Disturbance 98L probably no threat to land

By: Dr. Jeff Masters , 1:46 PM GMT on September 18, 2009

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A tropical disturbance (98L), is located midway between Africa and the Lesser Antilles Islands. This disturbance has a well-defined surface circulation, and has developed a modest amount of heavy thunderstorm activity overnight. This morning's QuikSCAT pass (Figure 1) shows a complete, circular wind pattern around the low pressure center of 98L, but top winds were only 25 mph. Wind shear is moderate, about 15 knots, and Sea Surface Temperatures are 28°C, which is about 2°C above the 26°C threshold needed to support a tropical cyclone. There is a large amount of dry air to the north and west of 98L, and this dry air is interfering with development.

The global computer models predict differing amounts of wind shear in the path of 98L as it moves west-northwest at 10 mph over the next three days. The ECMWF, GFS, and UKMET models do not develop 98L, while the NOGAPS, GFDL, and HWRF do. The models that do develop 98L predict that a strong trough of low pressure will turn 98L to the northwest and then north beginning on Monday, with the result that 98L misses the Lesser Antilles Islands by at least 500 miles. Given the moderate or higher wind shear in 98L's path, and dry air to the northwest, the system should develop only slowly. NHC is giving 98L a medium (30 - 50%) chance of developing into a tropical depression by Sunday. At this time, it does not appear that 98L will ever threaten any land areas.

The remains of Hurricane Fred are still spinning away, near 25N 66W, about 900 miles east of Florida. Wind shear is 20 knots, which is marginal for development, and there is very dry air surrounding ex-Fred on all sides. None of the computer models develop ex-Fred, and it will have a tough time regenerating with so much dry air and wind shear. The remains of Fred should move over Florida Monday night or Tuesday morning.


Figure 1. Morning QuickSCAT image of the Atlantic, showing the well-defined surface circulation of disturbance 98L. Image credit: NOAA/NESDIS.

One year anniversary of Hurricane Ike
I've been focusing this week on the 20th anniversary of Hurricane Hugo, but we also passed the one year anniversary of Hurricane Ike. Many areas along the Texas and Louisiana coast affected by Ike have fully recovered, but recovery efforts will still take many more years in other areas. In Galveston, which suffered $3.2 billion in damage, 75% of the businesses have reopened, and 95% of the population has returned. Boston.com has posted a very nice series of clickable images that show before and after scenes of some of the areas that have recovered from Hurricane Ike.

Ike washed away huge sections of beach and dunes that helped protect the Texas coast from more serious damage, and this week the state legislature approved $135 million in funds to help replace these critical natural protection systems. The restored beaches will probably last ten years, barring another strike by a hurricane of Ike's stature. Texas considers two-thirds of its 367-mile shoreline to be critically eroding, which it defines as a historical rate of more than 2 feet a year. Much of this erosion can be blamed on sea level rise. Global sea level rose seven inches over the past century, and is expected to rise at least that much over the coming century.


Figure 2. Villagers in Haiti plant one of their "Million Tree Campaign" trees. Image credit: Lambi Fund of Haiti.

Hurricane relief donations
There hasn't been a need for new hurricane-related disaster relief efforts this year, in stark contrast to 2008. However, the charities we rely on to provide disaster relief still require funds to operate in quiet years, and I encourage you to consider a donation at this time to one of my two favorite disaster relief charities. Portlight.org, which was very effective at helping out isolated, under-served communities in the wake of Hurricane Ike, is committed to raising $12,000 to purchase and outfit a mobile kitchen. This kitchen will be capable of feeding up to 2,000 people two hot meals per day in post-disaster situations. The Lambi Fund of Haiti has launched its "Million Tree Campaign", which aims to use local labor to plant a million trees over the next three years along severely deforested slopes in Haiti. Both of these charities wrote to me several times last year about the stunning generosity readers of this blog showed with their donations. Thanks!

Twenty years ago today
As Hurricane Hugo approached the U.S. Virgin Islands in the early morning hours of September 18, 1989, the storm slowed down to 10 mph. The slower speed allowed Hugo to punish the island of St. Croix with the worst beating of any location along the hurricane's destructive path. At 2am local time on September 18, 1989, Hurricane Hugo's eyewall struck St. Croix, bringing incredibly ferocious Category 4 winds, sustained at 140 mph. The hurricane's gusts were remarkably violent, and many residents witnessed tornado-like vorticies barreling across the island as the hurricane raged about them. A storm surge of 2 - 3 feet, topped by battering waves 20 - 23 feet high, assaulted the coast, adding to the destruction. Wunderground member Mike Steers wrote me to describe his experience on St. Croix: "Hugo was incredible. Many vortexes came in that night. The roar and intensity of the winds that night were incredible. When the eyewall came over, we were forced to take refuge in the bathroom as the rest of the house came apart. The pressure was so low outside the house that all of the water was sucked out of the toilet and an air draft was created through the toilet. Just when I thought it was as bad as it would get, the intensity of it all dialed up even higher. Dozens and dozens of times, my ears would violently pop due to rapid pressure changes. The next morning, of course, the devastation was unbelievable. In my front yard was a 18-foot boat with an outboard on it, that had been picked up from a marina two miles away. I had lost my house, and job, the Seaplane company I was a pilot for. After a couple months, I had to leave everything behind. In some respects, after 20 years, there an many aspects of the society that have yet to recover". Two people were killed on St. Croix, 80 injured, and 90% of the buildings were damaged or destroyed. Damage estimates for St. Croix were astronomical, over $1 billion, and the island's entire infrastructure was virtually wiped out. Six weeks after the hurricane, only 25% of the public roads had been cleared, and only 25% of the island had power.


Figure 3. GOES visible satellite image of Hurricane Hugo taken on September 18, 1989. Note the lack of cloud cover on the hurricane's southwest side, indicating that strong upper-level winds from the southwest were likely creating wind shear, weakening the storm. Image credit: Google Earth rendition of the NOAA HURSAT data base.

As Hugo departed St. Croix, strong upper-level winds from the southwest created wind shear that weakened the storm to a Category 3 hurricane with 130 mph winds. The upper level winds also caused Hugo to accelerate to 15 mph and turn more northwest. The eye passed over Puerto Rico's Vieques Island at 8am and over Fajardo on the extreme northeastern tip of Puerto Rico at 9am. On Culebra Island, an island twelve miles east of Fajardo, a gust to 170 mph was recorded by the ship Night Cap in the main harbor. The south-facing harbor received sustained southerly winds in excess of 120 mph for several hours as Hugo roared by to the south. The resulting wave "set-up" created a storm surge in excess of 13 feet in the supposedly hurricane-proof harbor. A large portion of the Caribbean's charter boat fleet, some 200 boats, was sheltering in Culebra's harbor, and 136 of these boats were badly damaged or sunk. Over 80% of the wooden structures on both Culebra and Vieques were destroyed.


Figure 4. Damage on St. Croix (two top photos), Culebra Island (bottom right), and Puerto Rico's Roosevelt Roads Navy Base (bottom left), after Hurricane Hugo. Image credit: NOAA Photo Library.

Along the northeastern coast of Puerto Rico, waves up to ten feet high riding on top of a 3 - 4 foot storm surge caused severe coastal flooding of low-lying areas. Hugo's winds tore into Puerto Rico's El Yunque rainforest, downing thousands of trees. The agricultural sector was devastated, with nearly all of the island's banana and coffee crops wiped out. Twelve deaths in Puerto Rico were attributed to Hugo, six of which occurred in the southern city of Guayama where some residents were electrocuted by downed power lines. Nearly 28,000 people were left homeless by the storm, and damage to the island exceeded $1 billion.

Storm chaser Michael Laca was at Luquillo Beach on the northeast shore of Puerto Rico, and has posted a remarkable 28-minute video on YouTube of Hurricane Hugo footage.

Jeff Masters

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842. rwdobson
9:23 PM GMT on September 18, 2009
"All of the present indicators are a big go-ahead for this thing to begin to regenerate anytime now."

The current reality is anything but that, my friend. The present indicators are for a low probability of minor regeneration.

The convection is very stretched N-S on the IR loops.
Member Since: June 12, 2002 Posts: 0 Comments: 1589
840. BurnedAfterPosting
9:23 PM GMT on September 18, 2009
Quoting tacoman:
burned you must have plenty of practice with that name..well my friend i can assure you if you know anything about tropical systems you have to agree this one looks shabby and is about to die any minute..get real..i wont get burned believe me..


LOL your ignorance amazes me, have fun with your guarantee LMAO

839. BDAwx
9:22 PM GMT on September 18, 2009
you know whats a scary thought?
around this time but in august four years ago we were watching the remnants of TD 10...
Member Since: August 3, 2009 Posts: 51 Comments: 545
837. tornadodude
9:22 PM GMT on September 18, 2009
Good evening Pat!
Member Since: June 28, 2006 Posts: 25 Comments: 8360
835. Patrap
9:21 PM GMT on September 18, 2009
Quoting pitviper:
Although I blog only once or twice a year, I lurk on a daily basis. My question is that with a wife who is dependent on oxygen 24 hours a day and living in Houston, Texas, what is the opinion of what will happen once Fred crosses Florida(if it does)and enters the GOM?


Register now in your community for Direct early assistance in case of any disaster or Hurricane. Im sure your Local Phone Book or other has that Numbers.
Member Since: July 3, 2005 Posts: 428 Comments: 129841
834. SWFLgazer
9:20 PM GMT on September 18, 2009
Fred had Pebbles. Barney had Bam Bam.
Member Since: August 14, 2006 Posts: 0 Comments: 448
833. homelesswanderer
9:20 PM GMT on September 18, 2009
Quoting laflastormtracker:


Rita did strengthen slightly before landfall remember xD


Sigh. And I thought I had it figured out. Thanks a lot! :P Lol. I knew she stalled right off shore but thought she was in a weakening phase at the time.
Member Since: August 15, 2008 Posts: 10 Comments: 3665
832. BDAwx
9:20 PM GMT on September 18, 2009
Link to Iwojima
Member Since: August 3, 2009 Posts: 51 Comments: 545
831. pitviper
9:19 PM GMT on September 18, 2009
Although I blog only once or twice a year, I lurk on a daily basis. My question is that with a wife who is dependent on oxygen 24 hours a day and living in Houston, Texas, what is the opinion of what will happen once Fred crosses Florida(if it does)and enters the GOM?
830. tornadodude
9:19 PM GMT on September 18, 2009
Quoting homelesswanderer:


Ah ok. Thanks. :) I read somewhere Rita had three concentric eye walls. That would explain the weakening from a 5 to a 3. And if that was a weakening Rita I'm glad we didn't see the strengthening Rita. Lol.


no problem :) yeah, I remember something like that, but I cant find anything
Member Since: June 28, 2006 Posts: 25 Comments: 8360
829. BenBIogger
9:18 PM GMT on September 18, 2009
Quoting tacoman:
reed its bound to move out one day..this is really a shabby looking system..they will cancel recon plane tomorrow..


Agree
Member Since: March 19, 2009 Posts: 0 Comments: 1421
828. BDAwx
9:18 PM GMT on September 18, 2009
looks like some of those small atoll - like islands are taking a pretty good amount of wind from Choi-Wan: Iwojima had an 86mph wind gust earlier today...
Member Since: August 3, 2009 Posts: 51 Comments: 545
827. laflastormtracker
9:18 PM GMT on September 18, 2009
Quoting homelesswanderer:


No. That seems to make sense. Because in Rita she ran out of water before the outer eyewall could take over. Thank you. :)


Rita did strengthen slightly before landfall remember xD
826. BurnedAfterPosting
9:17 PM GMT on September 18, 2009
Quoting tacoman:
reed its bound to move out one day..this is really a shabby looking system..they will cancel recon plane tomorrow..


you seem to be ignoring what is actually going on and guaranteeing things

I have found that if you are going to guarantee something when it comes to weather, more often than not you will make a fool out of yourself
825. homelesswanderer
9:15 PM GMT on September 18, 2009
Quoting BDAwx:


from what i know usually the larger one takes over and the inner one collapses and thusly temporarily weakening a storm but then the outer one would typically contract and then the storm would we able to strengthen again. like in Ike when it hit cuba... an outer concentric eyewall is pretty much just a rainband that has wrapped all the way around the storm, and shows how great the upper level support for the system is on top of how large it is.

i could be wrong.


No. That seems to make sense. Because in Rita she ran out of water before the outer eyewall could take over. Thank you. :)
Member Since: August 15, 2008 Posts: 10 Comments: 3665
821. reedzone
9:13 PM GMT on September 18, 2009
Quoting BurnedAfterPosting:


I watched the loop, that is not convection wrapping, all that is is the high clouds moving over the center


Ahh I see, thanks. Still, I think it will move out of the 20 knot zone tonight.
Member Since: July 1, 2008 Posts: 13 Comments: 7437
819. homelesswanderer
9:12 PM GMT on September 18, 2009
Quoting tornadodude:



From NOAA-

"Concentric eyewall cycles" (or "eyewall replacement cycle" ) naturally occur in intense tropical cyclones , i.e. major hurricanes (winds > 50 m/s, 100 kt, 115 mph) or Categories 3, 4, and 5 on the Saffir-Simpson scale. As tropical cyclones reach this threshold of intensity, they usually - but not always - have an eyewall and radius of maximum winds that contract to a very small size, around 10 to 25 km [5 to 15 mi]. At this point, some of the outer rainbands may organize into an outer ring of thunderstorms that slowly moves inward and robs the inner eyewall of its needed moisture and momentum. During this phase, the tropical cyclone is weakening (i.e. the maximum winds die off a bit and the central pressure goes up). Eventually the outer eyewall replaces the inner one completely and the storm can be the same intensity as it was previously or, in some cases, even stronger. A concentric eyewall cycle occurred in Hurricane Andrew (1992) before landfall near Miami: a strong intensity was reached, an outer eyewall formed, this contracted in concert with a pronounced weakening of the storm, and as the outer eyewall completely replaced the original one the hurricane reintensified. Another example is Hurricane Allen (1980) which went through repeated eyewall replacement cycles -- going from Category 5 to Category 3 status several times.

link


Ah ok. Thanks. :) I read somewhere Rita had three concentric eye walls. That would explain the weakening from a 5 to a 3. And if that was a weakening Rita I'm glad we didn't see the strengthening Rita. Lol.
Member Since: August 15, 2008 Posts: 10 Comments: 3665
818. BurnedAfterPosting
9:11 PM GMT on September 18, 2009
Quoting reedzone:
Light convection starting to wrap around the circulation of 07L, maybe it's moving out of the 20 knot shear now.





I watched the loop, that is not convection wrapping, all that is is the high clouds moving over the center
815. BDAwx
9:09 PM GMT on September 18, 2009
Quoting homelesswanderer:


Yep. Not a math wiz by any means. But I am counting my blessings. :) Was wondering what concentric eye walls do. Do they strengthen or weaken a storm?


from what i know usually the larger one takes over and the inner one collapses and thusly temporarily weakening a storm but then the outer one would typically contract and then the storm would we able to strengthen again. like in Ike when it hit cuba... an outer concentric eyewall is pretty much just a rainband that has wrapped all the way around the storm, and shows how great the upper level support for the system is on top of how large it is.

i could be wrong.
Member Since: August 3, 2009 Posts: 51 Comments: 545
814. reedzone
9:09 PM GMT on September 18, 2009
Light convection starting to wrap around the circulation of 07L, maybe it's moving out of the 20 knot shear now.



Member Since: July 1, 2008 Posts: 13 Comments: 7437
813. tornadodude
9:08 PM GMT on September 18, 2009
Quoting hydrus:
That post was for Floodman. My Mistake.


oh its fine, thats why I was confused
Member Since: June 28, 2006 Posts: 25 Comments: 8360
812. Keys99
9:08 PM GMT on September 18, 2009
Interesting First Hand Accounts of Hugos Passing


Virgin Islands Daily News
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811. BurnedAfterPosting
9:07 PM GMT on September 18, 2009
Quoting CosmicEvents:

If I looked correctly the Bam(deep) has a track to the south, the Bam(medium) is more North, and the Bam(shallow) is northernmost of all. Seems odd, just the opposite of what you'd expect. According to the Bam, the stronger the storm, the further south it goes.
.
.
Even Fred can't figure it out. And he's got a child named Bam-Bam.


I meant in terms of numbers, BAMD is for stronger systems, what is the guidance saying in terms of strength

reed already answered my question
810. tornadodude
9:07 PM GMT on September 18, 2009
Quoting homelesswanderer:


Yep. Not a math wiz by any means. But I am counting my blessings. :) Was wondering what concentric eye walls do. Do they strengthen or weaken a storm?



From NOAA-

"Concentric eyewall cycles" (or "eyewall replacement cycle" ) naturally occur in intense tropical cyclones , i.e. major hurricanes (winds > 50 m/s, 100 kt, 115 mph) or Categories 3, 4, and 5 on the Saffir-Simpson scale. As tropical cyclones reach this threshold of intensity, they usually - but not always - have an eyewall and radius of maximum winds that contract to a very small size, around 10 to 25 km [5 to 15 mi]. At this point, some of the outer rainbands may organize into an outer ring of thunderstorms that slowly moves inward and robs the inner eyewall of its needed moisture and momentum. During this phase, the tropical cyclone is weakening (i.e. the maximum winds die off a bit and the central pressure goes up). Eventually the outer eyewall replaces the inner one completely and the storm can be the same intensity as it was previously or, in some cases, even stronger. A concentric eyewall cycle occurred in Hurricane Andrew (1992) before landfall near Miami: a strong intensity was reached, an outer eyewall formed, this contracted in concert with a pronounced weakening of the storm, and as the outer eyewall completely replaced the original one the hurricane reintensified. Another example is Hurricane Allen (1980) which went through repeated eyewall replacement cycles -- going from Category 5 to Category 3 status several times.

link
Member Since: June 28, 2006 Posts: 25 Comments: 8360
809. hydrus
9:05 PM GMT on September 18, 2009
Quoting tornadodude:


me?
That post was for Floodman. My Mistake.
Member Since: September 27, 2007 Posts: 1 Comments: 22618
808. tornadodude
9:05 PM GMT on September 18, 2009
Quoting Floodman:
Okay folks, out of here!


have a good one!
Member Since: June 28, 2006 Posts: 25 Comments: 8360
807. CosmicEvents
9:05 PM GMT on September 18, 2009
Quoting BurnedAfterPosting:
where is the model guidance that shows the coordinates from the BAM guidance but also shows the intensity

I was just wondering what the models are saying in terms of strength of Ex Fred

If I looked correctly the Bam(deep) has a track to the south, the Bam(medium) is more North, and the Bam(shallow) is northernmost of all. Seems odd, just the opposite of what you'd expect. According to the Bam, the stronger the storm, the further south it goes.
.
.
Even Fred can't figure it out. And he's got a child named Bam-Bam.
Member Since: August 3, 2005 Posts: 10 Comments: 5684
806. weatherbro
9:05 PM GMT on September 18, 2009
Quoting BurnedAfterPosting:


you completely missed the joke lol


opps...
Member Since: May 26, 2007 Posts: 47 Comments: 1393
805. homelesswanderer
9:05 PM GMT on September 18, 2009
Quoting tornadodude:


Im going to have to agree with you :P


Yep. Not a math wiz by any means. But I am counting my blessings. :) Was wondering what concentric eye walls do. Do they strengthen or weaken a storm?
Member Since: August 15, 2008 Posts: 10 Comments: 3665
803. Floodman
9:04 PM GMT on September 18, 2009
Okay folks, out of here!
Member Since: August 2, 2006 Posts: 10 Comments: 9922
802. tornadodude
9:04 PM GMT on September 18, 2009
maybe fred will be the next nor easter?
Member Since: June 28, 2006 Posts: 25 Comments: 8360
801. rwdobson
9:03 PM GMT on September 18, 2009
Quoting weatherbro:
Fred might become sub-tropical or diaappear all together over s Florida.


Yeah, I was wondering if it might not just become another extra-tropical low when it gets to FL or the eastern US.
Member Since: June 12, 2002 Posts: 0 Comments: 1589
Quoting Tazmanian:
zombie fred looks more like a open wave right now


Here's the link for the 18z NAM
Member Since: Posts: Comments:
Quoting Tazmanian:
zombie fred looks more like a open wave right now


That may be what they're showing here sitting over the norther Bahamas Monday. Then it disappears and something shows up on the mid Atlantic coast. But I don't know if its the same thing. Very confusing.

Link
Member Since: August 15, 2008 Posts: 10 Comments: 3665
Fred might become sub-tropical or diaappear all together over s Florida.
Member Since: May 26, 2007 Posts: 47 Comments: 1393
Quoting homelesswanderer:


WOW! Glad that's not sitting on our coast.


Im going to have to agree with you :P
Member Since: June 28, 2006 Posts: 25 Comments: 8360
Quoting weatherbro:


Na...It looks to be mostly an end of the next week/weekend event. It's about time! whew


you completely missed the joke lol
Quoting Tazmanian:
zombie fred looks more like a open wave right now


A clear visible circulation, not an open wave. The NHC has it too as a weak low.
Member Since: July 1, 2008 Posts: 13 Comments: 7437
Quoting BurnedAfterPosting:


Are those long ranch models calibrated in Hidden Valley? lol


Na...It looks to be mostly an end of the next week/weekend event. It's about time! whew
Member Since: May 26, 2007 Posts: 47 Comments: 1393
Quoting tornadodude:


WOW! Glad that's not sitting on our coast.
Member Since: August 15, 2008 Posts: 10 Comments: 3665
Member Since: June 28, 2006 Posts: 25 Comments: 8360

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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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