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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1342. centex
I see bright red. Not just last hour.
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1341. IKE
Copy and Paste....

TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
200 AM EDT SAT SEP 19 2009

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

A SMALL LOW PRESSURE AREA...ASSOCIATED WITH THE REMNANTS OF FRED...
CENTERED ABOUT 500 MILES EAST OF THE NORTHWESTERN BAHAMAS IS
PRODUCING MINIMAL SHOWER AND THUNDERSTORM ACTIVITY. UPPER-LEVEL
WINDS COULD BECOME A LITTLE MORE FAVORABLE FOR SOME DEVELOPMENT
DURING THE NEXT DAY OR TWO AS THE SYSTEM MOVES WEST-NORTHWESTWARD
AT 10 TO 15 MPH. THERE IS A LOW CHANCE...LESS THAN 30 PERCENT...OF
THIS SYSTEM BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS.

SHOWER ACTIVITY ASSOCIATED WITH A BROAD AREA OF LOW PRESSURE
CENTERED ABOUT MIDWAY BETWEEN AFRICA AND THE LESSER ANTILLES SHOWS
SOME SIGNS OF ORGANIZATION. THIS SYSTEM HAS THE POTENTIAL FOR SLOW
DEVELOPMENT OVER THE NEXT COUPLE OF DAYS AS IT MOVES TOWARD THE
WEST-NORTHWEST AT AROUND 10 MPH. THERE IS A MEDIUM CHANCE...30 TO
50 PERCENT...OF THIS SYSTEM BECOMING A TROPICAL CYCLONE DURING THE
NEXT 48 HOURS.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

$$
FORECASTER AVILA
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2am and status on 98L unchanged...still orange!

Nite all..I'll leave you folks with it!
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1339. centex
The Texas ULL has finally moved out. We had beneficial rain but east of lakes in central texas.So expect restrictions until water supply satisfied.
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According to the new shear map, 07L is now entering favorable conditions. Tomorrow should make things interesting. If anything happens with 07L, it has to be tomorrow. Dry air will be the only blockage from regeneration.
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1335. centex
Quoting IKE:
What happened to FRED-EX? He go bye-bye again?

He will be back tomorrow. LOL.
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Quoting iceman55:
homelesswanderer why


That we're cool with each other. At least I hope so.
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1333. IKE
What happened to FRED-EX? He go bye-bye again?

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I'm glad Ice. :)
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1329. centex
Got my eye
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Quoting iceman55:
homelesswanderer :)


Sorry Ice. Peace. :)
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Quoting centex:
OK, it's data, but models at this point have little value. I still wonder why forecast people rely so much on models even when they know when they are not reliable. We need to know when to discount them. Not saying post which point out model changes are wrong, it's imporant data we watch.


Look I been here all season. I know the models have been screwed up. And I said the CMC was showing strong ridging. Which apparently most on here agree with. But how could the CMC have any more validity at this point than any other? Sorry if I disappoint people with my post. I want it to go out to sea. Seeing models like that makes me feel better. I get it you don't have to believe in them. This far out neither do I. But it is a ray of hope.
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ok now I will be back soon lol
Quoting centex:
In this difficult environment I've only seen one system predicted well this year. Bill


yup once they got a handle on Bill they did very well, but if you remember when it was invest, the consensus didn't have Bill getting past 50W
1321. centex
In this difficult environment I've only seen one system predicted well this year. Bill
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Quoting centex:
OK, it's data, but models at this point have little value. I still wonder why forecast people rely so much on models even when they know when they are not reliable. We need to know when to discount them. Not saying post which point out model changes are wrong, it's imporant data we watch.


well not just that but the GFS has been overdoing the trofs all season long
and with that, I will be back soon
1317. centex
Pre TD are like cutoff lows, they do not know where they will drift.
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Quoting Relix:
The models are in such agreement that they make me optimistic.


While I agree with you there, 2 things to be weary of

#1 the weakness is going to be short-lived as has been stated by 456 and several others, timing will be everything with this. If the timing is off just a bit the weakness may not pull it far enough north or it may miss it completely

#2 the consensus has been off quite a bit this season and to the east. They have had Ana, Bill, Danny, Erika and Fred all further north and east than where they ended up.

Oh wait thats right, vince says these arent reasonable points cuz Im just wishcasting LMFAO
1315. centex
Quoting homelesswanderer:
GFS picks 98l up again then takes it to sea. Another low off Africa strait north. First time I saw a model take this trough thats been over us and weakens the ridge. be interesting to see what the others do. The CMC showed strong ridging. One of em gotta be wrong. Lol.

Link
OK, it's data, but models at this point have little value. I still wonder why forecast people rely so much on models even when they know when they are not reliable. We need to know when to discount them. Not saying post which point out model changes are wrong, it's imporant data we watch.
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1314. Relix
The models are in such agreement that they make me optimistic.
Member Since: August 3, 2006 Posts: 0 Comments: 2639
Yo vince take the bug out of your butt, I know its past your bedtime

You dont know me, so dont pretend you do. Fact is several knowledgeable folks on here tonight said it was too early to tell and guess what

IT IS!!!!

So back off buddy and actually look at whats going on before you accuse.
It's one of those 'wait and sees' lol

Have you ever heard of 'em?

Such is life ... i mean the tropics
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Quoting BurnedAfterPosting:


yup it always is too early, yet people still ask or assume it will go out to sea
Well the pros feel it will not be a bother to anyone, why the negative slant on what the PAID PROFESSIONALS POST? Oh I know, someone needs to have a wish.....I hope you get yours.
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GFS picks 98l up again then takes it to sea. Another low off Africa strait north. First time I saw a model take this trough thats been over us and weakens the ridge. be interesting to see what the others do. The CMC showed strong ridging. One of em gotta be wrong. Lol.

Link
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1306. centex
Quoting Relix:
So 98L is surely missing into the sea?
FWIW, I would, trend is not showing any signs of waning. Must be in favorable environment to do what it is doing.
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Quoting iceman55:
100% to early ;)


yup it always is too early, yet people still ask or assume it will go out to sea
The weakness the models are seeing is very short lived, the timing will need to be perfect. I know StormW was not buying 98L getting into the weakness enough to go out to sea and I agree
1302. JRRP
Quoting serialteg:


pero yo te he visto hablando ingles aki en todo momento o no?

:/


jejeje.... solo un poquito
yo entiendo casi todo lo que ustedes dicen aqui
pero las cosas que quiero decir aveces no las digo por q no se ponerlas en ingles....
Member Since: August 16, 2007 Posts: 0 Comments: 5073
Quoting Relix:
So 98L is surely missing into the sea?


No, again like it always is this early on, too early to tell

1300. Relix
So 98L is surely missing into the sea?
Member Since: August 3, 2006 Posts: 0 Comments: 2639
Quoting centex:
just logged in and cheked sats. First impression, should be red, >50. The last update was a understatment


you mean the invest?
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Quoting JRRP:

por q no se hablar ingles
no es por q quiera hablar en espa�ol si no por q no pueda hablar en ingles :D


pero yo te he visto hablando ingles aki en todo momento o no?

:/

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1297. centex
just logged in and cheked sats. First impression, should be red, >50. The last update was a understatment
Member Since: Posts: Comments:
1295. JRRP
Quoting serialteg:


cual es el guille de estar hablando en espaol? :D

i see our invest is puttin up a show

por q no se hablar ingles
no es por q quiera hablar en espaol si no por q no pueda hablar en ingles :D
Member Since: August 16, 2007 Posts: 0 Comments: 5073
Quoting JRRP:

si todo continua como va podria ser q tenga circulo rojo a las 8am
pero no creo q lo sea a las 2am
aun que deberia tenerlo :P


cual es el guille de estar hablando en español? :D

i see our invest is puttin up a show
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1292. will40
LOL ice
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About JeffMasters

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