Atlantic Invest Thread 2009

[kold weather]

Well after nearly a month of inactivity we now have our next Invest, 93L. This has developed from a convective pulse that has stayed in the W/C Central Caribbean over the past 12-18hrs roughly. Convection is reasonably deep and for the moment it does look like shear isn't that high, so development does seem possible.

Some uncertainties about the track of this convection, some models are taking it into the Yucatan but I wouldn't like to say the likely track, I'm sure the 12z will give a better idea.

[Cookie]

after so long of not much this came as a bit of a surprise!

this needs to be kept an eye on.

http://www.stormpulse.com/

Tropical Weather Outlook

National Oceanic and Atmospheric Administration

Zczc miatwoat all

ttaa00 kNHC ddhhmm

NWS Tropical Prediction Center

National Hurricane Center, Miami, FL

200 pm edt fri jun 26 2009

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

1. A tropical wave over the western Caribbean Sea continues to produce

a large area of showers and thunderstorms from Cuba and the Cayman Islands southwestward to Honduras. No significant development of this system is expected before it reaches the yucatan peninsula early Saturday, but conditions are forecast to become a little more favorable once it moves into the southern Gulf of Mexico late Saturday or Sunday. There is a medium chance, 30 to 50 percent, Of this system becoming a tropical cyclone during the next 48 hours. Locally heavy rains will continue over portions of Cuba and the Cayman Islands today and spread westward over northern Central America and the yucatan peninsula over the next day or so.

Elsewhere, tropical cyclone formation is not expected during the next 48 hours.

[Cookie]

medium risk still up

[Iceberg]

93L is looking quite impressive atm and is odds on IMO to be the first named storm of the season.

Very good convection, although we are lacking T numbers due to weak circulation.

Some models notably HWRF and SHIPS are keen to take this to a strong Tropical storm, the globals less so, but the system is expected to remain very small so it probably not going to be picked up by the globals very well.

Steering as you expect from the small storm is highly variable and track could be anywhere atm, but a movement towards New Orleans westwards looks likely.

A TD by tomorrow is a real possibility.

[Cookie]

surprised their isn't more talk on this, didn't look great earlier looks better now

[Cookie]

back to low chance.

Code Yellow

ABNT20 KNHC 272333

TWOAT

TROPICAL WEATHER OUTLOOK

NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 800 PM EDT SAT JUN 27 2009

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

DISORGANIZED SHOWERS AND THUNDERSTORMS CONTINUE IN ASSOCIATION WITH A TROPICAL WAVE LOCATED OVER THE FAR NORTHWESTERN CARIBBEAN SEA.

WHILE NO DEVELOPMENT OF THIS SYSTEM IS EXPECTED TONIGHT AS IT MOVES ACROSS THE YUCATAN PENINSULA...SOME SLOW DEVELOPMENT IS POSSIBLE AFTER IT MOVES INTO THE SOUTHERN GULF OF MEXICO ON SUNDAY. THERE IS A LOW CHANCE...LESS THAN 30 PERCENT...OF THIS SYSTEM BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS. LOCALLY HEAVY RAINS AND GUSTY WINDS WILL CONTINUE TO AFFECT PORTIONS OF THE YUCATAN PENINSULA AND WESTERN CUBA THROUGH SUNDAY.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE NEXT 48 HOURS.

$$

FORECASTER BRENNAN/BLAKE

[Iceberg]

Yep it's crossing over land now, I missed that bit !.

A TD once it enters the BOM looks good though. Shear is very low and even GFDL now makes it a TS. Path is still unknown though as it's so slow moving.

[Cookie]

it really isn't doing much at the moment just a waiting game really.

[Cookie]

its gone, dead.

its not all bad though we're still only 1 system behind this time last year.

[Cookie]

94L still hanging on in their.

[londonsnow]

slow start to the season, i think the slowest since 2004. that year did however go on to deliver 9 hurricanes.

[Gray-Wolf]

I was gonna blame the forming El-Nino but then saw this

http://www.time.com/time/health/article/0,...=rss-topstories

so now even Nino years needn't squish out the 'canes?

[Iceberg]

97L has been named and at last we get the SST's and northward ITCZ to give a normal storm path.

Very little data currently and it's certainly not up to much atm, but worth watching.

SHIPS take it to a boarderline Cane, but only really because of the classic track.

[kold weather]

I'd say this has about 5% chance of forming in the next 3 days or so. Circulation is at higher levels at the moment whilst convection earlier was helped along by D-Max. The D-min that is now present combined with a lack of surface circulation is allowing the convection to totally poof and so right now there is little convection with the wave and what there is of it is shallow. There is some dry air about it though its not the type that can stop development in the right set-up, however it is going to slow down the system...

The biggest issue it has is the powerful jet streak which is to its north, making a wall of shear right across the Atlantic over the next 24-48hrs. Shear values are expected to be around 30-50kts which will destroy any system that is trying to get going. So its probably got another 2 days to do something and work with what is a marginal set-up. SST's are just on the right side of favorable, dry air is an issue though with any D-max I;d expect convection to flare. It also will flare as it gets closer to the jety core but after 12hrs of that occuring shear should increase to the point where it will struggle in a big way.

I believe the best chance this system will have is much further down the line, if it cxan get north of the shear wall that is present then there should be lower shear and a more favorable region for it to move into, but to get there its got some very nasty conditions first.

[Cookie]

thanks for the updates guys

97L

[Cookie]

97L

was deactivated last night and we activated again today and is looking better again.

Edited July 19, 2009 by cookie

[Somerset Squall]

Yes, 97L is in lower shear and moister air which has allowed the system to get slightly better organised with some deep convection that has fair rotation. However, the system is moving briskly westwards, and to the west lies destructive levels of shear, across the entire Caribbean. Unless this shear eases, 97L will be more likely ripped apart than to organise into a tropical depression. The only way it can avoid the shear is if it moves to the south, but then development would struggle to occur due to land interaction/dry air from South America. I personally don't think this one will form into a tropical cyclone anytime soon.

[kold weather]

This one isn't easy to forecast. Shear is high right now but some models are forecasting a small upper high forming over the central Caribbean which would leave a small window of better conditions.

Before then 97L currently sits in a decent atmosphere. The convection is wrapping around the developing circulation quite well though its hard to tell if that circulation is at the surface. Quikscat did show turning but it was far from the closed circulation that is required. It does appear to be wrapping up quite rapidly and thus it could yet become a tropical depression before it reaches the higher shear. Odds are probably about 30-40% IMO of that happening.

The situation is complicated because the models are seeing the wave split once it reaches the central Caribbean with the northern section eventually heading towards the Carolinas. Several models develop it however from what is happening right now it seems like they have a very poor grip on where the energy of 97L is right now. With 97L still heading west it may be the models are picking up on the wrong region of the wave for development.

Conditions in the Caribbean right now aren't great but as I mentioned over the enxt day a small upper high forms which does lower shear. Before then though near the Lesser Antillies there is a screaming jet streak that is only slowly lifting up as the upper high tries to form. It seems highly likely that in the next 12-24hrs 97L will run into the shear which may cause it some big issues, hard to call at this stage. Beyond that much depends on track that 97L. In easy terms the further south it stays the better for it. Above 15N the jet blazes pretty strong which is obiously a killer for TCs. If it stays south of there shear isn't quite as bad and so development is possible there as well if it fails this first time.

So a fairly complicated set-up, we shall see!

[Cookie]

Thanks for the updates guys

[Cookie]

97L

[Iceberg]

97L is looking alot healthy this morning, isn't it Cookie, HWRF has even taken it on this morning.

Track is very complicated but a GOM entry is very possible.

[Somerset Squall]

Shear is really taking it's toll on 97L now, convection is less organised and rotation isn't as strong indicating that any LLC is weak at best. I still think chances for development are slim in the near term but if the wave survives it may find a better environment later down the line. We shall see.

[Cookie]

this system is blowing my mind, I didn't realize how complex this all is and how fast things can improve and go down the pan!

so really, I don't want to say anything at the moment!

[Somerset Squall]

this system is blowing my mind, I didn't realize how complex this all is and how fast things can improve and go down the pan!

so really, I don't want to say anything at the moment!

Yes, 97L is in a very complex environment at the moment, as Kold's post describes. I'm not saying it won't ever develop, because really I'm very uncertain about that, but I don't think it will develop within the next couple days as shear is pretty high at the moment and if you look at 97L on satellite imagery you can the see the invest is really suffering at the moment. The wait for an Atlantic TC continues!

[Cookie]

its not just that, from when this came off Africa till now, been times where its looked like a forming into a tropical storm and looking good and then back to not being again, just seems to have happened so many times.