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Ida takes aim at the U.S. Gulf Coast

By: Dr. Jeff Masters , 11:17 PM GMT on November 08, 2009

Hurricane Ida burst into the Gulf of Mexico as a Category 2 hurricane with 100 mph winds this afternoon, and is poised to deliver a solid blow to the U.S. Gulf Coast between Southeast Louisiana and the Florida Panhandle on Tuesday morning. Radar imagery out of Cancun reveals that Ida has retained its tight inner core this afternoon, with only limited rain bands affecting Mexico and western Cuba. Top winds at Cancun, Mexico today were only 15 mph, despite the fact that Ida passed just 60 miles east of the city. Infrared and visible satellite loops show little change in the intensity of Ida's heavy thunderstorms this afternoon, but the cloud pattern is beginning to become distorted due to strong upper-level winds from the southwest that are creating 20 - 25 knots of wind shear over the hurricane. Water vapor satellite imagery reveals a large area of dry air to the southwest of Ida, but this dry air has not yet intruded into Ida's core. The latest 5:30 pm EST vortex report from the Hurricane Hunters showed that the central pressure had risen 1 mb, to 977 mb, but that the surface winds were still near 100 mph. They noted that the eyewall was open to the east, a sign that Ida's inner core may be in trouble.


Figure 1. MODIS satellite image from NASA's Terra spacecraft, taken at 1:35 pm EST 11/08/09. Image credit: NASA.

The intensity forecast for Ida
The high wind shear of 20 - 25 knots currently affecting Ida is forecast to persist at that level until Monday night. With the storm now beginning to show a distortion of the cloud pattern due to this shear, it would not be a surprise of the shear managed to inject some dry air into Ida's core Monday morning, significantly weakening the storm. Aiding this process will be cooler waters. Early Monday morning, Ida will be crossing over waters of 26°C, which is barely enough to support a hurricane. By Monday night, wind shear is expected to increase to 40 knots, which ordinarily would begin to tear the storm apart. This wind shear is due to an extratropical low pressure system over the western Gulf of Mexico, and this low will begin dumping cold, stable air into Ida Monday night through Tuesday. This will cause Ida to begin transitioning to an extratropical storm, and it is possible that during the transition Ida's winds will die down relatively slowly, despite the wind shear. The intensity forecast has a high amount of uncertainty, and I wouldn't be surprised at a landfall strength anywhere in the range of 45 mph - 80 mph. My personal best guess is a 50 - 60 mph tropical storm at landfall. Regardless of Ida's strength at landfall, the storm will be able to dump 4 - 8 inches of rain along the Gulf Coast, from New Orleans to Panama City. Isolated tornadoes will also be possible, primarily to the right side of Ida's track.


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 probably be weaker, so surges will not be this high. 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 will drive tides 3 - 5 feet above normal from New Orleans to the Florida Panhandle tonight. As Ida approaches on Monday, an additional rise in water will occur, and a large stretch of coast will be subject to very high water levels for an extended period of time. With battering waves building Monday afternoon into Tuesday morning, a significant coastal erosion event is shaping up. A particular concern is the western end of Alabama's Dauphin Island, where storm surges from four hurricanes over the past fifteen years have caused heavy damage to the low-lying heavily developed island. If Ida makes a direct hit on Mobile Bay as a Category 1 hurricane with 85 mph winds, a storm surge of up to six feet is possible there, assuming the storm hits at mean tide. The tidal range along the Gulf Coast varies by about 1.5 feet between low and high tide (Figure 3). High tide is near 2 am EST on Tuesday, but the official NHC forecast currently has the storm hitting between 6 am - 9 am, when the tide will be going out, so the storm may indeed be hitting at about mean tide.


Figure 3. The tide forecast for the Gulf Coast calls for high tide to occur around 2 am EST Tuesday morning. Ida is expected to hit later that morning, while the tide is going out.

I'll have an update Monday morning.

Links to follow:

U.S. Severe Weather Page
Cancun radar

Jeff Masters

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Quoting P451:
Here she goes again....one more attempt at intensification. Looking better.



so far so good...
Member Since: September 6, 2009 Posts: 2 Comments: 4249
Quoting IKE:


Hopefully it will weaken to what Dr. Masters is calling for...on the low end.

I could handle that.


I would like it too, though I wouldn't mind a day of classes being canceled, though I do love my classes so... hmmmm LOL.

seriously, weaker would be nice.
Member Since: September 6, 2009 Posts: 2 Comments: 4249
any ideas on why schools haven't reported closings? local met in Mob/Pensacola area seems to be concerned about the winds and up to 6' inches of rain. Wouldn't that warrant school closings?
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Where is the trough right now
TIA
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Quoting Orcasystems:
I love multiple blog days :)

Haha, me too. Its like Christmas.
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Are my eyes tired or is the COC headed east of the next forecast point on sat again?
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34. IKE
Quoting ElConando:
Ike i'd say at the current motion Ida made make a closer swipe at both of us.


Hopefully it will weaken to what Dr. Masters is calling for...on the low end.

I could handle that.
Member Since: June 9, 2005 Posts: 23 Comments: 37938
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Quoting nrtiwlnvragn:


The wind speed reported was 46 knots, so subtract 4 mb. If a drop in the eye results in 100 knots, you did not drop it in the eye.


oh nvm *big facepalm* sry that measurement is fine. I thought you were doing something else really sorry.
Member Since: September 6, 2009 Posts: 2 Comments: 4249
Ida definitely weakening expect a Cat 1 at 7PM.
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We have a self sufficient kitchen capable of serving 2000 meals per day enroute to the Destin area...and another at our disposal within 24 hours...and up to four crew prepared to leave within 36 hours...a truck load of durable medical equipment and clinical/surgical supplies sits ready at our Atlanta warehouse ready to travel...

Please...give early...and give often...
Link
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Quoting ElConando:



That is too crude lol no offense. You could get a 995mb 100k system.


The wind speed reported was 46 knots, so subtract 4 mb. If a drop in the eye results in 100 knots, you did not drop it in the eye.
Member Since: September 23, 2005 Posts: 19 Comments: 12176
SE U.S., Gulf of Mexico Marine Weather





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Everyone should check out crown's website www.crownweather.com. His thoughts are that it won't die down quite as much as what Dr. Masters is forecasting.
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I love multiple blog days :)
Member Since: October 1, 2007 Posts: 81 Comments: 26525
Thanks Doc.

Previous:
Quoting DestinJeff:
i think many are hanging their hat on the "extra-tropical" nature of Ida at some point .. the important thing to remember is that, say, 80 MPH wind in an extra-tropical system is no different than that of a tropical system

if it makes you sleep better thinking "extra-tropical" means no big deal, cool, but just know that the wind doesn't know the difference and neither does the surf/tides

Actually a broadening TS-force windfield could be far worse than a relatively small 80 mph cane.
Member Since: August 16, 2007 Posts: 6 Comments: 12463
Ike i'd say at the current motion Ida made make a closer swipe at both of us.
Member Since: September 6, 2009 Posts: 2 Comments: 4249
Recon going home in about 30 minutes or so. Probably will go back in soon.
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22. IKE
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOBILE AL
319 PM CST SUN NOV 8 2009

.SHORT TERM...(TONIGHT THROUGH TUESDAY) QUITE A COMPLEX AND
CHALLENGING FORECAST WITH THE APPROACH OF HURRICANE IDA. HURRICANE
IDA HAS SLOWLY STRENGTHENED FOR MUCH OF THE DAY WITH THE SYSTEM
LOOKING IMPRESSIVE ON SATELLITE AND CANCUN RADAR. HOWEVER...THE LAST
FEW SATELLITE PICTURES SHOW A LITTLE MORE RAGGED CONVECTIVE ENVELOPE
WITH SIGNS OF SOUTHERLY SHEAR MAY BE STARTING TO AFFECT THE SYSTEM.

IDA IS FORECAST TO LEVEL OFF IN INTENSITY THIS EVENING AS IT
CONTINUES NORTH NORTHWESTWARD INTO THE GULF OF MEXICO. WEAKENING IS
STILL EXPECTED AS WE PROGRESS THROUGH THE DAY MONDAY AS IDA
APPROACHES MUCH COOLER GULF WATERS. IN ADDITION...UPPER LEVEL WINDS
WILL BEGIN TO BECOME MORE HOSTILE AS AN UPPER LEVEL TROUGH OVER
WESTERN TEXAS MOVES EAST TOWARD THE GULF. THIS SAME UPPER LEVEL
TROUGH WILL CONTINUE TO SEND IDA NORTHWARD AND IT IS EXPECTED TO
APPROACH THE NORTHERN GULF COAST BY LATE MONDAY NIGHT/EARLY TUESDAY
MORNING. THE BIG QUESTION MARK IS HOW FAST DOES IDA WEAKEN AND WILL
IT MAINTAIN TROPICAL CHARACTERISTICS AS IT APPROACHES OUR AREA?
THERE ARE DEFINITELY SOME MIXED SIGNALS OUT THERE AND FORECASTING
EXTRATROPICAL TRANSITION IS ALWAYS CHALLENGING. THE GFS HAS
DEVELOPED AN INTERESTING SCENARIO WHERE IT FORECASTS A BAROCLINIC
LOW TO DEVELOP IN THE WESTERN GULF TOMORROW...WHICH IN TURN HANGS UP
THE EASTWARD MOVING COLD FRONT. THIS ALLOWS IDA TO SHOOT
NORTH...REMAINING IN THE WARM SECTOR AND DELAYING A TRANSITION. IN
FACT...THE CYCLONE PHASE DIAGRAM CHART FROM THE GFS REVEALS THE MODEL
MAINTAINING A TROPICAL SYSTEM UP UNTIL LANDFALL. HOWEVER...EVEN WITH
THE TROUGH HOLDING BACK...THE COOLER WATER...COOLER DRIER
CONTINENTAL AIR...AND INCREASING SHEAR WOULD SUGGEST THE SYSTEM MAY
BEGIN TO LOSE ITS TROPICAL FEATURES. TO MAKE IT EVEN MORE
COMPLICATED...THE HURRICANE WILL BEGIN TO INTERACT WITH A STRONG
UPPER LEVEL JET STREAK TO ITS NORTH...WHICH MAY SERVE AS A STRONG
POLEWARD OUTFLOW...HELPING TO MAINTAIN ITS INTENSITY.
ALL IN ALL...IT
IS GOING TO BE A VERY CLOSE CALL AND THE POSSIBILITY OF THIS SYSTEM
MAINTAINING THE PUNCH OF A CATEGORY ONE HURRICANE IS HIGH ENOUGH TO
WARRANT THE ISSUANCE OF A HURRICANE WATCH FOR OUR ENTIRE COAST.

IT SHOULD BE NOTED THAT IF INDEED IDA BECOMES EXTRATROPICAL...WE ARE
STILL LOOKING AT A SIGNIFICANT WIND AND COASTAL FLOODING IMPACT. AS
IDA TRANSITIONS...ITS WIND FIELD WILL BROADEN AND THE GRADIENT
BETWEEN IDA AND THE HIGH TO OUR NORTH WILL PUT US IN QUITE THE
`SQUEEZE PLAY`...RESULTING IN STRONG GRADIENT WINDS. GIVEN THE
POSSIBILITY OF SIGNIFICANT WINDS SPREADING INLAND...HAVE ALSO ISSUED
A INLAND TROPICAL STORM WIND WATCH FOR INLAND ZONES. IT IS IMPORTANT
TO STRESS NOT TO FOCUS ON WHETHER THIS IS TROPICAL OR NON TROPICAL.
INSTEAD...PREPARE FOR THE WINDS AND POTENTIAL COASTAL FLOODING
REGARDLESS. PLEASE REFER TO OUR HURRICANE LOCAL STATEMENTS FOR
SPECIFIC INFORMATION REGARDING THE THREATS ASSOCIATED WITH IDA.

TONIGHT LOOKS MOSTLY DRY WITH JUST INCREASING CLOUDS AND WINDS AS
THE PRESSURE GRADIENT BEGINS TO TIGHTEN. REALLY RAMP UP POPS BY
TOMORROW AFTERNOON WITH ALL ZONES CATEGORICAL TOMORROW NIGHT WITH
THE STORM APPROACHING THE COAST. HEAVY RAIN CERTAINLY A THREAT WITH
TOTALS OF 2-4 INCHES WITH ISOLATED 6 INCHES POSSIBLE. SINCE FLASH
FLOOD GUIDANCE IS RATHER HIGH...HAVE DECIDED TO HOLD OFF ON A FLASH
FLOOD WATCH FOR NOW. LATEST NHC TRACK HAS THE REMNANTS OF IDA
SHIFTING EAST OF THE AREA ON TUESDAY...AND WILL FOLLOW SUIT ON
REDUCING POPS FROM WEST TO EAST THROUGH THE DAY. STUCK CLOSE TO MOS
TEMPS THROUGH PERIOD.
Member Since: June 9, 2005 Posts: 23 Comments: 37938
Quoting nrtiwlnvragn:


Not a met, but the general rule of thumb is subtract 1 mb for each 10 knot.



That is too crude lol no offense. You could get a 995mb 100k system.
Member Since: September 6, 2009 Posts: 2 Comments: 4249
some rough stuff coming up offshore of Galveston...

Tonight
Northeast winds around 25 knots. Seas 8 to 10 feet. Showers and thunderstorms likely.

Monday
North winds 20 to 25 knots. Seas 9 to 11 feet. A chance of thunderstorms in the morning. A chance of showers. Isolated thunderstorms in the afternoon.

Monday Night
North winds 20 to 25 knots. Seas 7 to 10 feet.

Tuesday
North winds around 20 knots. Seas 6 to 9 feet.

Tuesday Night
North winds 20 to 25 knots. Seas 6 to 8 feet.

Wednesday
North winds 15 to 20 knots. Seas 5 to 7 feet.

Wednesday Night
Northeast winds 10 to 15 knots. Seas 4 to 6 feet.

Thursday
Northeast winds 10 to 15 knots decreasing to 5 to 10 knots in the afternoon. Seas 3 to 5 feet.

Thursday Night
East winds 5 to 10 knots becoming southeast after midnight. Seas 3 to 4 feet.
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Ida now moving N.

*355.10°........ as of where the lowest pressure is from where it was last.
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Thanks DRM.
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Quoting amd:
Repost from last blog:

I found this a bit interesting:

Question for the pro mets:
The latest vortex found a pressure of 977 mb due to a dropsonde report. However the same dropsonde measured winds from the NNW at 53 mph (46 kts). Wouldn't this suggest that the central pressure is actually a couple of mb's lower?

Information from that dropsonde:
Level: 977mb (28.85 inHg)
Geo. Height: Sea Level (Surface)
Air Temp.: 26.8°C (80.2°F)
Dew Point: 26.1°C (79.0°F)
Wind Direction: 330° (from the NNW)
Wind Speed: 46 knots (53 mph)


Not a met, but the general rule of thumb is subtract 1 mb for each 10 knot.
Member Since: September 23, 2005 Posts: 19 Comments: 12176
Quoting stormy2008:
977.7 mb
(~ 28.87 inHg)

74 knots
(~ 85.1 mph)
Vortex should show a pressure of about 978 or so.
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Quoting aquak9:
slide-crash-boom

made the hyper-jump safely, whew

LOL!
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nevermind guess Florida is in the clear for the most part lol

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Appear that base on the latest center fix... that it's trying to have a more northerly track.
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Quoting aquak9:
slide-crash-boom

made the hyper-jump safely, whew


LOL
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10. amd
Repost from last blog:

I found this a bit interesting:

Question for the pro mets:
The latest vortex found a pressure of 977 mb due to a dropsonde report. However the same dropsonde measured winds from the NNW at 53 mph (46 kts). Wouldn't this suggest that the central pressure is actually a couple of mb's lower?

Information from that dropsonde:
Level: 977mb (28.85 inHg)
Geo. Height: Sea Level (Surface)
Air Temp.: 26.8°C (80.2°F)
Dew Point: 26.1°C (79.0°F)
Wind Direction: 330° (from the NNW)
Wind Speed: 46 knots (53 mph)
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Thank you Dr.M!
Member Since: September 6, 2009 Posts: 2 Comments: 4249
slide-crash-boom

made the hyper-jump safely, whew
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Thx for the update...
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977.7 mb
(~ 28.87 inHg)

74 knots
(~ 85.1 mph)
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thanks Jeff!
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Thanks Dr. Jeff!
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Thanks
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