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: 1755 - 1705

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 1726. Chicklit:
Evening, folks. 97L makes you go hmmm....

Also at 40% with NHC, so word to the wise is to expect the worst and hope for the best.
notting going to happern with invest 97L ONLY a rain storm or maying nottting at all if it die out tonight.
Member Since: Posts: Comments:
1754. docrod
Quoting 1743. Patrap:




Quoting 1743. Patrap:




Needs to thread a very fine needle for a feline number four.
Member Since: Posts: Comments:
Member Since: Posts: Comments:
1752. Skyepony (Mod)
Quoting 1747. moonlightcowboy:



So, Skye, the problem must be the fact that the circ is just so broad, still elongated, maybe not at the surface. I can't see much else inhibiting it. Your thoughts?

It's really big and has a another vorticity trailing it too close.
Member Since: Posts: Comments:
1751. docrod
Quoting 1744. Skyepony:
97L TRMM kinda old..but shows all that has height. It's not all that shallow.


- thanks Skye - cannot that vertical structure change quickly (shear?)
Member Since: Posts: Comments:
Quoting 1748. sunlinepr:
Notice that the ULL N of 97L is being affected by the front coming out from Conus.... It looks like its going to split in two... That will leave 97L free of the effect that the ULL had on it.... Looks like 97L stall will end and it will have more potential for strengtening....



Good observation about how are things doing in the upper levels.
Member Since: April 29, 2009 Posts: 75 Comments: 14906
Notice that the ULL N of 97L is being affected by the front coming out from Conus.... It looks like its going to split in two... If that happens.... It will leave 97L free of the effect that the ULL had on it.... Looks like 97L stall will end and it will have more potential for strengtening.... and keep moving W

Member Since: Posts: Comments:
Quoting 1744. Skyepony:
97L TRMM kinda old..but shows all that has height. It's not all that shallow.



So, Skye, the problem must be the fact that the circ is just so broad, still elongated, maybe not at the surface. I can't see much else inhibiting it. Your thoughts?
Member Since: Posts: Comments:
Quoting 1727. Jamiekins:


And a strong enough hurricane can easily pile up more than that against the dike. Not panic but realistic awareness.



That's right. Awareness and preparedness is the name of the game!
Member Since: Posts: Comments:
1745. docrod
(nervously watching "Gab")

and the tree frogs were rejoicing ....
from the NWS KeyWest ...

.CLIMATE...
ON THIS DATE IN KEYS WEATHER HISTORY...IN 1980...3.25 INCHES OF
RAINFALL WAS RECORDED IN KEY WEST. THIS SET THE RECORD FOR RAINFALL
FOR SEPTEMBER FIRST. RAINFALL RECORDS FOR KEY WEST DATE BACK TO 1871.
Member Since: Posts: Comments:
1744. Skyepony (Mod)
97L TRMM kinda old..but shows all that has height. It's not all that shallow.
Member Since: Posts: Comments:
1743. Patrap


Member Since: July 3, 2005 Posts: 428 Comments: 129902
Quoting 1581. weatherlover94:
Im shocked the Intensity models havent backed down yet


They most likely will.
Member Since: Posts: Comments:
Quoting 1737. Chicklit:
To get into the more favorable part of the Caribbean, 97L will have to survive 30 knots of shear. Certainly not impossible for a system of this size and this amount of moisture around it.

Levi's blog raised the question of whether the system would split or remain intact. Should be interesting to watch for the next few days.


And opposite to what the NHC calls for at the moment - will be fun to see how this plays out.
Member Since: Posts: Comments:
1740. KEEPEROFTHEGATE (Mod)
Member Since: Posts: Comments:
Quoting 1737. Chicklit:
To get into the more favorable part of the Caribbean, 97L will have to survive 30 knots of shear. Certainly not impossible for a system of this size and this amount of moisture around it.

Levi's blog raised the question of whether the system would split or remain intact. Should be interesting to watch for the next few days.


Shear actually is virtually nonexistant over the system. Can't trust those CIMSS shear charts all the time, that ULL is backing out from 97L, giving it ventilation.
Member Since: July 8, 2005 Posts: 259 Comments: 24576
1738. KEEPEROFTHEGATE (Mod)
Member Since: Posts: Comments:
To get into the more favorable part of the Caribbean, 97L will have to survive 30 knots of shear. Certainly not impossible for a system of this size and this amount of moisture around it.

Levi's blog raised the question of whether the system would split or remain intact. Should be interesting to watch for the next few days.
Member Since: Posts: Comments:
1736. KEEPEROFTHEGATE (Mod)
POSS T.C.F.A.
97L/INV/XX/XX
Member Since: Posts: Comments:
Quoting 1609. Seflhurricane:
If the models are true this will be a Tropical system that South Florida needs to monitor models bring 97L as a strong hurricane which would be catastrophic for south florida
Just because a strong Hurricane hits South Florida does not mean it is going to be a catastrophic event or has to be. We have a very strong building code down here and if everyone would just take the proper precautions and use common sense the population should get through it alright. (But I know that's asking for too much) right?
Member Since: Posts: Comments:
1733. docrod
Quoting 1710. RyanSperrey:
I still think the name GRACE should be retired.  They dont call it the Perfect Storm for nothing.


Amazing.
Member Since: Posts: Comments:
yes watching the invest
good evening
Member Since: Posts: Comments:
Meanwhile...




Diana Nyad “looking very good” on Cuba-to-Florida swim

By Cindy Boren, Published: September 1 at 1:54 pm


Diana Nyad is churning through the water between Cuba and Florida once again, trying for the fifth and, she says, final time to make the three-day, open-water swim.

Nyad, whose last attempt a year ago was derailed by jellyfish stings, is wearing a specially designed face mask this time and, with her crew surrounding her, she set out at 8:59 a.m. EDT Saturday morning on the 103-mile swim to Key West.

“We’re optimistic,” Dr. Derek Covington, who examined her this morning, said in an update on Facebook. “She’s looking very good.”

The prosthetic mask has been more of an annoyance than a hindrance. “She is doing remarkably well in that jellyfish suit,”John Berry, the operations chief, told her blog, diananyad.com. “And she is going at her expected pace in it, which is 47 strokes per minute.”

....
Member Since: Posts: Comments:
Quoting 1724. EyEtoEyE:
. I doubt they are right , models are useless !



This year they seem to be
Member Since: September 8, 2010 Posts: 0 Comments: 2232
Really dryin' out now...

Member Since: Posts: Comments:
So, the devil is in the details. This should be rather fun to watch!

TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT SUN SEP 01 2013

CARIBBEAN SEA...

....THE TROPICAL WAVE IN THE SPECIAL FEATURES (97L) WILL ENTER THE CARIBBEAN TONIGHT REACHING THE CENTRAL CARIBBEAN TUE...AS A POSSIBLE TROPICAL CYCLONE.

HISPANIOLA...
A TROPICAL WAVE (97L) WILL ENTER THE CARIBBEAN TONIGHT AND PASS OVER THE ISLAND TUE THROUGH EARLY THU.

ATLANTIC OCEAN...
THE N PORTION OF THE TROPICAL WAVE (is this 97L?) APPROACHING THE LESSER ANTILLES WILL PASS THROUGH THE W ATLC S OF 21N FROM THE LEEWARD ISLANDS TO PUERTO RICO THROUGH TONIGHT AND APPROACHING TO THE MONA PASSAGE ON MON AND TUE THEN THROUGH THE ATLC APPROACHES TO THE WINDWARD PASSAGE ON WED. THE WAVE WILL WEAKEN SOME AS IT CONTINUES W THROUGH THE SW ATLC WATERS BETWEEN CUBA AND THE BAHAMAS LATE IN THE WEEK.

Essentially, the NHC is taking the position of the Euro - sending fragments of this wave to the south and north. A possible tropical storm forming in the central Caribbean, although passing over Hispanolia as a wave (for now).

Everything sounds 50/50 at this point - but the next couple of days are going to be interesting to say the least. Heavy rain for the northern Antilles, regardless.

Edit: Those in BOLD are my additions.


Member Since: Posts: Comments:
Quoting 1723. WellingtonR:


Lake O can take another 3-5 feet before it "might" have a major issue. No need to scare people. The lake does not rise in 1 day it takes weeks to go up or down even after a hurricane.


And a strong enough hurricane can easily pile up more than that against the dike. Not panic but realistic awareness.
Member Since: March 22, 2009 Posts: 43 Comments: 2064
Evening, folks. 97L makes you go hmmm....

Also at 40% with NHC, so word to the wise is to expect the worst and hope for the best.
Member Since: Posts: Comments:
It looks to me like the main convection has moved out to meet the moisture from the wave approaching from the East. Probably as that moisture gets absorbed by 97L the convection will move back over the center with more fuel to fire up.
Member Since: Posts: Comments:
Quoting 1720. weatherlover94:
All GFS Ensemble models call for OTS
. I doubt they are right , models are useless !
Member Since: Posts: Comments:
Quoting 1662. Seflhurricane:
NO we would have a severe Breach in the levee especially with the west season we have been having


Lake O can take another 3-5 feet before it "might" have a major issue. No need to scare people. The lake does not rise in 1 day it takes weeks to go up or down even after a hurricane.
Member Since: Posts: Comments:
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE SAN JUAN PR
906 PM AST SUN SEP 1 2013

.SYNOPSIS...MID-UPPER LEVEL RIDGE WILL BUILD OVER THE REGION LABOR
DAY AND HOLD THROUGH THE END OF THE WEEK. WEAK ELONGATED AREA OF
LOW PRES OVER THE WINDWARD ISLANDS WILL MOVE ACROSS THE ERN CARIB
SEA MON-WED BRINGING SIG RAINS TO ERN PR AND USVI TUE-WED.

&&

.DISCUSSION...QUIET WX NEXT 12 HRS UNDER BUILDING UPPER LEVEL
RIDGE...DRY AIR AND NEGATIVE H85 THETAE AIR ADVECTION. MOISTURE
BEGINS TO INCREASE MON WITH SCT AFTERNOON TSRA EXPECTED ACROSS
SOUTHERN PR UNDER A NE STEERING FLOW.

BIG SLUG OF MOISTURE ASSOCIATED WITH WEAK AREA OF LOW PRES AND
TROPICAL WAVE ALONG 61W WILL BEGIN TO REACH ERN PR AND THE USVI
TUE MORNING WITH SIG FLOODING RAINS LIKELY. ECMWF AND GFS CONTINUE
TO DIFFER ON EXACT TIMING OF HEAVIEST RAINS BUT BOTH PAINT A VERY
WET SCENARIO FOR ERN PR...CULEBRA...VIEQUES AND THE USVI MID WEEK.
WAVE AXIS IS EXPECTED TO REACH 70W BY 12Z WED WITH WX LIKELY TO
IMPROVE BY LATE WED ACCORDING TO 18Z GFS AND GEFS GUIDANCE ALTHOUGH
ECMWF IS SLOWER BY 24 HRS WITH HEAVY RAINS LINGERING THRU THU.
Member Since: April 29, 2009 Posts: 75 Comments: 14906
Member Since: Posts: Comments:
All GFS Ensemble models call for OTS
Member Since: September 8, 2010 Posts: 0 Comments: 2232
Quoting 1717. BrandenCordeiro:
97L looks like its having a rough night.


They all do. Literally every storm that enters the Caribbean waxes and wanes when the sun sets/rises. It'll blow right back up in the morning if at all.
Member Since: July 8, 2005 Posts: 259 Comments: 24576
Quoting 1699. CybrTeddy:
Levi, I understand it's quite a long ways out and it's very difficult to predict these things (from experience I know), but I'm curious to hear your thoughts on a "worst case scenario" if 97L manages to get named in the western Caribbean.
Clearly, the worst case scenario is that:
1. No piece of energy ejects towards PR...and it stays west.
2. Development occurs 1 day from Jamaica.
3. The trough over the NE pulls out, and the system is turned towards the Florida Straits
4. RI occurs, the storm heads into the Gulf as a weak Cat2.
5. A massive meltdown occurs at Fukashima, releasing massive radiation.
6. As the Cat 4 storm bears down on New Orleans, our guard is down as we await the first radiation on the West Coast.
7. An uncharted rogue asteroid approaches, only 1/4 mile long...unsure how much gets through our atmosphere.

This is the worst case scenario.
Member Since: Posts: Comments:
97L looks like its having a rough night.
Member Since: August 16, 2013 Posts: 0 Comments: 45
Quoting 1710. RyanSperrey:
I still think the name GRACE should be retired.  They dont call it the Perfect Storm for nothing.
Grace fed a much larger Extra-tropical low,then we had a no-name hurricane form in the muddle of the extra-tropical storm,weird stuff!
Member Since: Posts: Comments:
I hope the GFS/EURO are RIGHT, and the UKM is WRONG
Member Since: Posts: Comments:
Quoting 1710. RyanSperrey:
I still think the name GRACE should be retired.  They dont call it the Perfect Storm for nothing.
What did "Perfect Storm" exactly do to land, though? Not much... the only reason it's so famous is because we lost a boat and there's a story or movie on it.
Member Since: Posts: Comments:
Quoting 1712. stormpetrol:
All developing systems wax and wane, even the developed do so. I personally think 97L is poised to become a dangerous hurricane for some in the coming the days, just my take! Everyone have a safe night!

Agreed
Member Since: Posts: Comments:
All developing systems wax and wane, even the developed do so. I personally think 97L is poised to become a dangerous hurricane for some in the coming the days, just my take! Everyone have a safe night!
Member Since: April 29, 2007 Posts: 0 Comments: 8134
Quoting 1677. stormpetrol:
Getting the shrimp look.
Member Since: Posts: Comments:
I still think the name GRACE should be retired.  They dont call it the Perfect Storm for nothing.
Member Since: Posts: Comments:
Severe thunderstorm moving into parts of metro chicago. dupage, and cook counties are under warning.
Member Since: Posts: Comments:
Quoting 1705. ncstorm:



all them GFS EB are out liners
Member Since: May 21, 2006 Posts: 5091 Comments: 115454
Quoting 1702. Patrap:



Over the next couple of days it will flip flop from N and E to S and W and so on till we get 97L upgraded or till recon flys
Member Since: Posts: Comments:
1706. pottery
Good evening.

97 is still ''iffy'' in fact.
Still has not developed, but is surely holding its own.
The longer it remains near-stationary, the more time conditions ahead of it will have to change.

For better? For worse??
Stay tuned.
Member Since: October 24, 2005 Posts: 0 Comments: 24906
1705. ncstorm
Member Since: Posts: Comments:

Viewing: 1755 - 1705

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

Overcast
38 °F
Overcast

JeffMasters's Recent Photos

Lake Effort Snow Shower Over Windsor, Ontario
Sunset on Dunham Lake
Pictured Rocks Sunset
Sunset on Lake Huron