Two African waves worth mentioning

By: Dr. Jeff Masters , 3:51 PM GMT on July 18, 2009

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There are two African tropical waves worth mentioning today, though neither looks particularly threatening. A tropical wave near 12N 45W, about 1200 miles east of the Lesser Antilles Islands (97 L), is moving west at 15 - 20 mph. This wave is now surrounded by an area of very dry air from the Sahara Desert. The dry air has disrupted most of the wave's heavy thunderstorm activity, and will continue to make it difficult for this system to develop over the next 2 - 3 days. Wind shear is a modest 10 knots over the disturbance, and should remain in the moderate 10 - 15 knot range over the next 2 - 3 days. Thereafter, shear is expected to rise to 20 - 30 knots. This morning's QuikSCAT pass showed no evidence of a surface circulation, and only a modest wind shift associated with 97L. The National Hurricane Center is giving this system a low (less than 30% chance) of developing into a tropical depression in the next 48 hours.

A second tropical wave now approaching the northern Lesser Antilles Islands is under 30 knots of wind shear, and has little prospect of development due to the high shear. However, the wave will bring heavy rain to the islands over the next two days.

None of the computer models are forecasting tropical storm development over the next seven days, and I don't expect either of the two African waves mentioned today to develop over at least the next three days.


Figure 1. Current satellite image of African wave 97L, 1200 miles east of the Lesser Antilles Islands.

I'll have an update Sunday afternoon.
Jeff Masters

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Quoting btwntx08:

yup 97L is too far to the left
yeah because its going faster than a cruise ship, 20+mph.
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the blob is heading for S-FL and 97L is heading for Cozumel, imo.
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Quoting canesrule1:
never heard of that theory?
Weak tropical cyclones tend to be steered more by lower-level winds.
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Quoting BurnedAfterPosting:
Weaker systems follow the lower level flow, that doesnt always mean it will move west

Stronger systems are steered by mid and upper level layers

Ok. I get it now. The 700-850mb steering says it will go into the Caribbean
Member Since: May 16, 2009 Posts: 1 Comments: 1231
Quoting Cotillion:
Cleared up, blue skies... England effectively 483-5 against the Aussies... reasons to smile.

Be more interesting in a few hours to see what 97L does, especially as it gets closer to the warmer waters.

wish they would hurry up and declare
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Quoting IKE:


Don't think that will happen.

By tomorrow morning the western wave should be heading for PR and the other one should be near 50W.
yeah but if they join the blob will get a low and it will have a lot of convection, so i would probably say a TD quicker but that just my opinion.
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193. HadesGodWyvern (Mod)
Japan Meteorological Agency

Tropical Disturbance Summary (1200z 18JUL)
=========================================
At 21:00 PM JST, Low Pressure Area (1010 hPa) located at 10.0N 136.0E has 10 minute sustained winds of 15-20 knots and is reported as almost stationary

---
next possible system..
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Weaker systems follow the lower level flow, that doesnt always mean it will move west

Stronger systems are steered by mid and upper level layers
look like a low level spin on sat hiding under the mid-upper level clouds around 12n 44.5w movement west
Link
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Quoting wunderkidcayman:
can someone send me the shear map and the nogap model
Click on the tropical/hurricane link at the top left of the page and scroll down. All links are there for you.
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Quoting weatherwatcher12:

I thought if a storm stays weak it goes west
never heard of that theory?
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188. IKE
Quoting 7544:
what happens if the two join forces will it be a td faster


Don't think that will happen.

By tomorrow morning the western wave should be heading for PR and the other one should be near 50W.
Member Since: June 9, 2005 Posts: 23 Comments: 37860
They need to move the floater
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Quoting hunkerdown:
All depends on the steering and features in the various layers.

Doesn't the current steering bring it into the Caribbean . That's what the 700-850mb steering current says
Member Since: May 16, 2009 Posts: 1 Comments: 1231
Alll I have to say about 97L right now, think of pre-Felix and Pre-Dolly.
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Quoting 7544:


looks like 97l is very close to inching its way into the wave could these 2 might connect and become one getting intresting to watch maybe by tonight we could see two waves become one
yeah, i asked Patrap on that scenario earlier, there could be possibility because 97L is going at 20mph, remember.
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can someone send me the shear map and the nogap model
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Quoting wunderkidcayman:
I see a spin in 97l at 11n 47w on the vis sat
Link


looks closer to 45W, there is definitely some cyclonic turning with this wave. Adding that to the fact that shear is getting more favorable in front of it
The two tone talk!
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178. 7544
what happens if the two join forces will it be a td faster
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Quoting weatherwatcher12:

I thought if a storm stats weak it goes west
All depends on the steering and features in the various layers.
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Quoting BurnedAfterPosting:


if the wave at 60W goes into the Caribbean, then yes it does have a shot to develop
but its not going to go to the caribbean, imo. You can't forget about the TUTT.
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Wunderkid I see it also thanks
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Quoting Acemmett90:

The straw is alomost there
yup
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Quoting canesrule1:
it might develop but not with that shear thats forecasted in the bahamas if this does develop ill say a TS for the areas of S-FL, if that shear were to stay in the caribbean which it wont then i would say maybe a CAT 1 or 2 but remember its still a blob those come and go.

I thought if a storm stays weak it goes west
Member Since: May 16, 2009 Posts: 1 Comments: 1231
Quoting hunkerdown:
Not sure I would go that far...maybe the path only.
yeah the path not the CAT 5 part maybe a CAT 3 at the most.
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Quoting btwntx08:
now i think the the wave at 60w has a chance to develop but its just a wait and see
it might develop but not with that shear thats forecasted in the bahamas if this does develop ill say a TS for the areas of S-FL, if that shear were to stay in the caribbean which it wont then i would say maybe a CAT 1 or 2 but remember its still a blob those come and go.
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Cleared up, blue skies... England effectively 483-5 against the Aussies... reasons to smile.

Be more interesting in a few hours to see what 97L does, especially as it gets closer to the warmer waters.
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I see a spin in 97l at 11n 47w on the vis sat
Link
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The vorticity on 97L has become more concentrated:

Member Since: May 16, 2009 Posts: 1 Comments: 1231
Quoting canesrule1:
yup, this is going to be Dean jr.
Not sure I would go that far...maybe the path only.
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166. 7544
Quoting canesrule1:
its going with the TUTT straight to S-FL but 97L will go to the Caribbean, though, so right now the invest is what we should keep two eyes on and one eye with the blob.


looks like 97l is very close to inching its way into the wave could these 2 might connect and become one getting intresting to watch maybe by tonight we could see two waves become one
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Still hearing passenger jet traffic overhead. *amazed* Not sure if they are taking off or landing.

Pressure keeps dropping. 986 hPa at Waglan

24 hour time series of sea level pressure for HK
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Quoting btwntx08:
now i think the the wave at 60w has a chance to develop but its just a wait and see


if the wave at 60W goes into the Caribbean, then yes it does have a shot to develop
163. IKE
12Z NOGAPS aims 97L into the Caribbean. Aims the wave near 60W on a WNW path for the next 2-3 days.
Member Since: June 9, 2005 Posts: 23 Comments: 37860
Quoting BurnedAfterPosting:
the chances of 97L developing to me have increased now looking at the shear, it is staying south, which is what we all said it needed to do. Moving basically due west, the shear is favorable all the way to the Caribbean and will continue to get better
yup, this is going to be Dean jr.
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exactly canesrule
the chances of 97L developing to me have increased now looking at the shear, it is staying south, which is what we all said it needed to do. Moving basically due west, the shear is favorable all the way to the Caribbean and will continue to get better
Quoting BurnedAfterPosting:
no it didnt Ace, I still think the wave at 60W has to go into the Caribbean if it wasnt to develop

If it goes north of the Islands, it will be going where the shear is the highest

Shear is lifting out of the Caribbean, and going north of the Islands
its going with the TUTT straight to S-FL but 97L will go to the Caribbean, though, so right now the invest is what we should keep two eyes on and one eye with the blob.
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156. HadesGodWyvern (Mod)
LOL DaaiTou

have fun.
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has wind shear begun to decrease in the vicinity of the tropical wave near 60W or in the carribbean if not when is it projected to decrease
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look i don't want to be a downcaster but with all the blobs we've had this year that have died, i cant help to think this thing over the USVI will die, and if im wrong ill eat my crow.
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no it didnt Ace, I still think the wave at 60W has to go into the Caribbean if it wants to develop

If it goes north of the Islands, it will be going where the shear is the highest

Shear is lifting out of the Caribbean, and going north of the Islands

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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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