First tropical depression of the season may form from 92L
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
Reader Comments
Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57 | 58 | 59 | 60 | 61 | 62 | 63 | 64 | 65 | 66 | 67 | 68 | 69 | 70 | 71 | 72 | 73 | 74 | 75 | 76 | 77 | 78 — Blog Index
I think the rule is if it is classified before 40W then yes it is a CV storm
thats actually a little old now
the pass was at 12Z, its 21Z
Nope. Not been renumbered yet.
It was made at 21:02. I used the ASCAT instead of the Windsat because the windsat was at 18.
And in reality it looks very impressive now due to its sheer size and structure.
the date of the pass is not the one in the bottom, its the one below each strip of info, it passed at 12:30z through that area
We're surely tracking a mid July storm, that's for sure. Only one other like it in history.
so basically if i understand what you saying is that shear will not be a problem for this system?
Sorry, not official. Opinion only. I guess you have to be careful about those kind of statements!
But I think the SW side is finally closed off.
Convection continues to wane in association with 92L as the diurnal minimum continues to affect it. This trend should continue for about another 7 hours, with each hour getting progressively weaker, as in convection not dying down as much as in the previous hours. Current motion associated with 92L is WNW at 14 miles per hour and should continue that way with minor fluctuations over the next several hours. As in the last report pressure associated with 92L remains at 1010 millibars and maximum sustained winds remain at 30 miles per hour.
I expect 92L to become a tropical depression at any time during the next 24 hours, with the possibility of rapid intensification taking place in the short to mid term.
I will have another update at 6:30 PM EDT or if the system gets renumbered before that I will have more extensive blog post.
-MiamiHurricanes09
I agree it seems there are some on here that are downcasting one second, then wishcasting the next. Can't we just observe lol
Can you imagine if the NHC was like that lol. Going for low probabilities to high probabilities alternating throuhgout the day
I think we have an Alex in the making
The rotation also cause winds which evaporate more moisture and release more heat to feed more convection than simple a large amount of convection does. Not that the following wave is not impressive.
92L will continue to fluctuate convection and become a tropical depression when the convection persists. I give it a 65% of developing or even higher.
Wave emerging off Africa does not impress me much until it is completely off shore and persists for a period of time. I give it a <5% of developing at the current time.
Hey Sweetpea,
Look it is headed WNW (westnorthwest) at the moment but then a little westword in a few days.
Now anything other than that it is a little early to say where this is going...
Could this be torn apart by shear in the Carribean or will it become our 1st Hurricane only time will tell...
I hope I was able to help out
Taco :o)
If it is classified it will be a CV system.
One of the more western forming CVs was Emily 2005 which formed 42.4W.
Does anyone have a link to find Africa satellite and infrared images?
That would be too hard to even follow...lol
lol
Imagine if we had JFV, eddye, and some of the other wonderful cast of characters that are around here running the nhc.
This has been going on for 4 years now...SO tired of it.
During the evening: "OH, look how strong XXX is, it'll be a depression in no time!"
During the day: "XXX looks pathetic, It'll probably dissipate soon".
That is almost a certainity!!
They would have Florida evacuated before the wave left Africa.
JSL Animation (Flash)
Agree.
Viewing: 1551 - 1601
Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57 | 58 | 59 | 60 | 61 | 62 | 63 | 64 | 65 | 66 | 67 | 68 | 69 | 70 | 71 | 72 | 73 | 74 | 75 | 76 | 77 | 78 — Blog Index