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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Quoting StormW:
Just a quick update concerning ex-Fred. Just looking at a few steering things, shallow layer steering has changed somewhat. ex-Fred should be allowed to move a little further north, as a weakness has become apparent NE of the Bahamas and the east of the SEUS coast



Think it entirely depends on what is left of Fred.... in its current state, which amounts to a Flock of Seagulls, then a hit on the east coast of Florida is likely...... but any organization whatsoever will have a tendency to shift things northward....

I am amazed there is even a circ left from Fred..... but I said before, Fred's circ was one of the strongest "naked" circs I have ever seen. I can only imagine under conducive circumstances, Fred could have been a "major"..... but this has, and contiinues to be, the year of the shear!

StormW.....I always enjoy your input..... hope to meet you some day..... you are a fixture here..... and deserve Kudo's for your work! :)
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1136. scCane
stormw do you have any good sites that shows fredex llc having trouble tracking it at the moment.
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1135. ncstorm
thanks so much!
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I've been trying to figure out if a trough will come eventually and take Fredex away. But I can't find any sign of one until later next week. I also found nothing saying the Bermuda High will keep building westward once it gets past Florida. So this one will give us all a nervous breakdown. Especially if it sits and intensifies. Lol. Found this about the troughs. I think...

ON TUESDAY...THE GFS/ECMWF HAVE COME INTO GOOD AGREEMENT ON A
SIGNIFICANT UPPER LOW DEVELOPING OVER THE CENTRAL PLAINS...WHICH
WILL DRIVE A DECENT LATE SUMMER FRONT INTO THE AREA. INCREASED
POPS TO LIKELY WITH THE HIGHER DEGREE OF CONFIDENCE. THOUGH
MOISTURE AND INSTABILITY APPEAR TO BE SUFFICIENT FOR SEVERE
THUNDERSTORMS...WIND SHEAR LOOKS MORE MARGINAL...WITH 0-6KM BULK
SHEAR PROGGED RIGHT AT 30KT.

THE GFS/ECMWF DIVERGE HEADING INTO WEDNESDAY...WITH THE ECMWF
SINKING THE UPPER LOW FARTHER SOUTH INTO OK AND THE GFS KEEPING IT
FARTHER NORTH OVER KS. THIS HAS IMPLICATIONS FOR US IN TERMS OF
HOW FAR TO THE SOUTH/EAST THE FRONT GETS...AND WHETHER IT RETREATS
BACK OVER US. GIVEN THIS UNCERTAINTY...CHANGES TO THE FORECAST
WEDNESDAY AND BEYOND WERE KEPT MINIMAL.

US is NW GOM.
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Hi all and good evening,
My question for the night.... One post said xfred was 400 some miles south southeast of bermuda and then I see a bunch of posts saying its between the bahamas and the keys...... Where exactly is it? thanks, just too new to be able to figure out what exactly I am looking at. (laughing at myself)
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Quoting WaterWitch11:


this one StormW - thank you

Water I think he would've answered but your quote really states no question. You may wanto to ask the actual question.
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Quoting WaterWitch11:


this one StormW - thank you

Quoting StormW:
I could be wrong on this...but I wouldn't be surprised to see a center reformation to the east on 98L. Has the classic "S" cloud pattern, along with the upper level anticyclone sitting over that big blow up of convection.

98L FUNKTOP LOOP

and how do you think a further east center would affect models?
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1127. ncstorm
Quoting StormW:


I believe what 456 was referring to was, if ex Fred stayed on a west course, he had about a 50% chance of entering the GOMEX. If he goes more north, and gets to 28N, the chance of entering the GOMEX goes down to about 30%, on a WNW course. If he reaches 30N, before going anymore west, the chances for it to get to the GOMEX are only at about 20%


cannot give you an exact % but with every latitude Fred inches northward, the chances become less. Remember the models take it westward so as Fred continues wnw, that westward track will shift more and more north. The current chance is about 50/50 but if Fred reaches 28N, that becomes 30/70 and 30N >20/<80


Hi StormW

Read your blog updates all the time..question?so if exFred takes that Northward movement, will that put SC/NC back in this..Dr. Masters had mentioned SC/NC earlier in the week in his blog
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You're welcome, and your invite to see the queen is, umm... well... err, in the mail!
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1119. JLPR
Quoting JRRP:

but has weakened a bit


the one from earlier today

nope the LLC has become better defined

the problem is with convection that's why its T# has gone down a bit
Member Since: September 4, 2007 Posts: 36 Comments: 5223
MARINE WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
250 PM EDT FRI SEP 18 2009

SW N ATLC...
A QUASI-STATIONARY TROUGH EXTENDS ALONG FROM 31N72W TO NW
BAHAMAS AND THEN BROAD TROFFING TO JUST E OF THE KEYS. THIS
TROUGH WILL MEANDER THROUGH TONIGHT AND THEN BECOME STRETCHED NE
TO SW...WITH SW PORTION MOVING NW INTO FLORIDA OVER THE WEEKEND.
WINDS ON BOTH SIDES OF TROUGH HAVE GENERALLY BEEN 10-15 KT. THE
REMNANTS OF TC FRED...A TIGHT LLVL SWIRL IN SATELLITE
IMAGERY...WAS ALONG 26N67W THIS AFTERNOON...MOVING NW 15 KT. THE
LOW LEVEL TROUGH THAT THIS FEATURE IS EMBEDDED WITHIN IS MOVING
WNW AND EXPECTED TO MOVE IN THIS MANNER NEAR 15 KT AND VERY
GRADUALLY SLOW...REACHING THE NW BAHAMAS IN 48 HOURS. A MORNING
QUICKSCAT PASS STILL SHOWED 20-25 KT WINDS IN N SEMICIRCLE OF
THIS SWIRL...WITH SEAS ESTIMATED 8 TO 10 FT WITHIN 240 NM N AND
NE. AS THIS MOVES WNW...THE LOW IS EXPECTED TO OPEN UP INTO A
MORE OBVIOUS TROUGH...THAT SHOULD MOVE NW REACHING THE SE FL
COAST MON. HIGH PRES WILL BUILD ACROSS THE AREA FROM THE E
BEHIND THIS TROUGH WITH E-SE WINDS 15 KT AND SOME SMALL AREAS
15-20 KT...BY LATE IN THE PERIOD.

This talks about the stall. But says it weakens?

Link
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1117. KEEPEROFTHEGATE (Mod)


INV/98/L
MARK
13.1N/39.2W
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Quoting StormW:


Yes sir! Should drift toward the direction you posted earlier. Have to see what comes next. This season has been a challenge.

Season of multiple vortices and naked swirls.


Certainly better than a season of low shear and well developed storms! We've seen enough of those lately! Great job on the blog tonite, Sir Storm(you've just been knighted - LOL!!!)
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Quoting BurnedAfterPosting:


you are aware that is 98L right? yes could be Grace in the making

Yes I know its 98L, Good Lord no pun intended ,I hope I'm not that dumb!
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Quoting WaterWitch11:


this one StormW - thank you


sorry that probably didn't help much, someone saying sf being in the clear and this was the response.
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1113. JRRP
Quoting stormpetrol:

Well defined LLC at around 13N/41W, potential Grace in the making?

but has weakened a bit
lol... i do not understand:P
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1112. hydrus
Quoting StormW:


Welcome...and thank you!
Storm.W. Were you able to determine whether or not there has ever been two named storms in the Gulf of Mexico at the same time?
Member Since: September 27, 2007 Posts: 1 Comments: 19504
1111. JLPR
Quoting stormpetrol:

Well defined LLC at around 13N/41W, potential Grace in the making?


yep 98L is tightening up

anyone else wanna agree? XD
Member Since: September 4, 2007 Posts: 36 Comments: 5223
1110. KEEPEROFTHEGATE (Mod)
Quoting Weather456:


the steering looks weak in vicinity of Fred..we'll see how that goes.
zombie fred sitting there lookin in
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Quoting OracleDeAtlantis:


Personally I think that shear won't be the big problem. I think the dry air, on two sides.

However, another big factor is the strange resilience of this crazy thing, as if it has a destiny of sorts. It's not very scientific, but this thing should have been dead a long time ago.


Something needs to be said for the strength and persistence of its circulation despite the shear. In light of it having been a major hurricane... a long... long time ago.

I can totally understand FredEx spending the next 6 days moving into Tennessee, and then curving north with the deep low headed towards Alaska.

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Quoting stormpetrol:

Well defined LLC at around 13N/41W, potential Grace in the making?


you are aware that is 98L right? yes could be Grace in the making

Well defined LLC at around 13N/41W, potential Grace in the making?
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We might have Nora in the EP soon it seems.

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Quoting lordhuracan01:
Evening guys!

Buenos Nachos
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Quoting Weather456:


no, I was giving the probabilities of several outcomes


this one StormW - thank you
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Evening guys!
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Good thing the waters of the Bahamas are relatively shallow, then. If it's going to sit there for a couple days, better to have water w/ lower TCHP....
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1100. JLPR
Quoting JRRP:
12 GMT 09/18/09 12.6N 39.2W 25 1008 Invest
18 GMT 09/18/09 12.8N 39.9W 25 1008 Invest
00 GMT 09/19/09 13.1N 40.4W 25 1008 Invest


18/2345 UTC 13.2N 40.6W T1.0/1.0 98L
18/1745 UTC 13.5N 40.2W T1.0/1.5 98L
18/1145 UTC 13.4N 39.0W T1.0/1.5 98L

weakening? O_o

LLC looks more defined
Member Since: September 4, 2007 Posts: 36 Comments: 5223
Quoting HurricaneKing:


You're welcome. That's the 2 main things that can influence steering but when something stalls anything can happen. Plus it's not even a storm.


That's true. Like Erika Fred is hard to get a handle on.
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Quoting JRRP:
12 GMT 09/18/09 12.6N 39.2W 25 1008 Invest
18 GMT 09/18/09 12.8N 39.9W 25 1008 Invest
00 GMT 09/19/09 13.1N 40.4W 25 1008 Invest
The invest is getting its act together, it seems...!
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Quoting StormW:


Just the convection. What happens is, the mid an upper portions get blown in the direction the shear is going, so the system is "tilted", or what we call not vertically stacked.


Personally I think that shear won't be the big problem. I think the dry air, on two sides.

However, another big factor is the strange resilience of this crazy thing, as if it has a destiny of sorts. It's not very scientific, but this thing should have been dead a long time ago.
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1093. fmbill
Quoting StormW:


I'll have to see what the updated steering layers show. That's one possibility. It's a pain trying to figure out when they stall.


LOL! That is so true.

When I send out the updates for a system that's stalled, I usually tell everyone that it's time to play, "Who wants to be a meteorologist?" Because wherever you "think" it will go, there will probably be a model run that agrees with you. :-)
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Quoting StormW:


Just the convection. What happens is, the mid an upper portions get blown in the direction the shear is going, so the system is "tilted", or what we call not vertically stacked.


BTW Storm you always have a patience and a way of explaining things that makes us novices feel important yet help us learn at the same time.
Thanks for your knowledge.
You definitely bring a levelheadedness to this blog.
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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.

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