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 BurnedAfterPosting:


way off again, center of Ex Fred is at 25.9N

not sure who is posting over there, but they are way off on both accounts


Don't know it a website someone tryng to sell their hurricane tracker software.

Link to Stormpulse

Glad to know this, someone told me this program was excellent...thanks for the info.
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Back later
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Quoting kmanislander:


Remember Erika ?. All the models had it making a sharp right turn into the N Atl near 35W and it finished up S of PR in the Caribbean.

Throw those out the window for now IMO


well the weakness for 98L is more pronounce than with Erika.
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Quoting tornadodude:


howdy, that sucks about the rain, wont you share?

I've had 0.06 IN this month!

Gladly, please take it.

Last 7 days:
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538. JLPR
I got it, I understand 98L
we got several swirls rotating around a broad area of low pressure =]

and I actually see the center of the broad low at 12.5N 40W
the thing is where will the center consolidate finally?
Member Since: September 4, 2007 Posts: 36 Comments: 5223
Quoting StormW:
18Z

STATISTICAL MODELS


DYNAMIC MODELS


Remember Erika ?. All the models had it making a sharp right turn into the N Atl near 35W and it finished up S of PR in the Caribbean.

Throw those out the window for now IMO
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Quoting WxLogic:


I would agree... but should be temporary. Pretty sure you noticed the weak trough extending SW to NE across Bahamas which is tarting to decay and replaced by a High. I believe the BAM suite has a better handle on 07.


Yeah. I can agree with a western BAM solution, I just don't see the southwest jog until much later (near the Bahamas) if at all. The ridging remains flat/weak with the trough over New England at the moment.

The GFDL has the center at 25N 70W at 12UTC tomorrow. It's already around 26N 68 West.

So to be on track it would have to slow WAY down and move WSW...

Low Level Steering Loop
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Quoting watcher123:
494:

The water Fred is about to move over tomorrow or the next day is just as hot, if not hotter than the Gulf.

The NHC always under-estimates the peak intensity in their forecasts, often by 10-20kts or more.

I shall have the audacity to say that I believe this will hit Florida as a major...twice...

Of course, I am going to get flamed for this, but pay attention.

I am no pro! BUT, given the TOTAL unpredictability of Danny, Erika and now "Fred", it is within the realm of possibility that Fred may suprise us within the next 24-36 hrs! So far, Fred is pretty quiet, BUT than can change without ANY notice!!
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Quoting nrtiwlnvragn:


NHC describes it as a broad area of low pressure so locating "a" center would be open to interpretation. You may be correct.


I agree that with these early stage systems the low is usually very broad but I really do not see anything closer to being a center than what I see near 13.3 and 41.

Where the "best" center is can make a huge difference to how the models initialise the feature and that is why I pay practically no attention to the early model runs in the formative stages of development. Big difference between due W at 13.3 and WSW at 12.8.
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Quoting watcher123:
504:

This is based on several things, but lets just wait and see before I say publicly. There is a lot of hot water in the bahamas, and there is also a lot of hot water moving into and through the gulf. I see no specific reason why this won't strengthen considerably starting about this time tomorrow or so.

I may decide to PM you something later which I am not going to say publicly, not just yet.

However, I stand by my position that I believe this will be a major at landfall in the general vicinity of Miami, and then again in the west-central panhandle.
You are going out a long way on this one 123.(a major hurricane in Miami?) however I can see it being a possibility.
Member Since: September 27, 2007 Posts: 1 Comments: 20509
Quoting Seasidecove:
And the center of X-Fred at: 24.3N 69.1W as of 1PM EDT


way off again, center of Ex Fred is at 25.9N

not sure who is posting over there, but they are way off on both accounts
And the center of X-Fred at: 24.3N 69.1W as of 1PM EDT
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Id say the center of 98L is 13.4N 40W
Looks like the BAMMS keep a weaker high pressure while the GFDL HWRF & TCVN build a stronger ridge. The strength of the ridge is a key player.
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Quoting Seasidecove:
Not sure how accurate this position is on Invest 98, but Storm Pulse has center located at: 12.4N 42.0W as of 1PM EDT


that is not even close lol
Not sure how accurate this position is on Invest 98, but Storm Pulse has center located at: 12.4N 42.0W as of 1PM EDT
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The high is centered just SE of Cape Cod. It will likely generate an easterly flow to its south (in a westward direction). This high remains in place through 3 days and given the current location and speed of 07L; the system will likely already be somewhere along 80W.

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Quoting kmanislander:


Not convinced about the current center position but that's my opinion.


NHC describes it as a broad area of low pressure so locating "a" center would be open to interpretation. You may be correct.
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523. JLPR
Quoting Weather456:


I agree with the lat but not the longitude.


yep 40W seems to be more reasonable =)
Member Since: September 4, 2007 Posts: 36 Comments: 5223
There is a trough weakness, just not in time for Fred. Fred is almost 2 days away from the SE USA.
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Quoting nrtiwlnvragn:
DISTURBANCE INVEST (AL982009) 20090918 1800 UTC


...INITIAL CONDITIONS...
LATCUR = 12.8N LONCUR = 39.9W DIRCUR = 260DEG SPDCUR = 7KT
LATM12 = 13.0N LONM12 = 38.6W DIRM12 = 257DEG SPDM12 = 7KT
LATM24 = 13.5N LONM24 = 37.2W
WNDCUR = 25KT RMAXWD = 45NM WNDM12 = 25KT
CENPRS = 1008MB OUTPRS = 1012MB OUTRAD = 210NM SDEPTH = M
RD34NE = 0NM RD34SE = 0NM RD34SW = 0NM RD34NW = 0NM


Not convinced about the current center position but that's my opinion.
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Quoting serialteg:
Very evident ridge breakdown here

guess this invest is also up and away if developed


Don't jump on that forecast too quick, going to be a close call
On the GHCC loop disturbance Fred moves westward in the last few frames. May just be a temporary jog.
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Quoting nrtiwlnvragn:


Darned TCVN.
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Very evident ridge breakdown here

guess this invest is also up and away if developed
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Quoting IKE:


I agree with you. I think it's going to turn back more to the west from the discussions I've read about high pressure building in.


Indeed...
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Today's Tropical Update
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513. IKE
Quoting WxLogic:


I would agree... but should be temporary. Pretty sure you noticed the weak trough extending SW to NE across Bahamas which is tarting to decay and replaced by a High. I believe the BAM suite has a better handle on 07.


I agree with you. I think it's going to turn back more to the west from the discussions I've read about high pressure building in.
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Quoting nrtiwlnvragn:


Aha, the 18Z. Thanks, and yes everybody, I know it's just an open swirl of clouds,etc.
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AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAMPA BAY RUSKIN FL
118 PM EDT FRI SEP 18 2009

.LONG TERM (SUNDAY NIGHT-SATURDAY)...THE GENERAL PATTERN FOR THE
EXTENDED FORECAST PERIOD WILL REMAIN WITH A STRONG RIDGE OF H5
HIGH PRESSURE OVER FLORIDA TO PROVIDE ABOVE AVERAGE DAILY
TEMPERATURES. THERE WILL BE A FOCUS SHIFTING TOWARDS THE REMNANTS
OF FRED AND WHAT...IF ANY...INTERACTION IT HAS WITH THE AREA.
FOR
NOW GIVEN THE CONSIDERABLE UNCERTAINTY WITH THIS SYSTEM...HAVE
ELECTED TO JUST NUDGE POPS UPWARD SLIGHTLY IN THE DAY 4 TO 5
TIMEFRAME. NEWEST MEX GUIDANCE DOES REFLECT SLIGHTLY HIGHER POPS
DURING THIS TIME.

TOWARDS THE END OF THE EXTENDED THE MODELS CONTINUE TO STRUGGLE
WITH SIGNIFICANT TROUGHING THAT WILL BE MOVING ACROSS THE CENTRAL
CONUS. WHILE YESTERDAY THE ECMWF AND GFS HAD SETTLED ON A DEEP
CUTOFF OVER THE FOUR CORNERS...NOW THE PREFERRED SOLUTION IS FOR
THE LOW TO MOVE ACROSS THE MID MISSISSIPPI VALLEY BY NEXT WEEKEND.
WITH THE CONSIDERABLE DIFFICULTY THE MODELS HAVE EXHIBITED WILL
NOT MAKE ANY CHANGES AT THIS TIME.
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DISTURBANCE INVEST (AL982009) 20090918 1800 UTC


...INITIAL CONDITIONS...
LATCUR = 12.8N LONCUR = 39.9W DIRCUR = 260DEG SPDCUR = 7KT
LATM12 = 13.0N LONM12 = 38.6W DIRM12 = 257DEG SPDM12 = 7KT
LATM24 = 13.5N LONM24 = 37.2W
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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Quoting kmanislander:


Actually, the center looks to be near 13.3 N and 41 W notwithstanding what the official position is stated to be IMO.

Run the loop


getting its act together, i believe the low eroding the high is already out and pushing it?

watching the maps... i believe it is the one now in canada going down double whammy
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Quoting kmanislander:


Actually, the center looks to be near 13.3 N and 41 W notwithstanding what the official position is stated to be IMO.

Run the loop


I agree with the lat but not the longitude.
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Quoting OSUWXGUY:
One things for certain... I'm not trusting any output from the models as of yet!

The HWRF and GFDL both move the storm west and then southwest.

Currently it is moving jogging northwest...

RGB LOOP


I would agree... but should be temporary. Pretty sure you noticed the weak trough extending SW to NE across Bahamas which is tarting to decay and replaced by a High. I believe the BAM suite has a better handle on 07.
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Ya know what they say Ike!

Never say "never". Especially true with meteorology.
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Quoting watcher123:
494:

The water Fred is about to move over tomorrow or the next day is just as hot, if not hotter than the Gulf.

The NHC always under-estimates the peak intensity in their forecasts, often by 10-20kts or more.

I shall have the audacity to say that I believe this will hit Florida as a major...twice...

Of course, I am going to get flamed for this, but pay attention.


ok, I wont "flame" you for this, but can you show some data etc. to back this up?
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Quoting OSUWXGUY:
I want to know when SSD will finally put a floater back over ex-Fred???



Probably when it shows some signs of organization.
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Quoting Weather456:
Good afternoon SW, you got mail.

I am good but you are better.

Meanwhile, 98L has lost most of the thunderstorms that were there this morning. However, a new area of thunderstorms developed on the northwest side of the circulation probably a hint of an increasingly conducive environment. From satellite animations it appears is moving a bit north of due west.



Actually, the center looks to be near 13.3 N and 41 W notwithstanding what the official position is stated to be IMO.

Run the loop
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Quoting OSUWXGUY:
I want to know when SSD will finally put a floater back over ex-Fred???



could be soon, looking at that shear map...
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deepening vorticity on the invest

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I want to know when SSD will finally put a floater back over ex-Fred???

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Quoting TriniGirl26:
shouldn't shear be taking 98L apart about now?


not quite, i believe a weak anticyclone might be converging? over it

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Quoting Patrap:


I never knew I yielded such power.

Im gonna have to Holster it...

Till then,beware the Patrap finger-O-doom.
I meant well. I was referring to the Murphy,s law ideology. Just when you think the coast is clear......Or the don,t say that, you will jinx us theory.... BTW..The withdrawal med thing was totally intended for Tornadodudes post, just in case you did not read that part.....lol
Member Since: September 27, 2007 Posts: 1 Comments: 20509
Ok, not trying to be a wishcaster or doomcaster here, but I have a question. Is there any possibility x-Fred gets into the GOM and pulls a Katrina on us? It's awfully hot in there. TIA
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One things for certain... I'm not trusting any output from the models as of yet!

The HWRF and GFDL both move the storm west and then southwest.

Currently it is moving northwest...


RGB LOOP
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Fred is being sheared by 20 knots of shear between a ridge over the Bahamas and the upper low that was over Fred (now to its southeast)

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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.