Two African waves, 92L and 93L, worth watching

By: Dr. Jeff Masters , 2:59 PM GMT on August 11, 2011

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An African wave is near 13°N 35°W, about 700 miles west-southwest of the Cape Verde Islands. This system, (Invest 92L), is moving west to west-northwest at 10 - 15 mph, and has the potential to develop into a tropical depression or tropical storm before arriving near the northern Lesser Antilles Islands early next week. Recent visible satellite loops show that 92L has less heavy thunderstorm activity near where it is trying to develop its circulation center than yesterday. Water vapor satellite loops that a large area of dry air lies just to the west of 92L, but the atmosphere in the immediate vicinity of 92L is moist. Even so, the decline of heavy thunderstorm activity since yesterday implies that dry air is probably working its way into 92L. The SHIPS model and University of Wisconsin CIMSS wind shear analysis are showing moderate wind shear of 10 - 15 knots affecting 92L. Sea surface temperatures are 26.5° - 27°C, which is very close to the 26.5°C threshold usually needed to support a tropical storm.


Figure 1. Morning satellite photo of Invest 92L and Invest 93L.

Forecast for 92L
Low to moderate wind shear of 5 - 15 knots is predicted along 92L's path over the coming three days, which should allow the storm to organize, assuming it can shut out any incursions of dry air that might intrude. The latest 00Z and 06Z model runs of the four best models for predicting tropical storm formation (GFS, ECMWF, NOGAPS, and UKMET) show weak development or no development of 92L, and NHC gave 92L a 30% chance of developing into a tropical depression by Saturday morning in their 8am outlook. A steady west to west-northwest motion for 92L is predicted by all of the models, which would put the storm in the vicinity of the northern Lesser Antilles Islands by Sunday. On Saturday and Sunday, 92L is expected to enter a region where an upper-level low pressure system will bring high wind shear of 20 knots to the storm, which should slow development. This upper-level low is also expected to turn 92L more to the northwest, so the storm is likely to pass north of the Lesser Antilles, though may pass close enough to give heavy rains to the northernmost islands. It is too early to know if 92L will recurve out to sea and potentially threaten Bermuda, or continue to the northwest towards the U.S. East Coast.

93L
An African wave that emerged off the coast of Africa is near 10°N 22°W, a few hundred miles south of the Cape Verde Islands. This system, (Invest 93L), is also moving west at 10 - 15 mph, and has the potential to develop into a tropical depression or tropical storm before arriving near the northern Lesser Antilles Islands near the middle of next week. Recent visible satellite loops show that 93L has a decent amount of heavy thunderstorms, but this activity is not well organized. There is not much spin associated with 93L yet. 93L is fairly well-protected from dry air to its north and west. The SHIPS model and University of Wisconsin CIMSS wind shear analysis are showing moderate wind shear of 10 - 20 knots affecting 93L. Sea surface temperatures are 27.5°C, which is one degree above the 26.5°C threshold usually needed to support a tropical storm.

Forecast for 93L
Moderate wind shear below 20 knots is predicted along 93L's path over the coming five days, which should allow the storm to steadily organize. 93L is about 600 miles east of 92L, which is close enough that the two systems may interfere with each others' organization. The latest 00Z and 06Z model runs of the four best models for predicting tropical storm formation (GFS, ECMWF, NOGAPS, and UKMET), have only one model, the GFS, that is indicating significant development of 93L. This model brings 93L near the northern Lesser Antilles Islands by Wednesday. NHC gave 93L a 20% chance of developing into a tropical depression by Saturday morning in their 8am outlook. Due to moister air, the potential for less wind shear, and a more southerly track, 93L is probably a greater threat to the Lesser Antilles than 92L.

Jeff Masters

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GFS is much weaker with 93L this run so far.
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Big wave C Africa
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1257. pottery
Quoting islander101010:
whats that red stuff over texas have not seen anything like that in a long time

Probably a sandstorm.....
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Quoting JLPR2:


Yes, I read about that, nuts!
Maybe I'll go live in Spain for while. XD
I want to see Spain someday.
Well have to admit ,that was my first tornado[F0 or F1 they said, and the first one ever to be recorded in Puerto Rico... Spain is beautiful, went there last month, but they also have tornados, not as strong as the U.S. though.
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Quoting atmoaggie:
LOL. Levi posted yesterday's 18 Z GFS a long time ago...

And we both used Linux, but used totaly different tools and programs.

No script, just 3 commands.

for i in `seq 0 3 192`; do paddednum=`printf "%03d" $i`; wget http://mag.ncep.noaa.gov/GemPakTier/MagGemPakImage s/gfs/20110810/18/gfs_atlantic_${paddednum}_10m_wn d_precip.gif; done
for i in `seq 204 12 384`; do paddednum=`printf "%03d" $i`; wget http://mag.ncep.noaa.gov/GemPakTier/MagGemPakImage s/gfs/20110810/18/gfs_atlantic_${paddednum}_10m_wn d_precip.gif; done

gifsicle --delay 30 --loopcount=0 --scale 0.75 -O2 gfs_atlantic_*.gif > gifanim.gif

I was little confused after the first sentence, but then it all came back to me as I read on.
Laymen's terms are not part of this equation,. You guys are great, just had to comment, keep up the good work and analysis
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1254. ackee
I wonder if Emily will come back from the dead to meet up with 92L
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Quoting JLPR2:


But that light would be green.
I believe I heard that under our current situation it would take a month or two to get most of the power grid back and running if we were hit by a major hurricane.


After Georges It took 2 weeks to power on here in Caguas... But the recently built Plaza Centro Shopping Center area had power just 2 days after the hurricane...

Interest$ like everywhere, move politicians....
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30 hours...93L down to 1010mb. You can see a hint of Ex-Emily, as well as 92L in between Emily and 93L. Also a nice looking wave emerging from Africa:

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1251. JLPR2
GFS strengthens 93L in the short term but in 24hrs it starts weakening, interesting run.

Member Since: September 4, 2007 Posts: 7 Comments: 8698
whats that red stuff over texas have not seen anything like that in a long time
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1249. JLPR2
Quoting sunlinepr:


PR power grid... After a Cat 3, it will be completly dark, except for the "ViaVerde" that will keep on shinning with dollars...





But that light would be green.
I believe I heard that under our current situation it would take a month or two to get most of the power grid back and running if we were hit by a major hurricane.
Member Since: September 4, 2007 Posts: 7 Comments: 8698
Quoting tropicfreak:


Boy taz is ex emily annoying or what? Get me a pic of ugly emily.



yup
Member Since: May 21, 2006 Posts: 5091 Comments: 115107
Quoting HuracanTaino:
Same happened to me 2 days ,withour power do to "the Moca Tornado" that you probably heard" about in the local news, with an storm or a hurricane I don't want to imagine what would happen ....


PR power grid... After a Cat 3, it will be completly dark, except for the "ViaVerde" that will keep on shinning with dollars...



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11/2345 UTC 10.6N 27.5W T1.0/1.0 93L
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Quoting j2008:

Sounds about right. Ill say,
92L 30%
93L 50-60%
Ex-Emily ghost 0-10%
SE USA disturbance 0-10%.
IMO 93L will be a TD by Saturday afternoon.



I agree, especially on 93L being TD 6 Saturday pm.
Member Since: September 2, 2006 Posts: 110 Comments: 6877
1244. JLPR2
Quoting HuracanTaino:
Same happened to me 2 days ,withour power do to "the Moca Tornado" that you probably heard" about in the local news, with an storm or a hurricane I don't want to imagine what would happen ....


Yes, I read about that, nuts!
Maybe I'll go live in Spain for while. XD
I want to see Spain someday.
Member Since: September 4, 2007 Posts: 7 Comments: 8698
1243. j2008
Quoting tropicfreak:


As for 92L not that low, maybe down to 30 or 20%, and 50 or 60% sounds right for 93L, think they will give ex emily 10% and the SE AOI 10% too.

Sounds about right. Ill say,
92L 30%
93L 50-60%
Ex-Emily ghost 0-10%
SE USA disturbance 0-10%.
IMO 93L will be a TD by Saturday afternoon.
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1242. Grothar
Quoting emcf30:


Well, you were the first one that said we need to watch this tropical wave several days ago when it was just a wave over Africa.


I wouldn't know if I was the first. I am sure there were many others that saw the same thing. Conditions were good for some type of development. (Actually I nailed this whole thing 5 days ago. hehehe)

I think P451, hydrus, Levi and I think JLPR & CyberTeddy posted images of the waves coming off and a few others. The blogs have been very good on all of them and quite consistent between many of them. Unusual to see that. Most of the time the blogs are quite divergent in their thinking, but most were pretty much on the mark with these systems. Now we have an entire week to see what is fact and what is conjecture.
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Quoting Tazmanian:




ok


Boy taz is ex emily annoying or what? Get me a pic of ugly emily.
Member Since: September 2, 2006 Posts: 110 Comments: 6877
1240. JLPR2
In 15hrs the GFS shows 92L's vort returning.

Member Since: September 4, 2007 Posts: 7 Comments: 8698
Quoting HuracanTaino:
Same happened to me 2 days ,withour power do to "the Moca Tornado" that you probably heard" about in the local news, with an storm or a hurricane I don't want to imagine what would happen ....


With only a thunderstorm,power went off in parts of Santurce.
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Quoting tropicfreak:


As for 92L not that low, maybe down to 30 or 20%, and 50 or 60% sounds right for 93L, think they will give ex emily 10% and the SE AOI 10% too.




ok
Member Since: May 21, 2006 Posts: 5091 Comments: 115107
Quoting JLPR2:
Lost power for two hours... sucks! I don't even want to imagine what would happen to PR's power grid if a storm passed over us.
Same happened to me 2 days ,withour power do to "the Moca Tornado" that you probably heard" about in the local news, with an storm or a hurricane I don't want to imagine what would happen ....
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1236. emcf30
Quoting Tazmanian:
at this time am droping 92L from 40% too to a low 10% ch


93L am upgradeing 93L from 40% too a high 60% and this is being nic


I think you are on the right track
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Quoting Tazmanian:
at this time am droping 92L from 40% too to a low 10% ch


93L am upgradeing 93L from 40% too a high 60% and this is being nic


As for 92L not that low, maybe down to 30 or 20%, and 50 or 60% sounds right for 93L, think they will give ex emily 10% and the SE AOI 10% too.
Member Since: September 2, 2006 Posts: 110 Comments: 6877
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Quoting MississippiWx:
GFS didn't initialize 92L as a low pressure area...has 93L:





did the GFS drop 92L?
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1231. emcf30
Quoting Grothar:


You are asking me???? Wow. I really don't know, but I would guess they expect that when 92L moves out, it will cause a ridging in the upper atmosphere and move 93L more westerly under it. I think that is the GFDL thinking on it. Of course I don't know much about the weather.


Well, you were the first one that said we need to watch this tropical wave several days ago when it was just a wave over Africa.
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at this time am droping 92L from 40% too to a low 10% ch


93L am upgradeing 93L from 40% too a high 60% and this is being nic
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GFS didn't initialize 92L as a low pressure area...has 93L:

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Quoting ackee:
I wonder if 93L will track similar to DEAN 07 gueess we see I do think the longer 93L waits to devlop the further west this go more likly that this could be a major storm for the carrb only time will tell


Have a nasty feeling 93L could be a Caribbean cruiser!
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00z GFS has initialized.
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1224. Grothar
Quoting atmoaggie:
Hum, tinypic rejecting 2 MB files, for some reason.


I know how you feel atmo. Things like that keep me up nights thinking.
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1223. ackee
I wonder if 93L will track similar to DEAN 07 gueess we see I do think the longer 93L waits to devlop the further west this go more likly that this could be a major storm for the carrb only time will tell
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Quoting tropicfreak:


Something worth watching though. If they don't I understand, the NHC is sick of dealing with Emily.


It's certainly worth watching. If it can stick together as it makes its trip around the Southern half of the ridge, it will be in a more favorable environment at that time with some of the warmest SSTs in the basin.
Member Since: July 15, 2006 Posts: 17 Comments: 10248
1221. Grothar
Quoting emcf30:


Hey Gro, Why do you think the models are not wanting the trough to take 93L more NW. You would think since the intensity forecast are increasing with each run it would have a tensity to be pulled towards any weakness in the High created by any trough like they do with 92L.


You are asking me???? Wow. I really don't know, but I would guess they expect that when 92L moves out, it will cause a ridging in the upper atmosphere and move 93L more westerly under it. I think that is the GFDL thinking on it. Of course I don't know much about the weather.
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Emily's remnants very close to doing a 360! Will 92L survive, looks as though 93L is becoming the real player!
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1219. Levi32
Quoting atmoaggie:
Hum, tinypic rejecting 2 MB files, for some reason.


My animations are typically ~2.5MB. It does randomly reject them once in a while, but after 2-3 tries it usually goes.
Member Since: November 24, 2005 Posts: 635 Comments: 26647
Quoting JLPR2:


Possible, seems 92L's broad circulation has taken a beating from being exposed for days.




wish i all so think 92L has all so open up too a open wave
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1216. JLPR2
Quoting Tazmanian:



i think 92L has had it i all so noted that they have not ran mode runs on 92L tonight wish all so may mean that they may plan on droping 92L



how evere in the mean time 93L really looks good tonight


Possible, seems 92L's broad circulation has taken a beating from being exposed for days.
Member Since: September 4, 2007 Posts: 7 Comments: 8698
Quoting Levi32:


It would be nice if I could get my animations a bit smaller in size. By the way, I don't know what your file size was, but tinypic seems to have the largeset limit that I know of (5mb).
Hum, tinypic rejecting 2 MB files, for some reason.
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Quoting MississippiWx:


Maybe...I doubt it though. It really doesn't have any model support, other than the NAM. It's in an unfavorable environment currently, being on the SE periphery of the Bermuda High.


Something worth watching though. If they don't I understand, the NHC is sick of dealing with Emily.
Member Since: September 2, 2006 Posts: 110 Comments: 6877
Quoting Unfriendly:


yea, those fishes better watch out. unless it fujiwaras around 92L and accelerates to 60 knots eastward


It's actually going to drift SW.
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Quoting Unfriendly:


yea, those fishes better watch out. unless it fujiwaras around 92L and accelerates to 60 knots eastward


Huh?
Member Since: July 15, 2006 Posts: 17 Comments: 10248
Quoting JLPR2:


The interesting thing is that it is stronger than 92L's.



i think 92L has had it i all so noted that they have not ran mode runs on 92L tonight wish all so may mean that they may plan on droping 92L



how evere in the mean time 93L really looks good tonight
Member Since: May 21, 2006 Posts: 5091 Comments: 115107
Quoting MississippiWx:
Emily's ghost has a decent amount of 850mb vorticity associated with it as well...Should definitely be watched:



yea, those fishes better watch out. unless it fujiwaras around 92L and accelerates to 60 knots eastward
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1209. Levi32
Quoting atmoaggie:
gifsicle is easier to use for resizing/scaling/optimizing (smaller file size), IMO.


It would be nice if I could get my animations a bit smaller in size. By the way, I don't know what your file size was, but tinypic seems to have the largeset limit that I know of (5mb).
Member Since: November 24, 2005 Posts: 635 Comments: 26647

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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.