Atlantic tropical disturbance 91L poses little threat

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

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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

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Quoting Grothar:
QUOTING KEEPEROFTHEGATE:

Just to clarify, I was not advocating staying in one's car. I was just showing the link as to why the question was asked. I believe the advice given by the Red Cross was bad information, as the article explained. I would never stay in a car during a tornado. I would be running faster than the car could drive anyway. Bet you didn't know I can run and scream at the same time.


Gro, I can't run fast. So I will be driving at approx. 90 knots southeast or northwest, whichever give me a reasonably clear path. I drive a big truck -- get the heck outta the way!
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The upper low is very close by to the WNW of the surface feature now. The best case scenario for 91L is probably to get vertically stacked under the upper low and quickly establish its warm-core presence beneath the cold pocket. It can do that under the divergent (SE-NE quads) flank of the upper low, but that leaves some wind shear over it that would be eliminated if it became vertically stacked. Already wind shear is much lower than it was last night.

Member Since: November 24, 2005 Posts: 635 Comments: 26661
Quoting Grothar:



I thought you moved to the other side of the world. How have you been? At least drop a line on the blog now and then so we know you are still with us.


I apologize my friend; I have been remiss. Caught up in life I suppose or perhaps just hibernating for the winter. My wife and I are both well thanks, and spent a lovely day up at the beach. Work is slow but we keep plugging along. I'll be checking in more often for sure as the season approaches. Gotta run now though, thanks for inquiring (typing this on my phone - it's quite tedious). See y'all again soon...
M
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"Okay, who has the map?"
"I thought you had it!"
"NO, I gave it to Fred"
"Well SOMEONE figure out which way is Arkansas."

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234. xcool
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QUOTING KEEPEROFTHEGATE:

Just to clarify, I was not advocating staying in one's car. I was just showing the link as to why the question was asked. I believe the advice given by the Red Cross was bad information, as the article explained. I would never stay in a car during a tornado. I would be running faster than the car could drive anyway. Bet you didn't know I can run and scream at the same time.
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91L won't form or turn into anything.Don't get your hopes up.
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Quoting mikatnight:
Howdy Folks,

Just popped in to post the link to this article that showed up in the Huffington Post on Climategate. Very interesting and in depth. Check it out if you're interested in the subject.

http://m.motherjones.com/environment/2011/04/hist o ry-of-climategate

Or click here.

Hope everyone's doing well (Hi Grother!)

Peace Out,
M



I thought you moved to the other side of the world. How have you been? At least drop a line on the blog now and then so we know you are still with us.
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The Models look like a squished spider...

So I am going with we really do not know where the thunderstorms will go... I don't see this being anything to panic about, regardless of whether it gets a name or not.
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Howdy Folks,

Just popped in to post the link to this article that showed up in the Huffington Post on Climategate. Very interesting and in depth. Check it out if you're interested in the subject.

http://m.motherjones.com/environment/2011/04/histo ry-of-climategate

Or click here.

Hope everyone's doing well (Hi Grother!)

Peace Out,
M
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Quoting Grothar:
Sorry to bring up old news, but just saw a few blogs about staying in your car during a tornado. There was a disagreement between the NWS and the Red Cross about the appropriate action to take. The Red Cross issued statements and advice to stay in your car and the NWS refused to go along with this advice, which was based upon new studies. If anyone is interested, here is the link. Heather Tesch was asking a good question, since there has been discussions on this very subject.

Link
this is the rule if in a thunderstorm with high winds rain and lightening its best to stay inside your car now if a tornado is about to occur or is occuring then its best to abandon the car as tornadic winds may pick up the car and toss into air therefore crushing anyone inside as oppose to a non tornado storm in which the tossing of a car is less likly


SEVERE THUNDERSTORM PREPARATION WHILE AT HOME:

1. Secure any loose, high profile and small objects outside before the storm hits
2. Stay inside during the thunderstorm
3. Try to protect vehicle from hail damage (such as placing vehicle in the garage) before storm hits
4. Unplug sensitive equipment such as computers and other electronic equipment
5. Stay off the telephone and electronic equipment (if needed use battery operated TV, radio and phone)
6. Stay out of bath or shower
7. Keep a distance from windows
8. Be ready to take shelter in center of building on lowest floor crouched low to the ground
9. Listen to battery operated NOAA weather radio for updates


SEVERE THUNDERSTORM PREPARATION WHILE TRAVELING:

1. Do not drive into a strong thunderstorm (especially when a severe thunderstorm or tornado watch is in effect in or near the area)
2. If trapped in a storm, stay in the vehicle if large hail and / or vivid cloud-to-ground lightning is occurring.
3. If trapped on the highway, try to safely park the vehicle under an overpass
4. Reduce speed significantly if driving through a thunderstorm
5. Do not drive through flooded streets with unknown depth of water. Most flooding deaths occur in cars at night. Moving water is much more dangerous to drive through than stationary water
6. Listen to battery operated NOAA weather radio for updates

**note: if a tornado is imminent, it will then be best to abandon vehicle
Member Since: July 15, 2006 Posts: 174 Comments: 54499
Looks like a Subtropical Storm to me, but we all know the NHC won't name it..
Member Since: July 1, 2008 Posts: 13 Comments: 7396
Quoting GeoffreyWPB:


I don't know about that canes. The models are really spread out. Plus who knows what is going to be left of this four or five days out?



The local mets are saying what I said. I'm pretty sure it'll make its way around the high and end up here.
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Quoting Grothar:


Wie geht's meine Freundin? We are watching our first little system. We need the rain badly, too. Heard it was dry there, too! Saw the images of your dust storm.


Danke, Grothar, quite well. I'm watching your early invest. Interesting! - Dust storm was quite far away from my place, but deadly, unfortunately. -- I'm going to Portugal (Lissabon) next week for some days. There's a lot of of rain right now.
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.
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Quoting barbamz:
Nothing really new for insiders, but I just stumbled across it:

Ring Around the Hurricanes: Satellites Can Predict Storm Intensity

http://www.sciencedaily.com/releases/2011/04/1104 20152102.htm

Greetings from Germany, already in early summer mood. Good for the humans, bad for nature (drought).
And special greetings to my friend Grothar ...


Wie geht's meine Freundin? We are watching our first little system. We need the rain badly, too. Heard it was dry there, too! Saw the images of your dust storm.
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Quoting caneswatch:
Well, one thing's for sure. Florida is gonna get this whether it be a big cluster of showers and thunderstorms or a TS.


I don't know about that canes. The models are really spread out. Plus who knows what is going to be left of this four or five days out?

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Another blob in the midwest.

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Well, one thing's for sure. Florida is gonna get this whether it be a big cluster of showers and thunderstorms or a TS.
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I hope all you folks in Florida will get some good rain out of this system. Maybe you guys could take some of our excess water here in Fargo, too! :-)

What would this thing have to do to be upgraded to a subtropical depression? It has a closed LLC, if I am understanding correctly.
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Okay, so I'm a bit of an optimist and no. I don't want any big storms. Ike was my first hurricane and I would be happy not to be in another. We lived about 20 miles from the coast when Ike hit and that storm was pretty bad.
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Nothing really new for insiders, but I just stumbled across it:

Ring Around the Hurricanes: Satellites Can Predict Storm Intensity

http://www.sciencedaily.com/releases/2011/04/1104 20152102.htm

Greetings from Germany, already in early summer mood. Good for the humans, bad for nature (drought).
And special greetings to my friend Grothar ...
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Quoting TXnovice:
Does the current weather pattern that is causing above-average temperatures in Texas (at least my part-houston area) effect the possibility of early tropical developement?

Dreamer! A nice, simple little tropical depression would be just what we need down here with everything drying up and no rain in sight. No more Ike's or Rita's, though, please.
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Quoting GeoffreyWPB:
LONG TERM...
BY THE SECOND HALF OF THE WEEKEND, THE RIDGE OF HIGH PRESSURE WILL
BEGIN TO MOVE OFF THE EAST COAST AND THE MOISTURE WILL START TO
RETURN TO THE AREA. THE CHANCE FOR SHOWERS AND THUNDERSTORMS WILL
INCREASE EARLY NEXT WEEK AS AN INVERTED TROUGH APPROACHES THE AREA.
MOISTURE ASSOCIATED WITH THIS SYSTEM LOOKS TO MOVE INTO THE AREA
DURING THE DAY ON TUESDAY. WE WILL CONTINUE TO MONITOR THIS SYSTEM
AND POPS MAY NEED TO BE INCREASED IN LATER FORECASTS AS THE EVENT
GETS CLOSER AND MODELS COME INTO BETTER AGREEMENT.

Miami NWS Discussion


We REALLY need the rain down in these parts (Jupiter Here). I'd hate to see another dry rainy season.
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Sorry to bring up old news, but just saw a few blogs about staying in your car during a tornado. There was a disagreement between the NWS and the Red Cross about the appropriate action to take. The Red Cross issued statements and advice to stay in your car and the NWS refused to go along with this advice, which was based upon new studies. If anyone is interested, here is the link. Heather Tesch was asking a good question, since there has been discussions on this very subject.

Link
Member Since: Posts: Comments:
LONG TERM...
BY THE SECOND HALF OF THE WEEKEND, THE RIDGE OF HIGH PRESSURE WILL
BEGIN TO MOVE OFF THE EAST COAST AND THE MOISTURE WILL START TO
RETURN TO THE AREA. THE CHANCE FOR SHOWERS AND THUNDERSTORMS WILL
INCREASE EARLY NEXT WEEK AS AN INVERTED TROUGH APPROACHES THE AREA.
MOISTURE ASSOCIATED WITH THIS SYSTEM LOOKS TO MOVE INTO THE AREA
DURING THE DAY ON TUESDAY. WE WILL CONTINUE TO MONITOR THIS SYSTEM
AND POPS MAY NEED TO BE INCREASED IN LATER FORECASTS AS THE EVENT
GETS CLOSER AND MODELS COME INTO BETTER AGREEMENT.

Miami NWS Discussion
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Convection on the North and North-east is starting to look much better and less sheared, starting to fire up a little at the centre too. Conditions should keep improving for the next 12-24 hours, certainly running out of time though.
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205. xcool



Central North Atlantic 4km Infrared
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I have a question. Probably dumb, but forgive me. At least I picked a quiet time to ask :) Does the current weather pattern that is causing above-average temperatures in Texas (at least my part-houston area) effect the possibility of early tropical developement? I'm just wondering if we could see earlier formation closer to home next month. Thoughts? Explanations? I'm very novice, but love to learn the why of these things. Thanks in advance for anyone who has an answer.
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Quoting RastaSteve:


That's It! That's exactly what she said. I was shocked when I heard that.


Actually the safest thing to do would be to drive your car into the ditch, best of both worlds.



lol, Weather Channel morons
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91L is moving NNE at the moment from what I can see, looks more consolidated than yesterday too , though now at 10%
Member Since: April 29, 2007 Posts: 0 Comments: 7932
You gotta be kidding me... A storm already...

Although if this is the only one.... I'll take it.
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Lacking luster on the IR.
Defiantly sub-tropical atm.
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Quoting Levi32:
The old center is becoming wrapped up in a larger circulation now. Notice how the main swirl is moving northward on the east side of a larger spin.

RGB Loop
Yep, I agree with you on that one. The low-cloud pattern on the rest of the larger circulation goes along with this. Its almost like the old center has become a vort within the larger circulation.
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196. JRRP
91L looks like Olga 2007

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It's likely because the upper low being in close proximity is lowering pressures at the surface on a broader scale.
Member Since: November 24, 2005 Posts: 635 Comments: 26661
Quoting jeffs713:
I think another question that deserves asking...

Why are you watching TWC?

You know what drives me bananas about them, they will have a video of a tornado touching down, but they will put a banner up across the bottom that says something like "Tornado destroys barn" but the banner is covering the barn! All you see is a bunch of debris flying around in the air. I have actually called them a few times to ask them if they are watching their own program.
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Well good night. See ya'll in the morning. Play nice:)
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Quoting Levi32:
The old center is becoming wrapped up in a larger circulation now. Notice how the main swirl is moving northward on the east side of a larger spin.

RGB Loop


Yeh, I think the centre has moved to the north-west. Probably explains why we lost the westerlies earlier today.
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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.