Atlantic Invest Thread 2009

[kold weather]

Believe me Cookie they can be far more complicated then this, in very basic terms it had a good mid level ciruclation for a while and it found fairly good conditions in the mid Atlantic which allowed it to start to organise. Then it went into a much worse region of shear, indeed the shear was awful between 3-9am today, its lessened a little bit recently but still there. Dolly last year was murder, for 3-4 days it looked like a TD, even a low end TS at times but it just couldn't close a low level circulation off, so despite how good it looked they couldn't upgrade it till it had one.

The main problem is once agiain with these upper features. The models forecasted a upper high forming in southern Central Caribbean which would divert the jet a little to the north of 97L current positon. Whilst the high did form it developed about 200 miles WSW which has meant the shear core is a good deal further south then was progged and arching to the north of 97L, which is causing some higher shear. On 97L's current track it may yet get into the lower shear for a small time but it looks like it won't have a huge amount of time there as it heads a little north of west back towards the higher shear region, which doesn't look like its moving anywhere fast.

[Cookie]

thanks for taking the time to post that mate and explaining it well

[Cookie]

99L

we know have 99L

[Cookie]

possibly Ana? at long last.

[kold weather]

Looks very much like a developing tropical cyclone to me. Not all that surprisingm given it had a very powerful mid level circulation even as it came off the coastline, so it didn't take much for it to get going. Convection is a little shallow but SST's are still fairly marginal at the moment so thats not al lthat surprising.

I've got a sneaky feeling this one will be a recurver eventually given its fairly high latitude its emerging at, reminds me a little of Alberto in 2000. Still to early to tell though...

[Cookie]

Code Orange

Code Orange

229

ABNT20 KNHC 091730

TWOAT

TROPICAL WEATHER OUTLOOK

NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL

200 PM EDT SUN AUG 9 2009

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

AN AREA OF LOW PRESSURE...ASSOCIATED WITH A TROPICAL WAVE...IS

CENTERED JUST TO THE SOUTHEAST OF THE SOUTHERN CAPE VERDE ISLANDS

AND CONTINUES TO SHOW SOME SIGNS OF ORGANIZATION. CONDITIONS

APPEAR FAVORABLE FOR THIS SYSTEM TO BECOME A TROPICAL DEPRESSION

DURING THE NEXT COUPLE OF DAYS AS IT MOVES GENERALLY WESTWARD AT 10

TO 15 MPH. THERE IS A MEDIUM CHANCE...30 TO 50 PERCENT...OF THIS

SYSTEM BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS.

REGARDLESS OF DEVELOPMENT...SHOWERS AND THUNDERSTORMS WITH LOCALLY

GUSTY WINDS COULD AFFECT PORTIONS OF THE CAPE VERDE ISLANDS OVER

THE NEXT DAY OR SO.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE

NEXT 48 HOURS.

$$

FORECASTER BERG/PASCH

[kold weather]

Yep NHC has held at code Orange though given its structure and the constant convection present near the center is suggestive to me that this system is a good bit more organised then the NHC are giving credit. If there was recon I'm almost certain this would be upgraded...

Still if it holds this it won't be long before the NHC will have to go code red, maybe just needs a little more in the way of deeper convection, which is lacking due to the marginal SST's that are around the latitude 99L is at.

[Cookie]

99L

A couple of things on this

http://www.accuweather.com/news-story.asp?article=6

from ACCUWEATHER

[Iceberg]

99L does look very good to me T numbers are still 1.5 so probably just shy of declaring a TD.

After the next 48 hrs the system looks to effected by Shear (particularly to the south) which then stops any further development, maybe maintaining a TD or TS if it's got the right set up.

Then probably path indicates a earlish turn to the north as the High moves eastwards probably keep the system out at sea.

A very reasonable change of being the first named system all in all IMO.

[Hurricane Debby]

Courtesy of Hurricane Track...Could see as many as three named storms come and go over the next two weeks ??!!

In the Atlantic, we are watching 99L, the very well organized tropical wave near the Cape Verde Islands. Although deep thunderstorms have pulsed down in the last several hours, this has the potential of becoming a tropical depression and maybe even our first named storm later this week. Most of the computer model guidance agrees that this will go on to develop but it will take some time. The track looks to take it steadily west with a slight just-north-of-west bearing over the next 3 to 5 days. Other than bringing squally weather to the Cape Verdes, it poses no threat to land areas and I do not see any long term modeling bringing this in to the Windwards or Leewards either. On the other hand, this does not look to be the only feature to watch this week. Almost all of the very reliable and modern global computer models show more development emerging from the coast of Africa over the next several days. The pattern is shifting in to a period when we could see as many as three named storms come and go over the next two weeks. As strong impulses of energy move westward across the Atlantic, tropical cyclone development chances will increase as the pattern settles in to being quite a bit more favorable than in recent weeks. This is important to take note of since many news headlines as of late proclaimed how inactive the hurricane season is forecast to be. I would suggest that anyone living along the coast of any land mass in the western Atlantic Basin pay attention to the tropics these next couple of weeks. You would probably do so anyway since it is August. As I said in my evening post last night, there are no imminent problems with any of these potential systems but that can change in fairly short order. Being aware and on top of the situation is vital to being prepared- especially when money and time are limited. I'll post updates at least twice a day and we'll discuss things in depth on Wednesday night's edition of HurricaneTrack News/Talk. The season has been a no show since June for the Atlantic- now that things are getting more active, it is time to pay attention. I'll have more here tonight.

[Cookie]

99L

can see after today why it wasn't code red yesterday and hasn't really look great all day.

but its early days on this system

[Cookie]

99L

looking better this morning IMO

[Iceberg]

Dvorak has increased to T2.0 which is 30Kts and might well be enough to support an upgrade to a TD today, with NHC discussions starting.

It is just starting to appear in Floater 1. So should be fully there later today.

Forgot to add there is a warm pool of SST's under the system at the moment (around 28-29C).

After around 3 days this go back down to 27C so the next 2 days before the lower SST's and shear come into play could well be the best this little system does.

[Coast]

99L latest model tracks:

[kold weather]

well looks like we now have 90L which has come from the African Wave.

I did write a massive post about this bt my comp died on me which is sooo annoying. Still a shorter version will suffice this time as I haven't the time to re-create it!

90L has a good circulation at the moment though its lacking somewhat on the deep convection which is going to need to be adressed at some point if this is going to be a tropical depression in the nextt 24hrs.

In terms of strength given it deep latitude in the tropics it should stay away from the higher shear that is present with TD2 right now. SST's also are decent probably throughout its entire journey given how low it is. TD2 is also acting as a very good buffer against the dry SAL air which is to its north. This is because TD2 has effectivly mixed out the dry air with its own circulation and this is leaving a much better set-up for 90L to move into.

Track is uncertain still, the ECM is still thinking of a recurve away from anyland and is to the north of the caribbean, whilst the GFS keeps 90L further south then the ECM and has it striking the Cariribean islands. The big difference between the two models is simply the forward speed as they both have a broadly similar evolution of the upper features. The ECM is a good deal slower then the GFS, as at 72hrs it has 90L at 35W, which seems IMO to be a little too slow but we shall see. TD2 was that slow but the flow should be a bit quicker now the upper high has strengthened.

[Cookie]

still a great post kold despite it being the edited version

http://www.stormpulse.com/disturbance-1-medium-potential-2009

below taken from

NWS Tropical Prediction Center

National Hurricane Center, Miami, FL

800 am edt thu aug 13 2009

For the North Atlantic, Caribbean Sea and the Gulf of Mexico:

The National Hurricane Center is issuing advisories on tropical

depression two, located about 840 miles west of the southernmost Cape Verde Islands.

1. Showers and thunderstorms continue in association with a broad area of low pressure and a strong tropical wave centered about 250 miles south-southeast of the Cape Verde Islands in the far eastern Atlantic Ocean. Conditions appear to be favorable for further development during the next few days, and there is a medium chance, 30 to 50 percent, of this system becoming a tropical cyclone during the next 48 hours while the low moves to the west at 10 to 15 mph.

[Cookie]

90L

[MR EXTREMES]

just thought this might be intresting although please post in the correct thread if in wrong place.

http://news.bbc.co.uk/1/hi/sci/tech/8197191.stm

[Cookie]

90L

http://cimss.ssec.wisc.edu/tropic2/real-time/europe/movies/m7ir/m7irjava.html

[Iceberg]

Remembering that nothing is certain until it happens with a Tropical storm. Here's a quick 12Z round up for Invest 90L

The circulation is really getting tighter Convection although still good has not yet wrapped around to consolidate at the centre.

Still for an Invest this is looking very good and NHC have accordingly raised it to a RED Alert.

The models clearly show why.

HWRF takes it to a hurricane within 48 Hrs and then later to a strong CAT 3 Major Hurricane before it reaches anywhere.

GFDL takes it to near hurricane strength, SHIPS to hurricane strength as well, as does METO.

Paths are now looking bad for Jamaica, with GFS still keen on keeping it in that area.

The tropical models where pretty terrible though at 06Z

Dvorak levels are only at T1 currently but are getting better.

[kold weather]

I actually think the NHC were a bit hasty in putting this upto red alert. This is a big broad circulation at the moment and its drawing from a large area in the ITCZ as well. I've been saying this on other forums day but it reminds me a lot of a large WPAC system. These can sometimes take a while to gather themself up and consolidate and I personally think we are a good 24-36hrs away from this being a depression. Circulation is good so the main issue is simply one of convection. The main reason appears to be one of lower level convergence. At the moment its somewhat higher to the south of the center and this is allowing the big flare up to the south of the circulation which is where 90L is drawing in its moisture from. This is going to be a good thing eventually but for now its preventing it from further tightening up and brewing convection over the actual center. This is something I've notice happen in other large WPAC storms and is another reason I make the comprasion. Still its only a matter of time before that happens, be it tonight, tomorrow or even Saturday and with a Cape Verde storm we have a long while to watch this.

Edited August 13, 2009 by kold weather

[Iceberg]

Agree Kold, These storms can take a long while to get going, or they can just explode. The models make the assumption of convection in or near the centre at initialisation so ther are probably to progressive. In the longer time frame they probably underestimate the sharp increase in intensity that's likely once it's got going to even it all out.

Not an easy invest to judge atm.

Circulation is still there and the centre is just on the edge of a large area of precip, which might be slowly making it's way there.

Quikscat indicates some 30Kt winds within the centre of the system away from the convection. With 40Kt plus in the convection.

It will be much easier to see when it's finally within the floater range, with much better coverage.

Needless to say all the models take it upto a hurricane of varying strength with a similar path. It will be interesting to see at 08.00 what the ECM makes of the ridge, GFS is still being insistant on a more westerly path along with METO, ECM takes it further north, probably missing land up till now.

[kold weather]

ECM is still recurving this very quickly, indeed this run it barely makes it to 60W which seems utterly baffling when every other model has either hitting or close to the NE Caribbean, there is no doubt its a total outlier this morning once again, still can't ever discount the Euro...

However I think its forward speed is once again Euro's biggest issue, with it progged to be around 43W by 96hrs, meanwhile the 06z GFS has this pretty much at 50W. Whilst that may not sound like a huge difference when there is a weakness between 40-50W at that time it becomes a huge difference. Whilst it only causes a WNW/NW jog on the other models, on the ECM because of the slow forward motion it gets lifted out totally and once that process is underway its hard to stop.

Anyway 90L has developed some convection closer t othe ciruclation center, Qscat shows the center now around 12.3N but it is jumping about quite a lot at the moment so it could change again. Either way a general track west or just a tiny bit north of west seems probably for now, though can't rule out a slight WSW jog between 24-48hrs if it is a developed TD.

Given the convection has developed near the center now its looking likely that this will be upgraded at some point today.

[kold weather]

Time for a quick update I think.

Convection has been sheared off from the main center by easterly shear over the last 9-12hrs or so. Convection is still bursting to the west of the center of circulation and the the circulation itself still appears to be quite tight and compact. Before it is upgraded it once again needs to get some more decent convection over the center. This is the same shear that had hammered TD2 however with 90L the impact shouldn't be so severe as it has a large circulation and a decent size moisture field with it and therefore a greater amount of resources to use so to speak. The shear extends to about 40W and that area is slowly shrinking eastwards so it 90L may reach better conditions before then. However as TD2 is showing conditions west of there look pretty decent and whilst it may be a depression before then I think it will start taking off around that region.

I'll make another short post tomorrow, wil ltry and find the time for a short talk bout the track, etc!

[Cookie]

we now have 91L in the Gulf of mexico things really kicking off now!!