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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Quoting JFV2013:


How'd you know? :0.
this blog knows all...or maybe it was a paid site :)
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Quoting JFV2013:
Pathetic GFS, will it ever get anything right? Obviously, the ECMWF has the best future track on 93L for now.


Well,definitly not pathetic for those of us who live in the Eastern Caribbean.
Member Since: April 29, 2009 Posts: 75 Comments: 13334
Quoting Twinkster:


well your paid site was off lol


Nah

I was looking at the 850 vort. On the MSLP plots you really can't see fine movements.

It appeared to move NE at 204 when it really was moving N.
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Quoting JFV2013:
Good morning, Adrian, by when do you expect things to begin to get exciting, if you will, for South Florida, good sir? =).


1271. hurricane23 12:15 AM EDT on August 12, 2011

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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Quoting sunlinepr:


No cost, Free.... Up to 264....

Link


I have a site for gfs already thanks anyways. I have it out to 384
Member Since: June 7, 2007 Posts: 4 Comments: 937
Quoting JFV2013:
Good morning, Adrian, by when do you expect things to begin to get exciting, if you will, for South Florida, good sir? =).
back from land of liquor already ? Did you borrow a hangover ?
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Quoting Twinkster:


how did you get out to 204 already?


No cost, Free.... Up to 264....

Link
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Quoting Twinkster:
well 93L doesn't get taken out by trough but rather by a weakness between 2 highs.


of course this will change. only thing to take away from this run is the trend south and west into carib during short term. anything after that is long term
No there is a trough that dips down, which is what causes the weakness. Look at the lower heights just north of the storm:

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Quoting Stormchaser2007:


Paid site.


well your paid site was off lol
Member Since: June 7, 2007 Posts: 4 Comments: 937
well 93L doesn't get taken out by trough but rather by a weakness between 2 highs.


of course this will change. only thing to take away from this run is the trend south and west into carib during short term. anything after that is long term
Member Since: June 7, 2007 Posts: 4 Comments: 937
There is a high probability that models will change, day to day... So it's good that today they are placing 93L across PR and DR... Hoping that when the moment of truth comes, deviation will favor us....
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Quoting hunkerdown:
there you have it, lets close the books on this one...ok, jokes aside, this is all fun and games at this point. Lets wait till he/she forms and see what it forms into till we make any plans.


Plus 1. And with that, I'm out for the night.
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Quoting Stormchaser2007:
GFS sends it NE at 204.

Should go OTS.
there you have it, lets close the books on this one...ok, jokes aside, this is all fun and games at this point. Lets wait till he/she forms and see what it forms into till we make any plans.
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Whoa... 93L seem to be VERY interesting for East Coast. Hope it doesn't turn into Hugo II. Meanwhile, 92L is another interesting storm, but slightly weaker and lest threat to USA... but it's way too early to predicts USA landfall for both systems (93L is more interesting)
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Quoting Twinkster:


how did you get out to 204 already?


Paid site.
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The strong MJO seems to be doing wonders on the GFS for the EPAC.

Develops about 3-4 storms this run.

Trend has been for the Atl to receive a weaker and weaker wave.
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Quoting Stormchaser2007:
GFS sends it NE at 204.

Should go OTS.


how did you get out to 204 already?
Member Since: June 7, 2007 Posts: 4 Comments: 937
looks like 93L might take an emily type track
Member Since: June 7, 2007 Posts: 4 Comments: 937
GFS sends it NE at 204.

Should go OTS.
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Link

cant get image to post for some reason anyways anyone wanting to see a wave from dean hitting cliffs in cayman and going about 200 feet into the air can check it out here
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Something wrong with GFS, 174 hrs.... then 180 hrs. the system is 500 miles NE???

Then

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Quoting JLPR2:


The fun part is that the next run of the GFS should be different.
I only trust the first 72hrs of the run.



ok
Member Since: May 21, 2006 Posts: 5089 Comments: 114072
Good thing there is many, many more GFS runs before these become a threat. That 00ZGFS would be a bad day for a lot of people.
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Quoting Tropicsweatherpr:
2007, does it moves more slowly when it is close to PR and crosses?



Doesn't seem like it, but it affects the whole island.

189 hours

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Quoting MississippiWx:
168:

taken for the grain of salt its worth but this appears it may track just north of Hispaniola and threaten the T&C/Bahamas...if you are around, sorry Baha.
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hurricane deans waves bashing cayman
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1328. JLPR2
Quoting Tazmanian:



poor poor PR


The fun part is that the next run of the GFS should be different.
I only trust the first 72hrs of the run.
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2007, does it moves more slowly when it is close to PR and crosses?
Member Since: April 29, 2009 Posts: 75 Comments: 13334
Quoting 3211976:
South east coming through Humacao and exiting through Arecibo North west.


Why not Naguabo and Rincon... Then why not, make it stationary over the island for, lets say, 24 hrs.

Then in the Mona passage, it turns South and comes back NE crossing from Cabo Rojo to Fajardo...

Then....

Too far away to know, Yet...
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174 its just NE of Hispaniola and heading WNW

Could be interesting if that trough lifts out.
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Quoting MississippiWx:
168:




poor poor PR
Member Since: May 21, 2006 Posts: 5089 Comments: 114072
Quoting Twinkster:



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


I'm in Florida, and i'm not liking that either. We could be dealing with a major hurricane, if conditions stay the way they are, and it looks like it will.
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168:

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Quoting Twinkster:
00z gfs


12z ECMWF



ECMWF portrays a much stronger B/A high and likely why it's 18 hours faster to the location in your image.
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Quoting Stormchaser2007:


It appears to be a piece of energy that split from the same trough that carried Emily into the NA graveyard.
you sure that isn't the remains (I don't want to use remnant here) of system formerly known as Emily ?
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Quoting Stormchaser2007:
Hits eastern PR by 159.

Could hit Hispaniola next.



Hispaniola that wont be good
Member Since: May 21, 2006 Posts: 5089 Comments: 114072
mark my words 93L will not go out too sea it will go see jason and JFV
Member Since: May 21, 2006 Posts: 5089 Comments: 114072
1316. JLPR2
Last run was Hugo reborn, now it is Georges reborn. *sigh*
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Quoting Tropicsweatherpr:


I better check the electric plant in my house tommorow.


156 hours

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Quoting docrod:


What a remarkable website ... thanks for the link


Very detailed African photos and info there...
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1313. 3211976
South east coming through Humacao and exiting through Arecibo North west.
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Hits eastern PR by 159.

Could hit Hispaniola next.
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Quoting Stormchaser2007:


Just east of PR by 150 hours.



I better check the electric plant in my house tommorow.
Member Since: April 29, 2009 Posts: 75 Comments: 13334
Quoting hurricane23:




Very powerful storm, nearly perfect spiral banding on all quads. Like Allen too.
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00z gfs


12z ECMWF

Member Since: June 7, 2007 Posts: 4 Comments: 937

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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.