Lesser Antilles Disturbance 97L a Threat to Develop

By: Dr. Jeff Masters , 2:46 PM GMT on September 01, 2013

Share this Blog
70
+

A tropical wave over the Lesser Antilles Islands (Invest 97L) is moving westward at 15 mph, and is bringing heavy rains and gusty winds to the islands. Top sustained winds in the islands as of 10 am AST Sunday were 26 mph at Monserrat. Heavy thunderstorm activity has sharply increased since Saturday, as seen on satellite loops. A large circulation is evident, with some westerly winds blowing to the south of the disturbance. However, the thunderstorms are poorly organized, and there is no sign of a well-organized surface circulation. Martinique radar shows some rotation to the echoes, though well-organized spiral bands are not evident, and do not appear to be forming. Wind shear has dropped to a moderate 10 - 20 knots over the system. An area of dry air from the Saharan Air Layer (SAL) surrounds 97L and is interfering with development.


Figure 1. Latest satellite image of Invest 97L.

Forecast for 97L
Wind shear is expected to be in the low to moderate range for the next five days, and ocean temperatures will be warm, 28 - 29°C. The disturbance is steadily moistening the atmosphere and is moving into a moister environment, so dry air will be less of an impediment to development as the week progresses. The main factor keeping the disturbance from developing over the next two days would appear to be the fact that 97L is quite large, and is stretched out from east to west over a wide expanse. Large, elongated systems like 97L usually take several days to consolidate and spin up. Another factor that will likely retard development is the presence of strong surface trade winds over the Eastern Caribbean ahead of 97L, south of the Dominican Republic. These strong trade winds are a common feature of the Eastern Caribbean, and make the region something of a hurricane graveyard. As the surface wind flow to the west of 97L accelerates into this wind max, air will be sucked from aloft downward towards the surface, creating sinking air, interfering with the formation of thunderstorm updrafts. The best chance for development of 97L would appear to be on Wednesday or Thursday, when the disturbance reaches the Central Caribbean. The wave will likely spread heavy rains to Puerto Rico, the Virgin Islands, and the Dominican Republic by Tuesday, and to Haiti by Wednesday. These rains will be capable of causing life-threatening flash flooding and mudslides in mountainous regions in Puerto Rico and Hispaniola. Of our three reliable models for predicting genesis, the UKMET, GFS, and European models, only the UKMET model develops the disturbance, predicting it will become a tropical depression south of Haiti on Wednesday, and near Jamaica on Thursday. In their 8 am EDT Sunday Tropical Weather Outlook, NHC boosted the 5-day odds of formation of 97L to 30%, and the 2-day odds to 20%.


Video 1. You can see why landslides triggered by heavy rains from a tropical cyclone are among the most dangerous hazards of these storms, thanks to a dashboard cam that caught this extraordinary rock slide in Northeast Taiwan on August 31, 2013, after heavy rains from a cold front drenched the island with up to 200 mm (7.87") of rain in 24 hours. The rains fell upon soils already saturated by Thursday's torrential rains from Tropical Storm Kong-Rey, which dumped up to 482 mm (19") of rain on Taiwan, killing three people. The driver of the car caught in the rock slide survived with minor injuries. Thanks go to wunderground member Robert Speta for bringing this video to my attention. A separate video showing the damage to the car and the course of the rock slide is here.

Jeff Masters

Reader Comments

Comments will take a few seconds to appear.

Post Your Comments

Please sign in to post comments.

or Join

Not only will you be able to leave comments on this blog, but you'll also have the ability to upload and share your photos in our Wunder Photos section.

Display: 0, 50, 100, 200 Sort: Newest First - Order Posted

Viewing: 705 - 655

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 | 50Blog Index

Quoting 701. weatherlover94:



It's when the sun goes down. When the sun goes down usually convection decreases

Allow for someone else, to answer this question further and with more accuracy. :)
Member Since: Posts: Comments:
Member Since: Posts: Comments:
The Strong Trade wind flow near 18N has really aided in the tightening of 97L's Circulation, and should allow for the system to consolidate even more so.

Though Convection is always the main feature to look at with Satellite images, what's under the hood is what really makes the storm.
Right now, 97L's engine is revving up.
Member Since: Posts: Comments:
Thanks Pat. Thats where I kept looking for circulation. Its the logical spot with the winds and all,but I couldnt pick it out.
Member Since: Posts: Comments:
Quoting 698. BrandenCordeiro:
Can someone explain to me what DMIN is?

Thanks :)



It's when the sun goes down. When the sun goes down usually convection decreases
Member Since: September 8, 2010 Posts: 0 Comments: 2142
Quoting 696. Jamiekins:


Does the Bullseye on that image indicate where the suspected COC is ?


Dat what it be do.

2km Storm Relative IR Imagery with BD Enhancement Curve

The same infrared imagery shown in the earth relative framework is displayed in a storm relative framework, with a 2km resolution and enhanced with the "BD Curve" which is useful for directly inferring intensity via the Dvorak Enhanced IR (EIR) technique. Scaling is provided by two lightly hatched circles around the center. The two circles have radii of 1 and 2 degrees latitude, respectively.


Member Since: Posts: Comments:
Quoting 688. Camille33:

You are so wierd this is not a joke anymore this could become a biggy storm!
Yes it very well could become a big time storm, but I want to see it survive tonight.

And I am weird? Btw learn to spell, you say every storm is going to be a CAT 5 lol.
Member Since: Posts: Comments:
Can someone explain to me what DMIN is?

Thanks :)
Member Since: Posts: Comments:
Quoting 683. unknowncomic:
Can't flatten Miami. Big ball game there Saturday.


Didn't you hear?

There's a big Category 5 coming there Saturday! ;)
Member Since: Posts: Comments:
Quoting 673. Patrap:
Ooooh, the anti-post was not I today, phew!

AL97 2 km Storm Relative IR Imagery with BD Enhancement Curve




Does the Bullseye on that image indicate where the suspected COC is ?
Member Since: Posts: Comments:
Unlike with previous systems, upper divergence is still rather impressive with 97L. Guessing it'll fade and blow right back up overnight.
Member Since: Posts: Comments:
Quoting 684. TylerStanfield:



Everyone must keep in mind that the Consistency rule is still in full play right now. The NHC will likely wait out a good 24 hours to see 97L cycle through. Diurnal Minimum is approaching and given the latest Low Level Convergence map on the CIMSS site, this large burst of convection will likely fade this evening giving the system a completely different and less-impressive look.
These systems go through cycles, and typically these invests look good for a bit after then fizzle during DMIN and then cycle right back through, at least once or twice before becoming a Tropical Cyclone.


I took that into account, hence the words " if it does not fade away this afternoon " in my post.
Member Since: Posts: Comments:
I don't think 97L is that close to becoming a tropical cyclone, honestly.

Firstly, we really don't have much of a clue as to what type of structure the surface circulation has beneath the convective canopy. Surface observations indicate a surface circulation that may be closed, but all other available data suggests that it's rather broad in nature, which will be a massive detriment in the intensification process if it can't find a way to consolidate it.

Furthermore, we don't know how the convection is going to interact with the diurnal minimum, and considering how the thunderstorm activity already appears to be waning due to the lack of surface convergence, it could be an ugly night for it.

I still think it has a good 2-3 days to go before it becomes a tropical depression, if it becomes one at all. At least until it reaches the longitude Hispañola.

Everything should be gradual; the system doesn't appear to be in any sort of hurry to become a hurricane.

Member Since: Posts: Comments:
Baby you can drive my car...

Yes I'm gonna be a Star'

Member Since: Posts: Comments:
Quoting 687. SCwannabee:

your not supposed to say that...




well any track is possible
Member Since: September 8, 2010 Posts: 0 Comments: 2142
Larger size of 97L will make it survive Hispanola better. Prefer not to see it go there though.
Member Since: August 2, 2011 Posts: 0 Comments: 1787
Although convective has warmed some which is expect this time of day the structure continues to improve.

Convection waning a little due to the approaching DMIN


Visible show a tightening circulation.
Member Since: Posts: Comments:
Quoting 676. SuperStorm093:
Yup convection already warming and we still have hours till dmin. Not good if you want this to form.

You are so wierd this is not a joke anymore this could become a biggy storm!
Member Since: Posts: Comments:

your not supposed to say that...

Quoting 675. weatherlover94:



An east coast track is not out of the question
Member Since: Posts: Comments:
Well fernand had little convengence at one time and some anticipated a loss of convection and it didn't. I expect that again.
Member Since: Posts: Comments:
I think too many people associate Dorian as a prime example of diurnal minimum. Convective weakening is expected in the afternoon as the instability between the ocean and the air begins to decline. Obviously it's an issue if convection completely fades, but I doubt 97L does that. Less intense thunderstorm activity right now does not suggest that 97L will not eventually become a system of interest.
Member Since: Posts: Comments:
Quoting 661. kmanislander:
Good afternoon all

97L looks to me to be on the verge of being classified as a TD. All the ingredients seem to be there and the low is consolidating quite nicely. If it does not fade away this afternoon I would give it a 65% chance of an upgrade this evening or early tomorrow morning.

Quoting 664. SLU:
Quite obvious now given the rapidly improving low level inflow that a tropical depression appears to be forming. West winds of 16mph have been reported from all the way south in Tobago. That means that the circulation has really tightened up and the pressures near the center (which is east of the new NHC position) are falling very quickly too.



Everyone must keep in mind that the Consistency rule is still in full play right now. The NHC will likely wait out a good 24 hours to see 97L cycle through. Diurnal Minimum is approaching and given the latest Low Level Convergence map on the CIMSS site, this large burst of convection will likely fade this evening giving the system a completely different and less-impressive look.
These systems go through cycles, and typically these invests look good for a bit after then fizzle during DMIN and then cycle right back through, at least once or twice before becoming a Tropical Cyclone.
Member Since: Posts: Comments:
Quoting 658. sar2401:

Also keeps it as a weak low and tropical wave. Should be interesting to see what pans out...TD, weak TS, or the monster cat 5 that flattens Miami. :-)
Can't flatten Miami. Big ball game there Saturday.
Member Since: August 2, 2011 Posts: 0 Comments: 1787
it's all over now

There's the ones
Member Since: Posts: Comments:
Member Since: Posts: Comments:
Member Since: Posts: Comments:
Member Since: Posts: Comments:
On a more local note: Relatively cooler air on the way!



Member Since: Posts: Comments:
I honestly don't see where dry air is going to be a problem for it. right now I see no signs of dry air getting in the system .
Member Since: September 8, 2010 Posts: 0 Comments: 2142
Yup convection already warming and we still have hours till dmin. Not good if you want this to form.
Member Since: Posts: Comments:
Quoting 656. Hurricanes305:
Interesting how the 18z plots are where the ''well defined low'' as the NHC said is showing a gradual WNW to NW that shows it skirting over southern Haiti and Eastern Cuba into the Southern Bahamas. Still very unsure where this will go if it makes it in the NW Caribbean and possibly into the Gulf or turn north out of the Caribbean and be track towards the SE US.




An east coast track is not out of the question
Member Since: September 8, 2010 Posts: 0 Comments: 2142
Wrong artist(s) 665! :)
Member Since: Posts: Comments:
Ooooh, the anti-post was not I today, phew!

AL97 2 km Storm Relative IR Imagery with BD Enhancement Curve


Member Since: Posts: Comments:
If 97L somehow manages to survive DMIN with a limited loss of convection and keeps the circulation intact, it may be in the clear to develop. I don't anticipate that though; convection is already warming and it has several hours to go before things can start getting better. I still think it is very much an uphill climb.



I should add though that overall its satellite appearance is quite a bit better than earlier.
Member Since: Posts: Comments:
Quoting 665. Patrap:


not fade away


LOL
Member Since: Posts: Comments:
Quoting 663. yonzabam:
Looks like Haiti might get clobbered again. Just doesn't get a break.


its location doesn't help it too. It's always in the bullseye of tropical activity.
Member Since: Posts: Comments:
Quoting 655. weatherlover94:
I still think the storm will lie on the south side of the guidance ...however there could be a trough capable of pulling the storm out of the Caribbean sea and out to sea....a little to early to say though

Most likely (As in 99.9%) not going to happen. When a System in September is below 15N and is in or near the Caribbean. The system will likely not be able to recurve fast enough, even if a trough is involved, to take the storm out to sea.
Member Since: Posts: Comments:
Depth of 26C Isotherm

Member Since: Posts: Comments:
Invest 97L is unlikely to track into the Greater Antilles like some models are indicating. It would have to become a decently-strong tropical cyclone in order to feel the weakness passing across the western Atlantic. I think this will be in the Caymans/Jamaica region come 3-4 days.
Member Since: Posts: Comments:
666. JLPR2
Reminds me of TS Emily in 2011, that one developed right over the Lesser Antilles, 97L is looking nice maybe it will try that.

Unless it falls completely apart.

Member Since: Posts: Comments:
Quoting 661. kmanislander:
Good afternoon all

97L looks to me to be on the verge of being classified as a TD. All the ingredients seem to be there and the low is consolidating quite nicely. If it does not fade away this afternoon I would give it a 65% chance of an upgrade this evening or early tomorrow morning.


not fade away
Member Since: Posts: Comments:
664. SLU
Quite obvious now given the rapidly improving low level inflow that a tropical depression appears to be forming. West winds of 16mph have been reported from all the way south in Tobago. That means that the circulation has really tightened up and the pressures near the center (which is east of the new NHC position) are falling very quickly too.

Member Since: Posts: Comments:
Looks like Haiti might get clobbered again. Just doesn't get a break.
Member Since: Posts: Comments:
I leave for a few minutes to check on Storms here in the Mobile Area and come back to 2 more pages gone....
Wow this Blog is flying and hard to keep up....
LOL

Taco :o)
Member Since: Posts: Comments:
Good afternoon all

97L looks to me to be on the verge of being classified as a TD. All the ingredients seem to be there and the low is consolidating quite nicely. If it does not fade away this afternoon I would give it a 65% chance of an upgrade this evening or early tomorrow morning.
Member Since: Posts: Comments:
Quoting 653. CybrTeddy:


Best guess it'll be gone nearly completely by 00z.
And they say I downcast, if I said that, although I agree it will, I would get ripped apart.
Member Since: Posts: Comments:
Quoting 651. MiamiHurricanes09:
Completely anticipated. With surface convergence this unimpressive, it's bound to struggle tonight convectively.


Yep. I'm already thinking ahead to the convective cycle that 97L is going to have to go through, and knowing that it probably won't look near this "Good" in a few hours. Given this, it still might be able to pull itself together over the coming days and Get going.
Member Since: Posts: Comments:
Quoting Stormchaser2007:
Hot off the presses...

TAFB keeps 97L well to the south of the GA


Also keeps it as a weak low and tropical wave. Should be interesting to see what pans out...TD, weak TS, or the monster cat 5 that flattens Miami. :-)
Member Since: Posts: Comments:
Interpolated models are going to be somewhat off this cycle since NHC relocated the center eastward. Original init at 12Z was 14.6N 60.5W, 18Z is now at 14.6N 59.7W.

So in the case of the HWRF, it forecasted for 18Z:
AL, 97, 2013090112, 03, HWRF, 006, 146N, 615W. Interpolation now moves that location to 14.6N 59.7W, so the whole 12Z track is shifted about 2 degrees east.
Member Since: Posts: Comments:
Interesting how the 18z plots are where the ''well defined low'' as the NHC said is showing a gradual WNW to NW that shows it skirting over southern Haiti and Eastern Cuba into the Southern Bahamas. Still very unsure where this will go if it makes it in the NW Caribbean and possibly into the Gulf or turn north out of the Caribbean and be track towards the SE US.

Member Since: Posts: Comments:
I still think the storm will lie on the south side of the guidance ...however there could be a tough capable of pulling the storm out of the Caribbean sea and out to sea....a little to early to say though
Member Since: September 8, 2010 Posts: 0 Comments: 2142

Viewing: 705 - 655

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 | 50Blog Index

Top of Page

About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

Local Weather

Partly Cloudy
80 °F
Partly Cloudy