An evening shift at NHC: A Shary situation

By: Dr. Jeff Masters , 2:57 PM GMT on October 28, 2010

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We have a rare late October triple threat in the Atlantic this morning, three "Invests" with a decent chance of developing. The most serious threat is Invest 91L, a tropical wave centered near 7N 49W, about 950 miles east-southeast of the Lesser Antilles Islands. 91L is moving west to west-northwest at 15 - 20 mph, and will spread heavy rains and gusty winds to the northern coast of South America and the southern Lesser Antilles Islands beginning on Friday night. The system is under low wind shear less than 10 knots, but is too close to the Equator to spin up very rapidly. The storm will also have difficultly developing due to land interaction with South America this weekend. However, several models are indicating the possibility that 91L could develop into a tropical depression in the Central Caribbean by the middle of next week. NHC is giving 90L a 20% chance of developing into a tropical cyclone by Saturday.

A low pressure system (Invest 90L) centered near 27N 42W in the middle Atlantic Ocean has developed a broad and elongated circulation. Heavy thunderstorms on its east side are generating tropical storm-force winds. However, the circulation of 90L has become increasingly stretched out this morning, and the storm is not as well organized as it was last night. NHC is giving 90L a 50% chance of developing into a tropical storm by Saturday.

Finally, a low pressure system (Invest 92L) centered 700 miles south-southeast of Bermuda is developing a surface circulation, and appears very close to tropical depression status. NHC is giving 92L a 60% chance of developing into a tropical cyclone by Saturday. The only land area that might be affected by 92L is Bermuda.


Figure 1. A rare late-October triple threat in the Atlantic: three areas of disturbed weather listed by NHC as areas of interest (Invests) worth running forecast models on. Image credit: National Hurricane Center.

A quiet Tuesday evening shift at NHC
Tuesday evening was a quiet shift at the National Hurricane Center, where I've spent the week as a participant in their visiting scientist program. Each week during hurricane season, NHC invites a hurricane researcher or forecaster in academia, government, or private industry to spend a week shadowing the NHC forecasters as they prepare their forecast products. The evening shift is chosen, since it is less of a zoo, and the presence of the visiting scientist will present less of a distraction to the forecasters.

There was only one area of interest (Invest 90L) on Tuesday. 90L was a disorganized low pressure system in the middle Atlantic that had gotten tangled up with an upper-level low pressure system that was bringing dry air and disruptive wind shear. I worked with senior hurricane specialist Dan Brown, who cheerfully analyzed 90L with me, but confided that this storm was barely worth keeping as an Invest. He lowered its chances of development to 10%, but did order one more run of the various forecast models, so I could see how that was done. He also pointed out two other systems he thought might turn into "Invests" worth watching later in the week, and noted in particular that the large tropical wave approaching South America was unusually vigorous for this time of year, and might be something to be concerned about if it managed to avoid South America and penetrate into the southern Caribbean.

Since there wasn't much else to see on the hurricane end of their operation, I spent the rest of the evening working with NHC's marine forecasting branch. The National Hurricane Center is responsible for preparing weather analysis charts and marine forecasts for the tropical Atlantic and Eastern Pacific, and I worked with meteorologist Felix Garcia of NHC's Tropical Analysis and Forecast Branch (TAFB). He prepared the 8pm Tropical Weather Discussion, and the 00Z tropical analysis chart. I'm highly envious of the software tools NHC has to prepare forecasts and make analysis charts! I want an NAWIPS and ATCF workstation like these guys have, which allows one to zoom, pan, overlay, and quickly change speeds of animations. I'm proud to say that I am responsible for a portion of the 1016 mb isobar on the 00Z tropical Atlantic surface analysis map for Tuesday night, which I drew using the fantastic map drawing software at NHC.

Wednesday evening: A Shary situation
Wednesday evening was a bit more interesting. Invest 90L had been joined by Invest 91L and Invest 92L, and odds for development of 90L had been bumped up to 30%. I spent the first portion of the shift working with TAFB forecaster Wally Barnes, who made the intensity and position estimates of the three invests based on infrared satellite imagery. This task is accomplished using the Dvorak technique, a system of classifying cloud patterns of tropical cyclones based on how cold the cloud tops are, how much spiral banding is present, and other factors. Wally let me determine where the center of 90L was at 00Z last night, and enter the fix into the official database. I am now forever responsible for a tiny piece of the 2010 Atlantic hurricane data base--an awesome responsibility! (It's my first addition to the cause since I sent in my final Hurricane Hunter VORTEX report from the eye of Hurricane Hugo on September 15, 1989, complaining about hitting 5.7 G's of acceleration.) We classified 90L as a T2.0, which is respectable, and meant the system might be on its way to status as Tropical Storm Shary. Wally had to do the analysis for the large, ill-defined tropical wave (Invest 91L), since his eye was much more highly trained to pick out subtle motions in the satellite animations that indicated where the most likely center of circulation might be trying to develop.


Figure 2. "My boat is right here!" Forecaster Wally Barnes of NHC's Tropical Analysis and Forecasting Branch (TAFB) shows where he suspects the center of rotation of Invest 91L might be at 00Z on October 28, 2010.

Wally and I printed out the fix information we'd come up with for 90L, and took it over to Dan Brown, who was working the evening shift again over at the hurricane side of NHC.

"What, you're giving this a T2.0?" Dan good-naturedly hassled us, as we presented the fix info. "You're just trying to get something going for Jeff here so he can see some advisories get issued." Wally defended our analysis, pointing out how the heavy thunderstorms of 90L were pushing closer to the center of circulation, and how the cloud tops had gotten much colder. Dan agreed that 90L really was worthy of more attention, and commented that there was a good chance one of our three invests would probably develop into something NHC would have to issue advisories on before my final shift at NHC ended on Friday night. His prediction was that it would be 92L, the system a few hundred miles north of Puerto Rico.

An hour later, Dan wasn't so sure that 90L wouldn't beat 92L to the title of Tropical Storm Shary. The European ASCAT satellite had just sent in an image of the surface winds over 90L, and ASCAT was showing that the storm had a closed circulation and a respectable area of 40 mph tropical storm-force winds. He gave a call to James Franklin, the head of the hurricane specialist unit at NHC, who was at home. I listened in.

"Hey, I just got ASCAT," said Dan. "It's 35 knots. You can see the center, and the convection is about 130 miles to the northeast. I'm thinking of starting it as a tropical storm, but I hate to start it now, since the convection started at 21Z, and I'd like to see it persist. The ASCAT pass shows the circulation is a bit elongated, and the most recent microwave images are also showing that."

After discussing whether or not to initiate advisories on Tropical Storm Shary for a few more minutes, Dan hung up, then told me the scoop. "This is one of the most difficult parts of the job. It's a real judgment call whether or not to name a storm, when it's such a borderline situation like this. What we're going to do is issue a Special Tropical Weather Outlook mentioning that 90L has gale-force winds, bump the probability of development up to 50 or 60%, watch it for a few more hours, then re-assess." Dan then proceeded to call his replacement, Eric Blake, who was due to work the night shift, to tell him to come in as planned, since it looked like there could well be a Tropical Storm Shary to deal with. Dan then proceeded to write the Special Tropical Weather Outlook and send it out.


Figure 3. "The one that got away was this big!" Wally Barnes tells hurricane specialist Dan Brown what he thinks of 90L's recent burst of heavy thunderstorm activity.

Next update
I'll have an update on Thursday morning from the National Hurricane Center on the latest from the tropics.

Jeff Masters

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Quoting Chicklit:

you can better take a hit than yucatan or mexico.
Mexico and the yucatan has been hit multiple times this year.So maybe Bermuda can take a hit for them?
Member Since: August 14, 2010 Posts: 10 Comments: 16406
Waiting patiently for the 11PM update ... on Invest 91L, of course!!!
Member Since: June 3, 2002 Posts: 0 Comments: 64
Quoting JLPR2:


Be optimistic saying things like: eh! it could fall apart, it could loose the anticlone, maybe it will head north.
Not saying things that are false.


I admit I don't 'do' technical weather stuff but I'm savvy enough to know we've had bad storms in November.... Kerry was doing 'her' best. :)
Member Since: August 21, 2010 Posts: 0 Comments: 96
728. ackee
so we now have TS Shary ?
Member Since: Posts: Comments:
Member Since: July 11, 2006 Posts: 14 Comments: 11173
726. JLPR2
Quoting CaribBoy:


Lenny was a high-end Cat4 in the NE caribbean on nov 17th 1999.......
Paloma was a Cat 4 in november 2008

So....


So... what?
Member Since: September 4, 2007 Posts: 7 Comments: 8499
Quoting KerryInNOLA:
Relax.Any day it will be November. Really bad storms don't form in November.
I guess you did not know anything about Paloma.
Member Since: Posts: Comments:
Quoting JLPR2:


I guess you missed Lenny. XD


Lenny was a high-end Cat4 in the NE caribbean on nov 17th 1999.......
Paloma was a Cat 4 in november 2008

So....
Member Since: Posts: Comments:
Quoting brohavwx:


Yeah, you Trinis don't usually have to worry about these things and most Bajans think God is a Bajan so we don't get hit too often - whatever, in modern terms, as they say.

BTW, I've been on about this for a while but how come you all Trinis (and Guyanese) get ya Doppler Radar on the internet and ours still is a no go? An outside opinion (or rumour) would be welcome.

True!
Usually it is you Bajans who are first with these things like Radar.
What is your take on the track?
Member Since: October 24, 2005 Posts: 0 Comments: 24024
I think 91L Tomas not far behind!
Member Since: Posts: Comments:
Quoting Stormchaser2007:
Next up, Tomas.


I'm sure we will see Tomas in the really near future.
Member Since: Posts: Comments:
Quoting pottery:

Agree with that.
You are talking the 'center' though.
Even if it gets as north as B'Dos, we will feel it.
Check the size of the thing!


I'm not sure which Island I prefer to be on, it looks big enough to cover the entire Island chain.
Member Since: August 21, 2010 Posts: 0 Comments: 96
Quoting pottery:
So, TROPICAL Storm Shary.
I was wrong.
Again.
Oh well....
Check this out..You may have to move the image. Use the cursory bar at the bottom of the image...Link
Member Since: September 27, 2007 Posts: 1 Comments: 20495
718. JLPR2
Quoting KerryInNOLA:
Just trying to be optimistic for Grenada. Y'all scaring him to death.


Be optimistic saying things like: eh! it could fall apart, it could loose the anticlone, maybe it will head north.
Not saying things that are false.
Member Since: September 4, 2007 Posts: 7 Comments: 8499
Next up, Tomas.

Member Since: June 9, 2007 Posts: 4 Comments: 15776
Quoting Stormchaser2007:
Tropical Storm Shary has formed.


Probably did it just for Dr.Jeff lol
I was thinking the exact same thing. LOL.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
Quoting DDR:

Hi
Yea im thinking the same thing here
Are you from San Fernando?


Yup...close to San'Do. I'm not venturing far away from there tomorrow.
Member Since: August 24, 2006 Posts: 0 Comments: 52
Quoting sunlinepr:


A More northerly track will split the island in two.....
I'm getting worried

We are almost certainly going to get bad weather out of this.. I can see no way around it. The ULL is moving NW at about the same rate as 91. You can see that in the sat loops so shear is not going to save us although it will hopefully keep it weaker. recurving south of us might be nice if there is enough shear to weaken it when it gets picked up..
A LOT now depends on that cold front and how fast 91 develops. Pressure is not going to keep it south either for at least the next 60 hours.

Member Since: September 1, 2009 Posts: 23 Comments: 1007
Quoting DDR:
wind shear appears slighty higher on the western side,my thinking is it will pass just north of Tobago,im expecting 4 + inches.

Agree with that.
You are talking the 'center' though.
Even if it gets as north as B'Dos, we will feel it.
Check the size of the thing!
Member Since: October 24, 2005 Posts: 0 Comments: 24024
Quoting washingtonian115:
Shary pleae don't give bermuda a hard time.

you can better take a hit than yucatan or mexico.
Member Since: July 11, 2006 Posts: 14 Comments: 11173
Shary pleae don't give bermuda a hard time.
Member Since: August 14, 2010 Posts: 10 Comments: 16406
710. JLPR2
Quoting washingtonian115:
And Paloma,and also Michelle.


Yep, quite a few strong ones in November.
Member Since: September 4, 2007 Posts: 7 Comments: 8499
Quoting pottery:

Long time, Shaman.
Rumours? They said that?
heheheh


Yeah, you Trinis don't usually have to worry about these things and most Bajans think God is a Bajan so we don't get hit too often - whatever, in modern terms, as they say.

BTW, I've been on about this for a while but how come you all Trinis (and Guyanese) get ya Doppler Radar on the internet and ours still is a no go? An outside opinion (or rumour) would be welcome.
Member Since: June 3, 2002 Posts: 0 Comments: 64
I see we have TS Shary, I thought she would be sub-tropical, but I knew 92L would get a name

Member Since: Posts: Comments:
Quoting sailingallover:
It's a Caribbean party tonight..where is weather456..

456 is being a daddy, tending to his wife and child.
A happy soul I hope.
Member Since: July 11, 2006 Posts: 14 Comments: 11173
92l, or should I say Shary.
Member Since: Posts: Comments:
The system is under low wind shear less than 10 knots, but is too close to the Equator to spin up very rapidly. The storm will also have difficultly developing due to land interaction with South America this weekend. However, several models are indicating the possibility that 91L could develop into a tropical depression in the Central Caribbean by the middle of next week. NHC is giving 90L a 20% chance of developing into a tropical cyclone by Saturday.

Dr. Jeff Masters
Inside the Hive
Member Since: July 11, 2006 Posts: 14 Comments: 11173
So, TROPICAL Storm Shary.
I was wrong.
Again.
Oh well....
Member Since: October 24, 2005 Posts: 0 Comments: 24024
It's a Caribbean party tonight..where is weather456..
Member Since: September 1, 2009 Posts: 23 Comments: 1007
701. washingtonian115
2:00 AM GMT on October 29, 2010
Quoting JLPR2:


I guess you missed Lenny. XD
And Paloma,and also Michelle.
Member Since: August 14, 2010 Posts: 10 Comments: 16406
700. sunlinepr
2:00 AM GMT on October 29, 2010
Quoting sailingallover:

I gotta go with a way more northerly course than the GFS. The 1800 model run has it going to just south of haiti..but the fact it is finally initializing and running with it is significant


A More northerly track will split the island in two.....
I'm getting worried
Member Since: August 2, 2010 Posts: 21 Comments: 9694
699. caneswatch
2:00 AM GMT on October 29, 2010
Quoting MiamiHurricanes09:
20L develops.

invest_RENUMBER_al922010_al202010.ren


Pottery was right, throw climatology out the door.
Member Since: October 8, 2008 Posts: 14 Comments: 4553
698. Stormchaser2007
2:00 AM GMT on October 29, 2010
Tropical Storm Shary has formed.


Probably did it just for Dr.Jeff lol
Member Since: June 9, 2007 Posts: 4 Comments: 15776
697. DDR
1:59 AM GMT on October 29, 2010
Quoting shamanTT:
Hey DDR,

I'm expecting almost everyone in T&T to leave work by noon tomorrow..... especially if that 91L turns from orange to red overnight.

Hi
Yea im thinking the same thing here
Are you from San Fernando?
Member Since: April 27, 2007 Posts: 14 Comments: 1685
696. hydrus
1:59 AM GMT on October 29, 2010
Quoting JLPR2:


I guess you missed Lenny. XD
Check out this link. It has awesome pics and loops of everything..Link
Member Since: September 27, 2007 Posts: 1 Comments: 20495
695. Neapolitan
1:58 AM GMT on October 29, 2010
BEGIN
NHC_ATCF
invest_al202010.invest
FSTDA
R
U
040
010
0000
201010290147
NONE
NOTIFY=ATRP
END
SHARY, AL, L, , , , , 20, 2010, TS, O, 2010102718, 9999999999, , , , , , METWATCH, , AL202010
AL, 20, 2010102618, , BEST, 0, 215N, 520W, 25, 1009, DB, 0, , 0, 0, 0, 0,
AL, 20, 2010102700, , BEST, 0, 217N, 523W, 25, 1009, DB, 0, , 0, 0, 0, 0,
AL, 20, 2010102706, , BEST, 0, 219N, 527W, 25, 1009, DB, 0, , 0, 0, 0, 0,
AL, 20, 2010102712, , BEST, 0, 222N, 531W, 25, 1009, DB, 0, , 0, 0, 0, 0,
AL, 20, 2010102718, , BEST, 0, 226N, 540W, 25, 1010, DB, 0, , 0, 0, 0, 0, 1013, 230, 40, 0, 0, L, 0, , 0, 0, INVEST, D,
AL, 20, 2010102800, , BEST, 0, 229N, 553W, 25, 1010, DB, 0, , 0, 0, 0, 0, 1012, 160, 60, 0, 0, L, 0, , 0, 0, INVEST, M,
AL, 20, 2010102806, , BEST, 0, 235N, 567W, 30, 1009, LO, 0, , 0, 0, 0, 0, 1011, 120, 80, 0, 0, L, 0, , 0, 0, INVEST, S,
AL, 20, 2010102812, , BEST, 0, 241N, 587W, 30, 1009, LO, 0, , 0, 0, 0, 0, 1011, 120, 80, 0, 0, L, 0, , 0, 0, INVEST, S,
AL, 20, 2010102818, , BEST, 0, 252N, 607W, 30, 1009, LO, 0, , 0, 0, 0, 0, 1011, 140, 80, 0, 0, L, 0, , 0, 0, INVEST, S,
AL, 20, 2010102900, , BEST, 0, 268N, 627W, 35, 1006, TS, 34, NEQ, 90, 0, 0, 90, 1012, 150, 50, 0, 0, L, 0, , 0, 0, SHARY, M,
Member Since: November 8, 2009 Posts: 4 Comments: 13456
694. Chicklit
1:58 AM GMT on October 29, 2010
An evening shift at NHC: A Shary situation

tee hee.
Member Since: July 11, 2006 Posts: 14 Comments: 11173
693. DDR
1:58 AM GMT on October 29, 2010
Quoting pottery:

I am not surprised to see the models trending a little more north right now.
As the system gets more organised it should tend to do that.
Also, a lot of upper level flow is acting on it, pushing it away somewhat.

It's a very big one though, we will all get some weather down here from this.
How much ????
wind shear appears slighty higher on the western side,my thinking is it will pass just north of Tobago,im expecting 4 + inches.
Member Since: April 27, 2007 Posts: 14 Comments: 1685
692. sailingallover
1:57 AM GMT on October 29, 2010
Quoting pottery:

Maybe you did'nt notice, but Climo is out the window, right now...

And i was sure we were done except a backwards storm..but 91 is going to affect us both ways unless that cold front MOVES and it is looking anemic too..Only way we have out of a mess is if it stays south and then shear rips it up before it gets to land..
Member Since: September 1, 2009 Posts: 23 Comments: 1007
691. MiamiHurricanes09
1:56 AM GMT on October 29, 2010
Shary develops.

invest_RENUMBER_al922010_al202010.ren

AL, 20, 2010102900, , BEST, 0, 268N, 627W, 35, 1006, TS
Member Since: September 2, 2009 Posts: 130 Comments: 21091
690. pottery
1:56 AM GMT on October 29, 2010
Quoting shamanTT:
How soon do you think Trinis will start to panic? CNC3 news mentioned that rumours were in abundance of a trpoical storm approaching.

Long time, Shaman.
Rumours? They said that?
heheheh
Member Since: October 24, 2005 Posts: 0 Comments: 24024
689. shamanTT
1:56 AM GMT on October 29, 2010
Hey DDR,

I'm expecting almost everyone in T&T to leave work by noon tomorrow..... especially if that 91L turns from orange to red overnight.
Member Since: August 24, 2006 Posts: 0 Comments: 52
688. sailingallover
1:55 AM GMT on October 29, 2010
Quoting sunlinepr:







I gotta go with a way more northerly course than the GFS. The 1800 model run has it going to just south of haiti..but the fact it is finally initializing and running with it is significant
Member Since: September 1, 2009 Posts: 23 Comments: 1007
687. JLPR2
1:54 AM GMT on October 29, 2010
Quoting KerryInNOLA:
Relax.Any day it will be November. Really bad storms don't form in November.


I guess you missed Lenny. XD
Member Since: September 4, 2007 Posts: 7 Comments: 8499
686. CaribbeanStorm
1:54 AM GMT on October 29, 2010
Quoting roleli:
91L looks like it will need to be watched carefully here in Jamaica. Our friends in Trinidad & Tobago and Northern part of South America will have to pay attention...


Yes, we have to watch this closely...memories of Gilbert?
Member Since: June 4, 2006 Posts: 9 Comments: 132
685. Chicklit
1:53 AM GMT on October 29, 2010
Quoting pottery:

Maybe you did'nt notice, but Climo is out the window, right now...
]
this is one reason i like you potts
Member Since: July 11, 2006 Posts: 14 Comments: 11173
684. DDR
1:53 AM GMT on October 29, 2010
ShamanTT
I don't think anyone is since the news said it was a rumor,but we should expect plenty rain
Member Since: April 27, 2007 Posts: 14 Comments: 1685

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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.