97L growing more organized, will bring heavy rain to the Lesser Antilles

By: Dr. Jeff Masters , 3:55 PM GMT on July 19, 2009

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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%).

None of the computer models are forecasting tropical storm development over the next seven days.


Figure 1. Current satellite image of African wave 97L.

I'll have an update Monday morning. As 97L approaches the islands, you may want to follow local observations there using our wundermap for 97L.

Jeff Masters

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97L is currently under 25kts of shear.
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Quoting homelesswanderer:


Yeah. I'm wondering if they'll deactivate it again.

Unlikely. The 850mb vorticity continues to increase. The convection may be gone but the circulation is still there.
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Quoting reedzone:
If that Anticyclone strengthens, shear should lessen more quicker then the forecast. One model shows shear subsiding and moving northwest by tomorrow, Can't count on that model run though.

I think it was the NOGAPS
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Good Morning everyone......Looks like 97L is getting hit with the higher shear i thought it would....
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Quoting weatherwatcher12:
NHC taking a long time to update


Yeah. I'm wondering if they'll deactivate it again.
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If that Anticyclone strengthens, shear should lessen more quicker then the forecast. One model shows shear subsiding and moving northwest by tomorrow, Can't count on that model run though.
Member Since: July 1, 2008 Posts: 13 Comments: 7437
NHC taking a long time to update
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Quoting homelesswanderer:
Reed if I read that right. This lil storm is under 30kts of shear. And its still firing up convection. With that and the increased vorticity it sure is trying hard to hang on. I don't know what the shear is coming from. Or if it will get worse but is it ever going to get into a favorale environment? I think if it makes it to a good environment it will rapidly intensify. I know it's July. But this storm has been tenacious.

Shear is predicted to lift in 2-3 days. Maybe even less.
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Reed if I read that right. This lil storm is under 30kts of shear. And its still firing up convection. With that and the increased vorticity it sure is trying hard to hang on. I don't know what the shear is coming from. Or if it will get worse but is it ever going to get into a favorale environment? I think if it makes it to a good environment it will rapidly intensify. I know it's July. But this storm has been tenacious.
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Quoting reedzone:


It sure is, this is the one I've been mentioning.. see the anticyclonic turning? It's an Anticyclone.

http://cimss.ssec.wisc.edu/tropic/real-time/atlantic/winds/wg8shr.html

On the satellite I'm seeing something that looks life a subtropical ridge. I could be wrong though.
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Quoting islagal:
is the blob behind 97L looking a little interesting?

Yeah. It's in the ITCZ, but if it can escape it could get interesting
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2054. islagal
is the blob behind 97L looking a little interesting?
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Quoting BurnedAfterPosting:


nevermind that isnt an anticylcone I dont think lol


It sure is, this is the one I've been mentioning.. see the anticyclonic turning? It's an Anticyclone.

http://cimss.ssec.wisc.edu/tropic/real-time/atlantic/winds/wg8shr.html
Member Since: July 1, 2008 Posts: 13 Comments: 7437
New model runs are out for 0z
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Looks like it's trying to rally against the shear and get that convection together.
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97l, new wave?, carlos reforming?? New blog entry, now i'm going to bed. :)

http://www.wunderground.com/blog/winter123/show.html
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That convection won't give up. It just keeps re-firing
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well I am going to bed, neat thing for me is that my cellphone rocks so much I can check the 2am TWO on it and not have to be on here to do so

I did that last night too lol

see you all tomorrow, when many tropical weather lovers will run to their computers in the morning to see what has become of 97L, I compare it to a kid coming down the stairs on Christmas morning to see what presents are under the tree LOL
Quoting winter123:
View Comments (2008)

lool irony. anyway i dont think 97l will be athreat unless it somehow survives into the gulf. which it wont. this season is a bust. NEXT


-facepalm- 2004.. 2004..2004..2004..2004..2004..El Nino..Cold Fronts.. pat, I need some 70's or 80's music that would be proper for this.
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Quoting BurnedAfterPosting:


yea but it has maintained its structure nicely so far, I even think the circulation has become even more defined despite the shear.

The 850mb vorticity has increased
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Quoting BurnedAfterPosting:
I see one forming in the Bahamas though

I think that black spot clearing out in the central Caribbean could be a developing anticyclone
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Quoting Stormchaser2007:
Just checking back in and it looks like 97L's central convection is getting sheared pretty nicely.



yup
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Quoting Stormchaser2007:
Just checking back in and it looks like 97L's central convection is getting sheared pretty nicely.


yea but it has maintained its structure nicely so far, I even think the circulation has become even more defined despite the shear.
Just checking back in and it looks like 97L's central convection is getting sheared pretty nicely.
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I see one forming in the Bahamas though
Quoting BurnedAfterPosting:


nevermind that isnt an anticylcone I dont think lol

lol
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Quoting weatherwatcher12:

Could you post a map. I'd like to see.


nevermind that isnt an anticylcone I dont think lol
Quoting BurnedAfterPosting:
that anticyclone over Panama has expanded

Could you post a map. I'd like to see.
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will take one name storm at a time and see how many we get at the end
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that anticyclone over Panama has expanded
Quoting winter123:
View Comments (2008)

lool irony. anyway i dont think 97l will be athreat unless it somehow survives into the gulf. which it wont. this season is a bust. NEXT


you are a bust; POOF!! lol
Quoting Tazmanian:



i think will see less then 5 too 7 name storms that is if we can get there


It is only July 19th and El Nino is still not projected to be very strong

I think we will get closer to 10-12 named storms; in the heart of the season we can rattle off 4 or 5 storms in a short amount of time. Based on what we have seen mostly favorable conditions will exist in August.
View Comments (2008)

lool irony. anyway i dont think 97l will be athreat unless it somehow survives into the gulf. which it wont. this season is a bust. NEXT
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It's still firing up convection:
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Quoting ackee:
this hurricane seasons shear rule Iam thinking we have less than ten name storms this seasons



i think will see less then 5 too 7 name storms that is if we can get there
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Quoting cchsweatherman:


I understand since they are the real experts and the people in charge. What my purpose is when creating those graphics and explanations is to try and offer people an easier perspective as to whats going on and try my best to provide easy-to-understand explanations since I know that some people who access this site don't have a deep meteorological background. In no way and shape do I intend to overrule the government-run agencies like the NHC and NWS.


Don't worry about it CCHS, you were asked by several of us to do this type of graphic last year, and we find it very helpful.

The information on this blog is the opinion of those who write it, and does not have to be only what nhc, etc say. That's why its a blog.

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Quoting Patrap:
On a serious note,..one has to wary of any intact CV circulation,..as 1995 and 2008 showed us,certain CV waves are tenacious and can survive the Trek to a more Favorable environment.

Jeff Masters will be the first to convey that lil bit o wisdom.

Never discount a CV circ till its inland or dissipated.

Nighty.



Well said
Dont try to act like you just dont love em!!! lol
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2024. Patrap
On a serious note,..one has to wary of any intact CV circulation,..as 1995 and 2008 showed us,certain CV waves are tenacious and can survive the Trek to a more Favorable environment.

Jeff Masters will be the first to convey that lil bit o wisdom.

Never discount a CV circ till its inland or dissipated.

Nighty.

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Quoting Tazmanian:
this time its rip up for good by the wind shear


You said that not to long ago..
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why do we love hurricanes?
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2021. ackee
this hurricane seasons shear rule Iam thinking we have less than ten name storms this seasons
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2020. Patrap
97 just got wacked upside its lil head..LOL




Floater - RGB Color Infrared Loop
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Quoting BurnedAfterPosting:


you tend to write things off before they are actually gone, seems you do it a lot as well



you no am this massing with evere one


LOL
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The vorticity continues to get stronger-
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taz your trying to rile up these 97ivest lovers? arent u lol
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New Map
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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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