Lesser Antilles Disturbance 97L a Threat to Develop

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

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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

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Quoting 1081. SuperStorm093:
which is why the gfs cant be discounted not showing any formation. lots of wishcasting going on here
True, but has it ever occured to some that the GFS might be placing that ULL over Hispaniola a lot closer to 97L causing it to shear the system, I mean it could be wrong in that placement of the ULL. Appears to be moving away from 97L, don't you agree with that as well? Now there is another one coming down and moving towards the Southwest, gosh this set-up reminds me of 92L. Right now I really think it is a wait and see, this could be nothing at all or something big.



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Quoting 1090. SuperStorm093:
One quick question, yes I say this a lot, but at this point I DONT CARE really.

Has my forecast for the storms this year been wrong? no, I got the 3 storms right and the other invest that didnt pan out right. I dont downcast, I just dont hype up the situation when I know it doesnt have a SOLID chance, this could become a nice storm, but its not even organized. looks like the past 5 invests we have had, BLOBS.


We bow to your infinite wisdom. No one on here is worthy of your time.

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Quoting Tazmanian:



go a head and hit ok you be fine am on that site all the time has well has evere other WU meber here

Ok will do. thanks for that!!
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The only thing I don't like about its chances is that it is going into such a climatologically unfavorable region. If it was anywhere else I'd be sure it would turn into a TD by tomorrow.
Member Since: June 29, 2013 Posts: 36 Comments: 2638
Quoting 1093. Maineweatherguy20023:


Gave me a security warning:
"You attempted to reach www.fnmoc.navy.mil, but the server presented a certificate issued by an entity that is not trusted by your computer's operating system. This may mean that the server has generated its own security credentials, which Chrome cannot rely on for identity information, or an attacker may be trying to intercept your communications.
You should not proceed, especially if you have never seen this warning before for this site."

Wonder if anyone else had that problem...



go a head and hit ok you be fine am on that site all the time has well has evere other WU meber here
Member Since: May 21, 2006 Posts: 5091 Comments: 115456
Quoting 1082. Gearsts:


NO please noooo!
Member Since: October 6, 2007 Posts: 0 Comments: 6456
1099. will40
on the navy site click show all
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1098. FOREX
Quoting 1092. prcane4you:
This thing is moving west? I don't think so.


East??
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Quoting 1049. interstatelover7165:
For the first time in its so-far short life, 97L actually looks like a reasonable, organized tropical cyclone...inb4 someone says dmin will ruin it...


It still a little broad for a cyclone but the forward motion will help it a lot to focus on one area. But its getting there. Midlevel spin becoming more apparent.
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Quoting 1067. GwadaGeek:
METEO France has just lowered warning from yellow to green (ie No threat, no substancial rain to come) for Guadeloupe.


bust
Member Since: October 6, 2007 Posts: 0 Comments: 6456
1095. JRRP
Member Since: August 16, 2007 Posts: 0 Comments: 6213
am discounteding the GFS and ecw for now
Member Since: May 21, 2006 Posts: 5091 Comments: 115456
Quoting Tazmanian:



some of you guys are using the wrong nvay site



ues the back up navy site


Link


Gave me a security warning:
"You attempted to reach www.fnmoc.navy.mil, but the server presented a certificate issued by an entity that is not trusted by your computer's operating system. This may mean that the server has generated its own security credentials, which Chrome cannot rely on for identity information, or an attacker may be trying to intercept your communications.
You should not proceed, especially if you have never seen this warning before for this site."

Wonder if anyone else had that problem...
Member Since: Posts: Comments:
This thing is moving west? I don't think so.
Member Since: June 23, 2011 Posts: 0 Comments: 1252
1091. barbamz
Short drop in with a "good evening everyone!". I see 97L is developing, and the WPac has a lot of work to do to catch up with recon skills which are natural for the Atlantic for a long time. Here some quotations from a new article ...

Making sense of typhoons by flying into the eye of the storm
Observatory scientists fly into the heart of tropical cyclones in order to better understand and predict their paths
South China Morning Post, Sunday, 01 September, 2013, 4:49am

Late in the afternoon of August 13, while the No 3 signal was issued in Hong Kong, the Observatory meteorologist Wong Wai-kin was in a small plane over the South China Sea, flying at 2,400 metres, just above the main clouds swirling around Severe Typhoon Utor.

The centre of the storm was nearby, and the plane began descending through dense clouds. Rain pummelled the windows. Visibility came down to almost zero, as if in thick fog. In the violently swirling air, the plane was tossed about like a sampan on two-metre waves.

After about 15 minutes, the plane emerged from the cloud, entering clear air, with a calm sea below and blue sky above: it was in the eye of Utor. For Wong, it was a precious moment: he was now the first of the Observatory staff to fly into the eye of a severe typhoon. It was also a significant milestone in research on typhoons, the west Pacific's mighty, sometimes devastating, storms. ...

With typhoons posing threats to life and property, the Observatory team is always seeking ways to improve its forecasts. One way is by using reconnaissance flights to gather data from within storms. The United States relies heavily on flights to assess hurricanes, but in this region, there have been few recent flights other than occasional research missions flown by Taiwan, which do not reach the South China Sea near Hong Kong.

Other than a trial flight in 1973 by late director Gordon Bell, the Observatory neither oversaw nor participated in such flights until two years ago. ...

After processing the data, Wong noted that winds were at least gale force until he reached 290 kilometres from the centre of Utor. This was consistent with satellite data, helping Shun come to his decision to issue the No 8 signal as Utor neared Hong Kong.

Successes like this mission spur the continuation and improvement of Hong Kong's typhoon reconnaissance flights. Later this year, the Government Flying Service will begin operating a new plane with better weather-monitoring equipment relaying information directly from the satellites. With Wong or a colleague on board, this will also release dropsondes - cylinders packed with sensors that descend on parachutes - transmitting information on wind speed and direction, air pressure, humidity and temperature until they hit the sea and are lost. ...


Whole article see link above. Found by Twitter: James Reynolds %u200F@typhoonfury 7h: Great article by my friend @docmartinhk on @ObservatoryHK flying recon into Pacific typhoons - http://www.scmp.com/lifestyle/technology/article/1 300881/making-sense-typhoons-flying-eye-storm %u2026
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Quoting 1084. Bluestorm5:
Says the known downcaster...
One quick question, yes I say this a lot, but at this point I DONT CARE really.

Has my forecast for the storms this year been wrong? no, I got the 3 storms right and the other invest that didnt pan out right. I dont downcast, I just dont hype up the situation when I know it doesnt have a SOLID chance, this could become a nice storm, but its not even organized. looks like the past 5 invests we have had, BLOBS.
Member Since: Posts: Comments:
Quoting 1081. SuperStorm093:
which is why the gfs cant be discounted not showing any formation. lots of wishcasting going on here


wishcaster? looks oh is talking downcaster


Member Since: May 21, 2006 Posts: 5091 Comments: 115456
1088. will40
Quoting 1083. Tazmanian:



some of you guys are using the wrong nvay site



ues the back up navy site


Link

wrong link
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The intensity models seem to like 97L, so I guess it's now up to 97L to decide whether it wants to develop or not. Conditions are definitely much more favorable this time around then say the conditions Chantal had to deal with.
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I really like 97L's chances of becoming a tropical cyclone sometime tomorrow if current trends continue. The only problem I can see occurring is if a dominant center doesn't take hold and keep convection firing once d-min hits. If that problem occurs, it will more than likely have to start the process all over again and the Eastern Caribbean graveyard will keep it from developing until the Western Caribbean. Other than that, it is still organizing fairly well, and this could end up being a very large storm if the circulation is any indication. The outflow pattern is superb for now.

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Quoting 1079. Maineweatherguy20023:
One question- I just went to the navy site to get satellite imagery from there however, It doesnt have 97L on the left hand sidebar... did it lose invest status?


No, for some reason NRL Monterey lost all storms except the new one in the West Pacific

15W TORAJI 130901 1800 26.2N 124.6E WPAC 30 1000
Member Since: September 23, 2005 Posts: 15 Comments: 11346
Quoting 1081. SuperStorm093:
which is why the gfs cant be discounted not showing any formation. lots of wishcasting going on here
Says the known downcaster...
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Quoting 1079. Maineweatherguy20023:
One question- I just went to the navy site to get satellite imagery from there however, It doesnt have 97L on the left hand sidebar... did it lose invest status?



some of you guys are using the wrong nvay site



ues the back up navy site


Link
Member Since: May 21, 2006 Posts: 5091 Comments: 115456
1082. Gearsts
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Quoting 1078. GTstormChaserCaleb:
Good structure on the simulated infrared.

which is why the gfs cant be discounted not showing any formation. lots of wishcasting going on here
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1080. JRRP
Quoting Gearsts:
15n 60w

yeah..
Member Since: August 16, 2007 Posts: 0 Comments: 6213
One question- I just went to the navy site to get satellite imagery from there however, It doesnt have 97L on the left hand sidebar... did it lose invest status?
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Good structure on the simulated infrared.

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Quoting 1055. Patrap:


This looks ominous
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1076. hydrus
Quoting 1064. Bluestorm5:
Usually do computer graphics for this but I got to eat something so I put in my thoughts on dry erase tracking map I brought with me to college. This depends on track location and how well it develops before Eastern Caribbean. Excuse my writing as the surface wasn't flat when I wrote on it.

Oh my Guuuuugggggggggg..
Member Since: September 27, 2007 Posts: 1 Comments: 22712
1075. SLU
Quoting 1052. JLPR2:
I know 97L has a closed circulation, now where exactly is the strongest closed LLC?

Hmm...

I guess anywhere between 62W and 56W. XD There's great cyclonic flow everywhere.



Somewhere to the NE of Barbados but south of 15 n.
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Quoting 1041. MiamiHurricanes09:
I have no idea what the climatological norm for trade winds are in the eastern Caribbean; but right now they're 10-15kts which is pretty normal and shouldn't inhibit development. The faster trade wind flow is located north of 20N (20 kts).


Thx.

Tomorrow morning should be quite interesting, depending on what convergence it's able to maintain.
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97L lacking on convergence, still going strong on divergence.
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I saw a graphic earlier with higher shear in the eastern Caribbean. Gotta say the wave is having a good D-Min though.
Member Since: June 29, 2013 Posts: 36 Comments: 2638
Quoting 1063. TropicalAnalystwx13:

It's one of 97L's remnant circulations.


Looks to be spinning up much tighter and faster than before, though.
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Quoting 1059. Stormyheart:
A quick question for the Mods-

How long do you hold your office? Is there a term limit? Or do you more follow the dedicated lines of a lifetime, like Kim Jong Un?

TIA~


Like Supreme Court..... lifetime appointment
Member Since: September 23, 2005 Posts: 15 Comments: 11346
1069. KEEPEROFTHEGATE (Mod)
Quoting 1059. Stormyheart:



that would likely be better if asked here SH

Link
Member Since: July 15, 2006 Posts: 178 Comments: 56141
1068. Gearsts
Quoting 1053. JRRP:

mmmm no i do not think so
Link
15n 60w
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METEO France has just lowered warning from yellow to green (ie No threat, no substancial rain to come) for Guadeloupe.
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Quoting 1049. interstatelover7165:
For the first time in its so-far short life, 97L actually looks like a reasonable, organized tropical cyclone...inb4 someone says dmin will ruin it...



Not a chance
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Anti-cyclone building over top 97L. Increasing in 850 and 500 mb. vort.





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Usually do computer graphics for this but I got to eat something so I put in my thoughts on dry erase tracking map I brought with me to college. This depends on track location and how well it develops before Eastern Caribbean. Excuse my writing as the surface wasn't flat when I wrote on it.

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Quoting 1057. RascalNag:
Guys, check the RGB or Visible satellite imagery. 15N, 62W. Does anyone see what I see?

It's one of 97L's remnant circulations.
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CLICK FOR LOOP

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1061. ackee
I think 97L is probably the best Invest I have seen so far this seasons whether or not it get classify
Member Since: July 15, 2008 Posts: 0 Comments: 1376
1060. Gearsts
Quoting 1045. tropicfreak:


Why not? Convection has held its own, outflow has improved (due to a developing anticyclone) and a circulation at the surface is tightening up (and closed I might add, albeit broad). The environment is also favorable.

It isn't the best looking system but it certainly appears it is on the brink of becoming a TD.

Well i have seen even tropical storms in that location that look like they are going RI but then next day is just a mess with and almost open COC. My point is that we should wait and see how well this thing is under that convection and a little more patience.
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A quick question for the Mods-

How long do you hold your office? Is there a term limit? Or do you more follow the dedicated lines of a lifetime, like Kim Jong Un?

TIA~
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It looks like D Min isn't touching 97L
Member Since: September 8, 2010 Posts: 0 Comments: 2232
Guys, check the RGB or Visible satellite imagery. 15N, 62W. Does anyone see what I see?
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Cybrteddy does the UKMET how 97L developing and if so where it take it
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1055. Patrap
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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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