
Quoting Joshfsu123:


Yep, the clear spot is dry air... the center is to it's south and is moving N/NNE.


After looking at the radar again, I'm not convinced I'm not right, but I definitely could be wrong.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting DrNo:
There are shenanigans here...

When using Dr. Masters' blog, please refrain from posting material not relevant to the discussion of tropical weather, or the topic of the blog entry itself. Please do not engage in personal attacks or bickering. Material not conforming to these standards should be flagged with the "!" button and ignored.


you was here trying to start trouble with Floodman earlier why don't you read what you write and do what it says then we will all be just fine. Sew what you reep. You like to start trouble we have been doing just fine all day with out your input. See ya. !!!!!!!!

Sheri
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Quoting IKE:
Think I got her COC on Mobile long-range radar now...



Wow, this makes her easy to watch.
Member Since: April 26, 2009 Posts: 3 Comments: 3667
388. IKE
Buoy at 28.8N and 86W.....

Wind Direction (WDIR): E ( 100 deg true )
5-day plot - Wind Speed Wind Speed (WSPD): 36.9 kts
5-day plot - Wind Gust Wind Gust (GST): 46.6 kts

5-day plot - Wave Height Wave Height (WVHT): 18.0 ft
5-day plot - Dominant Wave Period Dominant Wave Period (DPD): 11 sec
5-day plot - Average Period Average Period (APD): 7.2 sec
5-day plot - Atmospheric Pressure Atmospheric Pressure (PRES): 29.90 in
5-day plot - Pressure Tendency Pressure Tendency (PTDY): -0.11 in ( Falling Rapidly )

5-day plot - Air Temperature Air Temperature (ATMP): 70.7 °F
5-day plot - Water Temperature Water Temperature (WTMP): 77.7 °F
5-day plot - Dew Point Dew Point (DEWP): 70.0 °F
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Or you could just print this :)

KTS to MPH 5 Knots = 5.8 MPH
10 Knots = 11.5 MPH
15 Knots = 17.3 MPH
20 Knots = 23.0 MPH
25 Knots = 28.8 MPH
30 Knots = 34.6 MPH
35 Knots = 40.3 MPH
40 Knots = 46.1 MPH
45 Knots = 51.8 MPH
50 Knots = 57.6 MPH
55 Knots = 63.4 MPH
60 Knots = 69.1 MPH
65 Knots = 74.9 MPH
70 Knots = 80.6 MPH
75 Knots = 86.4 MPH
80 Knots = 92.2 MPH
85 Knots = 97.9 MPH
90 Knots = 103.7 MPH
95 Knots = 109.4 MPH
100 Knots = 115.2 MPH
105 Knots = 121.0 MPH
110 Knots = 126.7 MPH
115 Knots = 132.5 MPH
120 Knots = 138.2 MPH
125 Knots = 144.0 MPH
130 Knots = 149.8 MPH
135 Knots = 155.5 MPH
140 Knots = 161.3 MPH
145 Knots = 167.0 MPH
150 Knots = 172.8 MPH
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Quoting Drakoen:
Her center is on the southern most portion of the radar Ike posted. It is not that clear spot.


Yep, the clear spot is dry air... the center is to it's south and is moving N/NNE.
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Quoting StormW:


How about just multiplying by 1.1516.


I can't do that in my head
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Quoting atmoaggie:
360:
When using Dr. Masters' blog, please refrain from posting material not relevant to the discussion of tropical weather, or the topic of the blog entry itself. Please do not engage in personal attacks or bickering. Material not conforming to these standards should be flagged with the "!" button and ignored.

That is the only remotely useful post I have ever seen from you. Can't you come up with anything at all to say related to tropical weather or are you really limited to self-appointed blog policeman?


+500 lol
They just said Satsuma High School and Burns is gonna be shelters and Mobile County Schools will be letting out at 1pm today and will not go back til thursday. Will be out for Veterans Day.. It is showing on the news people in the water at Pensacola Beach. Oh yeah they just said they have a shelter in Pensacola at a work release place for bad people.

Sheri
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Quoting StormChaser81:
Or to make it easier here's a knots to mile per hour converter.

Knots to mile per hour converter

Or you could get a $300,000 256-processor Linux cluster and build a program that calculates knots to mph really fast.
Or, we can all just find our own ways to compute mph x 1.15=knots
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378. IKE
Quoting atmoaggie:
360:
When using Dr. Masters' blog, please refrain from posting material not relevant to the discussion of tropical weather, or the topic of the blog entry itself. Please do not engage in personal attacks or bickering. Material not conforming to these standards should be flagged with the "!" button and ignored.

That is the only remotely useful post I have ever seen from you. Can't you come up with anything at all to say related to tropical weather or are you really limited to self-appointed blog policeman?


+1.
Member Since: June 9, 2005 Posts: 23 Comments: 37858

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