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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3247. xcool
2.0 OR 1.5 NEXT TIME.
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Quoting xcool:
gained convection
92L

FLPandhandleJG .HE DO VERY GOOD HE GO ON 6
month ON JUNE 24..






awesome pimp.. so you think this invest will do anything later today or into tuesday?
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3243. Relix
92L has some convection problem it seems
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3242. JLPR2
14/0545 UTC 9.1N 38.6W T1.0/1.0 92L

We are still in 1.0
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3241. xcool
gained convection
92L

FLPandhandleJG .HE DO VERY GOOD HE GO ON 6
month ON JUNE 24..




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Quoting xcool:
FLPandhandleJG HEY


how you doing xcool.. its been awhile.. hows ur new baby and all?
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Ok 92L looks manky. What happened to it last night?

Very amusing:

Member Since: April 27, 2008 Posts: 29 Comments: 2097
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3236. xcool
June 2010 Tropical Weather Analysis
After a very slow first half of June, with almost no tropical disturbances to speak of, it now appears we're on the verge of the first tropical cyclone forming in the North Atlantic. The disturbance of interest is at roughly 37 W and 9 N, and has been organizing steadily for the past couple of days. The structure of the disturbance is impressive. It appears that the broad circulation of it is tightening, with convection forming near the center. The outflow structure of the disturbance is about as perfect as it gets, with ventilation in nearly every quadrant. This evacuation of air at upper-levels in the disturbance provides a conducive environment for low-level convergence and even more convection. Additionally, the environment around the disturbance is very moist since it's practically in the inter tropical convergence zone (ITCZ), vertical wind shear is almost absent, sea surface temperatures are warm, and the disturbance has gained enough latitude so lack of coriolis force won't hinder it. All of these factors suggest that the disturbance will continue organizing, and it's possible we'll have the first Atlantic tropical depression by tomorrow. As for the forecast, this system will head on a WNW track towards the Lesser Antilles. It's about 5 days away from making any impact. The future intensity of this is a big unknown. Some models want to dissipate it before it reaches the islands, while one of them makes it a minimal hurricane. I think there's a higher chance of it dissipating due to the high shear ahead of it, but we shall see. One more note, it is highly unusual to see a Cape Verde style system like this in June. It may be an indication that this season will be very active if it's already that favorable out there in the eastern Atlantic
http://hurricanewarning1.com/
by
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3235. xcool
FLPandhandleJG HEY
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3234. xcool
92L HEADING IN TO HOTHOT SST
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3233. JLPR2
Looking better, not as good as last night, but at least its not convection-less

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3232. EricSFL


See what I mean?
Member Since: May 26, 2010 Posts: 0 Comments: 804


color-image

Hey.. how is everyone doing.. I have been real busy.. hope is well!
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3230. xcool
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3228. EricSFL
Not only a midget, but a deformed midget!
Member Since: May 26, 2010 Posts: 0 Comments: 804
3227. JLPR2
Quoting btwntx08:

indeed way better lol ana was a midget lol


haha! XD
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3226. xcool
EricSFL soso true
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3224. xcool
wnw 40w.
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3223. EricSFL
In my opinion, 92L looks even better than TS Ana did during most of her life.
Member Since: May 26, 2010 Posts: 0 Comments: 804
Quoting weathersp:
Looks like it has consolidated and looks good, also looks like it's taken a westward jog over the past few frames.


Could be, but really hard to tell with storms that are in the early formation process. We will have a better handle on the track and direction once the TD is declared. It needs to fully consolidate first.
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3220. xcool
btwntx08 HAH
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Looks like it has consolidated and looks good, also looks like it's taken a westward jog over the past few frames.
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Quoting btwntx08:

it will be today trust me lol this flare up will make it a td


I fully believe it will be TD 1 sometime tomorrow morning. What I am not sure about is whether it will make it to Alex. Regardless, my local weather met said Alex by Tuesday. He seemed very impressed with the storm.
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Quoting KoritheMan:


Looks nice. Thanks. Bookmarked.


Thanks :~) made it myself. I'll continue to be adding more links as I stumble across the good ones.
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Quoting SouthDadeFish:
For anyone looking for links to track 92L and the rest of the tropics, you can check this site out.


Looks nice. Thanks. Bookmarked.
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3214. xcool
ROB Remember 2009 HURRICANES SEASON.SO DAM BORED
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For anyone looking for links to track 92L and the rest of the tropics, you can check this site out.
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3212. xcool
92L POPOP
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3210. 7544
starting to opop now just intime for dmax
Member Since: May 6, 2007 Posts: 0 Comments: 6874
3209. EricSFL
So do you think ExFred's naked swirl is still spinning somewhere on the planet?
Member Since: May 26, 2010 Posts: 0 Comments: 804
3208. xcool



wowwwwwwwwwwwww
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The most recent flare-up of convection on the SW edge of the previous flare-up, I believe is very important. That is much closer to the center, and this could lead to consolidation of the elongated center. Possible banding convection developing again to the S.
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3206. xcool
tennisgirl08 you so rigth
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Usually a lurker here...but wanted to comment that 92L looks to be restructuring and is becoming its' own storm - out of the ITCZ. In the satellite imagery posted by Tampa Spin, it definitely is popping more convection around a center - not so disorganized. I think we will see a more compact system by tomorrow morning with TD 1. The storm has potential to weaken in 2-3 days due to high wind shear, but I worry about where the remnants or remaining energy might go. I never write a system off..ever..
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3203. EricSFL
I just noticed we have double trouble on the EPAC (two yellow circles).
Member Since: May 26, 2010 Posts: 0 Comments: 804
3201. xcool



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3200. xcool
HAHA
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3198. xcool
wrap around the COC
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ok well time for bed night everyone
Member Since: March 10, 2010 Posts: 1 Comments: 7874

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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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