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 2422. CybrTeddy:
Here's the shear forecast at about 114 hours out, rather light at about 5-10kts. This can and will change before we get too excited.

Member Since: August 14, 2010 Posts: 10 Comments: 16828


It has a nice moisture envelope.... Dry air may not be a huge problem however, it's entering cooler water now

And the shear forecast isn't very promising... 30-40knots ahead

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Intensity models have updated, the consensus is that Dorian will level off at as 55kt storm. LGEM has Dorian approaching Category 2 status by the end of the forecast period, but discount it due to the fact it's alone with that. SHIPS is also showing a hurricane.
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Quoting 2405. 69Viking:


Have you looked at the forecast for the ULL before you made that statement? My guess is the ULL will have moved on before Dorian gets there, moving West now and looks to stay ahead of Dorian. Things don't generally sit in one place in the Tropical Atlantic.


It ain't going anywhere. I'd be surprised if there even is a Dorian by the end of the weekend.
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2424. Grothar
Looks like the Bahamas and Florida will eventually be in the Cone of Concern soon.
Member Since: July 17, 2009 Posts: 71 Comments: 26010
2423. LargoFl
9am..........TROPICAL DEPRESSION FOUR FORECAST/ADVISORY NUMBER 1
NWS NATIONAL HURRICANE CENTER MIAMI FL AL042013
0900 UTC WED JUL 24 2013

TROPICAL DEPRESSION CENTER LOCATED NEAR 13.9N 28.1W AT 24/0900Z
POSITION ACCURATE WITHIN 40 NM

PRESENT MOVEMENT TOWARD THE WEST-NORTHWEST OR 285 DEGREES AT 17 KT

ESTIMATED MINIMUM CENTRAL PRESSURE 1008 MB
MAX SUSTAINED WINDS 30 KT WITH GUSTS TO 40 KT.
WINDS AND SEAS VARY GREATLY IN EACH QUADRANT. RADII IN NAUTICAL
MILES ARE THE LARGEST RADII EXPECTED ANYWHERE IN THAT QUADRANT.

REPEAT...CENTER LOCATED NEAR 13.9N 28.1W AT 24/0900Z
AT 24/0600Z CENTER WAS LOCATED NEAR 13.6N 27.2W

FORECAST VALID 24/1800Z 14.6N 30.8W
MAX WIND 35 KT...GUSTS 45 KT.
34 KT... 40NE 0SE 0SW 40NW.

FORECAST VALID 25/0600Z 15.5N 34.4W
MAX WIND 40 KT...GUSTS 50 KT.
34 KT... 50NE 0SE 0SW 50NW.

FORECAST VALID 25/1800Z 16.2N 37.8W
MAX WIND 40 KT...GUSTS 50 KT.
34 KT... 50NE 0SE 0SW 50NW.

FORECAST VALID 26/0600Z 16.8N 41.2W
MAX WIND 40 KT...GUSTS 50 KT.
34 KT... 50NE 0SE 0SW 50NW.

FORECAST VALID 27/0600Z 18.2N 49.0W
MAX WIND 40 KT...GUSTS 50 KT.
34 KT... 50NE 0SE 0SW 50NW.

EXTENDED OUTLOOK. NOTE...ERRORS FOR TRACK HAVE AVERAGED NEAR 150 NM
ON DAY 4 AND 200 NM ON DAY 5...AND FOR INTENSITY NEAR 15 KT EACH DAY

OUTLOOK VALID 28/0600Z 19.3N 56.5W
MAX WIND 40 KT...GUSTS 50 KT.

OUTLOOK VALID 29/0600Z 20.0N 62.0W
MAX WIND 40 KT...GUSTS 50 KT.

REQUEST FOR 3 HOURLY SHIP REPORTS WITHIN 300 MILES OF 13.9N 28.1W

NEXT ADVISORY AT 24/1500Z

$$
FORECASTER BROWN
Member Since: August 6, 2011 Posts: 4 Comments: 38107
Here's the shear forecast at about 114 hours out, rather light at about 5-10kts. This can and will change before we get too excited.

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Dorian is a he..not sure why some people are saying she...it looks like that wave over africa wants to become something to.
Member Since: August 14, 2010 Posts: 10 Comments: 16828
Quoting 713. indianrivguy:


I heard Dexter was looking to trade Mik in for a more exciting life than chasing crabs... He wants to train to be a Hurricane Hunter... :)



Flying with man's best friend
Text and Photos by Jim Urquhart/Reuters


I missed this - thanks for pointing it out IRG.

Just incredible. Though I don't believe he'd ever talk to me again if I even suggested it.
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2419. Patrap
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2418. LargoFl
one of the sites said its up to 70% now...
Member Since: August 6, 2011 Posts: 4 Comments: 38107
2417. LargoFl
Quoting 2410. CaribBoy:


I'm ready. My location : 18N 62.5W
good..i have a friend in ponce..he's getting ready also..its a good thing people down there are informed
Member Since: August 6, 2011 Posts: 4 Comments: 38107
2416. Dakster
Quoting 2402. TampaSpin:


Ya....those Shields are doing well.....LOL


Can you extend them around the remainder of the state?
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2415. junie1
That sure looks like an eye feature on this system is so she may be developing faster than expected
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Quoting 2392. Chucktown:


Dorian will not become a hurricane. The storm may be peaking right now at 40-45 mph. Conditions will become more unfavorable over the next few days. Dry air and eventually the ULL near the islands is going to take its toll. Chantal comes to mind.


Chantal died because of its fast forward speed. Never really had a chance.
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Quoting 2400. mikatnight:



Really?
...it belongs in a box...
Member Since: May 16, 2010 Posts: 0 Comments: 1471
2412. Grothar
Quoting 2370. Levi32:


Yup, woke up to it this morning. I'm going to miss thunderstorms when I leave the south.


We throw some good ones down here, too! If you ever are down this way, I promise I won't tease. (By the way, I know exactly where this one is going)
Member Since: July 17, 2009 Posts: 71 Comments: 26010


Wrapping up a bit
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Quoting 2404. LargoFl:
P.R. and the islands had better be finishing preps huh......


I'm ready. My location : 18N 62.5W
Member Since: October 6, 2007 Posts: 0 Comments: 6164
Good Morning all , I see we have Dorian , looks very likely , on it's way to cane status , shortly! But what is that monster wave, or blob , behind him , could be Erin ? If so the CV season is rapidly starting , maybe we will have the numbers , the forecasters talked about, who knows?
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2407. Mclem1
Quoting 2400. mikatnight:



Really?

I know, Ive been waiting patiently for the images of Dexters sunrise stroll!
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Quoting 2392. Chucktown:


Dorian will not become a hurricane. The storm may be peaking right now at 40-45 mph. Conditions will become more unfavorable over the next few days. Dry air and eventually the ULL near the islands is going to take its toll. Chantal comes to mind.


Have you looked at the forecast for the ULL before you made that statement? My guess is the ULL will have moved on before Dorian gets there, moving West now and looks to stay ahead of Dorian. Things don't generally sit in one place in the Tropical Atlantic.
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2404. LargoFl
P.R. and the islands had better be finishing preps huh......
Member Since: August 6, 2011 Posts: 4 Comments: 38107
Quoting 2393. LargoFl:
Tampa Officials are doing a last checkup on the Shields..


Ya....those Shields are doing well.....LOL
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Quoting 2336. Grothar:


Mik, you think we can have a "Dexter Box"?



Really?
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2399. Patrap
Storm Relative 16km Geostationary Water Vapor Imagery

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Quoting 2383. lottotexas:
seems more NW than WNW


Nawww XD
Member Since: October 6, 2007 Posts: 0 Comments: 6164
2397. StormWx
Quoting SecretStormNerd:


We almost named my last son Dorian. We went with Declan, though.


Declan, that has a nice ring to it. Dorian however may recurve, it appears there may be a weakness in the ridge and a trough that may pull it out to sea in a week or so.
Member Since: July 10, 2013 Posts: 0 Comments: 922
Quoting 2380. Hurricanes305:


Starting to go west again along the 14N line. Dorian is up to some tricks like Chantal. Trying to dodge those cool temperatures.


Good, Chantal did NOT want to go more north than forecast ... so I hope Dorian will do the same.
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2395. Patrap
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Quoting 2299. MisterPerfect:


Sure was. August 25th. It was my first hurricane experience. And what a monster it was. Will never forget it. I was 20 or so miles north of the eye. Scarred for life.
I think you did forget it...the date was actually Aug. 24th (landfall)
Member Since: May 16, 2010 Posts: 0 Comments: 1471
2393. LargoFl
Tampa Officials are doing a last checkup on the Shields..
Member Since: August 6, 2011 Posts: 4 Comments: 38107
Quoting 2387. Tazmanian:
.


The cold. Water is not taking a toll or it will not be a 50mph storm all ready this storm is well under way of becomeing a hurricane


Dorian will not become a hurricane. The storm may be peaking right now at 40-45 mph. Conditions will become more unfavorable over the next few days. Dry air and eventually the ULL near the islands is going to take its toll. Chantal comes to mind.
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2391. help4u
I do disaster relief so I get forcast from Bastardi site,storm can survive because it is so small,likely,he used Charley as example.Tight little storm make it own enviroment.
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2390. LargoFl
I guess what we DONT want..is dorian going into that 85-86 degree water in the gulf huh..but..that IS a possibility down the road
Member Since: August 6, 2011 Posts: 4 Comments: 38107


So.... IF the track doesn't switch further north (omg I'd hate that).... 20N 62W is not very far from the N(most) Leewards. But DORIAN has to get bigger in size so I can enjoy the bad weather!!
Member Since: October 6, 2007 Posts: 0 Comments: 6164
Quoting 2386. TampaSpin:


Hey Brother....LETS KEEP THEM STORMS AWAY!


Please DO extend the shield.. :)
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Quoting 2379. Patrap:
Dvorak was bright, 4 ring, now less..as the cooler waters take its toll.

.


The cold. Water is not taking a toll or it will not be a 50mph storm all ready this storm is well under way of becomeing a hurricane
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Quoting 2381. indianrivguy:
Tim, good to see ya!


Hey Brother....LETS KEEP THEM STORMS AWAY!
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2385. scott39
Goodmorning, Dorian is nudging back to more of a W movement.... 7/24 0Z 6 hour movement WNW 291 degrees.....7/24 0Z 12 hour average movement WNW 289 degrees.....7/24 6Z 6 hour WNW 286 degrees ....7/24 6Z 12 hour average 288 degrees ....7/24 12Z 6 hour WNW 283 degrees....7/24 12Z 12 hour average WNW 284 degrees.
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2384. Patrap
Nice Convective ring still.


The Gain in Lat is obvious as well..to 14 N.





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Quoting 2371. Patrap:
TS Dorian RGB Loop

seems more NW than WNW
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Models are in very good agreement with the Track To the WEST North West toward generally Puerto Rico area. Unknown yet is weather it enters the Caribbean or go north into the Bahamas. Stay tuned! I have all the models that stay current on my Website with all the Satellite you need. Good chance Dorian will develop very slowly. If she stays South she avoids stronger Shear. If she goes North into the Bahamas an Upper Level Low should still be there and hamper much development because of much stronger Shear.
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Tim, good to see ya!
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Quoting 2371. Patrap:
TS Dorian RGB Loop



Starting to go west again along the 14N line. Dorian is up to some tricks like Chantal. Trying to dodge those cool temperatures.
Member Since: May 25, 2012 Posts: 0 Comments: 2043
2379. Patrap
Dvorak was bright, 4 ring, now less..as the cooler waters take its toll.

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2378. will40
Quoting 2360. SecretStormNerd:
At what location does a storm need to be for recon to be sent out?


i think they can go as far as 50W this year
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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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