Rains From Invest 96L Kill 55 in Mali

By: Dr. Jeff Masters , 3:40 PM GMT on August 31, 2013

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A tropical wave that emerged from the coast of Africa on Friday (Invest 96L) is headed west-northwest towards the Cape Verde Islands. This wave is struggling against high wind shear of 20 - 25 knots. The shear is expected to drop to the moderate level on Sunday, then increase again to the high level on Monday through Thursday. In their 8 am EDT Saturday Tropical Weather Outlook, NHC put the 5-day odds of development at 40%, and the 2-day odds at 40%. Our reliable models for tropical cyclone genesis show little or no development of 96L. This disturbance is unlikely to affect any land areas except the Cape Verde Islands.


Figure 1. MODIS satellite image of Invest 96L off the coast of Africa, taken at 8:30 am EDT on August 31, 2013. Image credit: NASA.

Disturbance 96L moved very slowly across the Sahel region of Africa during the week, dumping torrential rains on Wednesday that triggered flash floods that killed at least 55 people in Mali's capital city, Bamako. Serious flooding also affected neighboring Burkina Faso, Gambia, Guinea, Niger and Senegal. Buildings have collapsed, roads have been rendered impassable, and valuable farmland is submerged beneath flood water, affecting over 200,000 people. More than 100 homes were swept away as the Niger River burst its banks, bringing down bridges and submerging entire streets.


Figure 2. People hold a rope to help rescuers climbing down a roof of a house in a flooded area of Bamako, Mail, on August 28, 2013. At least 55 people have been killed in flash floods caused by torrential rain. Image credit: HABIBOU KOUYATE/AFP/Getty Images)


Figure 3. MODIS satellite image of tropical wave 96L over Mali on August 28, 2013. The storm dumped torrential rains on Mali's capital city, Bamako, which killed at least 55 people. Image credit: NASA.

Disturbance approaching Lesser Antilles no immediate threat to develop
A tropical wave located about 400 miles east of the Lesser Antilles Islands is moving westward at 15 mph, and has changed little over the past three days. The wave has a modest amount of spin, but only a limited amount of heavy thunderstorm activity. In their 8 am EDT Saturday Tropical Weather Outlook, NHC put the 5-day odds of formation of this disturbance at 10%, and the 2-day odds at 0%. Wind shear is a high 20 - 30 knots over the system, and is expected to stay high through Monday. An area of dry air and dust from the Saharan Air Layer (SAL) surrounds the disturbance and is interfering with development. Wind shear may fall to the moderate level in 4 - 5 days when the wave reaches the Central Caribbean, increasing the odds of development then. 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 Thursday. The wave will spread heavy rains and gusty winds to the Lesser Antilles Islands on Sunday and Monday.

Jeff Masters

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Quoting 1154. TropicalAnalystwx13:

There's a very robust circulation. Both satellite and data from the Global Hawk mission this afternoon showed that. It is broad in nature though...very broad.


A lot has changed with this since the aircraft left station several hours ago. No one disputes there is a low "spinning" out there I just dont think it is closed anymore unlike earlier today when it certainly appeared to be.

I don't think it matters much either way because it will soon enter the Caribbean unclassified unless a miracle happens overnight.
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Quoting 1159. sar2401:

Are we talking about circulation or a closed low level COC? I sure don't see that now.

Both.
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1167. Levi32
Quoting 1162. pottery:

At what height though.?
Has there been a surface circulation?


The cumulus clouds in the region are very close to the surface. In fact, it is at the mid-levels that it is not closed according to global hawk data. Westerlies exist at the surface.
Member Since: November 24, 2005 Posts: 635 Comments: 26700
How did the models do for hurricane jeanne in 2004?
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Intensity -
Tropical Storm
Center position of probability circle N33°35'(33.6°)
W178°50'(178.8°)
Direction and speed of movement E Slowly
Central pressure 1000hPa
Maximum wind speed near the center 18m/s(35kt)
Maximum wind gust speed 25m/s(50kt)
Radius of probability circle 410km(220NM)
Another IDL-crossing storm. It will probably be the fourth tropical storm to be tracked by the CPHC. It must be some kind of record.
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Quoting 1158. Levi32:


Positive. It's just elongated. Westerlies SE of Barbados have been pretty obvious on visible all day. I'm not sure you could pick a "center" given that it's so elongated, thus two main "lobes."


And would it be conceivable for the eastern lobe entering the shear to pop off and leave a better defined circulation under the convection in the other lobe?
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1163. sar2401
Quoting redwagon:


If you go back a few hundred, sunlinerpr posted a some-scat with a decidedly closed.

Indeed, but that was this afternoon, and it wasn't low level, as I recall. It looks quite disorganized tonight compared to this afternoon.
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1162. pottery
Quoting Levi32:


Positive. It's just elongated. Westerlies SE of Barbados have been pretty obvious on visible all day.



Climatologically the trade winds are always their strongest in July and get weaker by early fall. Relative to late August climatology they are about normal today, but much slower than they were in July.


At what height though.?
Has there been a surface circulation?
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Quoting 1155. redwagon:


If you go back a few hundred, sunlinerpr posted a some-scat with a decidedly closed.


I saw an Ascat pass with a wind shift but no closed low if that is what you are referring to.
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1160. Levi32
Quoting 1151. kmanislander:


What data shows it to be closed ?


Daylight.

Member Since: November 24, 2005 Posts: 635 Comments: 26700
1159. sar2401
Quoting TropicalAnalystwx13:

There's a very robust circulation. Both satellite and data from the Global Hawk mission this afternoon showed that.

Are we talking about circulation or a closed low level COC? I sure don't see that now.
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1158. Levi32
Quoting 1149. pottery:

You sure there's circulation ?


Positive. It's just elongated. Westerlies SE of Barbados have been pretty obvious on visible all day. I'm not sure you could pick a "center" given that it's so elongated, thus two main "lobes."

Quoting 1150. Tropicsweatherpr:


You said in a video that the Eastern Caribbean trade winds would slaken after July. How are those right now?


Climatologically the trade winds are always their strongest in July and get weaker by early fall. Relative to late August climatology they are about normal today, but much slower than they were in July.

Member Since: November 24, 2005 Posts: 635 Comments: 26700
1157. pottery
Quoting TropicalAnalystwx13:

There's a very robust circulation. Both satellite and data from the Global Hawk mission this afternoon showed that.

I didn't see that....
But if there was one then, I'm not seeing any sign of one now.
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1156. sar2401
Quoting Levi32:


It's closed, just broad and elongated WSW to ENE. There is "no convergence" because the circulation is very weak with few thunderstorms, as one would expect. Development, if any, will be slow, and may take a complete hiatus between 65W and 75W due to the typical Caribbean trade wind trap. One can see why this wave has to be watched farther west, though.

Levi, I think it's already in the hiatus stage. I don't buy that it has a closed low level circulation. Even with a weak circulation, we should be seeing some convergence, and not as much divergence. If this is going to do something, I suspect it will be after 70W, as you said.
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Quoting 1130. kmanislander:


If the maps I posted are correct I do not see how it could possibly be closed with virtually no convergence. There may be the odd West wind produced by the large gyre that is the broad low associated with the feature but even the cloud deck lacks the appearance of a defined circulation unlike today when the convection was very meager but the convergence map squared away with the visible wind field.

I ran the shortwave loop and cannot detect a surface circulation either save for a faint signature ahead of the convection between 57 and 58 West
The strong rotation seen near 14 N and 55 W appears to be the 850 mb level unless a new center is forming there. That would not be out of the realm of possibility as sheared systems are known to have the center jump around following a new blow up of convection.
This happens because falling pressure associated with a thunderstorm complex is usually lower than the original center out ahead in the clear so the new area of lowest pressure becomes the new center. Have to wait and see what happens overnight.




If you go back a few hundred, sunlinerpr posted a some-scat with a decidedly closed.
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Quoting 1149. pottery:

You sure there's circulation ?

There's a very robust circulation. Both satellite and data from the Global Hawk mission NOAA Gulfstream aicraft this afternoon showed that. It is broad in nature though...very broad.
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It appears the coc has moved straight west while the convection as continued it's wsw track. The convergence has disappeared each night that I have watched it.
Member Since: July 30, 2012 Posts: 4 Comments: 614
1152. pottery
Quoting sar2401:

Indeed. Even from the days of weather fax, I always kept my eyes on the MDR this time of year, even in Grenada and St. Vincent. From the late 80's to 2003, there were always lows in the MDR that were moving either west or northwest. I stopped being a live aboard in 2003, and it really cranks me off. From 2006, I could have spent my time sailing the Virgins and the northern Caribbean and never have been troubled by more than a few wimpy TD's. Who would have thought we could go this many years and I could have anchored out almost anywhere and never seen anything more than a few vigorous tropical waves

LOL, put it down to bad timing !
On your part, of course.

:):))
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Quoting 1145. Levi32:


It's closed, just broad and elongated WSW to ENE. There is "no convergence" because the circulation is very weak with few thunderstorms, as one would expect. Development, if any, will be slow, and may take a complete hiatus between 65W and 75W due to the typical Caribbean trade wind trap. One can see why this wave has to be watched farther west, though.


What data shows it to be closed ?
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Quoting 1145. Levi32:


It's closed, just broad and elongated WSW to ENE. There is "no convergence" because the circulation is very weak with few thunderstorms, as one would expect. Development, if any, will be slow, and may take a complete hiatus between 65W and 75W due to the typical Caribbean trade wind trap.


You said in a video that the Eastern Caribbean trade winds would slaken after July. How are those right now?
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1149. pottery
Quoting Levi32:


It's closed, just broad and elongated WSW to ENE. There is "no convergence" because the circulation is very weak with few thunderstorms, as one would expect. Development, if any, will be slow, and may take a complete hiatus between 65W and 75W due to the typical Caribbean trade wind trap. One can see why this wave has to be watched farther west, though.

You sure there's circulation ?
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1148. JLPR2
97L seems to have traded in its nice circulation for convection. Buoys say east winds and convergence disappeared along with the 700mb vort.



Ah, oh well... XD
Member Since: September 4, 2007 Posts: 7 Comments: 8747
1147. sar2401
Quoting pottery:

Good point.
Tomorrow is September.
See my post below, re 'climate'.........

Indeed. Even from the days of weather fax, I always kept my eyes on the MDR this time of year, even in Grenada and St. Vincent. From the late 80's to 2003, there were always lows in the MDR that were moving either west or northwest. I stopped being a live aboard in 2003, and it really cranks me off. From 2006, I could have spent my time sailing the Virgins and the northern Caribbean and never have been troubled by more than a few wimpy TD's. Who would have thought we could go this many years and I could have anchored out almost anywhere and never seen anything more than a few vigorous tropical waves
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1146. pcola57
Well whatever shape 97L is in right now..
It has some very cold cloud tops and is moving quite a bit of heat ATM..

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1145. Levi32
Quoting 1133. clwstmchasr:


Kman - you are all over it. No way this has a closed circulation.


It's closed, just broad and elongated WSW to ENE. There is "no convergence" because the circulation is very weak with few thunderstorms, as one would expect. Development, if any, will be slow, and may take a complete hiatus between 65W and 75W due to the typical Caribbean trade wind trap. One can see why this wave has to be watched farther west, though.
Member Since: November 24, 2005 Posts: 635 Comments: 26700
Quoting 1139. sar2401:

Best analysis I've read so far. That was exactly my conclusion as well. It looks like the Antilles are going to get some much needed rain and a little wind. Things might get more dicey in the Western Caribbean, but not now.


Take a look at the loop I just posted at 1142. Looks like a classic sheared system. Winds at Barbados are out of the North which ties in with the Ramsdis loop
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Quoting 1103. HadesGodWyvern:
NAME 1316 YUTU

FORECAST
24HR
POSITION 020000UTC 33.1N 177.6E WITHIN 75NM
PRES/VMAX 998HPA 37KT
48HR
POSITION 030000UTC 33.3N 179.0E WITHIN 125NM
PRES/VMAX 998HPA 37KT
72HR
POSITION 040000UTC 33.4N 178.4E WITHIN 175NM
PRES/VMAX 1000HPA 35KT
96HR
POSITION 050000UTC 33.6N 179.3E WITHIN 250NM
PRES/VMAX 1000HPA 35KT
120HR
POSITION 060000UTC 33.9N 179.6E WITHIN 295NM
PRES/VMAX 1000HPA 35KT

KOREA METEOROLOGICAL ADMINISTRATION.


---
Korea may have made a mistake...

It's certainly possible they did. I think they will probably change the forecast in the next advisory.
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TROPICAL STORM KIKO DISCUSSION NUMBER 5
NWS NATIONAL HURRICANE CENTER MIAMI FL EP112013
800 PM PDT SAT AUG 31 2013

KIKO IS CONTINUING TO INTENSIFY AT A FAST PACE. MICROWAVE IMAGES
INDICATE THAT THE STORM HAS AN INNER CORE...AND EVEN THE LAST FEW
VISIBLE IMAGES SUGGESTED A WEAK EYE FEATURE WITHIN A MORE
SYMMETRICAL CDO. THE INTENSITY IS SET TO 60 KT...A BIT HIGHER THAN
THE LATEST SATELLITE CLASSIFICATIONS...WHICH HAVE HAD A HARD TIME
KEEPING UP WITH THIS CYCLONE. THE PACE OF STRENGTHENING SHOULD
DIMINISH SOON AS KIKO IS MOVING ACROSS COOLING WATERS...AND WILL BE
CROSSING THE 26C ISOTHERM WITHIN 12-24H. AFTER THAT TIME...A MORE
STEADY DECREASE IN STRENGTH SEEMS PROBABLE DUE TO INCREASING
SOUTHWESTERLY SHEAR...COOLER WATERS...AND ENTRAINMENT OF DRY AIR
ALOFT. THE LATEST NHC PREDICTION IS CLOSE TO A BLEND OF THE
PREVIOUS FORECAST...THE INTENSITY CONSENSUS...AND THE FLORIDA STATE
SUPERENSEMBLE. THE CYCLONE IS LIKELY TO BECOME A REMNANT LOW IN
ABOUT THREE DAYS AND DISSIPATE IN ABOUT FOUR DAYS...CONSISTENT WITH
THE GLOBAL MODEL SOLUTIONS.

KIKO HAS BEEN SURPRISINGLY MOVING A BIT EAST OF NORTH DURING THE
PAST FEW HOURS...010/6. IT APPEARS TO BE ROTATING AROUND THE EAST
SIDE OF A MID/UPPER-LEVEL LOW...WHICH SHOULD CAUSE THE STORM TO
GRADUALLY TURN TO THE NORTH AND NORTH-NORTHWEST OVER THE NEXT DAY
OR SO. MODEL GUIDANCE HAS TAKEN A NOTABLE SHIFT TO THE EAST...AND
THE NHC FORECAST IS SHIFTED EASTWARD BY 30-45 NMI AT MOST TIME
PERIODS ON THIS PACKAGE. IN 36-48H...THE CYCLONE WILL LIKELY
DECOUPLE VERTICALLY...AND THEN BECOME NEARLY STATIONARY FOR A
COUPLE OF DAYS IN LIGHT LOW-LEVEL FLOW.
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1139. sar2401
Quoting kmanislander:


If the maps I posted are correct I do not see how it could possibly be closed with virtually no convergence. There may be the odd West wind produced by the large gyre that is the broad low associated with the feature but even the cloud deck lacks the appearance of a defined circulation unlike today when the convection was very meager but the convergence map squared away with the visible wind field.

I ran the shortwave loop and cannot detect a surface circulation either save for a faint signature ahead of the convection between 57 and 58 West
The strong rotation seen near 14 N and 55 W appears to be the 850 mb level unless a new center is forming there. That would not be out of the realm of possibility as sheared systems are known to have the center jump around following a new blow up of convection.
This happens because falling pressure associated with a thunderstorm complex is usually lower than the original center out ahead in the clear so the new area of lowest pressure becomes the new center. Have to wait and see what happens overnight.



Best analysis I've read so far. That was exactly my conclusion as well. It looks like the Antilles are going to get some much needed rain and a little wind. Things might get more dicey in the Western Caribbean, but not now.
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1138. pottery
Quoting sar2401:

Having sailed so much in that area, it's looking like a typical tropical wave so far, with lots of outflow and very little inflow. It's actually quite surprising that from the MDR north, there's nothing I can really identify as a true low.

Good point.
Tomorrow is September.
See my post below, re 'climate'.........
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1135. sar2401
Quoting pottery:

Yeah, I would go along with that.
But if it keeps building those strong thunderstorms and can hang onto them tomorrow, I'll change my mind.

It's looking 'iffy'.

Having sailed so much in that area, it's looking like a typical tropical wave so far, with lots of outflow and very little inflow. It's actually quite surprising that from the MDR north, there's nothing I can really identify as a true low.
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1134. pottery
Quoting clwstmchasr:


Yea, lets see what this looks like tomorroe afternoon. Climate tells us that if it doesnt develop soon it wont until the NW Caribbean or like its predeceor, the BOC. However, I'm more inclined to think that it will get pulled a little bit poleward

I'm not putting too much faith in that, these past couple years...
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1132. Pallis
Quoting 1104. Patrap:
The Rainbow Eye Look

I hate it when storms start using invisible lines demarcated by honkeys. That is when you know there is trouble brewing.
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Quoting 1117. stormpetrol:


I personally think 97L has a closed circulation.


If the maps I posted are correct I do not see how it could possibly be closed with virtually no convergence. There may be the odd West wind produced by the large gyre that is the broad low associated with the feature but even the cloud deck lacks the appearance of a defined circulation unlike today when the convection was very meager but the convergence map squared away with the visible wind field.

I ran the shortwave loop and cannot detect a surface circulation either save for a faint signature ahead of the convection between 57 and 58 West
The strong rotation seen near 14 N and 55 W appears to be the 850 mb level unless a new center is forming there. That would not be out of the realm of possibility as sheared systems are known to have the center jump around following a new blow up of convection.
This happens because falling pressure associated with a thunderstorm complex is usually lower than the original center out ahead in the clear so the new area of lowest pressure becomes the new center. Have to wait and see what happens overnight.


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1129. sar2401
Quoting GatorWX:


LoL and maybe by pros and there are a few, I could have stated respected bloggers?? Those were the good old days.

Yes, there were some good people back then. Unfortunately, when an entire page scrolls by in about a minute, we now have a lot more really annoying people without the slightest understanding of weather, not mention the trolls and other assorted nitwits. It was a lot easier to ignore them then. I must say though, that if you eliminate the types I just wrote about, we really have more knowledgeable people now than then. I remember very few that really understood models like many that we now.
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1128. pottery
Quoting redwagon:


We have got to solve the multiple center question, it's impeding our understanding of cyclogenesis and cyclostayingness. And throwing off our forecasts.


:):))
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Quoting 1112. moonlightcowboy:


It would not surprise me to see multiple vortices in this circ as the westerlies try to wrap into the system. As convection build though, those are likely to thin out and give way to a more dominate coc. Key now is just to keep building convection, get some lower pressures and some surface lift.


We have got to solve the multiple center question, it's impeding our understanding of cyclogenesis and cyclostayingness. And throwing off our forecasts.
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1126. pottery
Quoting clwstmchasr:


97L is not as well organized as some want it to be. This is why the NHC is saying development is not expected for 4-5 days - if at all.

Yeah, I would go along with that.
But if it keeps building those strong thunderstorms and can hang onto them tomorrow, I'll change my mind.

It's looking 'iffy'.
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I am seen a strong easterly low level flow coming in, and that might kill the chance of seen 97L develop at least for now.

Winds in the buoy to the east should be blowing from the SE like it did during the morning.
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97L currently lacking lower level convergence with a small amount of upper level divergence. Has a surface reflection (850mb), elongated 700mb, little 500mb. Shear is around 20-25knots over it and 97L is quite elongated.
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1123. pottery
Good evening, all.
97 Looks to be building some height and finding itself some moisture from somewhere.
Suspicions of west winds there too.
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Ha.

THE INTENSITY IS SET TO 60 KT...A BIT HIGHER THAN
THE LATEST SATELLITE CLASSIFICATIONS...WHICH HAVE HAD A HARD TIME
KEEPING UP WITH THIS CYCLONE.
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Quoting 1117. stormpetrol:


I personally think 97L has a closed circulation.

Agreed and also new map indicates that 97L is now gaining mid level vorticity (500mb)
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1119. ryang
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