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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When I go outside to mow the lawn and I start to sweat trying to get the darn thing started. Then I know that it is too hot and head for the pool.
Ehh you have some on here, actually alot on here saying that 92L is slowly dying out, then some on here like me saying that it's organizing.. Regular drama on the blog!
If these are needed. Thurday or Friday.
NHC - PRODUCT CHANGES FOR THE 2010 HURRICANE SEASON
It's very close, and it's very hard to tell if it is or not by satelite, however i wouldn't be surprized if it's a depression by 2pm.
Thanks!
116
NOUS42 KNHC 141600
WEATHER RECONNAISSANCE FLIGHTS
CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.
1200 PM EDT MON 14 JUNE 2010
SUBJECT: TROPICAL CYCLONE PLAN OF THE DAY (TCPOD)
VALID 15/1100Z TO 16/1100Z JUNE 2010
TCPOD NUMBER.....10-014
I. ATLANTIC REQUIREMENTS
1. NEGATIVE RECONNAISSANCE REQUIREMENTS.
2. SUCCEEDING DAY OUTLOOK: POSSIBLE LOW LEVEL
INVEST NEAR 14N 53W AT 16/1800Z.
II. PACIFIC REQUIREMENTS
1. NEGATIVE RECONNAISSANCE REQUIREMENTS.
2. OUTLOOK FOR SUCCEEDING DAY.....NEGATIVE.
JWP
I think it was a TD for a few hours this morning ;)
NOW after looking at the IR, convection has waned a bit and elongated, I still believe classification to TD1 or Alex will be either tonight or tomorrow morning.
LEVI ROFLMAO......that video that Hurricanejunky just posted shows clearly that was the WAVE i was talking about that is now in the BOC.......:)...LOL
Of course. Thanks.
Looks like they should rescale that Caribbean&GoM SeaSurface Temperature chart. Only goes up to 30.5degreesCelsius(86.9degreesFahrenheit), and there's already been reports here of localized SSTs of 33degreesC(91.4degreesF) or so at eg DauphinIsland.
Just cause a low pressure system develops a closed circulation in the tropics, that does not classify it as a TD. It's just a tropical
low. What it needs to have is T-Storms near the LLC for @ least 12hrs and also winds of 25-30mph.
If there is pulsating or no T-storms persisting
near the LLC. Then all it will be is a tropical
low pressure system.
MARK
11.4N/40.1W
The upper trough cutting off outflow mentioned in post 263, and the colder SSTs in post 289. Convection is also becoming ragged in recent frames. While I believe this was or is a TD, it has some fighting to do to get west of 46W and get to warmer SSTs, plus shaking off the upper trough and battling the TUTT at the same time.
lol you said that each day for the past 3 days now. Eventually it will come true.
I do not think they will issue a 2pm advisory on a Tropical Depression that far out to sea. They will wait until 5 pm or 11 pm at the earliest.
you will won't be able to confirm a lot of things, until they can get a plan out there.
You said 2am, 5am......what is next......LOL
Is there an 11am advisory by the NHC?
At 200 pm
10% of it...yes. Not gonna develop with the thing on the other side of Mexico, plus it takes a lot of time to interact with a 200mb trough and make it work.
It doesn't have a closed LLC, it has weak vorticity and convergence, and the convection is becoming detached from the COC. It's not a TD yet.
Exactly........Scott....finally someone with reasoning......Bro i don't see 92L very well organized at all that some are seeing.....AM I WRONG!
Would be funny if the GFS was correct. So far it has been with this most recent development. It showed it as a broad closed low that opened back up into a trough...
That is a lie and you know this scottsvb. I did not say 92L was a depressing last night, I said it was close, just needed better convection, which happened, but now is waning. I've only been on since Saturday night btw, know your facts Mr. Met. I first said my forecast for this to possibly be classified a TD from 5 a.m. to 11 a.m. today, which almost panned out, now I'm pushing it to this evening. Stop trying to bash me, that's not what a real MET does.
Just because you don't hear about it doesn't mean it's gone away. Frankly, I don't think they are talking about the spill enough.
I will respectfully disagree to an extent. I think it needs to be regionalized a little better. Florida's West Coast local is just going a bit too much. Daily, "The Sky is Falling" type reporting has citizens calling in reports of oil covered animals, etc that turn out to be false. Responders and responses that are costing money out of simple fear from these newscasts. I personally don't need updates on what BP and the President/Government is or isn't doing every five minutes. I also don't need daily newspaper columns about how this is going to destroy Florida tourism. It isn't, and when/if the winds shift or current shifts, then do some responsible reporting, for now it's just needless panic inducing. Some other current event news would be very welcome.
I think you are starting to see some of what I was posting earlier.
National Hurricane Center Product Description Document: A User’s Guide to Hurricane Products
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