Tropical Storm Henri forms

By: Dr. Jeff Masters , 21:37 GMT le 06 octobre 2009

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The tropics spawned another October surprise today, when Tropical Storm Henri formed in the face of adverse levels of wind shear. Henri is under about 20 - 25 knots of wind shear, which ordinarily prevents rapid development like we witnessed this afternoon. However, the environment is quite moist, and Henri is over warm waters, 29°C. An ASCAT pass from 11:37am EDT showed Henri had winds of 40 mph. Satellite loops show that Henri has managed to rapidly develop a large area of intense thunderstorms with cold cloud tops in just a few hours, though the high shear is keeping any thunderstorms from developing on the west side of the center. Water vapor satellite images show that there is some dry air to Henri's northwest, and this dry air will act to slow Henri's growth some. The dry air is creating strong downdrafts that are apparent on visible satellite images as arcs of cumulus clouds spreading out from where the downdraft hits the ocean surface, along the northwest side of Henri's center.

None of the reliable global computer models showed Henri would develop, and the models all favor weakening and dissipation of Henri by Thursday, due to high wind shear of 20 - 25 knots. The official NHC forecast goes along with this scenario, but think there is a medium (30 - 50% chance) that Henri will not dissipate. By Friday, wind shear in the vicinity of Henri (or its remains) is predicted to fall to the low to moderate range. Even if Henri has dissipated by that point, regeneration into a tropical storm may occur. The track of Henri after Friday is problematic, as the storm will be in an area of weak steering currents. Several of the models favor a track to the west-southwest into the Caribbean, across Hispaniola. Residents of the Dominican Republic and Haiti should anticipate that Henri or its remains may bring flooding rains to Hispaniola by Saturday. It is also possible that Henri will get pulled northwards and recurved out to sea, and not affect the Caribbean at all, though.


Figure 1. Latest satellite image of Henri.

A little tropical weather for England
The remnant circulation of Tropical Storm Grace is currently making landfall in Southwest England. Grace's remains brought sustained winds of tropical storm force--41 mph--to one buoy off the coast last hour, and 38 mph to the Sevenstones Lightship buoy. you can track the progress of Grace via our wundermap for the region.


Figure 2. The remnant circulation of Tropical Storm Grace scoots by to the south of Ireland in this visible satellite image taken at 1pm EDT 10/06/09. Image credit: UK Met Office.

Jeff Masters


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Quoting ElConando:


its a glory ho- I mean special place.


I see nothing there..diddly?

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Quoting WeatherStudent:
Loved the update, tim, :)



Thanks WS
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Quoting Orcasystems:


I give up.. whats the yellow circle for?


I guess you did not read this.....sorry!

Gulf of Mexico analysis:

Tropical development is not expected in this area in the next 24hrs.

There is nothing expected in the next 24hrs but, i have this as an AOI. Watch for a front to stall out across the GOM and something try to develop in about 7 days!


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Quoting Orcasystems:


I give up.. whats the yellow circle for?


its a glory ho- I mean special place.
Member Since: 6 septembre 2009 Posts: 2 Comments: 3768
Quoting TampaSpin:


Tropical Update with Henri


I give up.. whats the yellow circle for?
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Amazing how we get some tropical moisture in the lower lattitudes at this point in the season. The temperatures of sea are warm enough to see a nice tropical event. Splendid.
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449. xcool


oh wow!!!!
Member Since: 26 septembre 2009 Posts: 2 Comments: 15684
Quoting CaribBoy:
Is there a COC at 17.3N 55.7W?


Close.

Big difference between 18.4N/55.3W and 17.2N/54.7W. And, by far the most W winds to date from sat wind data.

Only caught the western edge, but center is S of official, imo. Bedtime. Goodnight.

Link
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Quoting ElConando:
night need a yellow on the disturbance to the South of Henri in the next 12 hrs.


Yep possibly so......i have it identified above.....It is part of the ITCZ and needs to come out soon to have a chance.
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Quoting JLPR:


lol to tell you the truth I have no idea xD
it seemed like it was but the NHC says wnw and they are the experts =)
Living in PR, I just hope they are not wrong again.
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night need a yellow on the disturbance to the South of Henri in the next 12 hrs.
Member Since: 6 septembre 2009 Posts: 2 Comments: 3768
Quoting homelesswanderer:


I was just fixing to ask if I was the only one who thinks it's moving west. Glad its not just me. :)
Im not an expert, just want to hear somebody's opinion, but looking very careful to the apparent center of circulation, IT already crossed 55w and seems to be still in the same latitude.
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Wow all 3 of the BAM models is in aggreement......haven't seen that all year!

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strengthening stops at 3.0 could bottom out 2 morrow morning at 50 mph.
Member Since: 6 septembre 2009 Posts: 2 Comments: 3768
441. JLPR
Quoting jurakantaino:
Is it ,moving do west? If so gettng pretty close to theisland, I wonder if they have to issue some warnings to the islands.


lol to tell you the truth I have no idea xD
it seemed like it was but the NHC says wnw and they are the experts =)
Member Since: 4 septembre 2007 Posts: 36 Comments: 5223
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Quoting Tazmanian:
Henri is geting shear a part right now


Hey , he was born in shear, and still looking better than ever, with the shear...so far of course.
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Quoting jurakantaino:
Is it ,moving do west? If so gettng pretty close to theisland, I wonder if they have to issue some warnings to the islands.


I was just fixing to ask if I was the only one who thinks it's moving west. Glad its not just me. :)
Member Since: 15 août 2008 Posts: 10 Comments: 3665
Is there a COC at 17.3N 55.7W?
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Tropical Update with Henri
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Quoting JLPR:
Henri's circulation is pretty apparent on the Ramsdis floater

Link
Is it ,moving do west? If so gettng pretty close to theisland, I wonder if they have to issue some warnings to the islands.
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434. xcool
JLPR :)XXXX
Member Since: 26 septembre 2009 Posts: 2 Comments: 15684
433. JLPR
Quoting xcool:
JLPR yea .im very surprised


me too xD
Member Since: 4 septembre 2007 Posts: 36 Comments: 5223
432. JRRP
see you tomorrow
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431. xcool
JLPR yea .im very surprised
Member Since: 26 septembre 2009 Posts: 2 Comments: 15684
430. JLPR
Quoting xcool:
ADVANCED DVORAK TECHNIQUE
ADT-Version 7.2.3
Tropical Cyclone Intensity Algorithm

----- Current Analysis -----
Date : 07 OCT 2009 Time : 024500 UTC
Lat : 18:22:30 N Lon : 55:14:55 W


CI# /Pressure/ Vmax
2.8 /1002.0mb/ 41.0kt


Final T# Adj T# Raw T#
(3hr avg)
2.8 3.0 3.0

Latitude bias adjustment to MSLP : 0.0mb

Center Temp : -28.3C Cloud Region Temp : -29.4C

Scene Type : CURVED BAND with 0.54 ARC in LT GRAY

Positioning Method : FORECAST INTERPOLATION

Ocean Basin : ATLANTIC
Dvorak CI > MSLP Conversion Used : ATLANTIC

Tno/CI Rules : Constraint Limits : NO LIMIT
Weakening Flag : OFF
Rapid Dissipation Flag : OFF



maintaining itself
Member Since: 4 septembre 2007 Posts: 36 Comments: 5223
429. xcool
ADVANCED DVORAK TECHNIQUE
ADT-Version 7.2.3
Tropical Cyclone Intensity Algorithm

----- Current Analysis -----
Date : 07 OCT 2009 Time : 024500 UTC
Lat : 18:22:30 N Lon : 55:14:55 W


CI# /Pressure/ Vmax
2.8 /1002.0mb/ 41.0kt


Final T# Adj T# Raw T#
(3hr avg)
2.8 3.0 3.0

Latitude bias adjustment to MSLP : +0.0mb

Center Temp : -28.3C Cloud Region Temp : -29.4C

Scene Type : CURVED BAND with 0.54 ARC in LT GRAY

Positioning Method : FORECAST INTERPOLATION

Ocean Basin : ATLANTIC
Dvorak CI > MSLP Conversion Used : ATLANTIC

Tno/CI Rules : Constraint Limits : NO LIMIT
Weakening Flag : OFF
Rapid Dissipation Flag : OFF

Member Since: 26 septembre 2009 Posts: 2 Comments: 15684
428. JLPR
Quoting 7544:
\\

got to agreee with this


me too
Member Since: 4 septembre 2007 Posts: 36 Comments: 5223
Yep, Henri is definitely holding its own against the shear.

Here's one thing I don't quiet get though. How is that REGARDLESS of how the upper atmospheric pattern sets up that there is ALWAYS a Bermuda-Azores surface high producing surface winds in the tropics that are easterly??

This is how I believe Henri is getting sheared, because its embedded in low-level easterlies in the tropics, but the upper winds are westerly.
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426. 7544
Quoting WeatherStudent:
Henri is a real trooper, he's been handeling tonight's bombartment of wind shear, remarkably well, thus far. The NHC even increased it's wind speed during tonight's advisory, very impressive.
\\

got to agreee with this
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424. xcool


Member Since: 26 septembre 2009 Posts: 2 Comments: 15684
Quoting cchsweatherman:


I'll be glad to host such a blog forum. We should discuss ideas as to what we should address. I really want to have a good discussion regarding wind shear since it has been such a major player this season and since I still don't have a full understanding regarding the issue.


Yeah, that would be exciting to have a forum on that:)! I also keep a journal of Atlantic tropical cyclone activity that I maintain for about about 15 minutes everyday. For this season, I noted some upper atmospheric patterns on a September 15 post I made on my blog (Trends in 2009 Atlantic Hurricane Season). I believe part of it what related to El Nino. But, I am stuck on understanding more shorter term evolutions of the upper atmosphere (how do we get stuck in patterns of aggressive upper troughs one week, and the next we see a nice 200 mb anticyclone in the Gulf of Mexico and western Caribbean like we do today?)
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422. JRRP
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Henri is geting shear a part right now


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Quoting cchsweatherman:


After hurricane season comes to a close, we should hold a blog forum dedicated to trying to understand the various factors that played big roles this hurricane season and analyze their affects on particular systems this year. It would be great to enrich the understanding of future and current forecasters while providing a wealth of knowledge for those who are enthusiasts wanting to learn this field.

That sounds like a great idea! I'm all in for that. Sounds like a great learning opportunity!

On another note, Dr. Paul Kocin (from the HPC and formerly from TWC) spoke in a seminar today at Texas A&M today. I made sure to make room for it in my schedule, and boy did that pay off. The seminar was very good and I actually got to talk with him afterwards. I even got a picture with him too! :)
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418. JLPR
Henri's circulation is pretty apparent on the Ramsdis floater

Link
Member Since: 4 septembre 2007 Posts: 36 Comments: 5223
417. xcool
7544 .imo looking very good :) guess have to waiting and seeing
Member Since: 26 septembre 2009 Posts: 2 Comments: 15684
416. 7544
Quoting xcool:


looking good evry hour xcool we may see a 50mph strom at damx up tonight
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415. xcool
Member Since: 26 septembre 2009 Posts: 2 Comments: 15684
456 and several others, I truly appreciate you guys and this is coming from someone that had no idea concerning weather and have no training whatsoever. The ones with knowledge is why I come here.
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Quoting Progster:


Thanks. I looked it up on the NHC website prior to your post. A hint of history and a bit of thermal forcing from the surface...as good as anything without much of an analysis to go by.


Yeah, me too. Couldn't remember exactly what type that model is.
G'Nite all.
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Hey all,

If anyone by chance has had an error message "ERROR: It appears this user does not have a WunderBlog" while you are trying to make a new blog post, I've found a fix (that's what I've been doing for the past half hour). If you have that problem, you can let me know.

By the way, the tropical latitudes in the Atlantic have gotten more interesting. There is a nice 200 mb anticyclone off of Africa and one big one that is coming in from the west over the Gulf of Mexico and western Caribbean. Does anyone understand how that happens? I've just accepted it as "these things just blow in," but I feel there's more to it. How can you look down next week and say, aha there's going to be a favorable 200 mb anticyclone here or there, etc.?

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Very much like SHIPS, except it has a bit less averaging of parameters along the forecast track.
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Quoting atmoaggie:

Well, it is a statistical model that uses some dynamical model results as input (mostly GFS?).

Full details here (midway down): http://www.nhc.noaa.gov/modelsummary.shtml


Thanks. I looked it up on the NHC website prior to your post. A hint of history and a bit of thermal forcing from the surface...as good as anything without much of an analysis to go by.
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Quoting Progster:


Is the LGEM the only dynamical model in the growth area?

Well, it is a statistical model that uses some dynamical model results as input (mostly GFS?).

Full details here (midway down): http://www.nhc.noaa.gov/modelsummary.shtml
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Quoting Weather456:


Maybe if I said "Am I the only one?"

That sounds better.


LOL.......Bro...its ok.......we know what you ment...YOU keep up your great work. It is really appreaciated a ton on here!
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407. JLPR
Henri and a little interesting TW to the SE

Member Since: 4 septembre 2007 Posts: 36 Comments: 5223

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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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