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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West...and nicely tightly clustered together??

Member Since: August 19, 2006 Posts: 13 Comments: 14452


Member Since: August 19, 2006 Posts: 13 Comments: 14452
Quoting pottery:

You just like to be 'out on a limb', dont you?



I was going to go with 39%, but I like to stretch the limit.
Member Since: July 17, 2009 Posts: 69 Comments: 25369
Hello Levi, your thoughts on the latest ECMWF model run???
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Quoting OracleDeAtlantis:
That's half of Emily you're looking at there. Show some respect ...
Or, the remnants could just hang around and, with the right steering conditions, we *could* have a vorticity advection boost for 92L or 93L...
(Is quite possible, really.)
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Quoting USAFwxguy:
You see now on the next frame that the 1016 isotach has lifted and is now out in the Atlantic. That means the TC should generally headed in the direction of the Bahamas, and if the trough remains it should recurve before striking the CONUS.



Isobar.
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Quoting xtremeweathertracker:
Looking at this last image is shows 93L possible impacting Florida if you look closely the closest isobar is still at 1016 keeping 93L moving westward!!!IMO


hmmm..let me find out this might be the 18Z run again like the GFS..
Member Since: August 19, 2006 Posts: 13 Comments: 14452
The recurving should start in the next few days



Member Since: July 17, 2009 Posts: 69 Comments: 25369
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.
That's half of Emily you're looking at there. Show some respect ...

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Hi! I haven't posted in a very long time. I'm glad to see the blog is still running and everything. 2011 Hurricane Season is going to be active. I hope everyone is prepared.

92 and 93L are certainly very interesting. Wether they are fish or not, or whatever the situation may be, they can at least be used to futher the common knowledge of meteorology. Thats the way I see it.
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Looking at this last image is shows 93L possible impacting Florida if you look closely the closest isobar is still at 1016 keeping 93L moving westward!!!IMO
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Quoting USAFwxguy:
You see now on the next frame that the 1016 isotach has lifted and is now out in the Atlantic. That means the TC should generally headed in the direction of the Bahamas, and if the trough remains it should recurve before striking the CONUS.

*Some* of that effect may simply be the diurnal cycle in MSLP.
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295. srada
StormW?
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Quoting atmoaggie:
Re 1016: Quite possibly true...except that would be isobar.
;-)


hmmmm, interesting
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Quoting Grothar:
I give them both 40%.






You just like to be 'out on a limb', dont you?
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289. SLU
918

WHXX01 KWBC 111846

CHGHUR

TROPICAL CYCLONE GUIDANCE MESSAGE

NWS NATIONAL HURRICANE CENTER MIAMI FL

1846 UTC THU AUG 11 2011



DISCLAIMER...NUMERICAL MODELS ARE SUBJECT TO LARGE ERRORS.

PLEASE REFER TO NHC OFFICIAL FORECASTS FOR TROPICAL CYCLONE

AND SUBTROPICAL CYCLONE INFORMATION.



ATLANTIC OBJECTIVE AIDS FOR



DISTURBANCE INVEST (AL932011) 20110811 1800 UTC



...00 HRS... ...12 HRS... ...24 HRS. .. ...36 HRS...

110811 1800 110812 0600 110812 1800 110813 0600



LAT LON LAT LON LAT LON LAT LON

BAMS 10.8N 24.0W 11.4N 26.3W 12.0N 28.8W 12.7N 31.6W

BAMD 10.8N 24.0W 11.1N 26.5W 11.6N 28.9W 12.1N 31.3W

BAMM 10.8N 24.0W 11.3N 26.7W 11.9N 29.2W 12.4N 32.1W

LBAR 10.8N 24.0W 11.1N 27.2W 11.7N 30.8W 12.0N 34.3W

SHIP 25KTS 35KTS 46KTS 55KTS

DSHP 25KTS 35KTS 46KTS 55KTS



...48 HRS... ...72 HRS... ...96 HRS. .. ..120 HRS...

110813 1800 110814 1800 110815 1800 110816 1800



LAT LON LAT LON LAT LON LAT LON

BAMS 13.4N 35.1W 13.8N 43.3W 13.2N 50.9W 13.5N 57.2W

BAMD 12.7N 33.8W 14.2N 38.2W 16.2N 41.2W 19.0N 43.4W

BAMM 13.0N 35.1W 14.0N 41.5W 15.2N 47.2W 17.1N 52.7W

LBAR 12.4N 37.9W 12.8N 44.2W 12.8N 48.8W .0N .0W

SHIP 61KTS 71KTS 74KTS 74KTS

DSHP 61KTS 71KTS 74KTS 74KTS



...INITIAL CONDITIONS...

LATCUR = 10.8N LONCUR = 24.0W DIRCUR = 280DEG SPDCUR = 15KT

LATM12 = 10.4N LONM12 = 21.0W DIRM12 = 278DEG SPDM12 = 15KT

LATM24 = 10.0N LONM24 = 18.0W

WNDCUR = 25KT RMAXWD = 45NM WNDM12 = 20KT

CENPRS = 1011MB OUTPRS = 1013MB OUTRAD = 150NM SDEPTH = M

RD34NE = 0NM RD34SE = 0NM RD34SW = 0NM RD34NW = 0NM



$$

NNNN





094

WHXX01 KWBC 111847

CHGHUR

TROPICAL CYCLONE GUIDANCE MESSAGE

NWS NATIONAL HURRICANE CENTER MIAMI FL

1847 UTC THU AUG 11 2011



DISCLAIMER...NUMERICAL MODELS ARE SUBJECT TO LARGE ERRORS.

PLEASE REFER TO NHC OFFICIAL FORECASTS FOR TROPICAL CYCLONE

AND SUBTROPICAL CYCLONE INFORMATION.



ATLANTIC OBJECTIVE AIDS FOR



DISTURBANCE INVEST (AL922011) 20110811 1800 UTC



...00 HRS... ...12 HRS... ...24 HRS. .. ...36 HRS...

110811 1800 110812 0600 110812 1800 110813 0600



LAT LON LAT LON LAT LON LAT LON

BAMS 13.3N 35.1W 14.3N 37.8W 15.2N 40.9W 16.1N 44.6W

BAMD 13.3N 35.1W 14.1N 38.0W 14.9N 41.2W 15.5N 44.5W

BAMM 13.3N 35.1W 14.2N 37.7W 15.1N 40.9W 16.0N 44.4W

LBAR 13.3N 35.1W 13.9N 37.8W 14.8N 41.3W 15.5N 44.9W

SHIP 25KTS 29KTS 36KTS 44KTS

DSHP 25KTS 29KTS 36KTS 44KTS



...48 HRS... ...72 HRS... ...96 HRS. .. ..120 HRS...

110813 1800 110814 1800 110815 1800 110816 1800



LAT LON LAT LON LAT LON LAT LON

BAMS 17.5N 48.6W 21.6N 56.5W 26.3N 62.9W 32.0N 65.7W

BAMD 16.2N 47.8W 17.7N 53.7W 19.2N 58.3W 20.1N 62.6W

BAMM 17.2N 48.0W 20.3N 54.9W 24.3N 60.2W 28.7N 64.0W

LBAR 16.2N 48.5W 17.8N 55.0W 18.7N 58.8W .0N .0W

SHIP 52KTS 61KTS 58KTS 55KTS

DSHP 52KTS 61KTS 58KTS 55KTS



...INITIAL CONDITIONS...

LATCUR = 13.3N LONCUR = 35.1W DIRCUR = 280DEG SPDCUR = 10KT

LATM12 = 12.9N LONM12 = 33.0W DIRM12 = 282DEG SPDM12 = 10KT

LATM24 = 12.5N LONM24 = 31.0W

WNDCUR = 25KT RMAXWD = 75NM WNDM12 = 25KT

CENPRS = 1010MB OUTPRS = 1012MB OUTRAD = 300NM SDEPTH = S

RD34NE = 0NM RD34SE = 0NM RD34SW = 0NM RD34NW = 0NM



$$

NNNN



Member Since: July 13, 2006 Posts: 12 Comments: 4859
I give them both 40%.





Member Since: July 17, 2009 Posts: 69 Comments: 25369
287. SLU
Quoting chriss1241:
Going to St. Lucia Sat. 8/13 - 8/20 for my honeymoon. Have insurance on the trip, but by the time anything develops out of 92l or 93l, we will be on our way (though we can cut the trip short and get some money back).

Anyway, though probably not enough info. yet, what are some thoughts on a depression, storm, or hurricane hitting or coming close to St. Lucia?

Thanks

Chris


Congrats!

Well Chris, it's too early to tell but if anything does happen the hotels have excellent disaster emergency plans and you will be well taken care of.

:)
Member Since: July 13, 2006 Posts: 12 Comments: 4859
Quoting debrisball:
Feeling likeAndy Dufrene right now crawling through the 500 yards of raw sewage about to get to the promiseland









Not going to put a dent in the drought by any means, but when you've had over 40 consecutive 100+ degree days (today's rain may have a chance to end the streak 2 days short of the record, we'll see) and over 2 months without a drop of rain it's pretty exciting to even see that coming on the radar.


Looks like it is falling apart...
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Quoting Twinkster:


Thus starts the blocking pattern shown clearly on the GFS and EURO ensembles.. 92L may just recurve before the high builds but I'm not so sure about 93L.
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Feeling like Andy Dufrene right now crawling through the 500 yards of raw sewage about to get to the promiseland









Not going to put a dent in the drought by any means, but when you've had over 40 consecutive 100 degree days (today's rain may have a chance to end the streak 2 days short of the record, we'll see) and over 2 months without a drop of rain it's pretty exciting to even see that coming on the radar.
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Quoting USAFwxguy:
Still a battle between the trough and high. Note the 1016 isotach stretching across Fl into AL. Wouldn't expect much movement beyond the 1016 line with a shallow system, although the trough will always exert some amount of steering influence.

Re 1016: Quite possibly true...except that would be isobar.
;-)
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Quoting HurricaneDean07:
i'd put 93L's developing center around 11.5 N; 27.5 W

ATCF says 10.8N, 24.0W
Member Since: November 8, 2009 Posts: 4 Comments: 13457
Quoting chriss1241:
Going to St. Lucia Sat. 8/13 - 8/20 for my honeymoon. Have insurance on the trip, but by the time anything develops out of 92l or 93l, we will be on our way (though we can cut the trip short and get some money back).

Anyway, though probably not enough info. yet, what are some thoughts on a depression, storm, or hurricane hitting or coming close to St. Lucia?

Thanks

Chris

Enjoy your Honeymoon, and Congratulations!
St. Lucia is Fabulous.
Have a great time, and let the Gods deal with the weather...
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AL, 92, 2011081112, , BEST, 0, 131N, 340W, 25, 1010, LO, 0, , 0, 0, 0, 0, 1013, 300, 75, 0, 0, L, 0, , 0, 0, INVEST, S,

AL, 93, 2011081118, , BEST, 0, 108N, 240W, 25, 1011, LO, 34, NEQ, 0, 0, 0, 0, 1013, 150, 45, 0, 0, L, 0, , 0, 0, INVEST, M,
Member Since: November 8, 2009 Posts: 4 Comments: 13457
Quoting USAFwxguy:
Still a battle between the trough and high. Note the 1016 isotach stretching across Fl into AL. Wouldn't expect much movement beyond the 1016 line with a shallow system, although the trough will always exert some amount of steering influence.


I appreciate your insight and agree with you entirely as long as these systems remain relatively weak as the models indicate the high will continue to exert more of a direct influence than the trough!!!IMO
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Hi Nar.
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i'd put 93L's developing center around 11.5 N; 27.5 W
Member Since: October 3, 2010 Posts: 40 Comments: 4129
Going to St. Lucia Sat. 8/13 - 8/20 for my honeymoon. Have insurance on the trip, but by the time anything develops out of 92l or 93l, we will be on our way (though we can cut the trip short and get some money back).

Anyway, though probably not enough info. yet, what are some thoughts on a depression, storm, or hurricane hitting or coming close to St. Lucia?

Thanks

Chris
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USAFwxguy where you stationed at? By the looks of the beaches in your picture I'm guessing somewhere in Florida or the Caribbean!
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Nice post, Squid!
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265. JRRP

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When describing this blog to other people

I like to use the analogy of getting six people together outside and asking them what color the sky is. Odds are you will get at least four different answers (light blue, blue, sky blue etc.)

Now take that same type of thought process and multiply it by thousands of participants who are extremely passionate about one specific subject.... To see the net effect, all you have to do is read a couple pages worth of posts here.

When you have folks from as many different ages, geographies, and backgrounds as we do here you are never going to win an argument. Sure there will be others who agree with you and others who disagree just the same. To try and argue your point, or just continually repost it is a waste of space, and will quickly get you put on a lot of ignore lists. To try and label an individual as a "caster" of any form will get you to the same end point pretty quickly as well.

Put your opinion/comment/question out in the blog once. If someone wants to comment great, if not move on (that is what I do at least).

While this is a weather blog everyones reason for being here is not the same. You have those that love to watch the models and watch a blob of clouds slowly coalesce into a storm, then there are those that find the aspect of a hurricane exciting, those who keep an eye on it for an early heads up, or those who have to watch it because preparedness is part of their employers expectation of them, and last but not least those who wish to judge a storms probability based upon empirical or non-empirical data, climatology, or just good ole "gut feel" or a possibly little of all of the above.

Bottom line is arguing about where a storm is going to go or not go, about which model is correct five days out, or what your interpretation of climatology is predicting gets you no farther than where you started off at.

I personally enjoy the contributors who try and post relevant information and while they may comment on it, they do not try to force feed it to me in large doses. Anyone who presents a calm rational debate on why they think the storm is going to do whatever; I will gladly read and consider. That does not mean I have to comment on it, if in the end I choose to think contrary to what they do.

For those who think a storm is not relevant just because it is not a threat to you (and feel the need to say so), there is a good chance that it is relevant to someone reading the blog.

I hope that everyone who finds the aspect of a hurricane exciting and wants to experience one gets a chance to do so before they die, without loss of life, property, or loved ones. Naturally, there are a lot of us here who do not wish to ever go through another one if we can help it. For those that do however, it might behoove you to listen to some of the old dogs on here who have been in a storm or two. Especially the ones who really suffered and lost it all, I am not talking about someone who needed a new roof and did not have power for a week (yeah it sucks). I am speaking specifically to the ones who have truly lost it all (homes, jobs, family, pets, finances, mental facilities) and there are many on here who have done so (you just might change your mind). They just might be able to teach you a thing or two, and you in turn by posting relative information and insight just might be able to give them a heads up, just in case they ever need it again.

Just something to consider, I will now put my soapbox back in th closet for the year....


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Quoting asgolfr999:


As for which pattern to watch for, I wouldn't watch any of them. They are all different both in set up and outcome. A series of identical setups and identical conditions often, nay always, brings different results.

With respect, to be sitting in Wilmington now and looking at 92 and 93 with more than passing interest is a complete waste of what I am sure is your valuable time.

Now, if the models point at your street 7 days from now, I would have a closer look, and in 10...well in ten I would show the concern that you have now...lol

Looooong way to go before anyone worries about where, if anywhere, these babies are going. Even the professionals are about two percentage points away from clueless right now.

Enjoy the watchful speculation though, lotta people here for just that purpose.



All due respect however, 7 days from now would be quite a bit late. This is the GFS 7 days from now. 92L in full re-curve and 93L traversing the islands.

Member Since: August 19, 2005 Posts: 5 Comments: 5043
262. JRRP
Quoting USAFwxguy:
Here is the ECMWF, well respected model, that shows 93L on a more southerly route and rather weak being guided west by the high to its north. Note the 1016 isotach just to the north.



Here is the 500mb signature with a tiny closed isobar:

93L stronger than 00z
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@ Pottery Lol! I should have figured that someone would say that.
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Have to head back to work now so will catch up later.
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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.