Karl near hurricane strength; Igor intensifying again

By: Dr. Jeff Masters , 2:00 PM GMT on September 16, 2010

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Tropical Storm Karl is back over water after popping off the coast of Mexico's Yucatan Peninsula early this morning. Despite being a small storm, Karl managed to keep a remarkable degree of organization during its crossing of the Yucatan. Karl has already regained all of its lost strength, and is near hurricane intensity. A Hurricane Hunter aircraft is currently in Karl, and at 8:47am EDT found winds at 5,000 feet of 85 mph, which suggest winds near 65 - 70 mph were occurring at the surface. The aircraft noted that Karl had built an eyewall that was open on the north-northeast side. The eye is now apparent in both visible and infrared satellite imagery. Mexican radar out of Alvarado shows the outer spirals bands of Karl are approaching the coast near Veracruz, and heavy rains of 2 - 4 inches can be expected today along much of Mexico's Bay of Campeche coast.

Figure 1. Image from NASA's Terra satellite taken at 12:40pm EDT Wednesday September 15, 2010 of Tropical Storm Karl over the Yucatan Peninsula. Image credit: NASA.

Forecast for Karl
Conditions for intensification are ideal in the Gulf of Mexico's Bay of Campeche, with wind shear expected to be low, 5 - 10 knots, SSTs warm, 29°C - 30°C, and the atmosphere very moist. These conditions, combined with the topography of the surrounding coast which tends to enhance counter-clockwise flow, should allow Karl to intensify into a Category 2 hurricane before making landfall between Tampico and Vercruz, Mexico Friday morning. NHC is giving Karl a 7% chance of reaching Category 3 strength, but the recent data from the Hurricane Hunters suggest that these odds are higher, perhaps 30%. The 06Z (2 am EDT) run of the GFDL model makes Karl a strong Category 2 hurricane with 105 - 110 mph winds at landfall Friday, and this is a reasonable forecast. Karl is a small storm, and is unlikely to bring any rain or wind to Texas.

Figure 2. Forecast swath of maximum winds from Karl, as predicted by the GFDL model on its 2am EDT (6Z) run this morning. The GFDL is predicting a 50-mile wide stretch of the Mexican coast will receive Category 1 (yellow colors, 64+ knots) or Category 2 (orange colors, 83+ knots) winds. Image credit: Morris Bender, NOAA/GFDL.

Hurricane Igor completed an eyewall replacement cycle early this morning, and has been intensifying. Igor is headed west-northwest to northwest at 7 mph, and this motion will carry the core of the hurricane close to NOAA buoy 41044 between 9 - 11 pm EDT tonight. Top winds at the buoy so far today have been 52 mph, gusting to 65, with a significant wave height of 32 feet (the significant wave height is the average height of the highest 1/3 of the waves.) The Hurricane Hunters are scheduled to make their first flight into Igor this afternoon, and we will see then exactly how strong Igor is. Satellite imagery shows that Igor looks a bit ragged on its north side, but the northern eyewall is getting stronger, and the eye is clearing out and contracting--signs of strengthening.

Figure 3. Morning satellite image of Igor.

Intensity forecast for Igor
Wind shear is low to moderate, 5 - 15 knots, and is expected to remain in this range through Saturday morning. Waters are warm, 29°C, and will remain 29°C through Saturday morning. Igor is well armored against any intrusions of dry air for at least the next two days. These conditions should allow Igor to remain at major hurricane status through Saturday afternoon. It is possible the hurricane will undergo another eyewall replacement cycle on Friday or Saturday, where the eyewall collapses and a new eyewall forms from an outer spiral band. This will weaken the hurricane by 10 - 20 mph if it occurs, but Igor may regain its lost intensity once the cycle is over, as it has done after the two eyewall replacement cycles it has already undergone. By Saturday morning, 36 hours before the core of Igor is expected to pass Bermuda's latitude, the trough of low pressure steering Igor northwestwards should bring moderate wind shear of 10 - 20 knots to the storm, potentially weakening Igor. The SHIPS models predicts shear will not rise to the high range, 20 - 30 knots, until after the hurricane reaches the island. Igor will also be tracking over cooler 28°C waters during this period, and substantial weakening by perhaps 20 - 30 mph can be expected about the time Igor arrives at Bermuda. Igor will still probably be at least a Category 2 hurricane on its closest pass by Bermuda on Sunday night, and perhaps a Category 3 storm. NHC is giving Bermuda a 21% chance of experiencing hurricane force winds from Igor, but this probability is likely too low. The Bermuda Weather Service is calling for Category 1 or 2 hurricane conditions for the island on Sunday, with 20 - 30 foot waves in the offshore waters.

Igor's impact on Bermuda
The track forecast for Igor remains unchanged. Igor is moving west-northwest, in response to the steering influence of a broad trough of low pressure moving across the Western Atlantic. This trough will steer Igor to the northwest and north over the next three days, bringing the core of the storm very close to Bermuda late Sunday night. Igor is a huge storm, and tropical storm force winds extend out 270 miles to the north of its center. As the hurricane moves north, it will expand in size, as it takes advantage of the extra spin available at higher latitudes due to Earth's rotation. By Saturday night, Igor's tropical storm force winds are expected to extend outwards 310 miles from the center. Igor will be moving at about 11 - 13 mph during the final 24 hours of its approach to Bermuda, so that island can expect a period of 39+ mph tropical storm force winds to begin near midnight Saturday night--a full 24 hours before the core of Igor arrives. Igor will speed up to about 15 mph as it passes Bermuda near midnight Sunday night. Hurricane force winds will probably extend out about 60 miles from the center then, and the island can expect to be pounded by hurricane force winds for up to 6 - 8 hours if the core of the hurricane tracks over the island. In all, Bermuda is likely to suffer a remarkably long 36-hour period of tropical storm force winds, with the potential for many hours of hurricane force winds. Long-duration poundings like this are very stressful for buildings, and there is the potential for significant damage on Bermuda.

Igor's impact on the rest of the Atlantic
The models have been in substantial agreement over multiple runs that Igor will miss the U.S. and Canadian coasts--with the possible exception of southeast Newfoundland, which the ECMWF model predicts could see a close pass by Igor. The chief danger to the U.S. and Canada will come in the form of high waves. Large swells from Igor have arrived in the Northern Lesser Antilles Islands and Puerto Rico, and will spread westwards over the next few days. By Saturday, much of the East Coast from northern Florida to Cape Cod Massachusetts can expect waves of 3 - 4 meters (10 - 13 feet), causing dangerous rip currents and significant beach erosion. These waves will continue through Sunday then gradually die down. The latest NOAA marine forecast for Cape Hatteras, North Carolina calls for 7 - 10 foot waves on Saturday, and 9 - 13 foot waves on Sunday.

Hurricane Julia put on a remarkable and unexpected burst of intensification yesterday morning to become the season's fourth Category 4 storm, but is now on a long steadily decline in intensity. The hurricane is currently over waters right at the lower limit for maintaining a hurricane, 26.5°C (80°F), and is undergoing high shear of 20 - 25 knots. While the shear will abate tonight and the water will warm some, Julia is headed towards some very hostile upper-level winds beginning on Friday. These strong winds, courtesy of the upper level outflow from Hurricane Igor, will bring 30 - 45 knots of wind shear to Julia Friday night through Sunday. The high shear should be enough to rapidly weaken Julia over the weekend. Julia is not expected to threaten any land areas.

Elsewhere in the tropics
The ECMWF model develops a new tropical depression a few hundred miles off the coast of Africa 2 - 4 days from now. The GFS and NOGAPS models are suggesting the eastern Caribbean could see a strong tropical disturbance form 6 - 7 days from now.

I'll have an update this afternoon.

Jeff Masters

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Pressure from Igor is 940

winds are 95 knts according to Recon
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431. Kearn
Karl is still a strong system, it is dragging half of its heavy thunderstorms over land and managed to become a hurricane again. I see this thing as a Cat 2-3 when it makes landfall...
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Quoting ClearH2Ostormchaser:
Hey Reed I have a question for you can i WU email you and if so how.

Go to my blog and click contact this blogs author.
Member Since: July 1, 2008 Posts: 13 Comments: 7437
Potential Bermuda response to IgorLink
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Quoting unf97:
Karl is intensifying very quickly at the moment. We probably will begin to see the eye on satellite imagery within the next 12 hours just prior to landfall.

I concur as the Land Topography,SST's,Shear all favor more development.

Where He crosses will be a Wild ride
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Quoting StormSurgeon:

Yuo have a quick link to that Tampa?
Quoting clwstmchasr:

How long can we continue to keep these storms away from us? It seems like for 25 years I've been worried that this is our year. 1921 was a long time ago.

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Quoting StormJunkie:

Go to the NCEP page under models. Click Western N Atlantic above the table, then select upper air graphics. The one I posted is the 850mb vorticity map.

I don't found the part "upper air graphics"
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Quoting 7544:
igor drifting west again ?

I believe the NHC got tired of all the phone calls and is now calling the intermittent westward movements post-EWRC "wobble" Hehe
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422. unf97
Karl is intensifying very quickly at the moment. We probably will begin to see the eye on satellite imagery within the next 12 hours just prior to landfall.
Member Since: September 25, 2007 Posts: 0 Comments: 1193
IGOR Floater - Rainbow Color Infrared Loop

TFP's are available
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recon close to igors eye
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Quoting TampaSpin:
The GFS long term run looks scary as hell......OUCH! Remember the Gods protect Tampa!

Yuo have a quick link to that Tampa?
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Impressive CDO with the Storm in RGB

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If Igor is only traveling 7 MPH, how is he going to catch up with the troughs off the EC? Maybe the NW turn is just temporarily. Someone mentioned in there post the Igor is drifting west. Even the NHC mentioned some wobbling taking place. Hmmmmm, don't like the sounds of it.
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Seems Karl has deepened more if the Pressure is correct.

A small compact Hurricane Heading West is going to come ashore in Mexico.

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The GFS long term run looks scary as hell......OUCH! Remember the Gods protect Tampa!
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The mission into Igor is nearing the center. The last burst found pressure down to 941.2 MB. Might go a little lower, but that reading was taken with low winds, so it's in the ballpark. The highest winds in the southwestern eyewall were recorded by SFMR at 80kts.
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+1000 and it won't get banned since I am now going to say, Those are really high SST's in the GOM!
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Quoting asgolfr999:

Now THATS wishcasting

Especially for someone hanging out on a blog...
Member Since: August 26, 2006 Posts: 16 Comments: 4766
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Thank God for the persistent blocking ridge over the SE US keeping Karl away, but can someone put in an order for enough of a weakness in the ridge to give us some rain? (Been bone dry in Mobile, AL)
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Recon has pressure down to 941 not quite to lowest pressure readings yet
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Quoting Kristina40:

LOL Patrap, I hope you are correct. At least you and Keeper are still here for we newbies that actually want to learn, not just disrupt.

The wunderground is all about sharing for sure.

Dont let a few who think its FACEBOOK ruin the experience. Use the controls,esp the Iggy Button,and things will be better,,and the filter setting works really well also.
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Quoting bird72:

I was reading and seeing your videos and info. about models, very good info.

Thanks bird, it's not much but I figured I would try to pass a little of what all of the great folks on this blog over the years have taught me.
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Alex - Hurricane.
Bonnie - TS.
Colin - TS.
Danielle - Major.
Earl - Major.
Fiona - TS.
Gaston - TS.
Hermine - TS.
Igor - Major.
Julia - Major.
Karl - Hurricane.

Member Since: August 23, 2008 Posts: 7 Comments: 5300
393. JLPR2
Quoting DestinJeff:


See Reed's response to me? Yeah.

Now I give Reed a hard time, almost all the time. I created The REED Model and the "Continent of Uncertainty" terms that are often used here on the blog.

But Reed gets it. Reed gets that it is just satire of the nuiances that exist in the blog. It isn't at all personal. None of it is. It is just a matter of being able to joke around while also discussing serious matters.

Thank you, Reed. Sincerely.

I don't know why I thought you would finish that with:
Sincerely Yours XD
It would have been too funny. LOL

The intimidating blob of fury is going out of view.
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CORRECTION.. 11/6/4 .. Karl is a Hurricane, even more impressive and may be 11/6/5 by tomorrow!
Member Since: July 1, 2008 Posts: 13 Comments: 7437
Quoting reedzone:
Our count now stands at...


11/6/4 I think Karl was upgraded at 11am EST. Alex had the pressure of major but not the winds.
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URNT12 KNHC 161541


A. 16/15:26:00Z

B. 19 deg 37 min N

092 deg 54 min W

C. 850 mb 1284 m

D. 59 kt

E. 318 deg 12 nm

F. 053 deg 72 kt

G. 319 deg 10 nm

H. 983 mb

I. 17 C / 1530 m

J. 21 C / 1519 m

K. 14 C / NA


M. E27/25/15

N. 12345 / 8

O. 0.02 / 2 nm

P. AF308 0313A KARL OB 17


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Polar Orbiter Swath Paths
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Hey Reed I have a question for you can i WU email you and if so how.
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Quoting reedzone:

It should be that by the end of the day, but I stand corrected,
11/5/4, soon to be 11/5/5

What an ACTIVE HURRICANE SEASON!! Eat that downcasters!

Isn't it 11-7-5?
EDIT: 11-6-4.
Member Since: August 26, 2006 Posts: 16 Comments: 4766

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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.

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