Unusually well-organized 92L disturbance may become a tropical depression
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
Reader Comments
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You forget the Caribbean too easily. We're talking about seasonal activity not US landfalls. Having the wave train heat up this early bodes bad for those areas that are threatened by Cape Verde systems, and those in the Caribbean remember 2007 with a lot more shadow than you do.
Its well-defined circulation will definitely help keep it alive for the time-being, but it has a need for deep convection right now, that it may not get until it makes it to 46W.
invest 92l
Your picture kind of reminds me of the former guitar player from Faith No More
On the contrary, SSTs are a big reason why 92L is struggling, and warmer SSTs would help it a great deal right now.
15 named storms was 'slighly' above average? 2004 also had 15 named storms and the Caribbean utterly suffered in 2007. 2 Category 5s.
NONE of the waves were anywhere near as organized as 92L was. The wave your thinking of happened in July, and it did bring a foreboding of the season to come. 2008 which featured Bertha, didn't see a CV wave with a Red alert in June.
A lot of us can be more respectful about things on here. If someone feels a system has no chance I'm not going to call them a troll or put them on ignore or seriously call them a downcaster.
But I will RIP...for now, 92L, based off of the latest TWO. It may come back, down the road somewhere.
-92L
Looks like 92L is making a beeline for the great invest home in the sky typically in the general direction of the north pole...
This was an impressive one, for sure!!!
The sheer size of it was mind boggling.
Anyway, try not to tear each other up too badly. Some invests develop; some don't. And it doesn't depend upon what we say about them!
ShortWaveLoop
100F readings would save it almost without doubt.
Absolutely unreal.
I think we should just ignore him. He doesn't know what he's talking I believe. He's a troll.
I'm guessing that since it stayed weak it will take a more southern course towards the lesser antillies or windward islands.
Very possible. The wave east of 92L continues to look impressive on satellite imagery, and should the wave maintain its convection and hold together, I would think we may see it designated as an invest by the middle of this week.
Yes! But it's really not dead yet. I might agree with "probably" dead but it does have a chance at the DMAX, as I said before around 11pm it will burst back to life, I think.
Oh I agree. Certain individuals just drive me nuts the way they treat each other... Espousing nonsense forecasting and BS science .. and then they get lucky and think they are the gods of weather. It's frustrating.
I hear ya.
hey, where are you from in Illinois?
I'm on iPad, so I cant post pics. African wave and 92L. African wave is also unusually well organized. This is incredible to see for June!
Sorry, this:
is nothing like this:
2007 is an analog year, but had issues with SAL and fast trade winds. The Atlantic was not the focus of global heat that year. It was far from the same thing, and we still got 15 storms and a very bad year for the Caribbean.
And then others, when they're prooved wrong, they don't even show up in here.
This thing, or what's left of it will be further north.. likely over the NE carib per 12Z GFS.
but the wave behind does look very good now so if 92l doesent make u happy that one might lol
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