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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00z gfs


12z ECMWF

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1308. 3211976
It could be a classic PR Hurricane hit.
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1307. JLPR2
Every run of the GFS is worse for me.
Member Since: September 4, 2007 Posts: 7 Comments: 8483
1306. JRRP

sorry taz...:P
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Quoting 3211976:
MMMM, is looking interesting for PR.


Just east of PR by 150 hours.

Member Since: June 9, 2007 Posts: 4 Comments: 15776



gfs looking more in line with ecmwf on track for 93L this run. I am not liking this run for florida. Florida might be in the crosshairs
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Quoting Twinkster:
mark my words 93L will not go out to sea


Marked
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Quoting hurricane23:




Real MW image of Dean south of Jamaica.

Incredible

Member Since: June 9, 2007 Posts: 4 Comments: 15776
1300. pottery
I'm out.
Have fun all.

Fantastic moon overhead.....
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1298. JLPR2
135hrs has 93L over the central Lesser Antilles, that's one heck of a change.
Member Since: September 4, 2007 Posts: 7 Comments: 8483
mark my words 93L will not go out to sea
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1296. 3211976
MMMM, is looking interesting for PR.
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Heading NW.

Not sure where this is going to end up. Trough seems to be weakening some.

Member Since: June 9, 2007 Posts: 4 Comments: 15776
1294. ackee
Quoting Tropicsweatherpr:


I remember when GFS had Dean as a 1007 mb low.
I NOTICE that the GFS Ensemble has been trending more west so guess we see
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Quoting Stormchaser2007:


Dean was an amazing system to track. It was a classic CV monster.

Remember those long nights watching recon.


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1292. Grothar
Quoting Stormchaser2007:


It appears to be a piece of energy that split from the same trough that carried Emily into the NA graveyard.


Is that a riddle?
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1291. pottery
Post 1287, thanks Cybr.
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Member Since: June 9, 2007 Posts: 4 Comments: 15776
Quoting ackee:
I said this earlyer post would not be suprise if 93L track similar to DEAN in 07 watch as model will continue to shift more west


I remember when GFS had Dean as a 1007 mb low.
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Quoting Stormchaser2007:
Karen is back in the basin it seems.




hey Karen where you been all my life
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Quoting pottery:

I would be interested to hear the differences?


The ridging and the troughs, plus Dean didn't have a possible storm in front of it also (92L).. but its interesting to note the similarities. Its really rare to get a Cape Verde major hurricane to truck all the way to the Yucatan like Hurricane Dean did, especially a Category 5.

Quoting Stormchaser2007:


Dean was an amazing system to track. It was a classic CV monster.

Remember those long nights watching recon.


Dean was a beast, those recon reports although they where no Wilma where amazing. I remember reading how there was frequent lightning in the eyewall the night Dean became a Category 5 first time around ~ though at the time it wasn't considered a Category 5 until it hit the Yucatan. I can't imagine how bad Dean would have gotten if there was a trough or a weakness in that monster ridge to cause it to head WNW into the Gulf without hitting the Yucatan. Thankfully, that didn't happen and Dean didn't cause the extreme amount of damage it could have too.
Member Since: July 8, 2005 Posts: 259 Comments: 23493
Quoting JRRP:
east of Barbados

114h



what kind of map is that i no its the GFS but what the
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ouch can you say strong high. 93L say hi to carib
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Karen is back in the basin it seems.

Member Since: June 9, 2007 Posts: 4 Comments: 15776
Quoting MississippiWx:


Someone called you a GIMP earlier...think it was TomTaylor.

I defended you though, as I always do.
ay!

Putting words in my mouth? lol. I can see where you were going with the word gimp, but idk how you pulled grothar into this

Quoting emcf30:


1. gimp

(1) a derrogatory term for someone that is disabled or has a medicial problem that results in physical impairment.

(2) An insult implying that someone is incompetent, stupid, etc. Can also be used to imply that the person is uncool or can't/won't do what everyone else is doing.

(3) A sex slave or submissive, usually male, as popularlized by the movie Pulp Fiction.

He probably was referring to #3. LOL
hahah

gotta love urban dictionary. And pulp fiction.
Member Since: August 24, 2010 Posts: 19 Comments: 4357
1282. ackee
Quoting CybrTeddy:
00z keeps it weaker, but on a much more dangerous path.
This satellite image from August 12th, 2007 looks not all that different from 93L, date and location is both pretty close. Take a guess (shouldn't be hard) what this became. Not saying 93L will be anything like that storm, but there are some small similarities, and some big differences.
I said this earlyer post would not be suprise if 93L track similar to DEAN in 07 watch as model will continue to shift more west
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1281. JRRP
east of Barbados

114h
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Quoting Grothar:
Can anyone tell me if this is Emily-ex-Emily, AOI?




It appears to be a piece of energy that split from the same trough that carried Emily into the NA graveyard.
Member Since: June 9, 2007 Posts: 4 Comments: 15776
Quoting MississippiWx:
GFS didn't initialize 92L as a low pressure area...has 93L:




And Remily don't forget, lol.
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notice difference in position of trough and strength

00z



18z




definitely will see some difference in track this run
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Tropical Cyclone heading towards the central/southern Lesser Antilles.

Member Since: June 9, 2007 Posts: 4 Comments: 15776
1276. Grothar
Can anyone tell me if this is Emily-ex-Emily, AOI?


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1275. pottery
Quoting CybrTeddy:
00z keeps it weaker, but on a much more dangerous path.
This satellite image from August 12th, 2007 looks not all that different from 93L, date and location is both pretty close. Take a guess (shouldn't be hard) what this became. Not saying 93L will be anything like that storm, but there are some small similarities, and some big differences.

I would be interested to hear the differences?
Member Since: Posts: Comments:
Quoting CybrTeddy:
00z keeps it weaker, but on a much more dangerous path.
This satellite image from August 12th, 2007 looks not all that different from 93L, date and location is both pretty close. Take a guess (shouldn't be hard) what this became. Not saying 93L will be anything like that storm, but there are some small similarities, and some big differences.


Dean was an amazing system to track. It was a classic CV monster.

Remember those long nights watching recon.
Member Since: June 9, 2007 Posts: 4 Comments: 15776
1273. docrod
Quoting sunlinepr:
Big wave C Africa


What a remarkable website ... thanks for the link
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1272. ackee
I like like this GFS run in terms of intensity think 93L will steadly devolop not as fast as other GFS run was showing
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This is going to be a tough one as the US landfall threat will be totally dependent on transient short wave in the northern stream- the models will likely be all over the place for quite a few days as they shift on the timing of those waves- we will have to be lucky (or unlucky, depending on your point of view) in getting the correct mid-latitude configuration to be in place just as this comes into either the Bahamas or the Caribbean. Right now with the general long-wave pattern being a ridge in the Rockies/Plains and a trough in the east a recurve is still the scenario that is probably the most likely but this one does at least have a shot at a landfall assuming it develops and misses Hispaniola.

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00z keeps it weaker, but on a much more dangerous path.
This satellite image from August 12th, 2007 looks not all that different from 93L, date and location is both pretty close. Take a guess (shouldn't be hard) what this became. Not saying 93L will be anything like that storm, but there are some small similarities, and some big differences.
Member Since: July 8, 2005 Posts: 259 Comments: 23493
Slowly gettin in shape...

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93L finally gets together by 84 hours. Seems pretty far south.

Should be interesting if it survives.
Member Since: June 9, 2007 Posts: 4 Comments: 15776
stronger trough this run, also trough is taking longer to move to coast and thus should take longer to move out
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1266. JLPR2
Barely impressive.

Member Since: September 4, 2007 Posts: 7 Comments: 8483
hmmm, I see something interesting near 26n and 54w
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Both systems are pretty weak by 72 hours. Seems to be a trend towards the ECMWF.

Member Since: June 9, 2007 Posts: 4 Comments: 15776
1263. ackee
Quoting Gearsts:
It will keep changing lol
agree until we have TS or TD model will be all over the place
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1262. Gearsts
Quoting Stormchaser2007:
GFS is much weaker with 93L this run so far.
It will keep changing lol
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1261. pottery
Quoting Stormchaser2007:
GFS is much weaker with 93L this run so far.

The secret to 93 will be revealed when/if 92 can swallow some of the dry air west of the two systems.
Right now, there is not a lot of moisture associated with 92, so I think it will be marginal for 93 to develop in the next 2-3 days.
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Quoting HuracanTaino:
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.


How close was the tornado from your place / did you watch it from far?
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GFS is much weaker with 93L this run so far.
Member Since: June 9, 2007 Posts: 4 Comments: 15776

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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.