African Tropical Wave 98L Moving Over Cooler Waters

By: Dr. Jeff Masters , 2:23 PM GMT on July 23, 2013

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A strong and well-organized tropical wave that moved off the coast of Africa on Monday (98L) is located a few hundred miles south of the Cape Verde Islands and is moving west-northwest at 15 - 20 mph. Satellite images show that 98L has a decent amount of spin, but only a modest amount of heavy thunderstorms that have not changed much in intensity or areal coverage this morning. The wave is under a moderate 10 - 20 knots of wind shear, which will tend to allow slow development. A large amount of dry air lies to the north and west of 98L, and this dry air will likely interfere with development later this week. The SHIPS model predicts that wind shear will stay in the moderate range through Saturday. Ocean temperatures are barely adequate for development, about 26.5°C today, and will be below average over the region of ocean 98L will be traversing on Wednesday and Thursday, 25 - 26°C. These temperatures are very marginal for development. The Madden Julian Oscillation (MJO), a pattern of increased thunderstorm activity near the Equator that moves around the globe in 30 - 60 days, does not favor increased chances of Atlantic tropical cyclone formation this week. The reliable computer models for tropical cyclone genesis do not predict that 98L will develop this week. In their 8 am EDT Tuesday Tropical Weather Outlook, NHC gave 98L a 40% chance of developing into a tropical cyclone by Thursday. 98L should maintain a west-northwest track through the week, and may spread heavy rains and gusty winds to the northern Lesser Antilles Islands beginning on Saturday night or on Sunday.


Figure 1. Satellite image of 98L off the coast of Africa taken at 8 am EDT Tuesday July 23, 2013, with a satellite analysis of where dry air is, as well. A large amount of dry air lies to the north and west of 98L, and will likely interfere with development later this week. Image credit: University of Wisconsin CIMSS and NOAA/HRD.

Jeff Masters

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Quoting 2249. Hurricanes305:
Here is the MJO right in time for August. Hurricane season about to flip the switch. And I'm not liking our Atlantic High right now



Lmao at the downcasters who said no storms for the rest of the season.


This is probably one of the most relevant comments made this season on this blog and everyone should read it.

MJO is a huge factor here, especially in the formation of these early season cyclones here in July. This coupled with the abnormally strong high pressure pattern in the Atlantic and over the U.S. are two of the major large scale key players to be aware of this season.
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Quoting 2253. PensacolaDoug:


Last eve it was dying as it came thru... Eve before it came thru strong. Blew over everything on my patio and destroyed the 2nd umbrella this season. BBQ grill over as well.


I always like it when the chairs blow in the pool. Gave up on the umbrellas some time ago.
Member Since: August 13, 2007 Posts: 10 Comments: 4158
Quoting 2271. Hurricanes305:


Just a bit from the file that brought you Dorian it confirms she has moved 0.1 N and 0.9W she in no real hurry to climb latitudes into cool temperature which may explain the deepening of her so quickly.


Good point........These storms sometimes amaze us when the seem to navigate through perceived obstacles in an effort to stay alive and thrive; amazing thing to watch.
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2275. Grothar
Quoting 2255. hurricanes2018:
someone need to update this!!


You mean make it more West Northwest??
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low level banding trying to develop with system over GA and SC, center of low about to emerge into the Atlantic and on the eastern side of circulation convection is developing quickly, but not until system is fully over water will development begin to occur, so another 12 hours before anything occurs.
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Quoting 2262. Hurricanes305:


You missed it we have Dorian already at 1006mb Sal is not a problem just a little shear for the sw and cooler ssts. After that a small system like this will have a chance of bulking up and becoming a very potent system for the Northern Antilles.


Re read my comment I edited that in when I saw the renumber on tcf.
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Quoting 2252. weathermanwannabe:


And jogging towards the West too.........


Just a bit from the file that brought you Dorian it confirms she has moved 0.1 N and 0.9W she in no real hurry to climb latitudes into cool temperature which may explain the deepening of her so quickly.
Member Since: May 25, 2012 Posts: 0 Comments: 2043
Quoting 2228. pcola57:


Morning Doug..
Did you get any of that weather that moved through last eve..
I lost some foilage..
Weird wind..


Yeah it was windy but I was glad the heavy rain only lasted a few minutes. Storm total for my place was half an inch. We're still under a 50% chance of storms today before it looks like we'll dry out a bit.
Member Since: August 25, 2006 Posts: 1 Comments: 3078
Worth noting here for everyone:

If the storm is alive after 50W and manages to strengthen by day four before shear increases, depending on how quickly it strengthens this could cause fairly large scale track changes due to deep layer steering influence. A strong storm will have a much higher chance of re-curving or going to the East Coast or Florida.

The past couple of years the models have been better about catching that sort of thing but when it becomes a situation of intensity guiding the track you cannot hope for very much. So folks on the east coast and florida, provided the system does not die before 50W (due to shear or inflow being choked out) you need to watch this very carefully. Should a northward jog occur near the end of the forecast period directing this toward the East Coast there would not be a heck of alot of time to react.

Figured I would mention this.
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2268. VR46L
Quoting 2254. SouthernIllinois:

So you are accucasting?


LOL

maybe so !

Just kind of think that he might be strong enough when he hits the shear to make it out pretty much alive and if he does he could be a landfall Storm ...
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Quoting 2260. stormwatcherCI:
That's what I thought but since I really do not know anything I kept my mouth shut :)

lol
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Quoting 2257. islander101010:
hebert box 2 near the yucatan is for later in the season i believe


A storm can go through them at any time during the season but you are correct; many of the later season storms can originate in the SW Caribbean and enter Box 2 on the way to the Gulf.
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Quoting 2258. TheDawnAwakening:
Large circulation associated with disturbance near SC coastline and GA coastline. Broad rotation associated with system and low level convergence is strengthening out ahead of system's low. Center appears to be over Savannah, GA.
I do not see anything spinning there
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Quoting 2239. Neapolitan:
2001 had three.
Thanks sir,I know you mean 2011 :D
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Quoting 2247. DataNerd:
Hello again all.

Good news is TD4 is now out from under meteostat 8 coverage and we now can get real imagery.

And what we see this morning rather troubling, it looks very much like the storm is escalating rather quickly.
The low level center has become significantly deeper since this morning with a tight thunderstorm core over it. The wind field is currently expanding rather rapidly, and so are the thunderstorms, there was even an earlier indication of a very small cdo feature though that is gone now.

Visible satellite bears this out:


I don't expect too much of an increase in strength just yet, because of the fact that the system is still not quit far enough out into the Atlantic and there is alot of SAL right now, however if this trend doesn't change you may see Dorian later.

Just as easily the cooler waters and/or SAL could choke off inflow at anytime and kill the thunderstorm core which would essentially end this. I give it about 50/50 at this early developmental stage.

At 5 days its anyone's ball game, we will have to see how the shear forecast evolves by that time before we know if this will pose a threat to the U.S.


You missed it we have Dorian already at 1006mb Sal is not a problem just a little shear for the sw and cooler ssts. After that a small system like this will have a chance of bulking up and becoming a very potent system for the Northern Antilles.
Member Since: May 25, 2012 Posts: 0 Comments: 2043
@2245:
Normally he is the first but Thing 342 beat him this time.
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Quoting 2252. weathermanwannabe:


And jogging towards the West too.........
That's what I thought but since I really do not know anything I kept my mouth shut :)
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Quoting 2251. indianrivguy:


1935


Thank you our Florida History Expert......I am making the correction below now.............. :)
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Large circulation associated with disturbance near SC coastline and GA coastline. Broad rotation associated with system and low level convergence is strengthening out ahead of system's low. Center appears to be over Savannah, GA.
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hebert box 2 near the yucatan is for later in the season i believe
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Quoting 2247. DataNerd:
Hello again all.

Good news is TD4 is now out from under meteostat 8 coverage and we now can get real imagery.

And what we see this morning rather troubling, it looks very much like the storm is escalating rather quickly.
The low level center has become significantly deeper since this morning with a tight thunderstorm core over it. The wind field is currently expanding rather rapidly, and so are the thunderstorms, there was even an earlier indication of a very small cdo feature though that is gone now.

Visible satellite bears this out:


I don't expect too much of an increase in strength just yet, because of the fact that the system is still not quit far enough out into the Atlantic and there is alot of SAL right now, however if this trend doesn't change you may see Dorian later.

Just as easily the cooler waters and/or SAL could choke off inflow at anytime and kill the thunderstorm core which would essentially end this. I give it about 50/50 at this early developmental stage.

At 5 days its anyone's ball game, we will have to see how the shear forecast evolves by that time before we know if this will pose a threat to the U.S.
Too late. It is now TS Dorian. Take another look at SAL. Not much left.
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someone need to update this!!
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Quoting 2228. pcola57:


Morning Doug..
Did you get any of that weather that moved through last eve..
I lost some foilage..
Weird wind..


Last eve it was dying as it came thru... Eve before it came thru strong. Blew over everything on my patio and destroyed the 2nd umbrella this season. BBQ grill over as well.
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Quoting 2248. VR46L:
I am going to hold back on the downcasting at the moment
He looks great considering he is in cooler water .. neat and Compact

developing Convection



And jogging towards the West too.........
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Quoting 2236. weathermanwannabe:
An issue related to the Hebert Box trajectory storms (assuming they make landfall) and their approaches to Bahamas/Florida (Box 1) or entry into the Gulf of Mexico (Box 2) is the very warm waters whether over the Florida Straits/Gulf stream (Box 1) or the eddies/warm pools in the Gulf (Box 2). That factor often gives them the extra kick that can cause increased strengthening or a rapid intensification event before landfall.

We all know that drill (think Andrew) and I would not be surprised if the Great Labor Day Hurricane in the Keys in the 20's got an extra kick from the Gulf Stream before hitting the keys. Not saying that it will happen with Dorian but just noting how dangerous Florida and Gulf storms can because of this potential RI issue if a warm pool coincides with an unexpected drop in sheer.


1935
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2250. KEEPEROFTHEGATE (Mod)
we have an active storm in the basin

things are to pick up from here till its declassified
or landfalls which ever comes first
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Here is the MJO right in time for August. Hurricane season about to flip the switch. And I'm not liking our Atlantic High right now



Lmao at the downcasters who said no storms for the rest of the season.
Member Since: May 25, 2012 Posts: 0 Comments: 2043
2248. VR46L
I am going to hold back on the downcasting at the moment
He looks great considering he is in cooler water .. neat and Compact

developing Convection

Member Since: March 1, 2012 Posts: 0 Comments: 6950
Hello again all.

Good news is TD4 is now out from under meteostat 8 coverage and we now can get real imagery.

And what we see this morning rather troubling, it looks very much like the storm is escalating rather quickly.
The low level center has become significantly deeper since this morning with a tight thunderstorm core over it. The wind field is currently expanding rather rapidly, and so are the thunderstorms, there was even an earlier indication of a very small cdo feature though that is gone now.

Visible satellite bears this out:


I don't expect too much of an increase in strength just yet, because of the fact that the system is still not quit far enough out into the Atlantic and there is alot of SAL right now, however if this trend doesn't change you may see Dorian later.

Just as easily the cooler waters and/or SAL could choke off inflow at anytime and kill the thunderstorm core which would essentially end this. I give it about 50/50 at this early developmental stage.

At 5 days its anyone's ball game, we will have to see how the shear forecast evolves by that time before we know if this will pose a threat to the U.S.

Edited, there was another renumber, so based on the deepening trend NHC went ahead and went with Dorian.

Pretty quick but given the Satellite appearance now not unexpected.

We will have to see if the storm can maintain its inflow now.
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Two TS before August that are CVs....
I'm not complaining but statistically, this could be a rough season.
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2244. SLU
4-0-0 and all 4 are fully tropical with 2 in the deep tropics by July 24th. Not too bad.

24/1145 UTC 14.2N 28.7W T2.0/2.0 04L -- Atlantic
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Quoting 2237. rhaynes7:


There were 3 in the 2011 Hurricane Season.
You are right,thanks for the clarification :D the month of the dry Don.
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Quoting 2233. hurricanes2018:
that crazy the water temp are warmer more north!


Except for where Dorian is right now most of the tropics are starting to warm up as well as off the East coast. this should continue to warm up for the peak. Also moisture in the Atlantic is starting to increase in general. A sign that the MJO is coming and we could see development right after Dorian. For early August as upward motion returns to our basin.
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Dorian..:
Member Since: August 14, 2010 Posts: 10 Comments: 17483
lets not get tropical storm DORIAN then she on the east coast.. the water is warmer there.
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Quoting 2234. allancalderini:
For the first time I believe since 2008 that we have two name storms in July.
2001 had three.
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2238. barbamz
Quoting 2215. Neapolitan:
AL, 04, 2013072412, , BEST, 0, 140N, 290W, 35, 1006, TS, 34, NEQ, 30, 0, 0, 30, 1012, 150, 20, 0, 0, L, 0, , 0, 0, DORIAN, D,


Wow, it's a boy!

(Sorry, couldn't resist :)
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Quoting 2234. allancalderini:
For the first time I believe since 2008 that we have two name storms in July.


There were 3 in the 2011 Hurricane Season.
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An issue related to the Hebert Box trajectory storms (assuming they make landfall) and their approaches to Bahamas/Florida (Box 1) or entry into the Gulf of Mexico (Box 2) is the very warm waters whether over the Florida Straits/Gulf stream (Box 1) or the eddies/warm pools in the Gulf (Box 2). That factor often gives them the extra kick that can cause increased strengthening or a rapid intensification event before landfall.

We all know that drill (think Andrew) and I would not be surprised if the Great Labor Day Hurricane in the Keys in 1935 got an extra kick from the Gulf Stream before hitting the keys. Not saying that it will happen with Dorian but just noting how dangerous Florida and Gulf storms can because of this potential RI issue if a warm pool coincides with an unexpected drop in sheer.
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Good morning Dorian. I go on vacation for 5 days and here you are waiting. Go away! And good morning bloggers all!
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For the first time I believe since 2008 that we have two name storms in July.
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that crazy the water temp are warmer more north!
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2232. KEEPEROFTHEGATE (Mod)
T.C.F.W.
04L/TD/XX/CX
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Are 4th name storm is here we are now tied with 2012
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Quoting 2212. Thing342:
AL, 04, 2013072412, , BEST, 0, 140N, 290W, 35, 1006, TS, 34, NEQ, 30, 0, 0, 30, 1012, 150, 20, 0, 0, L, 0, , 0, 0, DORIAN, D,

Interesting it puts it where that N band is near that dry spot movement WNW and now TS hmm I wonder what NHC will say in 11am advisory
Member Since: June 13, 2009 Posts: 2 Comments: 12479
Quoting 2215. Neapolitan:
AL, 04, 2013072412, , BEST, 0, 140N, 290W, 35, 1006, TS, 34, NEQ, 30, 0, 0, 30, 1012, 150, 20, 0, 0, L, 0, , 0, 0, DORIAN, D,


It has moved 0.1N and 0.9W in about 4 hours.
Member Since: May 25, 2012 Posts: 0 Comments: 2043
2228. pcola57
Quoting 2225. PensacolaDoug:
Dorian at 11AM I do believe. (I have been wrong before however)


Morning Doug..
Did you get any of that weather that moved through last eve..
I lost some foilage..
Weird wind..
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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.