First tropical depression of the season may form from 92L

By: Dr. Jeff Masters , 3:38 PM GMT on June 13, 2010

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An unusually large and well-developed African tropical wave for so early in the season has developed midway between the coast of Africa and South America. The storm was designated Invest 92L by the National Hurricane Center yesterday, and has a good chance of becoming the first tropical depression of the Atlantic hurricane season. Surface winds measured by the 8:23am EDT pass of the European ASCAT satellite revealed that 92L already has a closed surface circulation, though the circulation is large and elongated. Top winds seen by ASCAT were about 25 mph. METEOSAT visible satellite loops show a large and impressive circulation that is steadily consolidating, with spiral bands building inward towards center, and upper-level outflow beginning to be established to the northwest and north.


Figure 1. Morning satellite image of Invest 92L.

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 - 30°C, which is warmer than the temperatures reached during the peak of hurricane season last year, in August - September. 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.) While 92L will cross over a 1°C cooler patch of water on Monday, the storm will encounter very warm SSTs of 28-29°C again by Tuesday.

The disturbance doesn't have to worry about dry air--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 300 - 400 miles from any substantial areas of dry air. The 60-day cycle of enhanced thunderstorm activity called the Madden-Jullian 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.

The forecast for 92L
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 is currently located at 7°N, well south of this band of high shear, and is only experiencing 5 - 15 knots of shear. This moderate amount of shear should allow for some steady development of 92L over the next few days as it tracks west-northwest at 10 - 15 mph. The National Hurricane Center is giving 92L a medium (30% chance) of developing into a tropical depression by Tuesday morning. Based on visible satellite imagery over the past few hours, I believe this forecast is not aggressive enough, and that 92L has a 50% chance of developing into a tropical depression by Tuesday morning. Another factor holding 92L back is its proximity to the Equator. I would give 92L higher chances of developing if it were not so close to the Equator. The system is organizing at about 7°N latitude, which is so close to the Equator that it cannot leverage the Earth's spin much to help it get spinning. It is quite unusual for a tropical depression to form south of 8°N latitude.

The farther south 92L stays, the better chance it has at survival. With the system's steady west-northwest movement this week, 92L should begin encountering hostile wind shear in excess of 30 knots by Thursday, which should be able to greatly weaken or entirely destroy the storm before it gets to the Lesser Antilles Islands. However, 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 by Saturday or Sunday next weekend. The GFDL and HWRF models are predicting that 92L will develop into a moderate strength tropical storm that will then be weakened or destroyed by the end of the week, before it reaches the islands. This looks like a reasonable forecast.


Figure 3. The departure of sea surface temperature (SST) from average for June 10, 2010. Image credit: NOAA/NESDIS.

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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Quoting hurricane23:
Not overly impressed with 92L this evening. Thunderstorm activity is still rather weak although the overall structure and organization is good.


I am starting to think that wave behind 92L has a lot more potential. Think about it. By the time it gets far west, wind shear should be low enough for it to develop. Even if 92L were to become a tropical depression, it has to go through high wind shear.
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"I don't like the looks of that XTRAP model..."
















...sorry just had to do it.
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Quoting wfyweather:
XTRP isnt a freakin model, it just shows its current motion


shhh..dont tell them that.. right now 40% of this room thinks we have a Tropical storm right now
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Yes it goes into the Thermodynamics of Meteorology
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SSD dvorak numbers are the same as this afternoon ones,1.0.

13/2345 UTC 7.8N 37.0W T1.0/1.0 92L -- Atlantic

Link
Member Since: April 29, 2009 Posts: 75 Comments: 14050
XTRP isnt a freakin model, it just shows its current motion
Member Since: July 12, 2008 Posts: 11 Comments: 422
92L is only 2,930 miles from Miami.
Spaghettios are two for $1. Should I stock up?
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92L is moving off the ITZ but lagging in convection over a LLC
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2938. Drakoen
Quoting louisianaboy444:


Pretty well i've taken the summer off to spend time with family but i'm jumping into the pit come fall...i have two physics classes A calculus, a high end atmospheric course, and two more electives including a Music Appreciate..ugh


Is the high end atmospheric course Atmospheric Dynamics?
Member Since: October 28, 2006 Posts: 57 Comments: 29918
Quoting Drakoen:


I thought so. How's that coming along?


Pretty well i've taken the summer off to spend time with family but i'm jumping into the pit come fall...i have two physics classes A calculus, a high end atmospheric course, and two more electives including a Music Appreciate..ugh
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Quoting AstroHurricane001:


Wow, this one is 12 x 11 deg in diameter. I have a really bad feeling about this season if that kind of wave train continues.


Oh, haha. Should have known.
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Quoting AstroHurricane001:


Wow, this one is 12 x 11 deg in diameter. I have a really bad feeling about this season if that kind of wave train continues.
No reason for the train to stop. Each one will just be more and more impressive.
Member Since: December 1, 2006 Posts: 2 Comments: 3619
Quoting hurricane23:
Only chance at getting a named storm is if it takes a southerly course. If it takes its current heading wnw-nw it will likely get torn apart pretty quickly.


Looks like from satellite imagery the northern part of the system was being affected by shear earlier. If you look closely, you can see the northern part sort of flattens out. However, the last few frames of the loop indicate the shear could have relaxed some. If the upper level high pressure system continues to move in tandem with 92L, shear may not be much of a player at all.
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The entire basin out ahead of 92l is looking fairly hostile on water vapor imagery. The system will be bumping up against an area of high shear and dry air soon.
Member Since: December 1, 2006 Posts: 2 Comments: 3619
2932. xcool
Member Since: September 26, 2009 Posts: 2 Comments: 15625
2931. Drakoen
Quoting louisianaboy444:


yes i'm currently a junior at ULM


I thought so. How's that coming along?
Member Since: October 28, 2006 Posts: 57 Comments: 29918
Quoting xcool:
92L ppopop


???
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CMC is on track (track wise)
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Quoting JLPR2:
the wave behind 92L has actually sustained convection in the land to water process



Wow, this one is 12 x 11 deg in diameter. I have a really bad feeling about this season if that kind of wave train continues.
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Quoting AstroHurricane001:


BAMS and BAMD look really scary, and what is that model taking the storm into Florida?!


XTRP
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2926. JLPR2
Quoting FLWeatherFreak91:
Yes and it is showing some signs of early banding.


banding? O_o
where?
Member Since: September 4, 2007 Posts: 7 Comments: 8503
Quoting pottery:


Downcasters Annonymous.

heheheh


I don't even try to cast... unless I am fishing :)
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Quoting Orcasystems:


AOI

AOI

AOI

AOI

TS BUSTED FORECAST ALIBI


BAMS and BAMD look really scary, and what is that model taking the storm into Florida?!
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2923. Drakoen
Quoting MississippiWx:


Drak,

Was reading your comment one page back about how it's going through some structural changes. Seems to me that it's becoming independent and detaching itself from the ITCZ. Could be why the convection isn't as impressive as it once was. However, as it becomes its own entity and a more established low pressure area, I see no reason for it not to strengthen further (unless shear increases).


Exactly
Member Since: October 28, 2006 Posts: 57 Comments: 29918
Quoting Drakoen:


Aren't you a met student?


yes i'm currently a junior at ULM
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2921. Ossqss
Quoting pottery:

LOL I agree!!
It's boring in here without Ptrap.
So I am going to bed.........



Did he hit the lottery?

L8R, have a good evening folks!

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2920. xcool
92L ppopop
Member Since: September 26, 2009 Posts: 2 Comments: 15625
Oh boy, how I love this blog and the differing opinions on here lol.
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Quoting JLPR2:
the wave behind 92L has actually sustained convection in the land to water process

Yes and it is showing some signs of early banding.
Member Since: December 1, 2006 Posts: 2 Comments: 3619
Only chance at getting a named storm is if it takes a southerly course. If it takes its current heading wnw-nw it will likely get torn apart pretty quickly.
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2916. JLPR2
the wave behind 92L has actually sustained convection in the land to water process

Member Since: September 4, 2007 Posts: 7 Comments: 8503
2915. pottery
Quoting Orcasystems:
None of the models are taking it above a TS anymore.


Downcasters Annonymous.

heheheh
Member Since: October 24, 2005 Posts: 0 Comments: 24059
Quoting Skyepony:
Meteosat shot of cloud top hieghts. Wave stepping off Africa is firing higher than 92L tonight.


That's quite a wave train! Maybe it'll set off a Fujiwara between 92L and the wave behind it. We should closely watch waves coming off Africa for signs of intense lightning activity because that can make a difference between a CV system that makes it to the Western Atlantic and one that fizzles out.
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Quoting Drakoen:


Aren't you a met student?


Drak,

Was reading your comment one page back about how it's going through some structural changes. Seems to me that it's becoming independent and detaching itself from the ITCZ. Could be why the convection isn't as impressive as it once was. However, as it becomes its own entity and a more established low pressure area, I see no reason for it not to strengthen further (unless shear increases).
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Quoting Orcasystems:
None of the models are taking it above a TS anymore.


As they shouldn't be.
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2911. xcool
Member Since: September 26, 2009 Posts: 2 Comments: 15625
92L is still alive and well...Think of tropical systems as a gas latern it will flicker a couple of times before getting enough power to stay lit....these systems take time....good outflow and good structure just waiting on the convection to start
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None of the models are taking it above a TS anymore.
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2908. KEEPEROFTHEGATE (Mod)
Quoting hurricane23:
Not overly impressed with 92L this evening. Thunderstorm activity is still rather weak although the overall structure and organization is good.


its doing somin
looks to be really tightening up going compact
if a convective cycle would to pop
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AOI

AOI

AOI

AOI

TS BUSTED FORECAST ALIBI
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Quoting KEEPEROFTHEGATE:
its runnin 240 242 comments per hr


Holy carp, that's one every 15 seconds! And I say holy carp because I hope this storm turns out to be a fish-spinner.
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2905. pottery
Quoting Ossqss:
As I exit, where the heck is Patrap? He is the master of tropical imagery after all. It certainly breaks up the text messaging.//// As I just do one :)

L8R >>>>




LOL I agree!!
It's boring in here without Ptrap.
So I am going to bed.........
Member Since: October 24, 2005 Posts: 0 Comments: 24059
2904. 7544
all and all i do believe this will be td1 and first ts of the season alex but how long it will surrive is all up the air stay tuned
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ONe would have to conclude with the CAPE VERDE season is already started looking at 92L and what is behind it......this does not look good for the season....GEESH
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2902. Drakoen
Quoting louisianaboy444:
I can try my best to answer your questions


Aren't you a met student?
Member Since: October 28, 2006 Posts: 57 Comments: 29918
2901. Skyepony (Mod)
Meteosat shot of cloud top hieghts. Wave stepping off Africa is firing higher than 92L tonight.
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2900. Ossqss
As I exit, where the heck is Patrap? He is the master of tropical imagery after all. It certainly breaks up the text messaging.//// As I just do one :)

L8R >>>>



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Quoting weathersp:


and this is diffrent form any other time there is a statem in the ATL how? ;)


Sometimes there is a 4th faction in the war:

| Miami is next! |

lol just like diurnals this blog goes in cycles.
Member Since: May 27, 2009 Posts: 0 Comments: 4436
2898. KEEPEROFTHEGATE (Mod)
Quoting AstroHurricane001:
Wow, this entry was written 12 hours ago and already we have over 2800 comments. And there is very little shear for 92L if it survives intact into the Caribbean.
its runnin 240 242 comments per hr
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Quoting txsweetpea:
What would happen if a hurricane hit the gulf coast with the oil spill out in the gulf?
Thats a Good Question...
If a storm comes in on th west side of the spill, it will bring the Oil to the east ashore... Although the waves would break up the oil it would send tar balls from MS to FL Panhandle.
If it comes to the east side of the spill, it would send the oil out to sea for a while longer and the waves still breaks up into tar balls....

Taco :o)
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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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