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Busy Times in the Tropics This Week!

By: Dr. Jeff Masters, 4:15 PM GMT on July 31, 2007

Guest blogger Margie Kieper


Tuesday lunchtime update: Because of a busy workload and a sick kitty (Squeak; aka Furball, Metcat), updates today will be minimal, but I'll update with satellite imagery tonight. If you have questions, email them to viewfromthesurface at gmail...and I'll answer them, if I'm able.

The Pacific Ocean is on a roll today.

Invest 99E is continuing to look good this morning, and is likely a TD by now. Update: was designated TD-Eight this afternoon.

Usagi's appearance on satellite continues to improve on IR and water vapor imagery, and the underlying structure continues to improve as well, as this latest of 37gHz microwave images shows, and can be compared with the two others posted earlier in this blog entry:

Usagi 37gHz


Usagi's intensity has been increased to 115 kt by JTWC (1-minute max surface windspeed) and 80 kt (10-min wind) by JMA, and it is close to it's maximum intensity, as ocean heat content will steadily lower, between now and landfall in Japan, which should have an impact regardless of the excellent outflow. At the moment, Usagi is a very powerful typhoon.

Regards all the angst on the blog comments yesterday on 99L: Most important is that you will never hear hype from me when blogging about tropical disturbances. Seeing the ocean of dry air ahead of 99L, it was not difficult to have an idea about what was going to happen. Here's something to note: that area just off the South American coast is a kind of a sweet spot. There is always good divergence flowing north that, while it may resemble outflow, is not necessarily indicative of an increase in vorticity. The low level winds are just so, to support a developing low, moisture is drawn from the ITCZ...but many lows associated with a tropical wave that look good there, will fade afterwards when gaining latitude and leaving those conditions behind, especially if moving into a more hostile environment.

It appears the surface circulation of the low associated with Invest 99L opened up or elongated this morning, both on satellite imagery and looking at the earlier QuikSCAT. The dry air is preventing moisture from the ITCZ from making it to the disturbance as it gains latitude, and so it is losing definition. The tropical wave may find a better environment by the time it moves into the western Caribbean or into the East Pacific.


Tuesday morning update: Usagi in the West Pacific continues to steadily strengthen and improve in structure. This morning the eye cleared out, and most recently the structure of the core has become more symmetric. Usagi has been a large, rather sloppy-looking tropical cyclone overall, but don't be fooled by this appearance. As I mentioned yesterday morning, this typhoon should be looking fairly impressive by 00Z 1 August, in about nine hours from this post. Here is a microwave from earlier this morning showing consolidation in the center and continued banding of convection around the center:

Usagi 37gHz


There are two other areas being monitored in the West Pacific for possible development.

* * * * * * *

In the North Atlantic, as predicted by NHC yesterday, TD-Three has strengthened into Chantal, and strengthening has continued, tilted but clearly tropical, moving rapidly northeast and being pulled into the strong trough coming off the East Coast, spinning furiously like a biker pedaling downhill, on its way to extratropical transition. Life in the fast lane.

Invest 99L underwent a little reorganziation overnight and the mid-level circulation redeveloped in early morning, along with some banding structure. Convection continues to have a hard time sticking due to the dry air, but the low level organization is still intact, so there is some potential to develop into a tropical depression over the next day or so -- but as I said yesterday, chances are that nothing is going to come of this over the next day or so.

More recent morning imagery shows the low level circulation is becoming a little looser, as convection cannot be maintained. It appears this will fall apart as the day progresses.

Finally, there looks to be some potential for development - really, more potential than 99L, as there is quite a lot of energy in this area of disturbed weather - at the tail of the trough coming off the East Coast, east of Georgia and the Carolinas -- but again, a fish spinner.

In the East Pacific, Invest 99E has developed some convection to the southwest of the low level circulation, so that it is no longer an exposed "swirly." A microwave pass from this morning covered enough of the area to show the banding convection and a solid low level structure, so expect this to have potential to develop into a tropical depression as it heads out into the Pacific. Recent visual imagery shows good outflow has started to develop.

* * * * * * *

Monday evening update: Convection was able to reform over the center of the exposed low level center of invest 98L tonight, and it has become TD-Three, very near tropical storm strength. It is now centered well north of Bermuda and tracking northeast towards the tip of Newfoundland. The satellite floater is positioned so that the low off the SE coastline can also be observed for development, while TD-Three is rapidly moving north out of the image frame.

Earlier this evening, easterly shear pushed the mid-level circulation and convection right off of the low level center of invest 99L, where it spun off to the west and evaporated, as the low level center continued to move to the northwest, a process that was captured very clearly on the satellite imagery, as seen here on an IR from the NRL web site -- the gray scale helps to determine the height of the clouds:

99L sheared


As I mentioned earlier today, 99L is headed for a large area of dry air. This can be seen on the IR satellite imagery (here, RGB), which I've marked to show the successive surges of the Saharan Air Layer (SAL).

99L and SAL


Here a water vapor image clearly shows the extent of the dry air across the Atlantic and eastern Caribbean.

99L and dry air


In the West Pacific, Usagi has been steadily strengthening and the eye is starting to become visible on IR and VIS imagery. A microwave from this afternoon shows the solid inner ring of the low level circulation surrounding the eye, partially banded by strong convection (pink).

Usagi 37gHz


* * * * * * *

Monday Afternoon update: The very nice tropical wave that moved off Africa last Thursday, that is now located at about 50W, has developed rotation and convection and has been designated invest 99L by NHC. While the most recent surge of SAL only extends out to about 40W, most of the tropical North Atlantic and eastern Caribbean remain very dry, so once this wave moves out of the ITCZ and into the eastern Caribbean, chances are that nothing is going to come of it for the next two or three days. The vis loop already shows convection on the northeast and northwest side of the disturbance dissolving as it moves into the dry air.

Convection momentarily burst near the center of 98L, well north of Bermuda and on its way to the middle of the North Atlantic, before getting sheared by the upper level flow.

More on Usagi tonight.

Don't try to adjust that dial: Yes, it does appear that over the past week the NRL TC website has been quietly going berserk. Dalila is done, but keeps coming and going, as do various invests intermittently labeled "Lima" or "Bilis." One could say the site is suffering from Bilis-Lima-ia.

* * * * * * *

For Jeffs early August hurricane outlook, which came out Sunday, link here.

The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

Reader Comments

I agree with you keeper, atlantic is awakening at very fast pace.
Yeh, i am really looking forward to it to Barbados!! :)
99LINVEST.25kts-1009mb-113N-533W.

Winds are 30MPH according to Navy and dropped 1MB also.

Not been classified as TD yet...
Look at the latest QuikScat. Its a cloud!..LOL
It's outrageous.
Bob we not wishcasting it says 30mph winds on the website and the pressure has dropped thats what the concern was about
1008. Ohio91
Posted By: bobw999 at 1:08 AM GMT on August 01, 2007.
it looks like i might have to stay to make sure people dont start listening to the wishcasters

repeat there is no td 4


i was just saying that the weatherunderground tropical weather page has 99L at 30 mph. it could be a mistake. or it could be right. well have to wait for the NHC to say something.
Just stating the facts according to the Navy unless they make up wind speeds and pressure.
Well, if those coordinates are right, then all the convection for 99l is north and west of the center.

But it is looking more organized, yet again, and is slightly stonger.
1012. bobw999
yes 99l may have winds of 30 mph but its no depression
1014. Drakoen
the convection has to be organized. 30 mph winds is interesting though...
No the Navy and NHC have not upgraded it to a TD they might they may not have to wait and see.
99L now has 30mph winds the navy site has update 99L to 25kt up from 20kt
1017. bobw999
this is what a depression looks like Link

this is 99l Link
Yeah Drak got it Organized one of the T-Storms could have 30 MPH winds.
Wait and see..LOL This thing is nothing right now. Here is the QuikScat
99L looks bad....hard to find a rotation
The 11:30 pm advisory ought to be interesting.

Maybe 99l is getting ready for its close up after all.
Taz does that mean that 99L might be actually getting its act together
Interesting?? Yeah, it should say this is almost dead!..LOL
Posted By: louisianaboy444 at 1:16 AM GMT on August 01, 2007.
just a question Bob if this storm does develop will you pretend like its not there or will you finally admit you was wrong?


ROFLMAO
wheres that blowup Drak shouldnt the fire be heating up right about now?
1029. bobw999
just a question Bob if this storm does develop will you pretend like its not there or will you finally admit you was wrong?

i will admit i was wrong

and if it doesnt.... i was right

i love how quikscat keeps missing this thing.
StormW you got mail
1032. Levi32
Finally the latest QuikScat is in....and Bob is right...it's a nothing lol. Now it's not over just yet until we see what happens during the diurnal max when the low might reform, but right now there is no closed circulation.
See that model (Wunderground's)Link
Local weather satellite of the gulf

Do the clouds down in the gulf look like they are cookin sumthun up or is it just me??
1035. bobw999
heres a better example for a tropical depression Link
Yeah, but it caught enough of it to see the circulation is sick.
1037. JLPR
compare td8e with 99l
come on it does not look like a depresion
hey i had a couple of drinks, stood up on my left foot, covered my right eye, squinted with my left until my contact blurred up then saw a COC at about 11.5N 54W!!!!
Yes, not over. But, right now its on life support.
Posted By: Bamatracker at 1:21 AM GMT on August 01, 2007.
hey i had a couple of drinks, stood up on my left foot, covered my right eye, squinted with my left until my contact blurred up then saw a COC at about 11.5N 54W!!!!


You forgot to swing the dead cat around your head!!
It looks to me that the quikscat pass missed whatever there is of a low center as 53W is not in the swath. Be that as it may, the center of the circulation now appears to be right underneath the only convection of note with the system.
It won't hurt anyone to exercise a little patience and see what the next 2 hrs bring in the way of any appreciable improvement in the overall convective pattern.
1042. LLJ
This is most likely the end scenario of 99L:


A LOW OVER THE TROPICAL ATLANTIC NEAR 12N 51W IS TO FILL TO AN
OPEN TROUGH BY 30-36 HRS. IT WILL THEN TRACK WEST INTO THE EASTERN
CARIBBEAN BY 36-42 HRS...TO CONTINUE SOUTH OF PUERTO RICO/VIRGIN
ISLES BY 60 HRS. GFS MODEL SHOWS A WIND SURGE OF 25-40KT TO
ACCOMPANY THIS TROUGH AS IT MOVES INTO THE EASTERN CARIBBEAN.
well see i hate being wrong lol so what i do is i stay on both sides of the fence i say why it can develop and why it cant....even if i think it might form or might not form i just state why i think a certain thing will happen its bad to make bold predictions that it WILL or WILL not develop becasue there is always that possibly you wrong...actually a 50 to 50 chance
Where is the west wind Kman??
groundman...possible the cloulds in the GOM might cook something up later this week. A nice big rainmaker for the big bend area of florida.
Posted By: Crisis57 at 6:18 PM PDT on July 31, 2007.

Taz does that mean that 99L might be actually getting its act together

yes
1047. CJ5
Posted By: bobw999 at 8:08 PM CDT on July 31, 2007.

it looks like i might have to stay to make sure people dont start listening to the wishcasters


lol...despite your forecast some still believe.
1048. Drakoen
Posted By: louisianaboy444 at 1:18 AM GMT on August 01, 2007.

wheres that blowup Drak shouldnt the fire be heating up right about now?


its already starting. you have to wait a few more hours. sleep on it lol.
1049. Levi32
Well hey I'll say this for 99L...it looks better than this morning, but the circulation is still sickly. It will need a huge night tonight to stay alive.
I have to agree with Bob. This should not be classifed as a Invest anymore. Quickscat confirmed that there is no closed circulation.
Of course, the minute we put it to sleep it will fire up and make us look dumb in the morning..LOL But, honestly, it does not look good tonite. See ya all later.
1052. CJ5
The coordinate info has been updated since i first visited about an hour ago. I luaghed to myself because the coordinates and pressures listed for the past two days had 8/31 and 8/30 listed. I now see it shows 8/31 and 8/1 as the only entry and a new 1009 pressure. Wierd.
Posted By: weatherguy03 at 1:25 AM GMT on August 01, 2007.

Where is the west wind Kman??

Hard to say IF there is a W wind out there. No QS pass to look at where the low would be centered and no ship or other reports. I never said it was a closed low and neither does the discussion. A low can be quite broad and not closed but still be a potent low
1054. Drakoen
Posted By: weatherguy03 at 1:28 AM GMT on August 01, 2007.

Of course, the minute we put it to sleep it will fire up and make us look dumb in the morning..LOL But, honestly, it does not look good tonite. See ya all later.


LOL.
Link

This storm is getting ready to explode look at the last few frames that blob of convection to the northwest of the COC is really blowing up nicely let it keep growing for a few more hours
99L needs to get more convection and keep it for a day...then we can see what it will do. Until then its just a wave that use to have a pretty swirl
Well, good night guys, i see you tomorrow.
1058. bobw999
sure convection will fire tonight just to dissipate tomorrow
99L looks to at long last getting it's act together. It is noe getting rid of any cloud attachments. there has recently been a burst of convection, and the dystem looks better this eveningLink
1062. JLPR
is it me or is a rotation at 13n 52w aprox.
1063. LSU
Heh, "the storm is getting ready to explode".

Yesterday at 2pm there were people saying it was dead. At 2am the same people were getting ready to pack their bags and evacuate because it flared up again. Today, rinse and repeat. Reading this board is hillarious.
1064. Drakoen
Posted By: LSU at 1:33 AM GMT on August 01, 2007.

Heh, "the storm is getting ready to explode".

Yesterday at 2pm there were people saying it was dead. At 2am the same people were getting ready to pack their bags and evacuate because it flared up again. Today, rinse and repeat. Reading this board is hillarious.


ROFL
1067. bobw999
goodnight aggie

Posted By: LSU at 1:33 AM GMT on August 01, 2007.

Heh, "the storm is getting ready to explode".

Yesterday at 2pm there were people saying it was dead. At 2am the same people were getting ready to pack their bags and evacuate because it flared up again. Today, rinse and repeat. Reading this board is hillarious.


Well I guess if Dr Gray and his team can change their forecast everytime it doesn't come to pass to meet how a season is unfolding and still be considered experts then the bloggers on here can do the same LOL
1069. Drakoen
Posted By: MonsterHCane at 1:34 AM GMT on August 01, 2007.

Posted By: louisianaboy444 at 1:30 AM GMT on August 01, 2007.

Link

This storm is getting ready to explode look at the last few frames that blob of convection to the northwest of the COC is really blowing up nicely let it keep growing for a few more hours

It needs to hold the convection also untill the recon flight...not disipate.


yes if it can hold till them we could have a depression/ TS...depends...
i have no doubt that 99L will get some convection going tonight....ok maybe some:/.

But it has to keep that convection tomarrow to be a serious threat.
Juat noticed that stormw....
Explode- Translation- After having no convection for most of the day it looks like the area of convection is expanding and it continue to expand as we get towards the diurnal max...and for the LSU dude L....S....U! lol but sorry my man i'm not going crazy i'm just saying if it the convection can bubble up tonight tomorow could be interesting....and yes they do have ups and downs thats what you call a developing system
Good evening. I see 99 L has done what i thought it would do, and did not generate anything too troubling to date. Its going to fizz I my veiw, and the wave behind it would likely suffer the same fate. If and when these things reach the central GOM, they may very well become major storms. \
But I feel convinced that the Atlantic is a no-no this year.
Posted By: StormW at 1:36 AM GMT on August 01, 2007.

Off for the night...but one quick item...run the DVORAK loop, and run IR2...there are 2 circulations...11N, 53W...and one may be mid level at 13N, 52W


99L has always had a tilted circulation.
Question, In Storm's blog he talks about the MJO not being present until the third week in August. And then things will "let loose". Does that mean that we really wont expect development until then? Are conditions not favorable for development now? Just trying to understand what he means. Thanks
hehe...99L has a limp
1081. Drakoen
people in this blog have no patience wait till tommorrow before you write the system of. Then and only then can you make fun of it and throw in all the negatives, and go back to watch blobs lol.
1084. Drakoen
Posted By: MonsterHCane at 1:39 AM GMT on August 01, 2007.

Drakeon do you think it will do what it got's to do to be a depression tomorrow when the recon fly's?


its has to flare up massively overnight. We won't see the untill 3-5am. Just starting lol. After that the convection needs to hold.
what is up everyone, it has been awhile,! so anything going on? LOL
I sure hope that 99L does not hear those of you who are you mocking it. Mother nature does not like being scoffed at.
well this system already has 30mph winds all it needs is to maintain convection if this convection that is developing right now can hold till tomorow afternoon when they fly in i think they will deem this thing td4
I'm waiting to see what happens in the GOM later this week. It could be interesting.
1090. bobw999
well 99l is nothing to waste sleep over

remember it isnt td 4 until it says it here Link
1091. Drakoen
Posted By: MonsterHCane at 1:42 AM GMT on August 01, 2007.

Posted By: Drakoen at 1:41 AM GMT on August 01, 2007.

Posted By: MonsterHCane at 1:39 AM GMT on August 01, 2007.

Drakeon do you think it will do what it got's to do to be a depression tomorrow when the recon fly's?

its has to flare up massively overnight. We won't see the untill 3-5am. Just starting lol. After that the convection needs to hold.

Sorry but you didnt answer my question, Do you think it will do that...and be a depression when they fly?


Its hard to say if it will do that... you just have to wait and see. It has the potential to do that...
the winds qualify it a depression Monster its just the convection needs to persist so the convection that will develop tonight will have to stick into tomorow afternoon if that occurs then yes it is possible in my opinion
sorry kman....you'll see 99L before me, make sure and tell it i didnt mean the limp comment.
1094. IKE
Posted By: Bamatracker at 8:42 PM CDT on July 31, 2007.
I'm waiting to see what happens in the GOM later this week. It could be interesting.


Same here...I'm in the panhandle of Florida. Could be a heavy rain event...maybe some winds.
The enviroment through most of the caribbean is pretty stable which is not going to help in any way towards development.
Guys, it aint over

theres alot of moisture out ahead of it 23 so that could possibly change we'll just have to wait and see everyone!
Posted By: Bamatracker at 1:44 AM GMT on August 01, 2007.

sorry kman....you'll see 99L before me, make sure and tell it i didnt mean the limp comment.


Will do. Should I pass on your address at the same time ? LOL
Looking at the water vapor it seems that the dry air has lessen. I say if it can't pull it off tonight, give it one more night, because the dry air might be gone by than.
1104. JLPR
well time to shut down the laptop i will be back tomorrow on the blog to speak of whatever is on the atlantic
goodnight everyone
:D
no no....dont send anything this way!!!
1106. JJACID
Just my opinion i think 99L will develop. It amazes me the people who write off storms one day then the next day they completely change there tune. What are the steering models set up like? last i looked it took it directly into Central America. I hope they are right and it stays out of the gulf low shear high sst. Only time will tell.
What are they forecasting for the gulf this weekend. Thanks
In response to 2 questions __

I think the Atlantic will be hard-pressed this year to produce a significant weather system. My reason for this is that the Sahara Air Layer ( dry air ) shows no signs of going away, and I dont see any reason for it to do so. The Sahara and the western Sahel are bonedry, getting dryer, and expanding south.
The idea that a storm system can form, far less intensify in dry air makes no sense to me.
I'm not a Met, but I've been watching tropical weather a long time, and the above is my humble opinion.

We wait and see, basically.
no k m its not keep ye'r head up and ye'r eyes wide open
Posted By: jphurricane2006 at 9:47 PM EDT on July 31, 2007. (hide)
adrian that dry air and stable conditions will move lol, it doesnt just sit there.

You have been saying that now for what 2-3 days now LOL...For me i need to see deep concentrated thunderstorm activity through tommorow night before i buy into this disturbance really starting to flurish.
1110. Drakoen
the LLCD (lower level cloud deck) is nice but the convection still needs to deepen and expand.
Well g'nite guys. Talk with you all tomorrow.
1112. RL3AO
BTW, Tropical Storm Erick has arrived.
the only thing lacking for 99L is a large area of deep convection so the mid-level and low-level circulations can get together we will just have to sleep on it and see in the morning!
Don't have access to the weather channel updates at :50. PLease let us know what is being said now.
Any comment on my previous post ??
hey hurricane you got mail
it looks to be trying to get better organized the thunderstorm action is increasing and it looks as if the low level circulation is trying to get connected with the mid level circulation...if they can get connect and storms can form over them then we can be talking a td but as for now it remains very unorganized
It would be very interesting to see some comparisons of the SAL for August ( for example ) going back 10 years or even better 20 yrs.
MonsterHcane. Agreed. But where does the convection come from ?
Good Evening evryone. Anything new besides 99 looking like its splitting into two?
1122. RL3AO
Don't have access to the weather channel updates at :50. PLease let us know what is being said now.

Nothing useful unless you have a headache.
Posted By: pottery2 at 1:56 AM GMT on August 01, 2007.

Any comment on my previous post ??


Hi Pottery, yes a few.

1. Dr Gray and his team gave up using Sub Sahara rainfall in any given year as one of the factors in predicting because they found that there was no longer any verifiable link between the two.

2. Strong SAL in the early season typically reverses itself later in the season and the W Atl has very little now compared to May, June and early July.

3. 2004 saw a dormant start to the season and then for 6 weeks every ingredient for a very active season seemed to fall into place overnight.

It is too early to make any judgments about the rest of the season as 90% is still to come

Just my take on it
No, Ivansvrivr...nothing new.
1126. msphar
The ambient wind in the tropics is usually about 15 to 20 with gusts to 25. So if this storm is only blowing 30, its not much of an event.
99L is not going to form.Looking at the new Quikscat,you can see there's no feature at the surface,not even a wave in the easterlies.The low simply spun down over the day,likely due to the loss of convection and thus upward motion supporting low level convergence.
Kris

From looking at the QS pass I would say that it missed where a low center would be ( assuming there is one )
okay, i was on here an hour ago, and they had 99l at 25mph and now they have it at 30mph? is it getting stronger???
No,Kman,it didn't.
Pottery, Dr. Masters opined last week that the SAL will weaken and move north by the middle of August (if my memory serves me well).
Pottery as the weeks go by i believe we will see less and less dust out in the tropical atlantic as you can already see signs of that take shape of the african coast.June and july in a normal season represent quite times and personally i wish some folks would understand that.The real season does not really get going till about august 18-20.Tommorow is august 1st and our chances of seeing a named system begin to grow dramatically as the weeks progress.

I see CSU lowering there numbers a bit due to cooler SST'S in parts of the tropical atlantic.A season with 10-14 named systems seems very possible to me.The all important question is how many will affect land.
NormalGuy,the convection is increasing,but there is no surface low.It isn't strengthening.
okay, thanks, can someone post the latest image of 99l???
By August 1st we've seen,on average,20% of all our cyclones.So,if that holds,we'd end up with 15 for the year,which is what it looks like to me right now.
Posted By: WizardApprentice at 2:08 AM GMT on August 01, 2007.

BREAKING NEWS: 99L has increased intensity to 30 miles per hour



It does not matter.There is no low.Unless one becomes apparent by tomorrow morning,the NHC won't fly,and it will not be named.
NEW BLOG
JJACID...this is what they are watching for...supposed to start 'happening' tomorrow and develop something by Friday....

A weakening front from the northern Gulf of Mexico extending eastward into the Atlantic has been the focus of several areas of thunderstorms pulsing in intensity. While nothing has shown signs of consistent development and there are no immediate concerns, the northern Gulf of Mexico and off the Southeast coast of the United States will need to be monitored.

By AccuWeather.com Expert Senior Meteorologist and Director of Forecasting Operations Ken Reeves

my call on 99l tonight..... it has improved in structure greatly in the past 6 hours, even though it is ragged on sat, and now that the circulation center is almost under the convection, has a really good shot at developing. I say...We see continued increased convection with colder cloud tops through the night, the recon kept on schedule and it named a depression tomorrow. Just my opinion.
Thats true Kman, and I stress that this is my opinion (obviously )
But it is strange that they stopped using sub- Sahara rainfall figures because there was a lack of co-relation to the formation of storm events. The SAL is a result of dry sub Saharan conditions. Cant be otherwise.
I agree that the SAL has tended to reverse itself, but less and less, generally speaking. There will always be peaks and valleys.
This year could be a repeat of 2004, but I have my doubts about that.

As I said, we all wait to see what happens next !
Dr. Lyons said that Chantel's remnants will become huge low pressure system in North Atlantic. I'm sorry but TWC has gone off the deep end with the global warming mumbo-jumbo. I'm not arguing that climate changes, but we haven't been collecting data long enough yet to know how (if at all) gw is affecting tropics. Some folks think it's all man made. There are others who believe it's other things. Both sides have valid arguements but TWC only shows one side. TWC needs to go back to showing WEATHER!
pottery2,
Here is a great link to watch the Dust Storms in N Africa.
Been watching one push off the coast. Most watch the waves but I find these dust storms just as interesting.
Magenta colours show the dust....If you havent seen it...enjoy
here
Latest sat pics suggest that the low and mid levels are merging and indications are that 99L is not far from TD4
Katadman. Yes, the SAL will possibly weaken, and will certainly move north. But weaken is not the same as " leave the area completely ".

The SAL never goes completely away, it does blow in different directions though, and is a nuisance in parts of Europe from time to time.
Thanks NeverPanic. Been watching those for a while too. Fantastic !
The thing that worries me about 99l is the mid level half that is farther north. I've had a gut feeling that if 99 got into far northern Carrib. or South Atlantic it would be something serious. Look at Chantel. She was written off but she came to life right afterthe northward turn. I think the warmer SST.s might have made the difference.
It seems like the warmer sst.s in august and september would moisten the atmoshphere to the point that moisture would tend to condensate on the sahara dust causing some of it land on the sea suface
1149. guygee
Posted By: Ivansvrivr at 2:34 AM GMT on August 01, 2007.
"It seems like the warmer sst.s in august and september would moisten the atmoshphere to the point that moisture would tend to condensate on the sahara dust causing some of it land on the sea surface"

Ivansvrivr - I think that there are at least three problems with the excess dust that inhibits convection.

One is that the dust reflects sunlight back up into the upper atmosphere, thus cooling the surface which helps to suppress convection. The dust layer also absorbs light and longwave radiation from the surface, causing heating in the dust layer.

This is still an area of active research, but another possible consequence of excess dust is that the heated layer above the surface alters the lapse rate and forms an inversion that leads to subsidence, which makes the formation of convection more difficult.

Finally, the are some theories that too many small hygroscopic aerosols in the atmosphere may inhibit the formation of clouds, since the overabundance of condensation nuclei help prevent coalescence into larger water droplets needed for cloud formation. Since there are plenty of salt particles over the ocean to start with, the extra dust may cause something like a "supersaturation" of condensation nuclei, that in combination with the first two factors inhibits cloud formation and convection.

I didn't dig out all the links I have read on this topic, but there are several discussions over on RealClimate, a great place where scientists discuss the scientific literature with lay-folk.

The literature is huge, but also of interest may be the following:
Direct radiative effect of dust on the climate system
Desert dust suppressing precipitation: A possible desertification feedback loop
Subsidence Inversions