ATL: INVEST (97L)

[Derek Ortt]

much to my surprise... it is better organized. However, I dont think it'll have much of a chance before encountering the shear

[cycloneye]

This is Jeff Masters take this morning on 97L.

Posted by: JeffMasters, 3:55 PM GMT on Julio 19, 2009

The tropical wave near 12N 52W, about 600 miles east of the Lesser Antilles Islands (97 L), has grown more organized this morning as it tracks west at about 20 mph. This wave is surrounded by an area of very dry air from the Sahara Desert, but 97L has been able to steadily moisten a large region of the atmosphere over the past day, insulating itself from the dry air. This moistening process has been aided by sea surface temperatures (SSTs) that have steadily increased from 26.5°C to 27.5°C, plus the presence of only 10 knots of wind shear. The system now has a small area of intense thunderstorms near its center, with some rotation of the cloud pattern evident at mid-levels of the atmosphere. An upper-level outflow channel has opened to the north, and there is evidence that surface spiral bands are beginning to form. This morning's QuikSCAT pass missed 97L, so we don't know what is happening at the surface.

Wind shear is a modest 10 knots over the disturbance, and is forecast to remain in the moderate 10 - 15 knot range through Monday morning. This should allow further development to occur today, and 97L could be approaching tropical depression strength on Monday as it moves through the central Lesser Antilles Islands. Monday night, shear is expected to rise to 20 - 30 knots, thanks to the presence of a trough of low pressure at upper levels of the atmosphere over the eastern Caribbean. Since 97L is a relatively small system, it is very vulnerable to wind shear. This shear may be able to drive some of the dry air west of 97L deep into its interior, significantly disrupting the disturbance. Shear will remain high along 97L's path through Thursday, when the storm should be in the western Caribbean near Cuba. If there is anything left of 97L by then, some development is possible. The National Hurricane Center gave 97L a low (less than 30% chance) of developing into a tropical depression in the next 48 hours in their 8am Tropical Weather Outlook. However, I'd say the odds are now in the medium range (30 - 50%).

[Aric Dunn]

I thought this thread was locked last night?

i was posting in the other all night in the non active

[cycloneye]

I thought this thread was locked last night?

i was posting in the other all night in the non active

Nope,the thread remained open all along after 97L was deactivated.

[Aric Dunn]

pretty impressive ball of convection firing again ... this time though its very concentrated.

considering the surface or low level circ that was evident yesterday and last night is, is much more evident this morning with some initial banding features now setting up. I would at least go with code orange at 2pm and if this trend continues as i said last night we could be looking at a depression before the islands. its a small system and none of the buoys are close enough to make and direct observations about a closed circ at the surface. so the only evidence is satellite analysis. which indicates especially the last few hours that we have a organizing TC

[Aric Dunn]

I thought this thread was locked last night?

i was posting in the other all night in the non active

Nope,the thread remained open all along after 97L was deactivated.

hhhmmm....posted like 2 pages worth of stuff all night last night ..lol in the other thread..

[Aric Dunn]

This is Jeff Masters take this morning on 97L.

Posted by: JeffMasters, 3:55 PM GMT on Julio 19, 2009

The tropical wave near 12N 52W, about 600 miles east of the Lesser Antilles Islands (97 L), has grown more organized this morning as it tracks west at about 20 mph. This wave is surrounded by an area of very dry air from the Sahara Desert, but 97L has been able to steadily moisten a large region of the atmosphere over the past day, insulating itself from the dry air. This moistening process has been aided by sea surface temperatures (SSTs) that have steadily increased from 26.5°C to 27.5°C, plus the presence of only 10 knots of wind shear. The system now has a small area of intense thunderstorms near its center, with some rotation of the cloud pattern evident at mid-levels of the atmosphere. An upper-level outflow channel has opened to the north, and there is evidence that surface spiral bands are beginning to form. This morning's QuikSCAT pass missed 97L, so we don't know what is happening at the surface.

Wind shear is a modest 10 knots over the disturbance, and is forecast to remain in the moderate 10 - 15 knot range through Monday morning. This should allow further development to occur today, and 97L could be approaching tropical depression strength on Monday as it moves through the central Lesser Antilles Islands. Monday night, shear is expected to rise to 20 - 30 knots, thanks to the presence of a trough of low pressure at upper levels of the atmosphere over the eastern Caribbean. Since 97L is a relatively small system, it is very vulnerable to wind shear. This shear may be able to drive some of the dry air west of 97L deep into its interior, significantly disrupting the disturbance. Shear will remain high along 97L's path through Thursday, when the storm should be in the western Caribbean near Cuba. If there is anything left of 97L by then, some development is possible. The National Hurricane Center gave 97L a low (less than 30% chance) of developing into a tropical depression in the next 48 hours in their 8am Tropical Weather Outlook. However, I'd say the odds are now in the medium range (30 - 50%).

That is a great analysis !! sounds pretty much dead on at the moment.. what time did he post that?

[HurricaneBelle]

This is Jeff Masters take this morning on 97L.

Posted by: JeffMasters, 3:55 PM GMT on Julio 19, 2009

That is a great analysis !! sounds pretty much dead on at the moment.. what time did he post that?

There's your answer.

[cycloneye]

what time did he post that?

He posted at 11:55 EDT or 3:55 GMT time.

[Aric Dunn]

This is Jeff Masters take this morning on 97L.

Posted by: JeffMasters, 3:55 PM GMT on Julio 19, 2009

That is a great analysis !! sounds pretty much dead on at the moment.. what time did he post that?

There's your answer.

hehe.. did not see the "GMT" i thought the 355 PM was a mistake from the copy .. lol thanks

[cycloneye]

Looking very good at the moment.

[cycloneye]

The 12z GFS shear profile shows less shear in the Eastern Caribbean in the next 36 hours.

[StormTracker]

Looking very good at the moment.

If it maintains that look or better for the next hour or so, I definitely think we go to code orange at 2PM!!!

[Aric Dunn]

Looking very good at the moment.

I was doing some long loop analysis from the images i saved last night from where the center was ( center last night meaning average center of cyclonic turing) and with extrapolation from that and the extrapolating the center from the ever improving banding features setting up along with the co-lacated midlevel circ that is pretty evident. i decided to draw on your nice pretty picture cycloneye sorry
but that is out center.. 12.1N 51.4W approximate

and sorry for the crudeness of the hand drawing with paint brush lol

[bvigal]

buoy data ~14.5 N 53W
buoy data

[Aric Dunn]

buoy data ~14.5 N 53W
buoy data

This is the location of the buoy BVIGAL posted with respect to the rough center White dot is the buoy

[StormTracker]

I think that's one, if not the best, Jeff Masters analysis posts I've ever read in the couple of years I've been a member of S2K! A very detailed & educating analysis! If what he thinks(and Aric you agree as well)holds even close, this system should definitely be able to strengthen itself enough to make it's way to wherever it's heading(through the shear)and still be able to fully develop at a later time!!!

[Gustywind]

The 12z GFS shear profile shows less shear in the Eastern Caribbean in the next 36 hours.

Allowing better and conductive conditions for 97L before approaching the Leewards...

[Aric Dunn]

This is from 6 hours ago..
but winds right support tropical depression status.. only thing left to do is confirm a closed low at the surface. at this moment thats not too difficult to do. but I imagine the NHC would wait till this evening to do any upgrading but not wait too long since its approaching the islands.. last night i said a depression this evening. and if the trend continues that is looking more likely..

and actually there are some 35k and 40kt winds in that image .. to bad quickscat missed it this morning..



and the other image from a different microwave pass again 9 hours ago

showing 40kt

[cycloneye]

It will be interesting to see if the Dim period will cause convection to go down before DMAX comes tonight.