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: 90 - 40

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

The GFS ensembles are interesting, showing an early flux of tropical moisture into the Caribbean in early May. This is supported by the dynamical MJO forecasts.

Member Since: Posts: Comments:
Quoting Levi32:
It's long-range model blob-watching season already?



A few long range models have been suggesting something in the Carribean during mid-May. Would be very interesting if our current 91L got Arlene, and a potential Bret in May could have us at two named storms before the season even starts. A lot of ifs there though....
Member Since: Posts: Comments:
Quoting DocNDswamp:
Yep, a very narrow swath, Drak... I'd guess west at around 5-7 mph or even to nearly calm just S of center...


And that only developed within the last 90 minutes or so. I imagine it will close off decently again later today and tonight, given that all the models agree on it slowly deepening for the next 24 hours or so.
Member Since: Posts: Comments:
Yep, a very narrow swath, Drak... I'd guess west at around 5-7 mph or even to nearly calm just S of center...
Member Since: Posts: Comments:
Quoting Neapolitan:

Yes, Qatar puts out more CO2 per capita than does the U.S. But while their numbers can't and shouldn't be discounted, Qatar's population is just barely one-half of one-percent of ours, so the comparison isn't an entirely accurate one.

The thing is, of the 10 nations that lead the U.S. in per capita CO2 emissions--Qatar, Netherlands Antilles, the UAE, Kuwait, Bahrain, Trinidad & Tobago, Aruba, Luxembourg, Brunei, and the Falkland Islands--seven have economies based in very large part on the production and export of crude oil and natural gas to consumer nations like ours. The excessive per capita CO2 numbers from those countries are due to that high-emitting oil/gas production sector combined with their small populations. In the U.S., however, our high per-capita numbers are due primarily to overconsumption--meaning that, yes, we Americans most definitely are the "big hogs".

Good point.+ one
Member Since: August 24, 2010 Posts: 19 Comments: 4357
Moving deeper southward...

Member Since: Posts: Comments:
It's long-range model blob-watching season already?

Member Since: Posts: Comments:
Nice structure to it for it being so early in the year. The circulation has become elongated that yesterday though and a due west wind may be difficult to find or at least in a very narrow area on the southern side of the circulation center.


Member Since: Posts: Comments:
Encouraging for the season is the fact that the CMC is showing the ability to adjust back to reality. 12z run
Member Since: Posts: Comments:
Member Since: July 15, 2006 Posts: 165 Comments: 52263
Noticed the NHC has issued a code yellow @ 20% development for 91L. First of the year no.
Member Since: Posts: Comments:
Member Since: July 15, 2006 Posts: 165 Comments: 52263
Quoting tkeith:
Invests before Easter?



TK, that's what we get having Easter come so late this year! Already up to our 2nd Invest...
Member Since: Posts: Comments:
Member Since: July 15, 2006 Posts: 165 Comments: 52263
Quoting Levi32:
I'm having trouble finding true westerlies south of the center now. RGB loop


Not surprising is it, given the disorganized, elongated structure... strong curvature on N side with the gradient, really flat to the S... and LL easterly trades impinging on it...

LOL, for that matter - outside of the initial recon finding, never could find any sfc westerlies after in TD #2 last year...
;)
Member Since: Posts: Comments:
Member Since: July 15, 2006 Posts: 165 Comments: 52263
Complete Update





Member Since: Posts: Comments:
Quoting Patrap:
When embedding here,,use the OLD embed codes,and post DIRECTLY in the comments section,bypassing the link and or image buttons


Thanks, Pat!
Member Since: Posts: Comments:
Quoting tkeith:
Invests before Easter?



Egg-citing! Isn't it!
Member Since: September 10, 2007 Posts: 0 Comments: 10578
Quoting Levi32:
Tropical Tidbit for Thursday, April 21st: Invest 91L continues to slowly develop

great update!!
Member Since: Posts: Comments:
Invests before Easter?

Member Since: November 1, 2004 Posts: 25 Comments: 8912
When embedding here,,use the OLD embed codes,and post DIRECTLY in the comments section,bypassing the link and or image buttons
Member Since: Posts: Comments:
Member Since: Posts: Comments:
Member Since: Posts: Comments:
Quoting jeffs713:

I can't see the video....

:*(


Hmm... I haven't figured out video embedding, but here's a LINK to it...
Member Since: Posts: Comments:
Quoting MrMixon:


Luckily there's no evidence for catastrophic subduction of tectonic plates in the geologic record. Plate tectonic activity happens slowly (relative to human lifespans) and, even though parts of continental plates do "sink" over time, even the most rapid rates of subduction ever recorded would not be sufficient to cause an island the size of Japan to "sink" in our lifetime.

EDIT: ah, forget the science! That was cool video Keep posted. :)

I can't see the video....

:*(
Member Since: Posts: Comments:
Quoting SQUAWK:


Maybe the whole island is going to sink. Wonder how we would deal with that?


Luckily there's no evidence for catastrophic subduction of tectonic plates in the geologic record. Plate tectonic activity happens slowly (relative to human lifespans) and, even though parts of continental plates do "sink" over time, even the most rapid rates of subduction ever recorded would not be sufficient to cause an island the size of Japan to "sink" in our lifetime.

EDIT: ah, forget the science! That was a cool video Keep posted. :)
Member Since: Posts: Comments:
Quoting KEEPEROFTHEGATE:


Keep, you truly are amazing!
Member Since: Posts: Comments:
Member Since: July 15, 2006 Posts: 165 Comments: 52263
Quoting RastaSteve:
Lots of siesmic energy off the coast of Japan is causing major concern for siesmoligist. (Not sure of spelling)


Maybe the whole island is going to sink. Wonder how we would deal with that?
Member Since: Posts: Comments:
148

WHXX01 KWBC 211336

CHGHUR

TROPICAL CYCLONE GUIDANCE MESSAGE

NWS NATIONAL HURRICANE CENTER MIAMI FL

1336 UTC THU APR 21 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) 20110421 1200 UTC



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

110421 1200 110422 0000 110422 1200 110423 0000



LAT LON LAT LON LAT LON LAT LON

BAMS 23.6N 62.9W 24.2N 64.3W 24.2N 65.1W 23.8N 65.8W

BAMD 23.6N 62.9W 26.0N 59.1W 28.7N 56.7W 31.2N 54.5W

BAMM 23.6N 62.9W 25.1N 62.6W 26.2N 62.4W 26.5N 62.2W

LBAR 23.6N 62.9W 24.7N 62.3W 25.5N 61.1W 26.5N 59.6W

SHIP 35KTS 35KTS 34KTS 31KTS

DSHP 35KTS 35KTS 34KTS 31KTS



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

110423 1200 110424 1200 110425 1200 110426 1200



LAT LON LAT LON LAT LON LAT LON

BAMS 22.9N 66.9W 21.9N 70.9W 21.9N 75.4W 23.0N 79.6W

BAMD 33.1N 50.7W 36.0N 37.3W 40.1N 31.4W 43.3N 26.1W

BAMM 25.6N 62.6W 23.0N 64.7W 21.7N 66.8W 22.0N 68.4W

LBAR 26.8N 57.9W 26.8N 54.1W 26.2N 50.8W 26.6N 48.8W

SHIP 22KTS 0KTS 0KTS 0KTS

DSHP 22KTS 0KTS 0KTS 0KTS



...INITIAL CONDITIONS...

LATCUR = 23.6N LONCUR = 62.9W DIRCUR = 280DEG SPDCUR = 7KT

LATM12 = 23.3N LONM12 = 61.6W DIRM12 = 278DEG SPDM12 = 8KT

LATM24 = 22.8N LONM24 = 59.8W

WNDCUR = 35KT RMAXWD = 105NM WNDM12 = 35KT

CENPRS = 1009MB OUTPRS = 1013MB OUTRAD = 150NM SDEPTH = D

RD34NE = 105NM RD34SE = 0NM RD34SW = 0NM RD34NW = 105NM



$$

NNNN
Member Since: July 15, 2006 Posts: 165 Comments: 52263
XX/INV/91L
MARK
24.88n/63.33w
Member Since: July 15, 2006 Posts: 165 Comments: 52263
91L IR Rainbow

Member Since: Posts: Comments:

Storm Relative 1km Geostationary Visible Imagery




2km Storm Relative IR Imagery with BD Enhancement Curve
Member Since: Posts: Comments:
Quoting Patrap:



What # post?

if #38 its here

rammb.cira.colostate.edu/products

Suggestion to admin, perhaps include the # of the post that one is quoting. It can get confusing when it is busy and people are quoting alot.
Member Since: December 13, 2009 Posts: 0 Comments: 122
Busy day underneath Japan today



DATE
LAT
LON
MAG
DEPTH km
REGION


21-APR-2011 13:54:01
35.60
140.53
4.7
52.9
NEAR EAST COAST OF HONSHU, JAPAN


21-APR-2011 13:47:12
35.76
140.70
4.9
46.1
NEAR EAST COAST OF HONSHU, JAPAN


21-APR-2011 13:37:03
35.62
140.45
6.1
42.9
NEAR EAST COAST OF HONSHU, JAPAN


21-APR-2011 08:18:14
38.33
142.21
5.3
27.8
NEAR EAST COAST OF HONSHU, JAPAN


21-APR-2011 07:01:12
38.90
142.97
4.5
22.3
NEAR EAST COAST OF HONSHU, JAPAN


21-APR-2011 04:11:15
32.36
-115.55
4.0
5.3
CALIF.-BAJA CALIF. BORDER REGION


21-APR-2011 03:08:40
37.29
142.34
5.0
44.3
OFF EAST COAST OF HONSHU, JAPAN


21-APR-2011 01:54:40
40.32
143.68
6.0
3.7
OFF EAST COAST OF HONSHU, JAPAN


21-APR-2011 00:39:04
40.50
143.48
5.8
15.0
OFF EAST COAST OF HONSHU, JAPAN
Member Since: Posts: Comments:
Yes indeed,the RAMMB page is a good link...along with all the others on the wunderground trop page
Member Since: Posts: Comments:
Thanks for the link Pat I bookmarked the page some useful tools on that site.
Member Since: Posts: Comments:
Member Since: Posts: Comments:
Quoting wxmobilejim:


Where do you get this chart?



What # post?

if #38 its here

rammb.cira.colostate.edu/products
Member Since: Posts: Comments:
Quoting Patrap:


Where do you get this chart?
Member Since: Posts: Comments:

Viewing: 90 - 40

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

Top of Page

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.