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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Quoting SLU:


more evidence that it's better organised than the hurricane center believes.


That data is from the hurricane center.
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Quoting Chicklit:

Don't rely on this site for weather information. Check with the NHC and your local weather authorities. Most of us, including me, just speculate and are often wrong!

Dr. Masters is usually right though. You should check back later to see what he has to say. I think he'll update his blog today.
The Dominican weather service is no help to me. Their office "onamet" lacks detail and is often very outdated and horribly inaccurate.
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DT=2.0 and we have TD2
Member Since: August 22, 2006 Posts: 0 Comments: 2720
Quoting FLWeatherFreak91:
Good morning everyone! I am currently in La Romana, Dominican Republic, and glad to see that 97l isn't anything to worry about since it's moving in my direction... but I am looking forward to its arrival (as an open wave I believe) to my area sometime tomorrow evening. These tropical waves can actually bring very high winds and extremely heavy rain to the islands... nice to see in a place that doesn't get many interesting storms.

Don't rely on this site for weather information. Check with the NHC and your local weather authorities. Most of us, including me, just speculate and are often wrong!

Dr. Masters is usually right though. You should check back later to see what he has to say. I think he'll update his blog today.
Member Since: July 11, 2006 Posts: 14 Comments: 11390
Quoting extreme236:
TAFB, GR, VI, 5, 1515 /////, , , GOES12, CSC, T, DT = 1.5 BASED ON 0.3 BANDING


What does that mean? TAFB is a new one to me. :)
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2309. SLU
Quoting extreme236:
TAFB, GR, VI, 5, 1515 /////, , , GOES12, CSC, T, DT = 1.5 BASED ON 0.3 BANDING


more evidence that it's better organised than the hurricane center believes.
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Good morning everyone! I am currently in La Romana, Dominican Republic, and glad to see that 97l isn't anything to worry about since it's moving in my direction... but I am looking forward to its arrival (as an open wave I believe) to my area sometime tomorrow evening. These tropical waves can actually bring very high winds and extremely heavy rain to the islands... nice to see in a place that doesn't get many interesting storms.
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Quoting stormsurge39:
What does 12z mean?


One of the problems of collecting Weather observations is that it is always changing and weather observation sites are spread across 24 major different "local times" around the globe. ( Believe it or not there are some local time zones that are 30 and even 15 minutes different than the one next to it)

To get a "Snap shot" of the world's weather, the powers that be agreed a long time ago that weather observers would take observations at "Synoptic Times" That is at the same point in time around the world. The agreed upon times for standard observations (no pending major weather activity) are 0000, 0600, 1200, 1800 UTC This standard is called Coordinated Universal Time, abbreviated UTC. This was formerly known as Greenwich Mean Time (GMT). Other terms used to refer to it include "Zulu time" (Z), "universal time," and "world time."

All of these are based on the (local)time it at Greenwich, England, which is located on the zero degree meridian (longitude)(from when the British Navy ruled the seas)

see http://www.dxing.com/utcgmt.htm
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yeay! texas finally getting some rain...
Link

it's going to be a wet day in Central Fla too.
Member Since: July 11, 2006 Posts: 14 Comments: 11390
Quoting Orcasystems:


The present early Tracks go from as far as south of Cancun to missing Florida to the east... so basically... pick a spot.


This got my attention...I know. I know. Get out the dart board. LOL. :)

CMC strait to Louisiana.



Link
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we haven't been driven this crazy since pre Dolly didn't form
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Blog Update
Reflector site for those at work, which includes Weather456, daily update.


AOI

AOI

AOI
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2302. SLU
Quoting extreme236:
AL, 97, 2009072012, , BEST, 0, 131N, 576W, 25, 1010,


thanks. 120 miles east of Barbados.
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00Z GFS shear forecast showed low to moderate shear in 97L's path...even though thats not what it looks like right now...
Member Since: August 2, 2007 Posts: 19 Comments: 19234
2300. beell
Hardly a place for a disturbance to hide...

Link is broken
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this 97L is driveing us all nuts


1st its gos poof



then it comes back then it gos poof so on so on so on
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TAFB, GR, VI, 5, 1515 /////, , , GOES12, CSC, T, DT = 1.5 BASED ON 0.3 BANDING
Member Since: August 2, 2007 Posts: 19 Comments: 19234
Quoting Orcasystems:


The present early Tracks go from as far as south of Cancun to missing Florida to the east... so basically... pick a spot.


I'm thinking missing Florida to the east as it will probably get snatched into the pooling energy over the Bahamas.
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AL, 97, 2009072012, , BEST, 0, 131N, 576W, 25, 1010,
Member Since: August 2, 2007 Posts: 19 Comments: 19234
Quoting hurricaneben:
One possible path takes 97L right towards Southeast Florida.


The present early Tracks go from as far as south of Cancun to missing Florida to the east... so basically... pick a spot.
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Quoting leftovers:
not that bad it will fill up the cisterns


Thanks......I did not know if you Folks down there needed more rain or not....Hope it's not too bumpy for you however.
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One possible path takes 97L right towards Southeast Florida.
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97L has proven to be real sneaky, you have to watch anything thats sneaky.
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This could possibly be 97L's last day of existence we will have to see! I'm out like a fat kid in dodgeball see you guys at noonish!
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Quoting Orcasystems:


Shear is having fun with 97


lol
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Quoting stormsurge39:
It also looks like the whole system is still turning with alot of convection! Does its chances get any better if it survives today? someone please enlighten me.

97L is not in an environment conducive to tropical development because the shear is just too high. You can expect rain, some gusty winds, but nothing tropical force IMHO.
Member Since: July 11, 2006 Posts: 14 Comments: 11390
Quoting SLU:


Ok. try a Caribbean cruise. You'll love it.


I plan on it, thanks.
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2285. IKE
Quoting alaina1085:

Ike, so far your prediction for the season is coming true..lol.


It'll ramp up in August. Mid-August through mid-October is when the action is...
Member Since: June 9, 2005 Posts: 23 Comments: 37860
2284. SLU
Quoting alaina1085:


Sadly no, I havent been out of the country yet. Something on my to do list in life. But I hear its beautiful.


Ok. try a Caribbean cruise. You'll love it.
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Shear is having fun with 97
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Quoting IKE:


Nope.

Shows nothing through the rest of July...tropically.

Ike, so far your prediction for the season is coming true..lol.
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Quoting sebastianflorida:
I think Just east of bahamas looks interesting; if I was in Carolinas I'd keep an eye on this area moving your way.

Yeah, I was looking at that also. A lot of moisture in that area.
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2280. IKE
Quoting louisianaboy444:
Does the GFS do anything with this system because the one i'm looking at drops the system immediately


Nope.

Shows nothing through the rest of July...tropically.
Member Since: June 9, 2005 Posts: 23 Comments: 37860
Does the GFS do anything with this system because the one i'm looking at drops the system immediately
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Hanging around in SRQ, not fishing.
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2276. SLU
The "z" in 12Z stands for Zulu time, its the same as GMT and UTC (Universal Time Coordinated)

Julie

Barbados should get some heavy wind and rains shortly.

The leading edge of the heavy convection is a few hours away from the rest of the islands.
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2275. beell
2258. KOG,

Quite the model run. 97L last seen moving SW at 26 knots!



0 12.1 54.2 280./17.1

6 11.2 56.6 250./25.8

STORM DISSIPATED AT 6 HRS AT THE ABOVE PSN.
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Quoting SLU:


lol .... ever been to St. Lucia before?


Sadly no, I havent been out of the country yet. Something on my to do list in life. But I hear its beautiful.
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I think Just east of bahamas looks interesting; if I was in Carolinas I'd keep an eye on this area moving your way.
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2272. SLU
Quoting alaina1085:


Ugh, your so lucky. You get to live in paradise everyday...


lol .... ever been to St. Lucia before?
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Quoting StormW:


Hope he feels better.

Thanks Storm, me too.

Quoting louisianaboy444:
Shear does't look to be favorable for a good while and i see no evidence of an anticyclone developing so this thing would need a prayer don't get me wrong i've seen it happen before (We all remember Barry lol) It is pretty much a wait and see game...how is everyone this morning


Im doing fabulous, how about yourself :)
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How far away is the leading edge from Barbados? When should we start to see the effect? Right now it is a bit overcast but i can still see the sun here. It was pouring earlier but that has stopped.
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It also looks like the whole system is still turning with alot of convection! Does its chances get any better if it survives today? someone please enlighten me.
Shear does't look to be favorable for a good while and i see no evidence of an anticyclone developing so this thing would need a prayer don't get me wrong i've seen it happen before (We all remember Barry lol) It is pretty much a wait and see game...how is everyone this morning
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Quoting SLU:
I am in St. Lucia. 12z is 8:00am EST


Ugh, your so lucky. You get to live in paradise everyday...
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the mid level circulation is now under the heaviest convection. leadind edge of 97L about 4 hrs away from SLU
Member Since: August 22, 2006 Posts: 0 Comments: 2720

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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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