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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1442. centex
I challenge for evidince 98L not td. NHC status does not count.
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1441. JLPR
Quoting homelesswanderer:


WOW! That's gotta be Grace. Soon anyway. :)


TD 8 yep I expect a red circle soon =P
but Grace ...ummm gonna wait a little more to say that xD
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1440. JLPR
what TAFB thinks is worrying =S


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Quoting TampaSpin:
The Mid Level Low in the Caribbean is starting fire thunderstorms on the center.......a strong sign its trying to work its way to the surface.....if this tracks toward the GOM the same time Fred gets there this will become very interesting.......


EURO showed some activity in Caribbean and BOC. Don't think was Fred though too far out in time.
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The Mid Level Low in the Caribbean is starting fire thunderstorms on the center.......a strong sign its trying to work its way to the surface.....if this tracks toward the GOM the same time Fred gets there this will become very interesting.......
Member Since: September 2, 2007 Posts: 177 Comments: 20430


WOW! That's gotta be Grace. Soon anyway. :)
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1436. centex
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1435. centex
Still waiting for updated sat.
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Quoting BurnedAfterPosting:
ECMWF isnt really anything to right home about yet, still several days away

updated image on Ex Fred shows it doesnt look all that bad
what are you looking at just lookes at the satellite avn he's toast
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1433. centex
Right about W, maybe WNW. Look at the flow of clouds 500 miles to N, they are moving W.
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Quoting iceman55:
bye all.


Nite Ice. :)
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ECMWF isnt really anything to right home about yet, still several days away

updated image on Ex Fred shows it doesnt look all that bad
1430. JLPR
Quoting iceman55:
bye all.


bye
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1429. JLPR
yep
no doubt on the west , west northwest movement for the time being

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1427. centex
Quoting JLPR:


im not sure what this one is going to end up doing
models have it going north but the high is strong and the weakness they predict will be short lived

but right now, it seems like W, WNW is the way to go
ok, like to see event starting before I believe it.
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Quoting iceman55:
homelesswanderer not good


Nope. :(
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HMMM? A lil something for the BOC and the Caribbean? haven't seen that all year.

Link

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1422. JLPR
Quoting centex:
Help me, I don't see WNW or NW, maybe 3 days out.



im not sure what this one is going to end up doing
models have it going north but the high is strong and the weakness they predict will be short lived

but right now, it seems like W, WNW is the way to go
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1419. JLPR
everything is starting to update =]

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1418. centex
Quoting JLPR:
navy rocks xD
98L
Help me, I don't see WNW or NW, maybe 3 days out.

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1416. JLPR
navy rocks xD
98L
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Link

tropical update video and see you en la maana

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1409. JLPR
Quoting iceman55:



NOT BEST


yeah, it sucks when they miss the good stuff :P
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Every one, 98L is still same strength; 25kt 1008 mb

...INITIAL CONDITIONS...
LATCUR = 13.2N LONCUR = 41.9W DIRCUR = 275DEG SPDCUR = 11KT
LATM12 = 12.9N LONM12 = 39.9W DIRM12 = 280DEG SPDM12 = 6KT
LATM24 = 13.0N LONM24 = 38.6W
WNDCUR = 25KT RMAXWD = 45NM WNDM12 = 25KT
CENPRS = 1008MB OUTPRS = 1012MB OUTRAD = 210NM SDEPTH = M
RD34NE = 0NM RD34SE = 0NM RD34SW = 0NM RD34NW = 0NM
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Clearly, this little guy wants to live, despite all odds.

By the way, if anyone wants to vote on where they want they'd like a hurricane party this year, here's [a poll,] but I must warn you, it's not for the [faint of TD4.]

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1404. JLPR
check it out
the image of west Africa updated and 98L is in the picture :)


....wow
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1403. centex
Quoting JLPR:


JLPR and JLPR2 is the same person =P
I created the secondary account a long time ago and sadly i only remembered the password to that one :|

me, I have been blogging here for 3 years
and who are you? =P
I'm also a multi year blogger, and very suspect of scientific evidence predicting tropical lows.
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1402. JLPR
Quoting centex:
JLPR and JLPR2 who are these guys?


JLPR and JLPR2 is the same person =P
I created the secondary account a long time ago and sadly I only remembered the password to that one :|

me, I have been blogging here for 3 years
and who are you? =P
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1401. JLPR
.
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1400. centex
JLPR and JLPR2 who are these guys?
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1399. JLPR
Quoting centex:
when will we get new sat images?


probably in an hour or a little earlier
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1398. JLPR2
anticlone is now right over 98L


this could get interesting :P
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1397. centex
when will we get new sat images?
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1395. JLPR2
Quoting homelesswanderer:


NP. I'm always hitting the wrong buttons on my IPOD touch. Lol. I don't have a pic of 38l but it seemed to be getting a lot better organized before blackout.


xD yep
im terrible with phones lol
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1394. JLPR2
Quoting iceman55:
JLPR hey


Yo! xD
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1393. JLPR2
The best image I could find of 98L
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About

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