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: 433 - 383

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

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:




Member Since: August 2, 2010 Posts: 21 Comments: 9821
It really does look like September.
Member Since: Posts: Comments:
m-j-o....is rising,lol..hope nothn pumps the ridge this time around,lol
Member Since: Posts: Comments:
Quoting Grothar:


Don't worry, pot. These things sometimes just break up. So what do you think of GW? LOL

What's GW stand for again?
Good Whisky?
I like it.
Member Since: Posts: Comments:
xx/xx/AOI
Member Since: July 15, 2006 Posts: 173 Comments: 54344
Member Since: August 25, 2009 Posts: 20 Comments: 6785
Quoting KEEPEROFTHEGATE:
and he thinks he is getting some golden girls tonight

lol

You guys are SO cruel....
heheheh
Member Since: Posts: Comments:
425. JLPR2
I had no idea 92L had a TCFA issued. O.o
Member Since: September 4, 2007 Posts: 7 Comments: 8733
#411..Great pic of the "Halloween Tri-fecta", compliments of the 2010 Atlantic Hurricane Season!
Member Since: August 25, 2009 Posts: 20 Comments: 6785
Quoting MiamiHurricanes09:
Trouble in the BOC? Might get a yellow circle at 8p.m.



I don't think that will develope due to dry air,and shear.It will probally cuase some rian showers and thats about it.
Member Since: Posts: Comments:
Quoting Grothar:


Nice guy. Didn't like his wig.


No argument there. I must admit, I was hoping for a more verbose response. Ah well, perhaps another time.
Member Since: Posts: Comments:
421. JLPR2
92L does look good.


But I want an ASCAt pass to see what we are dealing with.
Member Since: September 4, 2007 Posts: 7 Comments: 8733

Member Since: August 25, 2009 Posts: 20 Comments: 6785
POSS T.C.F.A.
INV/91L/XX
MARK
9.33n/51.12w
Member Since: July 15, 2006 Posts: 173 Comments: 54344
Quoting AstroHurricane001:


OK, seriously...I MUST say that 92L looks like a full-fledged hurricane at first glance on infrared. We had some 90 km/h gusts in S. Ontario yesterday.


looks like when katrina and ike was strengthening over the gulf wow!
Member Since: Posts: Comments:


One red circle, two orange circles and a possible fourth yellow circle...what an unusual sight for the end of October.
Member Since: Posts: Comments:
You know, for "disorganized showers," 90L looks pretty good. I'd still give it a chance to be named.
Member Since: Posts: Comments:


OK, seriously...I MUST say that 92L looks like a full-fledged hurricane at first glance on infrared. We had some 90 km/h gusts in S. Ontario yesterday.
Member Since: Posts: Comments:
Quoting MiamiHurricanes09:
Trouble in the BOC? Might get a yellow circle at 8p.m.


It will be interesting to see what the NHC does with this AOI!
Member Since: August 25, 2009 Posts: 20 Comments: 6785
Quoting PSLFLCaneVet:


George Washington? Are you going to give us some first hand accounts of your relationship? Outstanding, a living history.


Nice guy. Didn't like his wig.
Member Since: July 17, 2009 Posts: 71 Comments: 26472
Trouble in the BOC? Might get a yellow circle at 8p.m.



Member Since: Posts: Comments:
Quoting KEEPEROFTHEGATE:
and he thinks he is getting some golden girls tonight

lol


Guess it's just a case of too little, too late! LOL
Member Since: July 17, 2009 Posts: 71 Comments: 26472
Member Since: Posts: Comments:
407. DDR
Quoting pottery:
HEH!!
Just in for a moment, before food...
I do wish you all would stop posting images of this Island.
Makes me feel like I am being Observed.

Looks to be a fun time, next few days.
The thing looks kind of dread!

Hi pottery
An interesting few days coming for sure,hope we don't get too much rain.
Member Since: Posts: Comments:
406. ackee
Iam thinking 91L should go the 50% or even 60% at 8pm this vey huge system that regradless of devlopment will bring a lot of rain
Member Since: July 15, 2008 Posts: 0 Comments: 1373
Quoting Grothar:


Don't worry, pot. These things sometimes just break up. So what do you think of GW? LOL


George Washington? Are you going to give us some first hand accounts of your relationship? Outstanding, a living history.
Member Since: Posts: Comments:
This is gonna tint dark blue skies in the Carib.... Looks with a more defined COC

Member Since: August 2, 2010 Posts: 21 Comments: 9821
Quoting RTLSNK:


Today is Thursday. :)

(chuckle, chortle, snort)


Oh! Then in that case I will be off at 11.
Member Since: July 17, 2009 Posts: 71 Comments: 26472
a very scary thought no doubt goes to show it is still hurricane season and the atleast 1 major landfalling hurricane this season this could be it
Member Since: Posts: Comments:
401. JLPR2
Quoting CaribBoy:


will be interesting to watch nonetheless


Agreed.
Member Since: September 4, 2007 Posts: 7 Comments: 8733
pressure 91L 1006 mb
Member Since: Posts: Comments:
Quoting pottery:
HEH!!
Just in for a moment, before food...
I do wish you all would stop posting images of this Island.
Makes me feel like I am being Observed.

Looks to be a fun time, next few days.
The thing looks kind of dread!


You are being observed, that is a rather large glass of rum you have there my good man! :)
Member Since: Posts: Comments:
Quoting JLPR2:


But Jose was in 1999, the NHC and the models are more reliable now than they were then.

*That's to keep my sanity intact, thank you very much. XD


will be interesting to watch nonetheless
Member Since: October 6, 2007 Posts: 0 Comments: 6229
Quoting MrstormX:
91L is making anxious.....


chris warren from twc says this one has a good chance of hitting the us probably a better chance than any so far this year
Member Since: Posts: Comments:
Quoting RTLSNK:


Today is Thursday. :)

(chuckle, chortle, snort)
and he thinks he is getting some golden girls tonight

lol
Member Since: July 15, 2006 Posts: 173 Comments: 54344
Quoting Grothar:
Can't wait for the diurnating tonight? Should be impressive.

At my age I look forward to that at anytime of day, even if it's not so impressive......
.
.
Member Since: Posts: Comments:
BOC is active this eve ...
Link
Member Since: Posts: Comments:
Quoting Grothar:


I've told you a hundred times, Friday night they let us stay up to watch the Golden Girls, all new episodes. Geez, and they call me old.


Today is Thursday. :)

(chuckle, chortle, snort)
Member Since: Posts: Comments:
391. JLPR2
Quoting CaribBoy:
Remembering HURRICANE JOSE in october 1999...

Here is the first official track from the NHC (Discussion #1) :
INITIAL 17/2100Z 10.0N 51.5W 30 KTS
12HR VT 18/0600Z 10.0N 53.2W 35 KTS
24HR VT 18/1800Z 10.5N 55.3W 45 KTS
36HR VT 19/0600Z 11.0N 57.5W 55 KTS
48HR VT 19/1800Z 12.0N 60.0W 65 KTS
72HR VT 20/1800Z 14.5N 63.5W 75 KTS

Now look where jose ended up (Discussion #14) :
INITIAL 21/0300Z 17.8N 63.0W 85 KTS
12HR VT 21/1200Z 18.4N 64.1W 90 KTS
24HR VT 22/0000Z 19.7N 65.5W 95 KTS
36HR VT 22/1200Z 21.6N 66.7W 95 KTS
48HR VT 23/0000Z 25.0N 67.0W 80 KTS
72HR VT 24/0000Z 36.0N 62.5W 70 KTS.

JOSE was supposed to enter the SE caribbean around 13N but finally moved much further north.
As of 91L and based on JOSE's track, I think the HWRF and LBAR shouldn't be ignored!!! It's late october not july nor august and storms move more north than west.

This was just my opinion :)


But Jose was in 1999, the NHC and the models are more reliable now than they were then.

*That's to keep my sanity intact, thank you very much. XD
Member Since: September 4, 2007 Posts: 7 Comments: 8733
Quoting pottery:
HEH!!
Just in for a moment, before food...
I do wish you all would stop posting images of this Island.
Makes me feel like I am being Observed.

Looks to be a fun time, next few days.
The thing looks kind of dread!


Don't worry, pot. These things sometimes just break up. So what do you think of GW? LOL
Member Since: July 17, 2009 Posts: 71 Comments: 26472
Remembering HURRICANE JOSE in october 1999...

Here is the first official track from the NHC (Discussion #1) :
INITIAL 17/2100Z 10.0N 51.5W 30 KTS
12HR VT 18/0600Z 10.0N 53.2W 35 KTS
24HR VT 18/1800Z 10.5N 55.3W 45 KTS
36HR VT 19/0600Z 11.0N 57.5W 55 KTS
48HR VT 19/1800Z 12.0N 60.0W 65 KTS
72HR VT 20/1800Z 14.5N 63.5W 75 KTS

Now look where jose ended up (Discussion #14) :
INITIAL 21/0300Z 17.8N 63.0W 85 KTS
12HR VT 21/1200Z 18.4N 64.1W 90 KTS
24HR VT 22/0000Z 19.7N 65.5W 95 KTS
36HR VT 22/1200Z 21.6N 66.7W 95 KTS
48HR VT 23/0000Z 25.0N 67.0W 80 KTS
72HR VT 24/0000Z 36.0N 62.5W 70 KTS.

JOSE was supposed to enter the SE caribbean around 13N but finally moved much further north.
As of 91L and based on JOSE's track, I think the HWRF and LBAR shouldn't be ignored!!! It's late october not july nor august and storms move more north than west.

This was just my opinion :)
Member Since: October 6, 2007 Posts: 0 Comments: 6229
Quoting KEEPEROFTHEGATE:
are they gonna let ya stay that late i heard lights out by 11 tonight


I've told you a hundred times, Friday night they let us stay up to watch the Golden Girls, all new episodes. Geez, and they call me old.
Member Since: July 17, 2009 Posts: 71 Comments: 26472
91L has nearly filled the floater image = large

Link
Member Since: Posts: Comments:
de nada....

;)
Member Since: Posts: Comments:
Quoting Grothar:


Ha, I am also part Italian. Besides, much taller than Dean and darker. You must be as old as hydrus to remember him.


Student of history LMAO
Member Since: Posts: Comments:
Quoting NRAamy:
Groth..... tres sexy....

;)


Tusen tak!
Member Since: July 17, 2009 Posts: 71 Comments: 26472

Viewing: 433 - 383

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.

Local Weather

Overcast
65 °F
Overcast