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 Vortex95:
Herbert is not ammused Orca


ROFL, its just my S&I acting up....
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237. Seflhurricane 5:27 PM GMT on July 18, 2009
Quoting KEEPEROFTHEGATE:


fading away
what is fading away????
Action: Quote | Ignore User

can ya see it now
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13 minutes ago, clouds are diminishing, looks to be fading, imo...
Link
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No change in tune at 2.
000
ABNT20 KNHC 181731
TWOAT
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
200 PM EDT SAT JUL 18 2009

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

A TROPICAL WAVE LOCATED NEAR THE LESSER ANTILLES IS PRODUCING
NUMEROUS SHOWERS AND THUNDERSTORMS AS IT INTERACTS WITH AN
UPPER-LEVEL TROUGH. WHILE RAINFALL ASSOCIATED WITH THE WAVE MAY BE
LOCALLY HEAVY AT TIMES...UPPER-LEVEL WINDS ARE NOT CURRENTLY
CONDUCIVE FOR SIGNIFICANT DEVELOPMENT OF THE SYSTEM AS IT MOVES
WEST-NORTHWESTWARD AT AROUND 15 MPH. THERE IS A LOW CHANCE...LESS
THAN 30 PERCENT...OF THIS SYSTEM BECOMING A TROPICAL CYCLONE DURING
THE NEXT 48 HOURS.

A TROPICAL WAVE LOCATED ABOUT 1000 MILES EAST OF THE WINDWARD
ISLANDS CONTINUES TO PRODUCE DISORGANIZED SHOWER ACTIVITY. ANY
DEVELOPMENT OF THIS SYSTEM WILL BE SLOW TO OCCUR AS IT MOVES
WESTWARD AT AROUND 20 MPH. THERE IS A LOW CHANCE...LESS THAN 30
PERCENT...OF THIS SYSTEM BECOMING A TROPICAL CYCLONE DURING THE
NEXT 48 HOURS.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

$$
FORECASTER BRENNAN/LANDSEA

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Quoting 7544:


the box only is good if a major strom passes thru it not a td or ts if im not mistaken


It was meant in Jest.. there are some on here who pull their hair out when mention is made of the "Box"
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It seems as though the omega block pattern may be changing over the gulf of mexico and the parade of african waves is beginning now.
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241. 7544
Quoting Orcasystems:
That box is getting busy



the box only is good if a major strom passes thru it not a td or ts if im not mistaken
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Quoting KEEPEROFTHEGATE:


fading away
yeah i see what you mean, but this wont die that quickly.
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That box is getting busy

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Quoting KEEPEROFTHEGATE:


fading away
what is fading away????
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Quoting InTheConeOIO:
TWC tropical updates has really gone to the dogs, they mine as well just say "back to you!"


Probably have to dumb it down...gotta appeal to those who just wanna know if its going to rain for their daughters 7th b-day party.

Member Since: July 31, 2006 Posts: 56 Comments: 8112
Quoting 7544:


cmc takes it over fla hmm
the CMC is the one i would follow.
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234. 7544
looks like a fay run up from cuba towards the tip of so fla lol could be Link
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fading away
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Quoting canesrule1:
u can see 97L breaking through the shear there, might mean formation might just happen quicker.
97L is not affected by shear so there is nothing to break throu. Also, that is not a shear map so it is not indicative of the shear amounts, locations or tendencies.
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97L is nearing the blob i think the will combine to one, imo.
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TWC tropical updates has really gone to the dogs, they mine as well just say "back to you!"
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Quoting weatherwatcher12:
u can see 97L breaking through the shear there, might mean formation might just happen quicker.
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Quoting 7544:


cmc takes it over fla hmm
What do those Canadiens care, they have all gone home for the summer ;)
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Quoting HadesGodWyvern:
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..


That's right about where Typhoon Molave started.
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TC formation probability up A LOT from yesterday actually.
Member Since: July 7, 2008 Posts: 2 Comments: 3237
Man this blog is getting busy, sometimes if you click on "Read This Blog Entry" it crashes lol.
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224. 7544
Quoting hunkerdown:
Is that the "wave/blob" the models are hinting at or 97L ?


cmc takes it over fla hmm
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water vapor loop
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yesterday i predicted that yesterdays dmin wouldn't have much effect because of dry air, but todays dmin would have more effect as it approaches warmer waters and less stable air.. i was right about the first part, now just gotta wait for the second part
Member Since: July 7, 2008 Posts: 2 Comments: 3237
Quoting heliluv2trac:
so which should we trust the nogaps,cmc or gfs
at this time really none lets wait and see who is right, they have been back and forth
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Quoting BurnedAfterPosting:


both the CMC and NOGAPS takes the wave into the Caribbean, that is the key

If it goes into the Caribbean it has a chance, if it goes north of the Islands it wont develop
Is that the "wave/blob" the models are hinting at or 97L ?
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Quoting BurnedAfterPosting:


both the CMC and NOGAPS takes the wave into the Caribbean, that is the key

If it goes into the Caribbean it has a chance, if it goes north of the Islands it wont develop
its probably going to stick northward but i wouldn't say won't develop i would say a TS with 50+mph winds, imo.
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Member Since: June 13, 2009 Posts: 2 Comments: 9587
so which should we trust the nogaps,cmc or gfs
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i think the nhc will say that thunderstorm activity has increased associated with a tropical wave near te lesser antillies , but upper level winds are currently not condusive for development
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Quoting Seflhurricane:
so it now appears computer models are projecting that the tropical wave near 60W has a chance to develop when shear relaxes somewhat


both the CMC and NOGAPS takes the wave into the Caribbean, that is the key

If it goes into the Caribbean it has a chance, if it goes north of the Islands it wont develop
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looking at buoys around the blob i see high pressure like 30.04 but they are falling, but i do see winds over 20+mph, a lot.
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Quoting WxLogic:


Appears to be the case for now...

So at least for now NOGAPS, CMC, and GFS appear to be developing the 60W wave as it moves through the Carib, with GFS being the E and N outlier.
so it now appears computer models are projecting that the tropical wave near 60W has a chance to develop when shear relaxes somewhat
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Quoting WxLogic:


Appears to be the case for now...

So at least for now NOGAPS, CMC, and GFS appear to be developing the 60W wave as it moves through the Carib, with GFS being the E and N outlier.


This could lead to an outbreak of development, because there are other waves that are following this system. A vigorous tropical wave is about to emerge off the African coast.

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Member Since: June 13, 2009 Posts: 2 Comments: 9587
209. 7544
looks like the blob is feeding off of 97l at this hour seems to be getting larger in size too
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Quoting futuremet:
12Z NOGAPS and CMC seem to be in conjunction.


Appears to be the case for now...

So at least for now NOGAPS, CMC, and GFS appear to be developing the 60W wave as it moves through the Carib, with GFS being the E and N outlier.
Member Since: August 14, 2008 Posts: 4 Comments: 4881
lets see what the NHC says at the TWO.
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if you look at the models right now the blob is in an area of high shear. I haave been told from the NWS that it will be a rainmaker for the SE. The GFS is the model that is showing this. It will need to be watched but until the NHC says something dont worrry.
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quick question. When you click ignore user underneath that person's name should it take you to your own blog? I am trying to ignore someone and it won't work for me so how do I ignore someone?
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the 60 degree storm has no lower circular character to it but if it did, then we would be in trouble here. It looks like a Hurricane 3 days old!!
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Quoting centex:
Weak tropical cyclones tend to be steered more by lower-level winds.
yeah that i know, now i understand what he ment, thanks.
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12Z NOGAPS and CMC seem to be in conjunction.

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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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About JeffMasters

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.