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: 483 - 433

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 Grothar:
Image with shear maps overlay.

It has the almighty anticyclone on top of it.Something that the stronger storms earlier this season had....not good.And why you switch your avatar?
Member Since: August 14, 2010 Posts: 10 Comments: 16981
I got booed last night by some for posting this same data from yesterday, but it is what it is: HAMweather says 41 record low, or record low maximum, temps have been set or tied in the past 24 hours, while in that same time frame, 473 record high, or high minimum, temps have been set or tied. (Very cold in a few places, though; Leadville, Colorado, broke its previous record low of 7 degrees by five, coming in at just 2. Of course, Leadville is at 10,152 feet in the Rockies, but still...)
Member Since: Posts: Comments:
Quoting jasoniscoolman2010xo:
HERE COME THE COLD WEATHER MAYBE SNOW SOON.
Yeah my overnight lows will drop into the 40's.I don't like cold air....
Member Since: August 14, 2010 Posts: 10 Comments: 16981
Quoting Grothar:
Image with shear maps overlay.



A little anti-cyclone over it. I have a bad feeling about this.
Member Since: October 8, 2008 Posts: 14 Comments: 4553
479. Skyepony (Mod)
GOM
Member Since: Posts: Comments:
91L is a huge tropical system. Some potential of threatening Hispanola as a significant hurricane.
Member Since: Posts: Comments:
Good Evening.
92L looks really good, while 91L has that dangerous look to it.
Member Since: Posts: Comments:
91L seems as if it wants to take a Ivan route so late in the season. I am a bit worried that it could impact Jamaica next week as a strong Hurricane. What do you all think? I know it is still a bit early out but it seems to be getting its act together.
Member Since: Posts: Comments:
473. Skyepony (Mod)
Cloudsat of the wave stepping low off Africa.. impresssive..brown line along bottom is Ground, blue is water.
Member Since: Posts: Comments:
Image with shear maps overlay.

Member Since: July 17, 2009 Posts: 71 Comments: 26156
When was the last time anything cropped up from this low, anyone remember??? I cannot, Ivan came from acroos, around 10N I think, but did not start as low as this one.....as for before that, I cannot remember any starting this low downm before it reached us in barbados.
Member Since: Posts: Comments:
Back in a while.......
Member Since: October 24, 2005 Posts: 0 Comments: 24314
Hi Pottery, its you and/or us this weekend with the rain and wind, but water can do some serious damage...
Member Since: Posts: Comments:
I suspect to see at least a red circle on the storm near south america sometime tonight or tomarrow,and a named storm as well.
Member Since: August 14, 2010 Posts: 10 Comments: 16981
Wow, out of nowehere, here it comes. The other two dont look like much, but 91 looks like to become a beast, possibly.

What a weird season.
Member Since: Posts: Comments:
465. DDR
Quoting Bordonaro:

No, you may need an ark :O)!!

The TWO has a 50% chance of developing that Invest off to your east!

LoL TO THAT
I live on a hill no need for that,but ill have to fill some sand bafs for my buisness place which is on the plain.
Member Since: Posts: Comments:
Did somebody say good wiskey? Come on pass around the bottle and we'll all take a drink!
Member Since: Posts: Comments:
Quoting alfabob:


It's current location in the flow of things will most likely allow for a strong circulation regardless of convection. Now it's starting to form convection by the LLC; so unless shear kills it, I think 90L is capable of at least TS.



NHC disagrees, and conditions will become increasingly unfavorable for development

Now 91L and 92L not only have a really good shot of forming but they could both impact land (91L in the Caribbean and 92L in Bermuda)
Member Since: Posts: Comments:
Member Since: July 15, 2006 Posts: 171 Comments: 53866
460. xcool
get ready for cold air in Louisiana temp 40 to 30c
Member Since: Posts: Comments:
Quoting HurricaneDean07:
POLL TIME:
Do you think 90L will have an...
(A) 50%
(B) 40%
(C) 30%
(D) 20% Or Lower

Do you think 91L will have an...
(A) 30% Or Lower
(B) 40%
(C) 50%
(D) 60%
(E) 70% Or Higher

Do you think 92L will have an...
(A) 60% Or Lower
(B) 70%
(C) 80%
(D) 90% Or 100%

Which invest will be named Shary?
(A) 90L
(B) 91L
(C) 92L

Will one of these invests become Tomas, If so which one?
(A) Yes
(B) No
_____91L___
(C) 90L
(D) 91L
(E) 92L

Will one of these invests become Virginie, If so which one?
(A) Yes
(B) No
________
(C) 90L
(D) 91L
(E) 92L

Will exhaust the naming list, If so will we reach the greek alphabet?
(A) Yes
(B) No
________
(C) Yes
(D) No
Member Since: Posts: Comments:
90L at 30%
91L at 50%
92L at 70%

that is the update for the TWO
Member Since: Posts: Comments:
Quoting DDR:
Hi bordonaro
You ever heard of the rain tree or samaan tree,we may need one of those.

No, you may need an ark :O)!!

The TWO has a 50% chance of developing that Invest off to your east!
Member Since: August 25, 2009 Posts: 20 Comments: 6785
92L up to 70%.. 91L up to 50%.
Member Since: Posts: Comments:
Quoting HurricaneDean07:
POLL TIME:
Do you think 90L will have an...
(A) 50%
(B) 40%
(C) 30%
(D) 20% Or Lower

Do you think 91L will have an...
(A) 30% Or Lower
(B) 40%
(C) 50%
(D) 60%
(E) 70% Or Higher

Do you think 92L will have an...
(A) 60% Or Lower
(B) 70%
(C) 80%
(D) 90% Or 100%

Which invest will be named Shary?
(A) 90L
(B) 91L
(C) 92L

Will one of these invests become Tomas, If so which one?
(A) Yes
(B) No
________
(C) 90L
(D) 91L
(E) 92L

Will one of these invests become Virginie, If so which one?
(A) Yes
(B) No
________
(C) 90L
(D) 91L
(E) 92L

Will exhaust the naming list, If so will we reach the greek alphabet?
(A) Yes
(B) No
________
(C) Yes
(D) No
i think.
B,D,B,C,A,C,A,E,A,D
Member Since: Posts: Comments:
453. DDR
Hi bordonaro
You ever heard of the rain tree or samaan tree,we may need one of those.
Member Since: Posts: Comments:
91 AT 50 PERCENT
Member Since: July 15, 2006 Posts: 171 Comments: 53866
Quoting hydrus:
He knows we are just having fun.:)...This 91L shows up well on everything..Levi showed it to us on the MJO forecast model..

Yeah, I know that.
Seems like he has nodded off again, anyway,
Member Since: October 24, 2005 Posts: 0 Comments: 24314
Quoting HurricaneDean07:
POLL TIME:
Do you think 90L will have an...
(A) 50%
(B) 40%
(C) 30%
(D) 20% Or Lower

Do you think 91L will have an...
(A) 30% Or Lower
(B) 40%
(C) 50%
(D) 60%
(E) 70% Or Higher

Do you think 92L will have an...
(A) 60% Or Lower
(B) 70%
(C) 80%
(D) 90% Or 100%

Which invest will be named Shary?
(A) 90L
(B) 91L
(C) 92L

Will one of these invests become Tomas, If so which one?
(A) Yes
(B) No
________
(C) 90L
(D) 91L
(E) 92L

Will one of these invests become Virginie, If so which one?
(A) Yes
(B) No
________
(C) 90L
(D) 91L
(E) 92L

Will exhaust the naming list, If so will we reach the greek alphabet?
(A) Yes
(B) No
________
(C) Yes
(D) No


91L will be still be at 50%
Member Since: July 17, 2009 Posts: 71 Comments: 26156
Lots of lightning; the entire Yucatan Peninsula is covered in red this evening, and the three invests have differing amounts of electrical activity:

Click for larger image:

Appropriate tropical weather-related image
Member Since: Posts: Comments:
Like I said on cyberteddy's blog(sorry if I'm spelling the name wrong).That I think some of this late activity has something to do with those record sst.All the heat in the ocean hasn't fully been released.Yet.And the system near south america looks as though it wants to develope fast.And also I predict 1-2 storms in november with at least 1 in december.Just my thoughts.
Member Since: August 14, 2010 Posts: 10 Comments: 16981
Quoting Bordonaro:

Ha, ha, ha :O)

Looks like a real good rain event for you & DDR over the next few days.

All joking aside, please keep an eye on this one!

Doing that, for the last 4-5 days, actually.
Member Since: October 24, 2005 Posts: 0 Comments: 24314
Quoting DDR:

I think should,we cancel our trip to Maracus bay.No bake and shark for me :(

I would stay away from the North Coast road, if heavy rains are anticipated, for sure!
Member Since: October 24, 2005 Posts: 0 Comments: 24314
Quoting stillwaiting:
m-j-o....is rising,lol..hope nothn pumps the ridge this time around,lol


Give it up already, it's a dead joke.

"THE ERSTWHILE WARM PATTERN PATTERN OVER MUCH OF THE EAST CHILLS
DOWN BY THE END OF NEXT WEEK TO A WINTRY LOOK OVER THE
EAST...FEATURING A COLD HIGH ACROSS THE EASTERN GREAT LAKES AND
SOUTHEAST QUEBEC...AND A SERIES OF LOW PRESSURE WAVES MOVING NEWD
OFFSHORE THE SE COAST OF THE CONUS. THE BOUNDARY LAYER THU/FRI
MIGHT BE EVEN BE COLD ENOUGH TO SUPPORT WET SNOW AT HIGHER
ELEVATIONS OF THE APPALACHIANS IF PCPN RATES ARE HEAVY ENOUGH."

HPC Extended Forecast Discussion
Member Since: Posts: Comments:
Quoting pottery:

Man!
That sounds like DOOM, to me.
I will have a word with the Tree, when the moon comes up...
Find out what the Truth is.

Ha, ha, ha :O)

TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
800 PM EDT THU OCT 28 2010

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

A SURFACE LOW PRESSURE AREA LOCATED ABOUT 450 MILES SOUTH-SOUTHEAST
OF BERMUDA IS MOVING WEST-NORTHWEST AT 20 TO 25 MPH. SHOWERS AND
THUNDERSTORMS ASSOCIATED WITH THE LOW CONTINUE TO SHOW SOME SIGNS
OF ORGANIZATION...AND THE CIRCULATION APPEARS TO BE GRADUALLY
BECOMING BETTER DEFINED. ENVIRONMENTAL CONDITIONS ARE FORECAST TO
REMAIN SOMEWHAT CONDUCIVE FOR THE DEVELOPMENT OF A TROPICAL OR
SUBTROPICAL DEPRESSION THROUGH FRIDAY...HOWEVER UPPER-LEVEL WINDS
ARE EXPECTED TO BECOME LESS FAVORABLE AFTER THAT. THERE IS A HIGH
CHANCE...70 PERCENT...OF THIS SYSTEM BECOMING A SUBTROPICAL OR
TROPICAL CYCLONE BEFORE IT MERGES WITH A COLD FRONT ON SATURDAY.

A VIGOROUS TROPICAL WAVE LOCATED OVER THE TROPICAL ATLANTIC ABOUT
725 MILES EAST-SOUTHEAST OF THE WINDWARD ISLANDS IS PRODUCING A
LARGE AREA OF SHOWERS AND THUNDERSTORMS. THIS SYSTEM CONTINUES TO
SHOW SIGNS OF ORGANIZATION...AND ENVIRONMENTAL CONDITIONS APPEAR
TO BE FAVORABLE FOR GRADUAL DEVELOPMENT OF THIS DISTURBANCE
DURING THE NEXT COUPLE OF DAYS. THERE IS A MEDIUM CHANCE...50
PERCENT...OF THIS SYSTEM BECOMING A TROPICAL CYCLONE DURING THE
NEXT 48 HOURS AS IT MOVES WESTWARD OR WEST-NORTHWESTWARD AT 15 TO
20 MPH. REGARDLESS OF DEVELOPMENT...THIS SYSTEM IS EXPECTED TO
BRING LOCALLY HEAVY RAINFALL AND STRONG GUSTY WINDS TO THE WINDWARD
ISLANDS...VENEZUELA...AND NORTHERN PORTIONS OF GUYANA DURING THE
NEXT COUPLE OF DAYS.

A LOW PRESSURE SYSTEM IS LOCATED ABOUT 1200 MILES NORTHWEST OF THE
NORTHERNMOST CAPE VERDE ISLANDS. ALTHOUGH SHOWER AND THUNDERSTORM
ACTIVITY ASSOCIATED WITH THE LOW HAS INCREASED DURING THE PAST FEW
HOURS...UPPER-LEVEL WINDS ARE EXPECTED TO BECOME LESS FAVORABLE FOR
DEVELOPMENT ON FRIDAY. THERE IS A MEDIUM CHANCE...30 PERCENT...OF
THIS SYSTEM BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS
AS IT MOVES SLOWLY WESTWARD.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

$$
FORECASTER BROWN/BERG

Looks like a real good rain event for you & DDR over the next few days.

All joking aside, please keep an eye on this one!
Member Since: August 25, 2009 Posts: 20 Comments: 6785
Quoting Bordonaro:

Pottery, I received a report that your Calabash tree is building an ark and installing storm shutters..


Man!
That sounds like DOOM, to me.
I will have a word with the Tree, when the moon comes up...
Find out what the Truth is.
Member Since: October 24, 2005 Posts: 0 Comments: 24314
Quoting pottery:

You guys are SO cruel....
heheheh
He knows we are just having fun.:)...This 91L shows up well on everything..Levi showed it to us on the MJO forecast model..
Member Since: Posts: Comments:
441. DDR
Quoting pottery:

True!
I think that my freinds who are celebratuing their Birthdays, Down De Islands, Saturday, may cancel.

I think they should,we cancelled our trip to Maracus bay.No bake and shark for me :(
Member Since: Posts: Comments:
Quoting alfabob:
90L and 91L will be named soon. 92L following if conditions are favorable, as convection has recently increased.


I dont think 90L will be named
Member Since: Posts: Comments:
Quoting pottery:

LOL. Your zoom feature is engaged, I see.

Pottery, I received a report that your Calabash tree is building an ark and installing storm shutters..

Member Since: August 25, 2009 Posts: 20 Comments: 6785
437. DDR
Hey pottery hope you have your guage ready?
Lets hope this stays a rain event only...
Member Since: Posts: Comments:
Quoting DDR:

Hi pottery
An interesting few days coming for sure,hope we don't get too much rain.

True!
I think that my freinds who are celebrating their Birthdays, Down De Islands, Saturday, may cancel.
Member Since: October 24, 2005 Posts: 0 Comments: 24314
Quoting KEEPEROFTHEGATE:
sorry to all members for my little outburst but NHC bashing is something i will not stand for they deserve more than just our respect
I totally agree! I hate when people think they know more than the professionals!
Member Since: Posts: Comments:
Quoting RTLSNK:


You are being observed, that is a rather large glass of rum you have there my good man! :)

LOL. Your zoom feature is engaged, I see.
Member Since: October 24, 2005 Posts: 0 Comments: 24314
POLL TIME:
Do you think 90L will have an...
(A) 50%
(B) 40%
(C) 30%
(D) 20% Or Lower

Do you think 91L will have an...
(A) 30% Or Lower
(B) 40%
(C) 50%
(D) 60%
(E) 70% Or Higher

Do you think 92L will have an...
(A) 60% Or Lower
(B) 70%
(C) 80%
(D) 90% Or 100%

Which invest will be named Shary?
(A) 90L
(B) 91L
(C) 92L

Will one of these invests become Tomas, If so which one?
(A) Yes
(B) No
________
(C) 90L
(D) 91L
(E) 92L

Will one of these invests become Virginie, If so which one?
(A) Yes
(B) No
________
(C) 90L
(D) 91L
(E) 92L

Will exhaust the naming list, If so will we reach the greek alphabet?
(A) Yes
(B) No
________
(C) Yes
(D) No
Member Since: Posts: Comments:

Viewing: 483 - 433

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.