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 SouthDadeFish:
Yeah the Euro isn't too enthusiastic about cyclogenesis with these two waves either. It has done a pretty darn good job so far this season, so I'm siding with the Euro on this one. There will be plenty more waves though...


the euro didnt develop Emily..all these models have been inconsistent this season..you just have to hope one of them gets it right when it counts..
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As I have said in the past, and notwithstanding threats to the Caribbean which NHC does not have direct jurisdiction over, the best that we can hope for is the NHC 3-Day track once a storm approaches landfall based upon the best short-term model guidance. We have to take it one storm at a time because of what can change more than 3 days out. At the end of the day the hope is that folks are given sufficient notice to prepare and/or evacuate as needed for each individual storm.
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Quoting reedzone:
You all are jumping the gun on this "pattern"
Reed to be honest, as long as is the Death Ridge is over Texas, we will see a pattern that favors troughing over the east coast.
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12Z GFS shows a pretty weak ridge. If 93L were any stronger it probably would be a recurve. But at this time we're getting into La-La land of the computer model runs. 180 hours + is too much for me.
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You all are jumping the gun on this "pattern"
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We saw this with Earl and Igor last year, saw this with Florence in 2006.. Models start recurving storms east of Bermuda, then the trends head west. I'm on a good confidence that 92L recurves WEST of Bermuda. 93L however, possibly gets caught under a developing ridge.
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Quoting reedzone:
I agree that 92L will recurve WEST of Bermuda but EAST of the USA. I don't agree that 93L will recurve, the blocking pattern will be in place.


How close 92L gets to the US has yet to be seen, but you're right, it looks like 92L should be a recurve, most likely west of bermuda and east of the US.
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XX/INV/92L
MARK
15.85N/35.86W
Member Since: July 15, 2006 Posts: 169 Comments: 53296
Quoting reedzone:


Adrian, I understand your rooting for recurvature.. but it's about a week away for us to watch, still too early and even Dr. Masters himself said it's too early to pinpoint a future for both 92L and 93L. Emily was supposed to recurve (according to the GFS) north of PR, instead, it was extremely close to Florida, to the point where wind and rain glazed the coastline. Earl last year was expected to recurve around Bermuda, instead it recurved dangerously close to the US. Even Igor was supposed to recurve east of Bermuda, rather then a bit west of the island. Things change and models recrve storms wayy too early then what mother nature does. It just needs to be watched and not taken for granted that a trough is gonna save us every time. This isn't 2010, the blocking pattern is coming quickly according to the ensembles of the GFS and EURO. If you listened to Levis video yesterday, he explains a good point. I'm not rooting for a landfalling storm, but I know in reality, models and models and they can be wrong, and have been wrong in the past. So it's just a wait and see if the EURO could be right and a huge unseasonable trough develops. I seriously doubt it. However, everybody on US Coastline should be preparing for a very active season.


I agree that its way too early to tell, but, we are allowed to have early speculations. I myself believe we will have more systems either heading too far south till they hit Central America, or Mexico, maybe Texas. Or the will curve out to sea.

The fact is, the pattern that is dominant now still favors storms curving out to sea. Until that changes, that is is going to often be the case. I'm not saying that can't or won't change, but looking ahead at the weather patterns in Florida, the trough pattern has not weakened, in fact, it has gotten stronger. The last trough sequence brought very heavy rains to much of Florida. Computer models are already showing another trough digging down for early next week.

Until this pattern changes, the highest chance is that tropical cyclones will curve out to sea. Or if they are far enough south in the Caribbean, they will go due west into Central America/Mexico.


Like I said, the pattern could change. But I don't want to be crying wolf by telling everyone that the Southeast could get battered by hurricanes later this season if the patterns don't favor so yet.

If the pattern changes, there will still be plenty of time to warn people if an approaching hurricane is a threat. But people have no need to be worried this season about storms that don't even exist yet, many of which may miss anyway.

If a hurricane develops and has a high threat to the Southeast U.S. there will be plenty of time to warn people. But there's no reason to warn them about threats that don't exist yet.



The fact is, people should always have a hurricane plan every year, and should have some sort of survival kit, and head warning of forecasters and evacuations. But people don't need to be, and shouldn't be told this year is going to be an active year for the U.S. they need to just prepared regardless. Telling people its going to be an active year will get people panicking.
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Quoting WxLogic:
Appears we might have a 4th area to watch in front of 92L (may be by this weekend):





If it pans out then this disturbance could become our 3rd possible TD/TS to develop.
Remains of Emily heading SE , interesting to see if Emily says" Im, Back!
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Quoting weatherman12345:
i definitely see a recurve out of 92l.... but as far as 93l it remains to be seen wether the high may build in and possibly affect the northern Antilles. the U.S. will most likely not be affected by either of these systems.


Too early to tell, don't make a call like that.
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Quoting hurricane23:


EURO has a huge 500mb trough off east coast next 10 days. Hard to see a US impact from anything out of the deep tropics.
Yeah the Euro isn't too enthusiastic about cyclogenesis with these two waves either. It has done a pretty darn good job so far this season, so I'm siding with the Euro on this one. There will be plenty more waves though...
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Quoting reedzone:
I agree that 92L will recurve WEST of Bermuda but EAST of the USA. I don't agree that 93L will recurve, the blocking pattern will be in place.


Well said - I agree completely. +1
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Sure is looking like 2010 all over again. If the pattern doesn't change it's going to be another snoozefest. We have many states that could use some rain from these tropical systems. It doesn't help when they all get punted out to sea.
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I agree that 92L will recurve WEST of Bermuda but EAST of the USA. I don't agree that 93L will recurve, the blocking pattern will be in place.
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83. SLU
93L has just crossed the buoy at 12n 23w.
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Quoting USAFwxguy:
Noticing 12Z is much stronger with 92L and weaker with 93L.

93L enetering the Caribbean here:




Thats going to be a big ouchie for Bermuda from 92L. (Future Franklin or Gert)
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81. HCW
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78. SLU
I see the 12z GFS has fallen in line with its ensembles and showing a southerly track into the Caribbean.
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Forgive me if I double post as my last attempt did not go through. Wanted to note that I agree with Dr. M's assessment that the moisture trial behind 92L will help 93L and so forth as the middle passage moistens up as each wave comes through. However, not thrilled about the current path trend for these two storms and it does not bode well for the systems that may follow towards the Antilles. Really need to keep an eye on the relative position of the A-B high over the next six weeks regardless of the timing of the trofs because if we get a cluster of CV storms in late-August through September, there is no guarantee that every one will be greeted with a weakness allowing a NW turn before getting into the Caribbean and onwards toward the Conus.
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Quoting reedzone:


Adrian, I understand your rooting for recurvature.. but it's about a week away for us to watch, still too early and even Dr. Masters himself said it's too early to pinpoint a future for both 92L and 93L. Emily was supposed to recurve (according to the GFS) north of PR, instead, it was extremely close to Florida, to the point where wind and rain glazed the coastline. Earl last year was expected to recurve around Bermuda, instead it recurved dangerously close to the US. Even Igor was supposed to recurve east of Bermuda, rather then a bit west of the island. Things change and models recrve storms wayy too early then what mother nature does. It just needs to be watched and not taken for granted that a trough is gonna save us every time. This isn't 2010, the blocking pattern is coming quickly according to the ensembles of the GFS and EURO. If you listened to Levis video yesterday, he explains a good point. I'm not rooting for a landfalling storm, but I know in reality, models and models and they can be wrong, and have been wrong in the past. So it's just a wait and see if the EURO could be right and a huge unseasonable trough develops. I seriously doubt it. However, everybody on US Coastline should be preparing for a very active season.


Not rooting for recurve or threat just pointing out the overall pattern thats been in place just about all summer. Until we get something going positive in regards to the NAO i see plenty of recurves. Again if something stays fairly weak it might have a shot.
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Quoting reedzone:


Adrian, I understand your rooting for recurvature.. but it's about a week away for us to watch, still too early and even Dr. Masters himself said it's too early to pinpoint a future for both 92L and 93L. Emily was supposed to recurve (according to the GFS) north of PR, instead, it was extremely close to Florida, to the point where wind and rain glazed the coastline. Earl last year was expected to recurve around Bermuda, instead it recurved dangerously close to the US. Even Igor was supposed to recurve east of Bermuda, rather then a bit west of the island. Things change and models recrve storms wayy too early then what mother nature does. It just needs to be watched and not taken for granted that a trough is gonna save us every time. This isn't 2010, the blocking pattern is coming quickly according to the ensembles of the GFS and EURO. If you listened to Levis video yesterday, he explains a good point. I'm not rooting for a landfalling storm, but I know in reality, models and models and they can be wrong, and have been wrong in the past. So it's just a wait and see if the EURO could be right and a huge unseasonable trough develops. I seriously doubt it. However, everybody on US Coastline should be preparing for a very active season.


Assuming we get Franklin and Gert out of 92L and 93L, maybe Harvey somewhere in there by the end of the weekend, we would be very close to tying 2005 in progression. At around this time we were dealing with Jose.

You are exactly right on recurvature. Even though it may sound like it to some, the well respected and reliable experts on here don't wish for a landfalling storm, but you have to go by common sense. Weather is constantly changing, and that always corresponds with the track of storms, whether it be a thunderstorm, coastal low (east coast snowstorm) or a hurricane. Predicting and nailing the track this far out is the luck of the draw. Good point there reed.
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Oddity worth noting. While 92L's position of 12.1n27.7w at 9August 6pmGMT remained the same,
93L's(starting)position (along with the rest of the data) was removed altogether.

So starting at 10August 12amGMT to make 92L's and 93L's coordinates cover the same time period:
12.2n28.5w, 12.2n29.5w, 12.2n30.6w, 12.3n30.7w, 12.7n31.4w have been re-evaluated&altered for 92L's_12pmGMT_ATCF
12.2n28.3w, 12.3n29.2w, 12.4n30.1w, 12.5n31.0w, 12.7n32.0w, 12.9n 33.0w, 13.1n34.0w are now the most recent positions
9.3n12.4w, 9.4n13.6w, 9.6n14.6w, 9.7n15.7w, 10.1n17.3w have been re-evaluated&altered for 93L's_12pmGMT_ATCF
9.6n13.5w, 9.8n15.0w, 9.9n16.5w, 10.0n18.0w, 10.1n19.5w, 10.2n20.5w, 10.3n21.5w are now the most recent positions

Original mapping from 9August 6pmGMT to 11August 12amGMT

Copy&paste 12.1n27.7w, 12.2n28.5w, 12.2n29.5w, 12.2n30.6w, 12.3n30.7w, 12.7n31.4w, vxe, 9.2n11.1w, 9.3n12.4w, 9.4n13.6w, 9.6n14.6w, 9.7n15.7w, 10.1n17.3w into the GreatCircleMapper to make your own map to fool around with.
New mapping from 10August 12amGMT to 11August 12pmGMT

Copy&paste 12.2n28.3w, 12.3n29.2w, 12.4n30.1w, 12.5n31.0w, 12.7n32.0w, 12.9n 33.0w, 13.1n34.0w, vxe, 9.6n13.5w, 9.8n15.0w, 9.9n16.5w, 10.0n18.0w, 10.1n19.5w, 10.2n20.5w, 10.3n21.5w into the GreatCircleMapper to make your own map to fool around with.

On both maps, the westernmost grouping of red dots represent 92L's path
and the easternmost grouping represent 93L's path
Member Since: August 21, 2007 Posts: 0 Comments: 4860
Quoting 69Viking:


What part of Australia are you in? I know it's winter over there, enjoy the cool weather while you can! Currently 91 with a heat index of 109 in NW Florida!

I am in Sydney Australia. I long for the summer. I may be moving to the Philippines in the next year, for health reasons.
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Quoting Neapolitan:
TIME has a worthwhile photo spread today titled "Picturing the American Drought".

An example: "'The Island,' a resort on Lake Travis, is normally a peninsula surrounded almost completely by water. The level of the Lake has dropped, and now it now sits on dry land, as do the neighboring boat docks."



Thanks for the link; that is just absolutely amazing.
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Thanks Dr. M.
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Quoting Neapolitan:
TIME has a worthwhile photo spread today titled "Picturing the American Drought".

An example: "'The Island,' a resort on Lake Travis, is normally a peninsula surrounded almost completely by water. The level of the Lake has dropped, and now it now sits on dry land, as do the neighboring boat docks."



Thanks for the link. That is truly amazing.
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Quoting AussieStorm:

Normally 1th 1st half of September is cooler than the 2nd half, I am looking forward to the 2nd half already. Have done so since halfway through Autumn.
thats when it starts to cool down for us as well mornings can be quite chilly by late sept daytime still warm till at least end of october
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Quoting hurricane23:


EURO has a huge 500mb trough off east coast next 10 days. Hard to see a US impact from anything out of the deep tropics.


Adrian, I understand your rooting for recurvature.. but it's about a week away for us to watch, still too early and even Dr. Masters himself said it's too early to pinpoint a future for both 92L and 93L. Emily was supposed to recurve (according to the GFS) north of PR, instead, it was extremely close to Florida, to the point where wind and rain glazed the coastline. Earl last year was expected to recurve around Bermuda, instead it recurved dangerously close to the US. Even Igor was supposed to recurve east of Bermuda, rather then a bit west of the island. Things change and models recrve storms wayy too early then what mother nature does. It just needs to be watched and not taken for granted that a trough is gonna save us every time. This isn't 2010, the blocking pattern is coming quickly according to the ensembles of the GFS and EURO. If you listened to Levis video yesterday, he explains a good point. I'm not rooting for a landfalling storm, but I know in reality, models and models and they can be wrong, and have been wrong in the past. So it's just a wait and see if the EURO could be right and a huge unseasonable trough develops. I seriously doubt it. However, everybody on US Coastline should be preparing for a very active season.
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Quoting WxLogic:
Appears we might have a 4th area to watch in front of 92L (may be by this weekend):





If it pans out then this disturbance could become our 3rd possible TD/TS to develop.


Quoting USAFwxguy:
12Z GFS sees a closed low is southern BoC at 18



[edit: it's a non-player]


Also note that closed area of low pressure in between the 2 highs, don't know if that is what Wxlogic is talking about.
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Quoting AussieStorm:

52.2°F here right now. getting down to 46°F overnight.


What part of Australia are you in? I know it's winter over there, enjoy the cool weather while you can! Currently 91 with a heat index of 109 in NW Florida!
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Quoting Neapolitan:
TIME has a worthwhile photo spread today titled "Picturing the American Drought".

An example: "'The Island,' a resort on Lake Travis, is normally a peninsula surrounded almost completely by water. The level of the Lake has dropped, and now it now sits on dry land, as do the neighboring boat docks."



Amazing photo yet tragic as well. Really shows the magnitude of the drought.
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Quoting KEEPEROFTHEGATE:
there is to be more cold yet

Normally the 1st half of September is cooler than the 2nd half, I am looking forward to the 2nd half already. Have done so since halfway through Autumn.
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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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