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 CyclonicVoyage:


I surely don't agree with you there. Saying anyone is out of the woods at this point is rather foolish.

Did Richard not school the best of them?


Yes richard has been a nightmarre to predict. However it's not possible to say with precision which area will be affected after the windwards.
Member Since: October 6, 2007 Posts: 0 Comments: 5930
Shary is more than likely not going to strengthen today...I don't know what is with it, but every time a storm gets close to Bermuda, it dies out.

With the case of Igor, becomes extra-tropical.

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Quoting Neapolitan:

ftp://ftp.tpc.ncep.noaa.gov/atcf/tcweb/


Thanks.
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1178. 7544
what time recon goes in tia
Member Since: May 6, 2007 Posts: 0 Comments: 6690
1177. KEEPEROFTHEGATE (Mod)
Quoting FtMyersgal:


Hello Keep. Do you think TD or TS? I think TD and NHC will wait for the recon reports
init will be TD 21L then during or after recon TS Tomas i reckon
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1176. 7544
once this is clasified the new model runs will be interesting as well as the big 5 day cone may go further west imo
Member Since: May 6, 2007 Posts: 0 Comments: 6690
1175. divdog
Quoting Jeff9641:
It looks like we are going to have a major hurricane in the Caribbean next week as 91L has a classic shape and this appears as if it wants to reall ramp up now. I would say this is a 50mph storm right now.
It would be classified as a tropical storm if it was. Quit trying to make yourself seem smarter than the NHC. It would be classified if it met the criteria for a TS.
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Quoting CaribBoy:


so 91L could be a problem anywhere from the windwards, to the N and NE caribbean... Models are just all over the place but there is a good agreement that Thomas will recurve in the caribbean.


I surely don't agree with you there. Saying anyone is out of the woods at this point is rather foolish.

Did Richard not school the best of them?
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Quoting CaribBoy:


No this thing can't hit haiti, I refuse to believe it.. but time will tell


I believe they have a name for that... I just can't remember what it is.. denial or something.
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Quoting TropicalAnalystwx13:
Can I have the link to the ATCF site?

ftp://ftp.tpc.ncep.noaa.gov/atcf/tcweb/
Member Since: November 8, 2009 Posts: 4 Comments: 13459
Quoting 7544:
haiti really needs to watch 91l then the bahamas imo


No this thing can't hit haiti, I refuse to believe it.. but time will tell
Member Since: October 6, 2007 Posts: 0 Comments: 5930
Can I have the link to the ATCF site?
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I think 91L's COC is now at 10N
Member Since: October 6, 2007 Posts: 0 Comments: 5930
Tropical Depression 20/Tropical Storm Tomas should be up in just a little bit.

We're undergoing a renumber.

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1167. 7544
haiti really needs to watch 91l then the bahamas imo
Member Since: May 6, 2007 Posts: 0 Comments: 6690
Quoting CaneBob:
It appears that 91L poses no threat to the Continental United States as it develops into a TS today and a hurricane within 24-48 hours if not earlier. The movement will take the storm Northwest eventually North and than Northeast. Residents of Hispanola, Puerto Rico, Cuba and the Turks and Caicos Islands should pay close attention to this storm as should all interests in the Caribbean and United States.


perfectly agree
Member Since: October 6, 2007 Posts: 0 Comments: 5930
Quoting KEEPEROFTHEGATE:
navy took down 91 l may be upgrade soon


Hello Keep. Do you think TD or TS? I think TD and NHC will wait for the recon reports
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Complete Update



AOI
AOI AOI AOI

AOI AOI AOI

TS BUSTED FORECAST ALIBI
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Probably a renumber by 9am.
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I will go with A seems we have had too may jump right to TS status this year...
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Quoting CyclonicVoyage:
Morning All. No land for 91L this time around. Development looks immanent. My initial thoughts are a turn Nward before 80W however, he's a biggin so, we'll let this one perculate a while.



so 91L could be a problem anywhere from the windwards, to the N and NE caribbean... Models are just all over the place but there is a good agreement that Thomas will recurve in the caribbean.
Member Since: October 6, 2007 Posts: 0 Comments: 5930
Quoting TropicalAnalystwx13:
Poll time!

A. Tropical Storm (Includes Subtropical)

B. Tropical Depression (Includes Subtropical)

C. None




B.

Due to the size it will take longer than normal.
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1155. 7544
starting to wrap around at this hour the plane may find a strong ts today
Member Since: May 6, 2007 Posts: 0 Comments: 6690
Poll time!

A. Tropical Storm (Includes Subtropical)

B. Tropical Depression (Includes Subtropical)

C. None

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1153. WxLogic
Positive MJO:



NAO... still in the negative, but trending towards neutral so it will be interesting for sure:

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Very Very close

AL, 91, 2010102912, , BEST, 0, 93N, 557W, 30, 1005, DB,
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1150. CaneBob
It appears that 91L poses no threat to the Continental United States as it develops into a TS today and a hurricane within 24-48 hours if not earlier. The movement will take the storm Northwest eventually North and than Northeast. Residents of Hispanola, Puerto Rico, Cuba and the Turks and Caicos Islands should pay close attention to this storm as should all interests in the Caribbean and United States.
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1149. WxLogic
Quoting rmbjoe1954:
91L will become Tomas and if Tomas tracks to the SW Caribbean (south of Jamiaca) climatology would indicate it would move north through central Cuba and then be flung NE through central Bahamas and back to the Atlantic. With that said, I hope I am right.


Well climatology said also that Richard was supposed to enter the E GOM and exit NE, but didn't pan out... as you hinted. It's a matter of waiting.
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91L is definitely a TD by now, they should have classified it at 8...

for comparison, here's TD5 from earlier this year:



They should upgrade it at 11

and it even looks better than Bonnie did:
Member Since: October 15, 2008 Posts: 11 Comments: 2305
Morning All. No land for 91L this time around. Development looks immanent. My initial thoughts are a turn Nward before 80W however, he's a biggin so, we'll let this one perculate a while.

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91L will become Tomas and if Tomas tracks to the Caribbean (south of Jamaica) climatology would indicate it would move north through central Cuba and then be flung NE through central Bahamas and back to the Atlantic. With that said, I hope I am right.
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Quoting Neapolitan:
I see a lot of the standard armchair mets here yet again this morning second-guessing the experts. I should be used to it by now; the conspiracy theorists, the anti-NHC'ers, the HAARP players--all of them claiming to know more than a widely-dispersed group of very talented meteorologists, many who've spent more years looking at hurricanes professionally than some of those here complaining have even been on earth...and that's not to mention their combined decades of advanced schooling leading to numerous doctoral degrees.

sigh...

Guys, there's one solid reason the NHC has not yet classified 91L as a TD or a TS: it's not one yet. Period. And when it is, they will.


Oh God, they've gotten to you too!

;)
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1142. 7544
might see 91L AS TD soon
Member Since: May 6, 2007 Posts: 0 Comments: 6690
I see a lot of the standard armchair mets here yet again this morning second-guessing the experts. I should be used to it by now; the conspiracy theorists, the anti-NHC'ers, the HAARP players--all of them claiming to know more than a widely-dispersed group of very talented meteorologists, many who've spent more years looking at hurricanes professionally than some of those here complaining have even been on earth...and that's not to mention their combined decades of advanced schooling leading to numerous doctoral degrees.

sigh...

Guys, there's one solid reason the NHC has not yet classified 91L as a TD or a TS: it's not one yet. Period. And when it is, they will.
Member Since: November 8, 2009 Posts: 4 Comments: 13459
Quoting cat5hurricane:
Relatively favorable conditions aloft should persist for 91L through at least today. Not a whole lot of shear right now.

Click To Enlarge

The 50knot shear area was centered over St Thomas yesterday..they are moving in tandem
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Quoting KEEPEROFTHEGATE:
2010 Storms
All Active Year


Atlantic
90L.INVEST
20L.SHARY



renumber coming Keeper?
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Quoting 7544:


and it was also said the area that 91L is in was close for bussiness tooo and look what happen ther lol nothing is set in stone this season see what happens first lol


Very true, but key word in my comment "appears" sometime things are not what they appear, you gave an excellent example, climo don't all the time either!
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HWRF still showing some crazy lenny-like / omar-like stuffs

Why is it insisting so much (with LBAR)??
Member Since: October 6, 2007 Posts: 0 Comments: 5930
1136. KEEPEROFTHEGATE (Mod)
2010 Storms
All Active Year


Atlantic
90L.INVEST
20L.SHARY


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Quoting 7544:


and it was also said the area that 91L is in was close for bussiness tooo and look what happen ther lol nothing is set in stone this season see what happens first lol

I don't think the states have to worry as much because of water temps..those area must have..
91 is working it's way between areas of shear and dry air..it is just in the perfect spot/timing/situation to allow development way out of climatology expectations. But the CONUS is soon to be surrounded by cold water while a remnant may hit probability of a strong storm is very slim...
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1133. KEEPEROFTHEGATE (Mod)
navy took down 91 l may be upgrade soon
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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.

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