Unusually well-organized 92L disturbance may become a tropical depression

By: Dr. Jeff Masters , 2:14 PM GMT on June 14, 2010

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Invest 92L, a remarkably well-developed African tropical wave for so early in the season, is midway between Africa and the Lesser Antilles Islands. Infrared satellite loops show a modest area of heavy thunderstorms along the north side of 92L's center of circulation, and the storm's heavy thunderstorms activity appears to be slowly increasing in intensity and areal coverage. Upper-level outflow is apparent to the west and north of 92L, and the outflow has been gradually improving this morning. Visible satellite loops do not show much in the way of low-level spiral bands, and my current take from the satellite imagery is that 92L is slowly organizing, and will not become a tropical depression any earlier than 11pm EDT tonight (Monday.) A 4:27 am EDT pass from the WINDSAT satellite saw a partially closed circulation at the surface (open on the south side), with top surface winds of 25 - 30 mph north of the center.


Figure 1. Morning satellite image of Invest 92L (left side of image) and a vigorous new tropical wave that has moved off the coast of Africa (right side.) None of models develop the new tropical wave, but it bears watching.

Sea surface temperatures
Climatology argues against development of 92L, since only one named storm has ever formed between Africa and the Lesser Antilles Islands in the month of June--Tropical Storm Ana of 1979 (Figure 2). However, sea surface temperatures (SSTs) underneath 92L are an extremely high 28°C, and will increase to 29°C by Thursday. In fact, with summer not even here, and three more months of heating remaining until we reach peak SSTs in the Atlantic, ocean temperatures across the entire Caribbean and waters between Africa and the Lesser Antilles are about the same as they were during the peak week for water temperatures in 2009 (mid-September.)

Dry air not a problem for 92L until Wednesday
The disturbance doesn't have to worry about dry air today or Tuesday--Total Precipitable Water (TPW) loops show a very moist plume of air accompanies 92L, and water vapor satellite loops show that the center of 92L is at least 200 - 300 miles from any substantial areas of dry air. As 92L continues to push northwest, though, the SHIPS model is predicting that relative humidity at middle levels of the atmosphere will fall from the current value of about 70%, to 60% on Wednesday. This dry air may begin to cause problems for 92L on Wednesday, especially since wind shear will be increasing at the same time. Tropical cyclones are more vulnerable to dry air when there is substantial wind shear, since the strong winds causing the shear are able to inject the dry air deep into the core of the storm.

Madden-Julian Oscillation
The 60-day cycle of enhanced thunderstorm activity called the Madden-Julian Oscillation is currently favoring upward motion over eastern tropical Atlantic, and this enhanced upward motion helps create stronger updrafts and higher chances of tropical cyclone development.


Figure 2. Tropical Storm Ana of 1979 was the only June named storm on record to form between Africa and the Lesser Antilles Islands.

Wind shear
A major issue for 92L, like it is for most June disturbances, is wind shear. The subtropical jet stream has a branch flowing through the Caribbean and tropical Atlantic north of 10° N that is bringing 20 - 40 knots of wind shear to the region. Our disturbance was located near 10°N, 40°W at 8am EDT this morning, a few hundred miles south of this band of high shear, and is currently only experiencing 5 - 10 knots of shear. This low amount of shear should allow for some steady development of 92L over the next two days as it tracks west-northwest or northwest at 15 mph. The latest run of the SHIPS model is predicting the shear will rise to 20 knots on Wednesday, which may start to cause problems for 92L.

The forecast for 92L
The National Hurricane Center is giving 92L a high (60% chance) of developing into a tropical depression by Wednesday morning, which is a reasonable forecast. The odds of development have increased since yesterday, as the storm has moved considerably to the northwest, away from the Equator. Now it can leverage the Earth's spin to a much greater degree to help get it get spinning. It is quite unusual for a tropical depression to form south of 8°N latitude.

I expect that 92L's best chance to become a tropical depression will come on Tuesday, and the storm could strengthen enough by Wednesday to be named Tropical Storm Alex. The farther south 92L stays, the better chance it has at survival. With the system's steady west-northwest movement this week, 92L will probably begin encountering hostile wind shear in excess of 20 knots by Wednesday, which should interfere with continued development. Several of our reliable models do develop 92L into a tropical storm with 40 - 55 mph winds, but all of the models foresee weakening by Thursday or Friday as 92L approaches the Lesser Antilles Islands and encounters high shear and dry air. I doubt 92L will be anything stronger than a 45 mph tropical storm when it moves through the northern Lesser Antilles Islands on Friday and Saturday, and it would be no surprise if wind shear has destroyed the storm by then. However, as usual, surprises can happen, and the GFS and the SHIPS model (which is based upon the GFS) do indicate that more modest levels of wind shear in the 15 - 20 mph range late this week may allow 92L to stay stronger than I'm expecting. Residents of the islands--particularly the northern Lesser Antilles--should follow the progress of 92L closely, and anticipate heavy rains and high winds moving through the islands as early as Thursday night.

Oil spill wind forecast
There is little change to the oil spill wind forecast for the coming two weeks. Light winds of 5 - 10 knots mostly out of the south or southeast will blow in the northern Gulf of Mexico all week, according to the latest marine forecast from NOAA. These winds will keep oil near the coast of Louisiana, Alabama, Mississippi, and the extreme western Florida Panhandle, according to the latest trajectory forecasts from NOAA and the State of Louisiana. The long range 8 - 16 day forecast from the GFS model indicates a typical summertime light wind regime, with winds mostly blowing out of the south or southeast. This wind regime will likely keep oil close to the coastal areas that have already seen oil impacts over the past two weeks.

Jeff Masters

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1891. Levi32
Quoting cchsweatherman:


I'm more impressed with the fact that its raining over the Central Saharan Desert. Quite something to see.


Yes it is.
Member Since: Posts: Comments:
1888. xcool
Miami lol fatallthat..
Member Since: September 26, 2009 Posts: 2 Comments: 15705
1887. SLU
Quoting pottery:
An interesting note, for those who are interested in the Workings of Calabash Trees as they relate to Weather (this is Serious, man!)

I came home today to find that my yard is smelling of a dead something. You know the smell. It conjures-up a grim 20 minutes of up-close Disposal of The Worst Kind. Dread, putrid aroma.

So I went seeking, and under my Calabash Tree, is growing a "Snake Plant" (local name) that puts out its weird and wonderful leaves around this time when the rains have wet it.
The Snake Plant has put out a Flower (I use the term loosely, as it is a large, purple/orange/mustard-coloured thing, that last bloomed in 2007!
The name of the plant (get this) is AMORPHOPHALLUS, and it has the unmistakeable aroma of Death, Rotting Flesh and All Things Horrid.

This is, to my mind (and with the Knowledge that the Calabash has already made Signs and Portents pertaining to this Season) a very sure sign of Bad Things to Come. Weather-Wise, of course.


That gave me the chills. SCARY, VERY SCARY

Before 2007, when last did it appear?
Member Since: Posts: Comments:
Quoting StormFreakyisher:



Banana oil!

Quoting pottery:
An interesting note, for those who are interested in the Workings of Calabash Trees as they relate to Weather (this is Serious, man!)

I came home today to find that my yard is smelling of a dead something. You know the smell. It conjures-up a grim 20 minutes of up-close Disposal of The Worst Kind. Dread, putrid aroma.

So I went seeking, and under my Calabash Tree, is growing a "Snake Plant" (local name) that puts out its weird and wonderful leaves around this time when the rains have wet it.
The Snake Plant has put out a Flower (I use the term loosely, as it is a large, purple/orange/mustard-coloured thing, that last bloomed in 2007!
The name of the plant (get this) is AMORPHOPHALLUS, and it has the unmistakeable aroma of Death, Rotting Flesh and All Things Horrid.

This is, to my mind (and with the Knowledge that the Calabash has already made Signs and Portents pertaining to this Season) a very sure sign of Bad Things to Come. Weather-Wise, of course.


Are you serious? Link

Member Since: Posts: Comments:
Quoting cchsweatherman:


I'm more impressed with the fact that its raining over the Central Saharan Desert. Quite something to see.
Yeah, I agree.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting xcool:
i need chocolate milk mmmmm
I'm eating string cheese, lol.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting MiamiHurricanes09:
The circular area of convection inside the green circle.



I'm more impressed with the fact that its raining over the Central Saharan Desert. Quite something to see.
Member Since: Posts: Comments:
1880. Levi32
Quoting KEEPEROFTHEGATE:


19 at 11/42
20 at 6/28
21 at 9/18

we are at 21


Any clue how that compares to normal climatology? I can't find a site with average wave counts per month of the season.
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Quoting Acemmett90:

ok this could be 93L in the Makeing i would recomend whatching this sucker closely like you would if dick chaniny had the us nuclear lunch codes

mmmmmm, nuclear lunch...my favorite!
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1878. Patrap
NOAA RAAMB AL922010 - INVEST
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1875. xcool
Acemmett90 lolohhhhhhh
Member Since: September 26, 2009 Posts: 2 Comments: 15705
Quoting Patrap:


Thanx for the input..

Im gonna go with your suggestion.


I'll bring the milk.
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1872. Patrap
Quoting LoneStarWeather:

I vote for oatmeal!


Thanx for the input..

Im gonna go with your suggestion.

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1871. xcool
i need chocolate milk mmmmm
Member Since: September 26, 2009 Posts: 2 Comments: 15705
1870. Patrap
100611-G-0000W-001-One ton tarball

GULF OF MEXICO – One of two one-ton masses of tarball material recovered south of Perdido Pass, Fla., by the crew of the lift boat Sailfish, a Vessel of Opportunity working in the largest oil spill response in U.S. history, on Saturday, June 11, 2010. Photo by Petty Officer 3rd Class John Walker, USCG.
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1869. KEEPEROFTHEGATE (Mod)
Quoting Acemmett90:

whats the wave count? cause each one is getting more intense


19 at 11/42
20 at 6/28
21 at 9/18

we are at 21
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1868. xcool
Acemmett90 .;0
Member Since: September 26, 2009 Posts: 2 Comments: 15705
Quoting Patrap:
Oatmeal or Chocolate Chip..?


Hmmm,..decisions,decisions

I vote for oatmeal!
Member Since: Posts: Comments:
Quoting MiamiHurricanes09:
Wait until the B/A high sets in place, but the safest choice regardless is NYC.


Although NYC is at lower risk than NOLA or Miami, I say it's still at increased risk this year due to possible highs building up over upper New England driving storms west. The Bermuda-Azores high is also small to begin with and will likely be offset to the northeast due to moisture.

Quoting Drakoen:
Look at the winds on the partially closed low



That looks like 35kt+ winds! Is ASCAT accurate?

Quoting MiamiHurricanes09:
In the long run yes. When there is a small amount of SAL during the stage of development chances are that the system will strengthen quite rapidly (if other conditions are right of course), and this could spell big trouble for the Caribbean, east coast, and GOM in the long run.


Low SAL and low pressure in the Caribbean is also bad news for parts of the Amazon rainforest as some areas could experience drought.
Member Since: Posts: Comments:
1864. pottery
An interesting note, for those who are interested in the Workings of Calabash Trees as they relate to Weather (this is Serious, man!)

I came home today to find that my yard is smelling of a dead something. You know the smell. It conjures-up a grim 20 minutes of up-close Disposal of The Worst Kind. Dread, putrid aroma.

So I went seeking, and under my Calabash Tree, is growing a "Snake Plant" (local name) that puts out its weird and wonderful leaves around this time when the rains have wet it.
The Snake Plant has put out a Flower (I use the term loosely, as it is a large, purple/orange/mustard-coloured thing, that last bloomed in 2007!
The name of the plant (get this) is AMORPHOPHALLUS, and it has the unmistakeable aroma of Death, Rotting Flesh and All Things Horrid.

This is, to my mind (and with the Knowledge that the Calabash has already made Signs and Portents pertaining to this Season) a very sure sign of Bad Things to Come. Weather-Wise, of course.
Member Since: Posts: Comments:
Quoting Patrap:
MODIS Truecolor Oil Spill June 12, 2010
Is that oil off the coast of the panhandle?
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1860. xcool
Acemmett90 lmao /StormFreakyisher haha
Member Since: September 26, 2009 Posts: 2 Comments: 15705
1859. Patrap
Oatmeal or Chocolate Chip..?


Hmmm,..decisions,decisions
Member Since: Posts: Comments:
I saw on the PBS Newshour that the U.S. has accepted help from several countries in regards to getting more skimmers & boom in the GOM. I would have swalled my pride & asked for this right away. Better late than never.

Yes, I think Joe Bastardi is member of WU. He mainly lurks and uses information on here for his "official" forecasts.
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Quoting xcool:


kaboom

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Quoting WindDamage:


really, kman? :(, but aren't they all ''unimpressive'' in your book? lol.


Not really. I call it the way I see it. This morning I said 92L was on the wane big time and so it was.
Member Since: August 19, 2006 Posts: 0 Comments: 15949
Quoting Levi32:


Dang, you're ill too? Hope you get better.
If people are getting ill from an invest, imagine what a CAT 5 will do to ya?
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting WindDamage:
guys, where's the low off Africa? :0
The circular area of convection inside the green circle.

Member Since: September 2, 2009 Posts: 130 Comments: 21194
1849. Levi32
Quoting StormW:
See all of you tomorrow. This sinus infection is kicking my butt!


Dang, you're ill too? Hope you get better.
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The ASCAT pass just off the West coast of Africa is totally unimpressive. Just a jumble of multi directional surface winds
Member Since: August 19, 2006 Posts: 0 Comments: 15949
1843. KEEPEROFTHEGATE (Mod)
Quoting Drakoen:
Possible low pressure center off the African Coast:

yep one right after another
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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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