Atlantic tropical disturbance 91L poses little threat

By: Dr. Jeff Masters , 2:15 PM GMT on April 21, 2011

Share this Blog
5
+

A tropical disturbance (91L) near 24N, 63W, midway between the Virgin Islands and Bermuda, is moving north-northwest at about 8 mph. The system's heavy thunderstorm activity has increased since yesterday, but 91L has an elongated and poorly-organized circulation, thanks to a hefty 80 knots of wind shear. The storm is over waters of 25°C, and these waters will cool to 24°C by Friday as the storm continues to the north-northwest. Before 91L reaches Bermuda, steering currents will reverse and force 91L to the south-southwest on Saturday, into a region of higher wind shear. The latest SHIPS model forecast predicts wind shear will drop to 50 knots over 91L by Friday, then increase again to 70 knots by Sunday. The high shear and relatively cool water temperatures will make it difficult for 91L to organize into a subtropical depression. I give 91L a 10% of becoming a subtropical depression. Climatology argues against 91L becoming the first named storm of the year; there has only been once named April storm in the Atlantic since 1851, Tropical Storm Ana of 2003. The formation of a tropical disturbance at this location this time of year is unusual, but is not necessarily a harbinger of a active season ahead.


Figure 1. Morning satellite image of the Atlantic tropical disturbance 91L.

Jeff Masters

Reader Comments

Comments will take a few seconds to appear.

Post Your Comments

Please sign in to post comments.

or Join

Not only will you be able to leave comments on this blog, but you'll also have the ability to upload and share your photos in our Wunder Photos section.

Display: 0, 50, 100, 200 Sort: Newest First - Order Posted

Viewing: 540 - 490

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11Blog Index

539. SQUAWK
2:46 PM GMT on April 22, 2011
Quoting IKE:

Come on 91L! Do it! Do it now!

That better?

There ya go!!!!
Member Since: December 9, 2008 Posts: 0 Comments: 2498
538. CyclonicVoyage
2:37 PM GMT on April 22, 2011
Quoting PolishHurrMaster:

So let'em choose a dominant one!They are professionalists,should be able to do this.


They won't name it with 2 vortice. Should acquire enough organization to be named 91L will eat that second center for lunch.
Member Since: January 30, 2010 Posts: 0 Comments: 3259
536. BahaHurican
2:33 PM GMT on April 22, 2011
Quoting AussieStorm:
Just a reminder....

I've made a blog entry, If anyone is interested. Feel free to write your location on this blog. Just so as to keep track of where people are in the event of severe weather/hurricane.

Just go here
This is a good idea. Thanks, Aussie.
Member Since: October 25, 2005 Posts: 19 Comments: 22357
535. PolishHurrMaster
2:32 PM GMT on April 22, 2011
Quoting CyclonicVoyage:


Competing centers would be my guess. Surely on an organizational trend though. Looks a little better with each refresh.

So let'em choose a dominant one!They are professionalists,should be able to do this.
Member Since: May 19, 2010 Posts: 0 Comments: 351
534. IKE
2:31 PM GMT on April 22, 2011

Quoting SQUAWK:

Ike, you leave a little to be desired on your wishcasting. Just not quite the enthusiasm I expected.

That 91L is a real fighter. It is hanging in there. It could be a contender. It is not going to let go easily. It is one tough hombre. Those winds are going to have to kick butt to kill this little die-hard. It has stamina. Dare I say it ------ we are all DOOM.
Come on 91L! Do it! Do it now!

That better?
Member Since: June 9, 2005 Posts: 23 Comments: 37858
533. Neapolitan
2:30 PM GMT on April 22, 2011
Quoting PolishHurrMaster:
Foreca's products are showing 45mph winds in 91L.Visually it looks better than some named storms.By naming it,we can make history(3rd tropical storm in April,behind unnamed one in 1992 and Ana'03).So why don't name it?Anyone know reason?I don't know one.

Maybe they got tired of all those last year who accused them of "promoting GW hype" by "naming storms they shouldn't have". ;-)
Member Since: November 8, 2009 Posts: 4 Comments: 13579
532. CyclonicVoyage
2:28 PM GMT on April 22, 2011


Shear is not ideal but lower for the time being.
Member Since: January 30, 2010 Posts: 0 Comments: 3259
531. SQUAWK
2:25 PM GMT on April 22, 2011
Quoting IKE:
DESIGNATE IT!

DESIGNATE IT!

They won't.....not w/a 20% chance. They would up the odds first.

Ike, you leave a little to be desired on your wishcasting. Just not quite the enthusiasm I expected.

That 91L is a real fighter. It is hanging in there. It could be a contender. It is not going to let go easily. It is one tough hombre. Those winds are going to have to kick butt to kill this little die-hard. It has stamina. Dare I say it ------ we are all DOOM.
Member Since: December 9, 2008 Posts: 0 Comments: 2498
530. CyclonicVoyage
2:24 PM GMT on April 22, 2011
Quoting PolishHurrMaster:
Foreca's products are showing 45mph winds in 91L.Visually it looks better than some named storms.By naming it,we can make history(3rd tropical storm in April,behind unnamed one in 1992 and Ana'03).So why don't name it?Anyone know reason?I don't know one.


Competing centers would be my guess. Surely on an organizational trend though. Looks a little better with each refresh.
Member Since: January 30, 2010 Posts: 0 Comments: 3259
529. PolishHurrMaster
2:22 PM GMT on April 22, 2011
Foreca's products are showing 45mph winds in 91L.Visually it looks better than some named storms.By naming it,we can make history(3rd tropical storm in April,behind unnamed one in 1992 and Ana'03).So why don't name it?Anyone know reason?I don't know one.
Member Since: May 19, 2010 Posts: 0 Comments: 351
528. CybrTeddy
2:20 PM GMT on April 22, 2011
Quoting IKE:
DESIGNATE IT!

DESIGNATE IT!

They won't.....not w/a 20% chance. They would up the odds first.


If 91L was to be designated shortly there would be a TWO upping it to 80-90% followed by an upgrade.

They won't go from 20% to STS Arlene.
Member Since: July 8, 2005 Posts: 259 Comments: 24248
527. BahaHurican
2:19 PM GMT on April 22, 2011
Quoting sammywammybamy:
Thanks, Hopefully it'll bring some rain to stop the wildfires from burning the Everglades . Most of the models take it into the southern Bahamas and then WNW towards Florida. By then it will just be a blob of rain.
This is kinda what I was hoping for... need to go look at some models at some point today [which is a public holiday in The Bahamas].
Member Since: October 25, 2005 Posts: 19 Comments: 22357
525. BahaHurican
2:16 PM GMT on April 22, 2011
Good morning, and Good Friday to all.

[cheeky grin] Looka the people.....

I haven't been following 91L very closely, but have been keeping an eye on it since last week in the unlikely hope that it will drift far enough west to bring us some showers here in the Bahamas. A pleasure to see it bringing some non-winter bloggers in, though....
Member Since: October 25, 2005 Posts: 19 Comments: 22357
524. CyclonicVoyage
2:15 PM GMT on April 22, 2011
If 91L can shed the multiple vortices it may have a better chance. Competing centers in a hostile environment is not to it's benefit one bit.
Member Since: January 30, 2010 Posts: 0 Comments: 3259
523. IKE
2:11 PM GMT on April 22, 2011
DESIGNATE IT!

DESIGNATE IT!

They won't.....not w/a 20% chance. They would up the odds first.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
522. flsky
2:10 PM GMT on April 22, 2011
The Science of Why We Don't Believe in Science
Link
Member Since: October 24, 2006 Posts: 0 Comments: 2036
521. CyclonicVoyage
2:07 PM GMT on April 22, 2011
Quoting Skyepony:
DATE/TIME LAT LON CLASSIFICATION STORM
22/1145 UTC 26.7N 63.0W ST1.5 91L
22/0615 UTC 25.9N 63.0W ST1.5 91L
21/2345 UTC 25.3N 62.9W TOO WEAK 91L
21/1745 UTC 24.2N 63.1W TOO WEAK 91L
21/1145 UTC 23.4N 62.9W TOO WEAK 91L
21/0515 UTC 23.1N 62.5W TOO WEAK 91L
20/2345 UTC 23.2N 62.0W TOO WEAK 91L
20/1745 UTC 23.0N 60.8W ST1.5 91L



Back on the map for the time being. I personally don't think they will call it though.
Member Since: January 30, 2010 Posts: 0 Comments: 3259
520. cg2916
2:07 PM GMT on April 22, 2011
*Sprints to computer* Ok, I'm here. How's 91L doing? *breathes heavily*
Member Since: December 21, 2007 Posts: 13 Comments: 3046
519. bajelayman2
2:02 PM GMT on April 22, 2011
I would not write 91L off yet. It has lasted this long and is not looking too bad for a developing system. Bear in mind too that nothing is certain and we have had some unusual events in the past few years.

It is already quite hot here in Barbados, last night was unusually warm for this time of year.

Together with that and 91L, three weeks ago we had a squall coming through here and the islands that caused severe flooding. It had some high winds too, again, unusual.

I think we are looking at 2011=2005, or thereabouts.

But, as I have warned many times in the past, I am no meteorologist.

Take care.
Member Since: August 13, 2007 Posts: 0 Comments: 488
518. Skyepony (Mod)
2:01 PM GMT on April 22, 2011
DATE/TIME LAT LON CLASSIFICATION STORM
22/1145 UTC 26.7N 63.0W ST1.5 91L
22/0615 UTC 25.9N 63.0W ST1.5 91L
21/2345 UTC 25.3N 62.9W TOO WEAK 91L
21/1745 UTC 24.2N 63.1W TOO WEAK 91L
21/1145 UTC 23.4N 62.9W TOO WEAK 91L
21/0515 UTC 23.1N 62.5W TOO WEAK 91L
20/2345 UTC 23.2N 62.0W TOO WEAK 91L
20/1745 UTC 23.0N 60.8W ST1.5 91L
Member Since: August 10, 2005 Posts: 178 Comments: 38316
517. CyclonicVoyage
2:00 PM GMT on April 22, 2011
Quoting JRRP:



Pretty safe bet neutral is coming our way. It doesn't make me rest easy in FL. Neutral brings with it an increased hurricane threat to the peninsula and seems an increased threat to the Leewards, PR ect.. naturally being downwind and all.
Member Since: January 30, 2010 Posts: 0 Comments: 3259
516. Jax82
1:47 PM GMT on April 22, 2011
You can definately see the main spin and center with the t-storms trying to fire, and then what appears to be a small swirl to the SW of the main center heading South.

Member Since: September 2, 2008 Posts: 1 Comments: 1261
515. TampaSpin
1:46 PM GMT on April 22, 2011
Member Since: September 2, 2007 Posts: 178 Comments: 20443
514. guygee
1:46 PM GMT on April 22, 2011
If 91L gets named I'll eat my avatar, but it is an optimistic 50/50 that is helps jump-start our FL rainy season...here is to hoping...
Member Since: September 16, 2005 Posts: 0 Comments: 3171
513. IKE
1:42 PM GMT on April 22, 2011

Member Since: June 9, 2005 Posts: 23 Comments: 37858
512. JRRP
1:40 PM GMT on April 22, 2011
Member Since: August 16, 2007 Posts: 0 Comments: 5995
511. MiamiHurricanes09
1:39 PM GMT on April 22, 2011
Quoting CybrTeddy:
Judging by the satellite 91L is trying to become vertically stacked with an Upper Low. Today's is its opportunity, if 91L doesn't develop today we won't have Arlene until May or June.
I agree, after tonight upper-level winds will probably kill it
Member Since: September 2, 2009 Posts: 130 Comments: 21194
510. AussieStorm
1:36 PM GMT on April 22, 2011
Quoting TampaSpin:

Member Since: September 30, 2007 Posts: 9 Comments: 15940
509. TampaSpin
1:34 PM GMT on April 22, 2011
Member Since: September 2, 2007 Posts: 178 Comments: 20443
508. TampaSpin
1:34 PM GMT on April 22, 2011
Member Since: September 2, 2007 Posts: 178 Comments: 20443
505. TampaSpin
1:29 PM GMT on April 22, 2011


Member Since: September 2, 2007 Posts: 178 Comments: 20443
504. HurricaneDean07
1:28 PM GMT on April 22, 2011
If this organization continues then we could see another special TWO on it forming.
Member Since: October 3, 2010 Posts: 40 Comments: 4129
503. Chicklit
1:28 PM GMT on April 22, 2011
Glad I won't have to put my hurricane shutters up early this year! lol
Still, 91L seems a harbinger of things to come.
Why does Shakespeare always come to mind as hurricane season begins to show itself? (rhetorical question)
For me, it's because we humans have no control over these events and can only observe what happens.
This was what Shakespeare was particularly good at showing about the ultimate human condition.
Once events begin to play out, we can only watch and wonder and try to adjust.
Member Since: July 11, 2006 Posts: 14 Comments: 11358
502. KEEPEROFTHEGATE (Mod)
1:26 PM GMT on April 22, 2011
733

WHXX01 KWBC 221219

CHGHUR

TROPICAL CYCLONE GUIDANCE MESSAGE

NWS NATIONAL HURRICANE CENTER MIAMI FL

1219 UTC FRI APR 22 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 (AL912011) 20110422 1200 UTC



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

110422 1200 110423 0000 110423 1200 110424 0000



LAT LON LAT LON LAT LON LAT LON

BAMS 26.9N 62.9W 27.3N 64.0W 27.2N 65.6W 27.1N 67.8W

BAMD 26.9N 62.9W 28.0N 62.2W 27.6N 62.6W 26.9N 63.2W

BAMM 26.9N 62.9W 27.2N 63.2W 26.5N 64.4W 25.7N 65.8W

LBAR 26.9N 62.9W 28.0N 61.4W 28.4N 60.1W 28.8N 58.7W

SHIP 30KTS 31KTS 30KTS 24KTS

DSHP 30KTS 31KTS 30KTS 24KTS



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

110424 1200 110425 1200 110426 1200 110427 1200



LAT LON LAT LON LAT LON LAT LON

BAMS 27.1N 70.2W 28.2N 75.5W 31.2N 80.3W 36.5N 80.9W

BAMD 26.2N 63.5W 25.0N 63.1W 25.8N 62.9W 26.7N 63.9W

BAMM 25.3N 67.4W 25.9N 70.5W 27.9N 74.0W 31.6N 75.1W

LBAR 28.3N 57.4W 26.7N 55.0W 25.9N 53.3W 25.2N 51.2W

SHIP 15KTS 0KTS 0KTS 0KTS

DSHP 15KTS 0KTS 0KTS 0KTS



...INITIAL CONDITIONS...

LATCUR = 26.9N LONCUR = 62.9W DIRCUR = 0DEG SPDCUR = 8KT

LATM12 = 25.3N LONM12 = 63.0W DIRM12 = 3DEG SPDM12 = 9KT

LATM24 = 23.7N LONM24 = 63.0W

WNDCUR = 30KT RMAXWD = 60NM WNDM12 = 35KT

CENPRS = 1007MB OUTPRS = 1013MB OUTRAD = 150NM SDEPTH = M

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



$$

NNNN
Member Since: July 15, 2006 Posts: 174 Comments: 54623
501. CybrTeddy
1:25 PM GMT on April 22, 2011
Judging by the satellite 91L is trying to become vertically stacked with an Upper Low. Today's is its opportunity, if 91L doesn't develop today we won't have Arlene until May or June.
Member Since: July 8, 2005 Posts: 259 Comments: 24248
500. TampaSpin
1:25 PM GMT on April 22, 2011
Member Since: September 2, 2007 Posts: 178 Comments: 20443
499. HurricaneDean07
1:20 PM GMT on April 22, 2011
There has been no Arlene whatsoever, and if 91L does form it will be Arlene. If the Mid-May storm forms then that would be Bret.
Member Since: October 3, 2010 Posts: 40 Comments: 4129
498. Grothar
1:18 PM GMT on April 22, 2011
Doesn't look like much left over when it moves South.

Member Since: July 17, 2009 Posts: 71 Comments: 26546
497. HurricaneDean07
1:17 PM GMT on April 22, 2011
the Upper low is right over top now...
Member Since: October 3, 2010 Posts: 40 Comments: 4129
496. CyclonicVoyage
1:17 PM GMT on April 22, 2011


I see 2 vortices, one @ 27.2N 63.2W and one @ 25.9N 65.0W rotating around a mean center @ 26.5N 64W.
Member Since: January 30, 2010 Posts: 0 Comments: 3259
495. HurricaneDean07
1:15 PM GMT on April 22, 2011
Really wrapping the convection around the center now. Becoming much more organized, and had even dropped it's pressure down to 1007 mb, but only has 35 MPH winds now. though it can still be a Depression with those winds...
Member Since: October 3, 2010 Posts: 40 Comments: 4129
494. Grothar
1:09 PM GMT on April 22, 2011
Banding not near the main center. Click on the IR-NHC button on top, then on the left click (image animation on the left (AnGIF button)

Link
Member Since: July 17, 2009 Posts: 71 Comments: 26546
493. CyclonicVoyage
1:08 PM GMT on April 22, 2011


The hammer is coming down, the flat top crew cut evidence that soon it will be forced down into the shredding belt that lie below.
Member Since: January 30, 2010 Posts: 0 Comments: 3259
492. stillwaiting
1:03 PM GMT on April 22, 2011
imo most of the convection associated with 91L is being caused by UL divergence,and not at all warm core associated convection,not even close to a std imo
Member Since: October 5, 2007 Posts: 20 Comments: 4970
491. MahFL
1:01 PM GMT on April 22, 2011
Lol the NHC says North...and its moveing South.....hm........
Member Since: June 9, 2004 Posts: 0 Comments: 3572
490. PolishHurrMaster
12:58 PM GMT on April 22, 2011
WTF?Only 20%?
Member Since: May 19, 2010 Posts: 0 Comments: 351

Viewing: 540 - 490

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11Blog Index

Top of Page

About

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

Local Weather

Overcast
55 °F
Overcast