An evening shift at NHC: A Shary situation

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

Share this Blog
8
+

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

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: 783 - 733

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28Blog Index

Quoting pottery:
Anyone else having trouble loading the Rainbow Loops, C. Atl.?


Sorry to say, No. Internet traffic jam from your part of the globe, perhaps.
Member Since: Posts: Comments:
Quoting brohavwx:
Lets face it, the models are very good during August/Sept/early Oct in the mid-lower Tropics but how much precedent do they have for late Oct. near Nov. systems in the deep tropics like 91L

Point.
Member Since: October 24, 2005 Posts: 0 Comments: 24038
Quoting Orcasystems:
POTTERY... what happened to your little blob.. what did you do?????

Complete Update



AOI
AOI AOI AOI

AOI AOI AOI

TS BUSTED FORECAST ALIBI

T'wernt me!
I was at a Funeral this morning, and mowing my lawn this afternoon.
Behaving myself with DecoRum and stuff....
Member Since: October 24, 2005 Posts: 0 Comments: 24038
Member Since: Posts: Comments:
778. Skyepony (Mod)
Quoting kimoskee:


Thank you.

It looks like alot of rain in the future in the caribbean.

Here in Jamaica we have several communities that are becoming submerged become of rising water. One community called "Chigwell" was featured last night. Unbelievable... a lake where a community use to be...


Is it the astronomically high seasonal tides, just worse than usual? Like Miami last month, South America last winter?
Member Since: Posts: Comments:
Lets face it, the models are very good during August/Sept/early Oct in the mid-lower Tropics but how much precedent do they have for late Oct. near Nov. systems in the deep tropics like 91L
Member Since: Posts: Comments:
POTTERY... what happened to your little blob.. what did you do?????

Complete Update



AOI
AOI AOI AOI

AOI AOI AOI

TS BUSTED FORECAST ALIBI
Member Since: Posts: Comments:
Is this trough from Conus to Gom the one that will wipe out 90 & 92L to the NE Atlantic??? Will it also help keep 91L in a southerly track???....

Member Since: Posts: Comments:
773. JLPR2
Quoting KerryInNOLA:
Sorry, just my sense of humor. Not touchy. No harm intended.


ha! Ok then.

That was some very dark humor. :D
Member Since: September 4, 2007 Posts: 7 Comments: 8500
Member Since: Posts: Comments:
Quoting Stormchaser2007:
18z HWRF for 91L



Do you have a link to that page? thanks
Member Since: Posts: Comments:
Anyone else having trouble loading the Rainbow Loops, C. Atl.?
Member Since: October 24, 2005 Posts: 0 Comments: 24038
Quoting ryang:


Hey pottery

Looks like a VERY wet weekend ahead. We had a wet start to the month and it now looks like we'll have a wet ending. The past two weeks have been very dry, however.

Here too.
Petit Careme has gone on for a while now.
Change is coming. Fast!
Member Since: October 24, 2005 Posts: 0 Comments: 24038
Levi seems to have the handle on this. Scary for us here in Jamaica,
Tropical Tidbits
Member Since: Posts: Comments:
766. ackee
once 91L reach central carrbean IT HAS better chance to be a TD OR TS cold front coming from us will detrmine where it will go from there good night
Member Since: Posts: Comments:
765. ryang
Quoting pottery:

Wondered when you would show up.
Good to see you!


Hey pottery

Looks like a VERY wet weekend ahead. We had a wet start to the month and it now looks like we'll have a wet ending. The past two weeks have been very dry, however.
Member Since: Posts: Comments:
Quoting alfabob:


Buoy 41101 nearly 200 miles to the west is also showing signs of gradual wind speed increase.

Hmm.
Member Since: Posts: Comments:
762. DDR
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.

Your Government is supposed to make it publicly accessible via the internet,so was ours which was completed in 08 but was only made availible when The people's partnership government(new government) came into power in May.
Member Since: April 27, 2007 Posts: 14 Comments: 1691
Quoting ryang:

Wondered when you would show up.
Good to see you!
Member Since: October 24, 2005 Posts: 0 Comments: 24038
Quoting Stormchaser2007:
18z HWRF for 91L


Oh My!!!
Member Since: October 24, 2005 Posts: 0 Comments: 24038
759. ryang
Member Since: Posts: Comments:
18z HWRF for 91L

Member Since: Posts: Comments:
Quoting sailingallover:
I'm off...will watch to see what happens but will probably end up having to move the boat Saturday..

You will out-haul?
Member Since: October 24, 2005 Posts: 0 Comments: 24038
756. JLPR2
Quoting KerryInNOLA:
You're right.

Grenada. 91 could be a Cat 4 like Lenny, but if you are lucky it might turn North and smack someone else.


Well you are very touchy...
But lets stick with reality please a cat 4 would be ridiculous, although not impossible.

Eh... Reality is that 91L has a high probability of developing, but there is the possibility that the high wind shear in the Caribbean doesn't allow it to strengthen so much.
Something like that is what I was expecting you to write. *sigh*
Member Since: September 4, 2007 Posts: 7 Comments: 8500
I think we hit 19 storms with 91L and we could possibly hit 20 with a random system later in November or December.

Pretty interesting season.
Member Since: Posts: Comments:
Good Night.
Member Since: September 1, 2009 Posts: 23 Comments: 1007
Quoting KerryInNOLA:
Thanks, honey. But I'm a guy. :)



So..... you called me a him :)
Member Since: August 21, 2010 Posts: 0 Comments: 96
So much for this season being a bust huh? All those cries from early August are gone.
Member Since: Posts: Comments:
Quoting Neapolitan:
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,


Welcome TS Shary :O)!!!


Let's see, hmmm!!!

That makes 18-10-5 and counting.....
Member Since: Posts: Comments:
91L has me storm watching and it is not even a depression yet or is it? Compared to Richard all the models seem to coming to quick agreements...
Member Since: Posts: Comments:
I'm off...will watch to see what happens but will probably end up having to move the boat Saturday..
Member Since: September 1, 2009 Posts: 23 Comments: 1007
Quoting brohavwx:
Waiting patiently for the 11PM update ... on Invest 91L, of course!!!

You are not alone.
(isnt that a nice feeling?)

P.S ex LodgeBoy here...
Member Since: October 24, 2005 Posts: 0 Comments: 24038
747. JLPR2
Quoting CaribBoy:


So................. powerful canes can occur late in the season


That's my point. XD
Member Since: September 4, 2007 Posts: 7 Comments: 8500
Quoting MiamiHurricanes09:
The 18 named storms this season ties us for the 5th most active season on record. The seasons ahead of us are 1969 (18 named storms), 1887 (19 named storms), 1995 (19 named storms), 1933 (21 named storms), and 2005 (28 named storms).
And soon we will have 19/11/21.Alot ain't it?
Member Since: August 14, 2010 Posts: 10 Comments: 16412
Quoting ackee:
so we now have TS Shary ?
Someone must have a bet...
Member Since: September 1, 2009 Posts: 23 Comments: 1007
91Lrolling



Member Since: July 11, 2006 Posts: 14 Comments: 11176
Quoting MiamiHurricanes09:
The 18 named storms this season ties us for the 5th most active season on record. The seasons ahead of us are 1969 (18 named storms), 1887 (19 named storms), 1995 (19 named storms), 1933 (21 named storms), and 2005 (28 named storms).

I think this season will end up being the 3rd most active season. (20 name storms)
Member Since: Posts: Comments:
Quoting KerryInNOLA:
You're right.

Grenada. 91 could be a Cat 4 like Lenny, but if you are lucky it might turn North and smack someone else.



Well at least you made I laugh lol
Member Since: August 21, 2010 Posts: 0 Comments: 96
Quoting hydrus:
Check this out..You may have to move the image. Use the cursory bar at the bottom of the image...Link

OH!
That's very nice, Thank you!
Member Since: October 24, 2005 Posts: 0 Comments: 24038
Does anyone have the current wind shear map? When I checked this morning, it looked like 90L was going to pass through a small bit of wind shear and reemerge later. I wouldn't write it off quite yet.
Member Since: October 15, 2008 Posts: 11 Comments: 2305
18/10/5
Member Since: July 1, 2008 Posts: 13 Comments: 7340
Quoting JLPR2:


So... what?


So................. powerful canes can occur late in the season
Member Since: Posts: Comments:
The 18 named storms this season ties us for the 5th most active season on record. The seasons ahead of us are 1969 (18 named storms), 1887 (19 named storms), 1995 (19 named storms), 1933 (21 named storms), and 2005 (28 named storms).
Member Since: September 2, 2009 Posts: 130 Comments: 21091
Quoting ackee:
so we now have TS Shary ?

Yep.
AL, 20, 2010102900, , BEST, 0, 268N, 627W, 35, 1006, TS
Member Since: Posts: Comments:
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: 16412

Viewing: 783 - 733

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28Blog Index

Top of Page

About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.