Tropical Storm Henri forms

By: Dr. Jeff Masters , 9:37 PM GMT on October 06, 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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How I learned to mind my own business

I was walking past the mental hospital the other day,
And all the patients were outside shouting, '13...13...13.'

The fence was too high to see over, but I saw a
Little gap in the planks, so I looked through to see
What was going on...

Somebody poked me in the eye with a stick!

Then they all started shouting '14...14...14'...

good evening everyone as always nice to read your posts
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Systems like Erika and Henri are far from boring, due to the uncertain they are more interesting than clear-cut storms like Bill.
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Quoting nrtiwlnvragn:
Slight indication of an LLC on the EUMETSAT Ocean and Sea Ice SAF Wind Processing Center version of the QuikScat data.


Click on image to view original size in a new window








Thanks, can I have a link?
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204. JLPR
Quoting nrtiwlnvragn:
Slight indication of an LLC on the EUMETSAT Ocean and Sea Ice SAF Wind Processing Center version of the QuikScat data.


Click on image to view original size in a new window








that confuses me more :|
farther to the south?
Member Since: September 4, 2007 Posts: 36 Comments: 5223
Quoting JLPR:


Erika definitely wins in that comparison xD


at first glance, yet Erika's LLC was never curved around the LLCC, while Henri's convection is curved around the LLCC. Structurally, Henri winds.
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I think tha Henri is relocating the COC that why Dpass doesn't show a close low also the COC of this Storm is a very small one, NHC will keep it as TS in the 11pm advidory maybe at 45mph. I expect a more westward track bringing Henri closer to the NE caribbean.
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Quoting markymark1973:
Just another complete mess like Ana and Danny. I hope it just dies. Weak storms like this are so boring to watch and track.


Not to attack you but I think with each storm something is learned. Grace was not suppose to develop in the cool waters but did. Henri should not have developed due to high wind shear but did. I could go on but it would take a while. I just think that "NOTHING" is text book.
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winds picking up here 30 to 40 kmh with mod rain as grt lakes system moves pass

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Slight indication of an LLC on the EUMETSAT Ocean and Sea Ice SAF Wind Processing Center version of the QuikScat data.


Click on image to view original size in a new window






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.
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Quoting CosmicEvents:

LOL...that's a good one.
.
.
I only brought up the whole pronunciation thing because the NHC started it. Today was the first time that I recall the NHC giving out proper pronunciation in a discussion.
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For years, we somehow got by without the pronunciation leson, and we also managed to get by without the "idiot" colors. For most, they never get past just looking at the NHC graphical map. They don't read the discussions. So they don't understand the reasoning behind the colors. Even those of us here, who go way beyond just reading the discussion, for most, I don't think that they understand the 24-48 hour probability window that these idiot colors represent.
Poof Gone
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196. JLPR
Quoting Weather456:
Henri



Erika



Erika definitely wins in that comparison xD
Member Since: September 4, 2007 Posts: 36 Comments: 5223
Quoting JLPR:


nope the supposed center is right on the edge of the westernmost area of convection


My mistake...you are correct.
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194. xcool


Member Since: September 26, 2009 Posts: 2 Comments: 15684
Henri



Erika

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It is closed , though small and very tight , jmo.
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Quoting GeoffreyWPB:
456...I have the "center" at about 54/18. Is that about right?


yea that's where I'm seeing the shortwave center
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Quoting GeoffreyWPB:
456...I have the "center" at about 54/18. Is that about right?

I would say you're correct, look at my post, we're just 6 miles different, thats well within the margin of error:)
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189. JLPR
Quoting Weather456:


Excellent point, really reinforces, don't jump on the model wagon so readily. Yes it is likely Henri has been altered by it and probably explain amd's post that is being steered at the levels of tropical waves - more west than wnw.


and the question is where will the center consolidate farther north or farther south?
also the more west than WNW makes sense, I hope it gets its LLC soon so it passes to my NE =)
Member Since: September 4, 2007 Posts: 36 Comments: 5223
188. xcool


Member Since: September 26, 2009 Posts: 2 Comments: 15684

17.9N /54W flat is closest I see to a closed LLC? Does anyone agree?
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456...I have the "center" at about 54/18. Is that about right?
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Quoting stormwatcherCI:
Thanks you. Just hope it doesn't get any sronger than a tropical storm but this year has been really weird. So was last year with the tracks. Gustav moved SW into the Caribbean too and he was nasty.


Yeah Ike did too. Looked like he was headed out to sea. Then he just turned around and went the other way. You're right last year had a lot of people scratching their heads too. Track-wise anyway.
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Quoting JLPR:


456, wouldn't this new development of LLCless Henri make the forecast track somewhat unreliable since the system hasn't actually consolidated a LLC?


Excellent point, really reinforces, don't jump on the model wagon so readily. Yes it is likely Henri has been altered by it and probably explain amd's post that is being steered at the levels of tropical waves - more west than wnw. However, i am not a 100% sure that this is open due to the conflict between shortwave imagery and QS.
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The NHC I believe determined earlier that 91L was a closed Low with TS winds, that's why its TS Henri.

Well, if the NHC was to go by "their established Tropical Cyclone rules" this year; they'd have had TS, then TD Danny every other advisory update. Same with Erika.
Member Since: August 25, 2009 Posts: 20 Comments: 6785
how accurate is the QS? looking at shortwave you can see clear circulation?
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hum, henry really looks like erika with that band of convection to the south
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Quoting markymark1973:

Seemed everyone on this board wanted to bash the NHC for their actions and look what kind of mess they have to deal with. One hour it's a TD or TS and the next it is an open wave. Weak Systems like these imo shouldn't get a name. I'm with Neil Frank on this one. Guess i'm just old school.


This was an image of 91L earlier today and met the criteria and thus was named. Whether or not it lost its LLC and became an open wave has nothing to do with earlier this afternoon.



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179. JLPR
Quoting KEEPEROFTHEGATE:
yep everything is north and east of centre


to the east yep but not much to the north =P
Member Since: September 4, 2007 Posts: 36 Comments: 5223
This is one weird year thats for sure, though storms in that area tend to lose the LLC " or apparently so" til they get into the Caribbean or further west in the Atlantic,for what ever reason I don't know, I 've seen this happen with a few storms over the years.
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Well, Good Evening.
Got 2" of much-needed rain here today (Trinidad). Looks like more to come too, especially from that wave east of here and heading west fast.
Plenty of moist stuff around all of a sudden....
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176. JLPR
Quoting Weather456:


well that's true, so its up the NHC for final verdict on whether they will go with continuity or downgrade Henri, I'm leaning towards the former since it may eventually get one.


456, wouldn't this new development of LLCless Henri make the forecast track somewhat unreliable since the system hasn't actually consolidated a LLC?
Member Since: September 4, 2007 Posts: 36 Comments: 5223
Quoting JLPR:


nope the supposed center is right on the edge of the westernmost area of convection
yep everything is north and east of centre
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Quoting Weather456:
I do not think the LLCC was blown away, did you realize thunderstorms that developed over the center. It's that QS versus the last few visible images and the shortwave infrared tonight. Something's not adding up.
let me rephrase that blown away by shear or maybe sheared apart llc that would be better
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Quoting kmanislander:
Well, here is another problem for the NHC.
Quikscat this evening does not show a closed low with Henri IMO but does show 45 knot TS winds.

Should they hold the TS classification ?.

I suspected this might well be the case from all that shear.
Quoting kmanislander:
Well, here is another problem for the NHC.
Quikscat this evening does not show a closed low with Henri IMO but does show 45 knot TS winds.

Should they hold the TS classification ?.

I suspected this might well be the case from all that shear.

Seemed everyone on this board wanted to bash the NHC for their actions and look what kind of mess they have to deal with. One hour it's a TD or TS and the next it is an open wave. Weak Systems like these imo shouldn't get a name. I'm with Neil Frank on this one. Guess i'm just old school.
Member Since: Posts: Comments:
172. JLPR
Quoting GeoffreyWPB:
All the convection to the west and north.

img src="Henri" alt="" />


nope the supposed center is right on the edge of the westernmost area of convection
Member Since: September 4, 2007 Posts: 36 Comments: 5223
Quoting kmanislander:


If there is no closed low it is not technically a tropical cyclone. BUT, the NHC maintained Dolly as a TS without a closed low.

Anyway, I did want to see that QS because this reminded so much of those systems that look like a TS on satellite but lack the true qualification to be so classified.

Gone to grill now LOL


well that's true, so its up the NHC for final verdict on whether they will go with continuity or downgrade Henri, I'm leaning towards the former since it may eventually get one.
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Quoting SouthALWX:

Good anticyclonic flow over it looks like.. wouldn't surprise me if it pulled into the SE caribbean. As you said, it really needs some cyclonic turning at the surface and a lowering in pressure to make that happen though.


The 00z GFDL run for 91L showed that spinning up briefly. Lowered it to 1008. You can also see on the 00z GFS MSLP that they briefly thought about sending it into the SE Caribbean too. With the way this year has been going and forecasted anything could happen.

Link
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All the convection to the west and north.

img src="Henri" alt="" />
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168. JLPR
Quoting Weather456:
I do not think the LLCC was blown away, did you realize thunderstorms that developed over the center. It's that QS versus the last few visible images and the shortwave infrared tonight.


maybe if convection persists tonight, tomorrow morning QS could show more of a LLC
Member Since: September 4, 2007 Posts: 36 Comments: 5223
Quoting Weather456:
I do not think the LLCC was blown away, did you realize thunderstorms that developed over the center. It's that QS versus the last few visible images and the shortwave infrared tonight.


If there is no closed low it is not technically a tropical cyclone. BUT, the NHC maintained Dolly as a TS without a closed low.

Anyway, I did want to see that QS because this reminded so much of those systems that look like a TS on satellite but lack the true qualification to be so classified.

Gone to grill now LOL
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Quoting Weather456:


The chances of Henri affecting that area is surprisingly high if it does make that southwest turn into the Caribbean, but I'm unsure of how far west it will go, 30-40%.
Thanks you. Just hope it doesn't get any sronger than a tropical storm but this year has been really weird. So was last year with the tracks. Gustav moved SW into the Caribbean too and he was nasty.
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165. JLPR
also here is the other CATL disturbance

Member Since: September 4, 2007 Posts: 36 Comments: 5223
I do not think the LLCC was blown away, did you realize thunderstorms that developed over the center. It's that QS versus the last few visible images and the shortwave infrared tonight. Something's not adding up.
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Just another complete mess like Ana and Danny. I hope it just dies. Weak storms like this are so boring to watch and track.
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162. JLPR
Quoting KEEPEROFTHEGATE:
blown away


yep me too
good winds but no LLC
Member Since: September 4, 2007 Posts: 36 Comments: 5223
Quoting FreelanceHistorian:
well, anyone here from Louisiana will know how to pronounce "Henri." I knew folks there that named their dog "Phideaux" :D

LOL...that's a good one.
.
.
I only brought up the whole pronunciation thing because the NHC started it. Today was the first time that I recall the NHC giving out proper pronunciation in a discussion.
.
.
For years, we somehow got by without the pronunciation leson, and we also managed to get by without the "idiot" colors. For most, they never get past just looking at the NHC graphical map. They don't read the discussions. So they don't understand the reasoning behind the colors. Even those of us here, who go way beyond just reading the discussion, for most, I don't think that they understand the 24-48 hour probability window that these idiot colors represent.
Member Since: Posts: Comments:
160. JLPR
Henri aka Erika part II
XD
looks good but its missing a good LLC
Member Since: September 4, 2007 Posts: 36 Comments: 5223
Quoting JLPR:
so to what conclusion do we get from this


Where is Henri's LLC? xD
blown away
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Well, here is another problem for the NHC.
Quikscat this evening does not show a closed low with Henri IMO but does show 45 knot TS winds.

Should they hold the TS classification ?.

I suspected this might well be the case from all that shear.
Member Since: Posts: Comments:
157. JLPR
so to what conclusion do we get from this


Where is Henri's LLC? xD
Member Since: September 4, 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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