New African disturbance 96L likely to develop

By: Dr. Jeff Masters , 2:55 PM GMT on September 07, 2009

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A tropical wave (96L) that emerged off the coast of Africa yesterday has organized rather quickly, and will likely become a tropical depression by Tuesday night. Satellite imagery from the European satellite shows a well-organized circulation, but not enough heavy thunderstorm activity near the center of circulation to be considered a tropical depression. The storm is far enough south that the dry air of the Saharan Air Layer is not a major impediment to development. Wind shear is moderate, 10 - 15 knots, and ocean temperatures are 1 - 2°C above the threshold needed for tropical cyclone formation.


Figure 1. Morning satellite image of 96L, off the coast of Africa. The remains of disturbance 95L, which are under 30 - 40 knots of wind shear, can be seen at upper left.

The forecast for 96L
Most of the models develop 96L, and the chances are that this disturbance will become Tropical Storm Fred later this week. The system will initially move west-northwest, but by Thursday, a strong trough of low pressure passing to 96L's north will pull the storm to the northwest, and may be capable of fully recurving the storm to the northeast. However, most of the models foresee that 96L will not move far enough north for this to happen, and that the storm will have to wait for the next trough of low pressure. With the steering pattern for this year continuing to feature plenty of deep troughs of low pressure moving off the U.S. East Coast, the odds of 96L making it all the way across the Atlantic to threaten land areas appear low. Still, much that is unexpected can and does happen in the world of tropical meteorology, and 96L bears watching.

North Carolina low
An area of concentrated thunderstorms has developed off the North Carolina coast in association with the remains of an old cold front. This system is under about 20 - 30 knots of shear, and is not tropical. However, it will bring heavy rain to eastern North Carolina today and Tuesday, as the storm slides north-northeastward along the coast.

I'll have an update Tuesday.

Jeff Masters

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My public advisory on Dujuan at 5PM
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Tropical Update by IPR365

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Quoting Weather456:
Lots of rain...rainfall totals have generally been 4 inches with 6 and 8 inches reported by several PWS






I just cannot imagine that much rain... for us a major rain storm is 2-3 inches in a 24 hour period..... I have seen people mention that amount in an hour.
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I'm thinking my September Outlook of 4-5 named storms will verify...its been 1 week so far and I'm half way there (if Fred is named this week)
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Will probably see some type of disturbance in the gulf later this week. Could perhaps develop into a tropical cyclone but its wait and see. Best chances for development still appear to be in the EATL with a couple more vigorous waves to emerge during the next week.
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I don't pay too much attention to official coordinate in developing systems. They relocate, I follow the larger system to get idea of trend.
Member Since: August 10, 2007 Posts: 0 Comments: 3293
Lots of rain...rainfall totals have generally been 4 inches with 6 and 8 inches reported by several PWS




Member Since: July 24, 2005 Posts: 407 Comments: 19076
820-but our line of troffy buddies will help to deflect any potential systems away from the conus, correct?
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Quoting futuremet:
It looks like we will have increase cape-verde systems during the end of September, as the MJO settles back in across the region. This is in conjunction with what the GFS and NOGAPS have been showing. The current GFS cycles are currently showing increased moisture and decrease vertial shear across the MDR, and as a result forms a parade of vigorous tropical waves ejecting off the African coast. The NOGAPS has been showing decreasing aerosol (SAL) levels near the region, due to the increased precipitation over semi-arid regions; which is caused by the positive MJO. The southwestern Caribbean will have to be watched in October, because SSTs will be above average across much of the region.





yea futuremet and to me this season will not end in September like so many claim it will. MJO shows a pretty strong upward motion for the GOM, Caribbean and West Atlantic starting during the last week of September and going through mid-October; to me in this time we could get 3 or 4 storms to form in that area with all those undisturbed waters.

For people who think this season is over, you are dead wrong.
Quoting centex:
My initial take on TD7 is it's trending S of W. So it will most likey miss first trough and continue west for couple of days. So I don't see it at 15N on Wednesday. Water vapor shows the N track has moved much further N since last system got picked up by it.


Actually its moving a bit north of west at 280 degrees. You can see in the center coordinates this as well.
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18z full atlantic GFS loop. Keep refreshing page as the images are added.

Link
Member Since: July 29, 2006 Posts: 28 Comments: 1802
Nice burst of convection over the circulation center. Will probably see TS Fred at 11 if trends continue.

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AOI

AOI

AOI

AOI
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We had a pretty heavy rain here in Norfolk this morning, with more to come. It was a cold rain, though. Or it wasn't the really warm rain that usually comes with tropical systems. Nice heavy warm rain falling hard in the streets making puddles all over the place and ... brb, bathroom.
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My initial take on TD7 is it's trending S of W. So it will most likey miss first trough and continue west for couple of days. So I don't see it at 15N on Wednesday. Water vapor shows the N track has moved much further N since last system got picked up by it.
Member Since: August 10, 2007 Posts: 0 Comments: 3293
Quoting emeraldcoast:
Patrap ... where you at? Need your obsv on BOC and GOM activity.


right now its just scattered convection, nothing imminent at this point. If anything were to form it would likely to take 4-5 days
It looks like we will have an increase cape-verde systems during the end of September, as the MJO settles back in across the region. This is in conjunction with what the GFS and NOGAPS have been showing. The current GFS cycles are currently showing increased moisture and decrease vertial shear across the MDR, and as a result forms a parade of vigorous tropical waves ejecting off the African coast. The NOGAPS has been showing decreasing aerosol (SAL) levels near the region, due to the increased precipitation over semi-arid regions; which is caused by the positive MJO. The southwestern Caribbean will have to be watched in October, because SSTs will be above average across much of the region.



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Quoting laflastormtracker:
I do not doubt specs of food in Cajun Land or in NOLA!

Somewhere between my house and Pat's he will be well fed
Member Since: September 5, 2007 Posts: 0 Comments: 3488
Patrap ... where you at? Need your obsv on BOC and GOM activity.
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I do not doubt specs of food in Cajun Land or in NOLA!
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come on 18z gfs! I'm sitting here f5ing because we finally have 2-3 interesting systems in the atlantic.
Member Since: July 29, 2006 Posts: 28 Comments: 1802
Its very unlikely that we will see a named storm out of the area by North Carolina, but in the end the effects will be the same.
Quoting laflastormtracker:
Wonder if CycloneOz is booking his trip to LA yet? LOL

If Oz comes this way he will be well fed and well taken care of!
Afternoon all...
Member Since: September 5, 2007 Posts: 0 Comments: 3488
Tropical update from today
Member Since: July 24, 2005 Posts: 407 Comments: 19076
The feature is currently a shallow warm-core system, likely due to the injection of warm tropical air...expected to transition to cold core soon.



Low level swirl evident

Member Since: July 24, 2005 Posts: 407 Comments: 19076
Wonder if CycloneOz is booking his trip to LA yet? LOL
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Quoting Levi32:


I don't think the system will ever be able to be thought of as fully tropical. It's one of those east coast hybrids that tries to go warm-core and can cause a lot of nasty weather that wasn't previously expected. However it's position in the upper-level flow with a baroclinic zone just to its west denies it the needed conditions to become a truly tropical system.


It is interesting though to remember that this system formed as the result of an African tropical wave that moved through the Bahamas last week phasing its energy into the old frontal boundary sitting along the eastern seaboard. I remember seeing some talk about this being Erika's remnants. That is not true, as this wave was the one in front of Erika in the Bahamas, that you can clearly see in archived satellite images when Erika was named.
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Does anyone have any more info on possible activity in the GOM?
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Quoting winter123:


This is a very unusual situation. Looks like us in the northeast are in for sticky tropical air and heavy rain? What do you think of the chances for a full tropical transition? (Sitting over the gulf stream for days, already subtropical but its sheared, if shear abates i think itll be td8)


I don't think the system will ever be able to be thought of as fully tropical. It's one of those east coast hybrids that tries to go warm-core and can cause a lot of nasty weather that wasn't previously expected. However it's position in the upper-level flow with a baroclinic zone just to its west denies it the needed conditions to become a truly tropical system.
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TD 7 is another fish in the sea.
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797. IKE
NO,LA long-term...

"LONG TERM...
FRIDAY WILL BE A TRANSITION DAY FOR THE PATTERN. BOTH GFS AND ECMWF
BRING A CLOSED UPPER LOW INTO THE NORTHERN PLAINS OVER THE WEEKEND
BEFORE MOVING IT INTO THE GREAT LAKES. AN IMPULSE GETS ADVECTED OUT
OF NORTHERN MEXICO AHEAD OF THE UPPER TROF...AND SOUTHWESTERLY FLOW
AHEAD OF THE IMPULSE PUMPS MASSIVE AMOUNTS OF MOISTURE INTO THE
AREA FOR THE WEEKEND. FORECAST PRECIPITABLE WATER VALUES IN EXCESS
OF 2.25 INCHES FOR SATURDAY AND SUNDAY. WITH SURPRISING CONSISTENCY
BETWEEN THE MODELS ON THIS SCENARIO...HAVE OPTED TO GO WITH LIKELY
POPS FOR SATURDAY AND SUNDAY. MAIN IMPULSE FORECAST TO MOVE BY ON
MONDAY AND WILL DROP POPS BACK INTO THE CHANCE RANGE. CLOUDS AND
PRECIPITATION SHOULD HOLD TEMPERATURES BELOW CLIMATOLOGY."
Member Since: June 9, 2005 Posts: 23 Comments: 37860
796. IKE
Long-term afternoon discussion from the beautiful city of Mobile,Alabama.....

"LONG TERM...(THURSDAY ON)THE END OF THE SHORT TERM...A SIGNIFICANT
SHORTWAVE SYSTEM MOVES ONSHORE OVER THE PACIFIC NORTHWEST. BY
FRIDAY...THIS SHORTWAVE SYSTEM ORGANIZES INTO A CLOSED LOW OVER THE
US/CA PLAINS BORDER...AND BEGINS TO PUSH THE OHIO RIVER VALLEY LOW
EAST. THE WEAK UPPER TROUGH REMAINS JUST EAST OF THE MISS
RIVER...WHILE THE WESTERN GULF/BAY OF CAMPECHE SYSTEM CONTINUES TO
ORGANIZE. THIS WILL ORGANIZE THE LOW LEVEL FLOW INTO A GENERALLY
SOUTHEASTERLY FOR THE WEEKEND. GUIDANCE IS ADVERTISING THE WESTERN
GULF SYSTEM TAKING A NORTH-NORTHEASTWARD TREK OVER THE WEEKEND INTO
THE COMING WEEK...INCREASING THE LOW LEVEL ONSHORE FLOW OVER THE
NORTHERN GULF...PUSHING THE CHANCE FOR RAIN ABOVE SEASONABLE...WHILE
LEAVING TEMPS AROUND SEASONABLE."
Member Since: June 9, 2005 Posts: 23 Comments: 37860
I can see why the NHC is going with the LGEM, it seems to be the model that is verifying with 96L/TD 7 intensity thus far.


The HWRF continues to over do intensity this year for example:

Intensity errors from when 96L was initialize to 1800Z 7 September

HWRF - 22 knots
LGEM - 5 knots
SHIPS - 12 knots

In other words, when 96L was initialize, the HWRF had it 52 knots by 1800Z today, but it only reached 30 knots, so you have a forecast error of 22 knots


Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting IKE:
18Z NAM...


It is still unsure where along the surface trough will the predominant low develop.
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Quoting centex:
I would keep an eye on TD7. No one predicted Erika would enter Caribbean except a few like me, and the few got blasted because most here are model worshipers. We learned shear forecast are totally unreliable and storms can and do go outside the cone, even in just 12 hour periods.


thank you. Many models are hinting at W movement starting 6 days out.
Member Since: July 29, 2006 Posts: 28 Comments: 1802
Quoting centex:
I would keep an eye on TD7. No one predicted Erika would enter Caribbean except a few like me, and the few got blasted because most here are model worshipers. We learned shear forecast are totally unreliable and storms can and do go outside the cone, even in just 12 hour periods.


I vouch I remember this. A group from Texas and I were concerned about Erika for awhile lo and behold we are still watching the remnants of Erika. Great job, man.
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Quoting HurricaneSeason2004:
Why isn't TD 7 going to be a hurricane?

Running into a very hostile environment in 2 days, to much shear from the SE,plus cooler waters if it follows the projected pass.
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Quoting Levi32:


There's a lot of rain in store for the eastern seaboard over the next 3-6 days. The GFS 72-hour surface map shows the long easterly fetch that sets up bringing a ton of moisture right into New Jersey and the surrounding coastline. The low gets trapped by a big surface high over New England and will be sitting near the coast for several days, making this a serious flooding threat with large amounts of moisture coming in from the easterly flow.

The 500mb map shows how the trough to the west digs in with a negative tilt and helps keep the low close to the coast and allow moisture to come piling into the eastern seaboard.





This is a very unusual situation. Looks like us in the northeast are in for sticky tropical air and heavy rain? What do you think of the chances for a full tropical transition? (Sitting over the gulf stream for days, already subtropical but its sheared, if shear abates i think itll be td8)
Member Since: July 29, 2006 Posts: 28 Comments: 1802
Quoting centex:
I would keep an eye on TD7. No one predicted Erika would enter Caribbean except a few like me, and the few got blasted because most here are model worshipers. We learned shear forecast are totally unreliable and storms can and do go outside the cone, even in just 12 hour periods.


Centex i agree but, only a half of 1 eye open tho....
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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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