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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I guess no advisorys for 91L yet
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Probably should wait for recon at 18z to see if the circulation is still broad or not.


Member Since: June 9, 2007 Posts: 4 Comments: 15921
Quoting cat5hurricane:

Recon will be around there at about 1pm EDT. Think they are waiting to get more from them.


I would agree... from what Jeff wrote, they appear to use facts, logic, and baseline criteria... apparently unlike many on here..they are not allowed to guesstimate.
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Quoting reedzone:
NHC did not pull the trigger on this update.
As I've said before they will probally wait to upgrade it when the hh gets in their this afternoon.
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1329. pottery
BBL.
It's a busy one here....
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Quoting Floodman:
We're getting ahead of ourselves here...there is hardly a model consesus on "Tomas" and most of what I'm seeing has him (if he gets that far) passing south of Puerto Rico. Hispaniola is at far greater risk at this point than Puerto Rico. Why don't we wait a bit and see how the next model run shakes out before we start screaming and standing on chairs...


Now stop that... you know better then to ruin the kids fun with facts and logic.
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VIS LOOP : NW JOG AT THE END
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Good Morning.........Just waiting for the update from Dr. M to clear the air but if "Thomas" does form from this disturbance, it does appear, for the moment, that it would be a rather large system with a broad area of potential impact.
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1323. pottery
Quoting Floodman:
We're getting ahead of ourselves here...there is hardly a model consesus on "Tomas" and most of what I'm seeing has him (if he gets that far) passing south of Puerto Rico. Hispaniola is at far greater risk at this point than Puerto Rico. Why don't we wait a bit and see how the next model run shakes out before we start screaming and standing on chairs...

Yeh!
But standing on chairs and screaming is much more fun, than sitting and waiting.
Get loose, man!
heheheheh
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Quoting Neapolitan:

Just a little bit of photoshop... ;-)


It can't be... the NHC forecaster is secretly Neapolitan... it says on the top bar!
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Quoting reedzone:


Impressive, how did you pull that one? :)

Just a little bit of photoshop... ;-)

Shary's ACE is now at 0.3675, putting her right up there with the 2010 powerhouse pair of Bonnie and Gaston.
Member Since: November 8, 2009 Posts: 4 Comments: 13571
We're getting ahead of ourselves here...there is hardly a model consensus on "Tomas" and most of what I'm seeing has him (if he gets that far) passing south of Puerto Rico. Hispaniola is at far greater risk at this point than Puerto Rico. Why don't we wait a bit and see how the next model run shakes out before we start screaming and standing on chairs...
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NHC did not pull the trigger on this update.
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Quoting TropicalMan2010:
1301:im watching it they havent mention it as a top story for this morning wierd.
This is when TWC goes into selfesh mode.if it's not affecting the united states or won't be affecting it in the coming days then it doesn't matter to them.When a storm hits another country it cuases death,and destruction just like when a storm hits the U.S.
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1316. JRRP
Member Since: August 16, 2007 Posts: 0 Comments: 5988
Quoting Neapolitan:
To those second-guessing the NHC, you should write to tell them you want to see more of the mets there doing this:

Appropriate tropical weather-related image

;-)


Impressive, how did you pull that one? :)
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1314. JRRP
Member Since: August 16, 2007 Posts: 0 Comments: 5988
NHC update on Shary... no difference in windspeed, just in forward speed.
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Quoting kshipre1:
thanks Reed. I have not seen the surface area map but is there a area of high pressure just off the florida coast? If so, is it not supposed to be strong enough to steer west?

I ask because of the strong storm system coming down to south next week (trough)


Any trough should keep the USA safe for the rest of the season. Its late October/Novemeber, we won't see a system travel very far to the west without being recurved. However, the EURO solution comes into mind that the storm does escape a trough and gets pushed southwest into the Western Caribbean, a possible scenario, but even if it recurves at that point, will be east of the USA. In order for Florida to get hit, a storm would have to be in the GOM.
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To those second-guessing the NHC, you should write to tell them you want to see more of the mets there doing this:

Appropriate tropical weather-related image

;-)
Member Since: November 8, 2009 Posts: 4 Comments: 13571
Quoting washingtonian115:
Can you belive what the weather channel said in their tropical update?."All is quite in the carribean and rest of atlantic".Do they not see the storm near the lesser antillies?


I used to watch TWC back when I was a teenager, after that, they really went low. They're pretty much runned by morons, the Hurricane Authority? I think not!
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thanks Reed. I have not seen the surface area map but is there a area of high pressure just off the florida coast? If so, is it not supposed to be strong enough to steer west?

I ask because of the strong storm system coming down to south next week (trough)
Member Since: July 12, 2010 Posts: 0 Comments: 1130
Complete Update



AOI
AOI AOI AOI

AOI AOI AOI

TS BUSTED FORECAST ALIBI
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Quoting KeysieLife:
Seems to have been a trend this year...storms becaming an Invest, then jumping straight to TS status...holy tomatoes this late in the season though!?

On Aug 15, 2010, many thought this season would be a bust, only 3 TC's on the books..

FAST Foward to Oct 28, 2010...

We are at 18-10-5 and 91L looks like a TS w/50-60 MPH winds!!
Member Since: August 25, 2009 Posts: 20 Comments: 6785
Can you belive what the weather channel said in their tropical update?."All is quite in the carribean and rest of atlantic".Do they not see the storm near the lesser antillies?
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1300. Gorty
I know I havent been on much here this past week its just I* have a really bad canker sore and I am fed up with the pain so I didnt feel like posting much on here and pretty much doing any talking. But today, the pain is less, so I hope over the weekend I will be feeling no pain but if not then, then early next week.

September 2010=record. No other season on record produced 8 named storms,

And October this year has been pretty active. 4 storms so far, and if Tomas dpes form in this month, that will be 5! It seems like 2010 wants to catch up to 2005.
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Quoting lovejessicaa9:


Rainbow imagery is probably the best IR in my opinion.
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Quoting Bordonaro:

This is a "Matthew"JR..Right past TD status..Just waiting for the "official word"!!
Seems to have been a trend this year...storms becoming an Invest, then jumping straight to TS status...holy tomatoes this late in the season though!?
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nice stormpetrol you also have a family member by the name of Tom well I have one too he can be great but sometimes a pain in the butt but a great guy
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It's interesting how this will come together. I believe the anticyclone will stick around it long enough to make the Hurricane number rise to 11. My prediction was 15-18 storms, 9 or 10 Hurricanes, and 5 majors.
Total count - 18/10/5, heading towards 19 storms later today.

I was actually below the actual count, which is unusual. Impressive Hurricane Season, not boring at all as most people say. I liked tracking awesome storms like Earl and Igor, where Earl was a close call for the USA and Igor was most likely a Category 5, should be bumped in post analysis.
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Quoting kimoskee:


LOL! Good Morning.

Looks like a busy weekend for us islanders.
Stay dry and get alot of indoor games for the kids to keep them busy. Cause I don't think they'll be outside much. :-(

This is a "Matthew"JR..Right past TD status..Just waiting for the "official word"!!
Member Since: August 25, 2009 Posts: 20 Comments: 6785
Quoting Bordonaro:

If the tree drives away in your auto, RUN!!


LOL! Good Morning.

Looks like a busy weekend for us islanders.
Stay dry and get alot of indoor games for the kids to keep them busy. Cause I don't think they'll be outside much. :-(
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Quoting stormpetrol:
I think no matter where future Tomas goes, most of the caribbean will feel some effects from it due to his enormous size!
Just like when the entire gulf coast felt the effects of Ike.And he made landfall in Galveston.
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Quoting kshipre1:
reed,

any chance you see of 91L moving futher westward instead of recurving near eastern cuba?

I am assuming the High above will not be that strong


I believe it will recurve at some point, most likely east of Florida.
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I think no matter where future Tomas goes, most of the caribbean will feel some effects from it due to his enormous size!
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What is taking the FNMOC Navy so long to put the new info up on Tomas????
Member Since: August 25, 2009 Posts: 20 Comments: 6785
Quoting wunderkidcayman:
kshipre1 I think that 91L will move south of Jamaica and recurve near the Caymans and into central Cuba and Central Bahamas

Please don't say that, one "tom" in the family is quite enough!
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Quoting pottery:

Nore have some of the Posters on here!
LOL
Now thats funny.
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1283. hydrus
Quoting CyclonicVoyage:
I think that's the best looking invest I've ever seen in my lifetime.
The NCEP has Haiti getting the worst of it..Link Cannot get the link to work..It shows the storm moving slowly right across the middle of the island.
Member Since: September 27, 2007 Posts: 1 Comments: 21433

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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.