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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heh Tropical Cyclone Warning Center Jakarta map shows "Melor" as a tropical depression

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Quoting Ameister12:

Did you read the section about the storm that is hitting England?


it doesn't say anything about when grace was... it just says where ex-Grace is now.

Same thing to you 456, doesn't say when and where it formed, a pic of ireland just shows ex-Grace where it is now.

I haven't been keeping up with weather in the past week and wasn't sure where Grace came from. Both Bill and Danny looked like that in the same place and form but they did different things before then. I just wanted to catch up on what was going on because I don't remember there being a grace.
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Water Vapor Imagery

Member Since: September 10, 2007 Posts: 0 Comments: 10978
Member Since: September 10, 2007 Posts: 0 Comments: 10978
Quoting Weather456:
Well My October Outlook was just issued a few days before Grace and Henri and I expected 2 storms, and becuz I did expected them so quickly we may get 1 or 2 more. No 1977 here which is no surprise becuz as I said back in July, 2009 lay a period of decadal high activity while 1977 laid in a period of low decadal activity so while the 2 have been inactive, 2009 will budge above the 2.


yea but think about this crazy scenerio, but really possible

2 more named storms this month is without a doubt possible based on forecasts; that brings us to 10. Then add to that possibly 3 more unnamed storms in post-season analysis and we go from one of the most inactive seasons on record, to one that could have 12 or 13 storms officially
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Quoting Cotillion:
2007 also had a lot of weak storms with small durations. (Barry, Chantal, Gabrielle, Jerry etc...)

2008 had Nana, which if you blinked, you would of missed it.

Short storms are by no means a rarity.


In fact, storms don't normally last more than 7 days.

2005 was the year of short-lived storms with Irene and Emily the 2 longest storms.
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Quoting Hurricane009:
low


Thats the big ?. whether Henri will be a player if it gets in the Carib.
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Quoting Hurricane009:
low


And the SST's?
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2007 also had a lot of weak storms with small durations. (Barry, Chantal, Gabrielle, Jerry etc...)

2008 had Nana, which if you blinked, you would of missed it.

Short storms are by no means a rarity.
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Well My October Outlook was just issued a few days before Grace and Henri and I expected 2 storms, and becuz I did expected them so quickly we may get 1 or 2 more. No 1977 here which is no surprise becuz as I said back in July, 2009 lay a period of decadal high activity while 1977 laid in a period of low decadal activity so while the 2 have been inactive, 2009 will budge above the 2.
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I guess the possibilities where this thing will end up are endless. What is shear expected to be like in the Carib and Southern GOM over the next week?
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Henri reminds me of Ana and Danny. Convection goes boom then sheared off repeat. I don't see why this storm is going to be any different. Eventually the LLC will be displaced and shredded apart from the shear. I can see Henri becoming a remnant low sooner than later. These weak struggling systems have been the format for this 2009 season.
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41. amd
Quoting BurnedAfterPosting:


actually considering that steering is expected to become weak in a few days and we are unsure of what Henri will even be at that point; it is hard to talk about Henri in terms of chances of impact.

This truly is one of those wait and see situations because everything is so up in the air.


good point bap, I shouldn't assume that a wsw or even sw motion is guaranteed after a couple of days.
Member Since: August 29, 2005 Posts: 0 Comments: 1024
Quoting BurnedAfterPosting:


actually considering that steering is expected to become weak in a few days and we are unsure of what Henri will even be at that point; it is hard to talk about Henri in terms of chances of impact.

This truly is one of those wait and see situations because everything is so up in the air.


Especially since the models have not verified thus far. Erika for 600 Alex.
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Quoting BurnedAfterPosting:


This truly is one of those wait and see situations because everything is so up in the air.


i wish i could have said that. lol
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Hebert in a "Press" Box..
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Quoting all4hurricanes:
wow this is like the season of short lived storms
Danny, Erika, Ana, and Fred all dealt with or died by wind shear. I have to say these storms this year are some of the most disappointing I've ever seen.


Be happy. Those that all insisted that we'd stop at 6 storms, and that this season will stop in the middle of September, on and on ad nauseum... despite the historical and climatological evidence which heavily suggested otherwise...

Were proven wrong as expected. :)
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Japan Meteorological Agency
Tropical Cyclone Advisory #65
TROPICAL STORM PARMA (T0917)
3:00 AM JST October 7 2009
================================

Subject: Category One Typhoon Overland Luzon (Philippines)

At 18:00 PM UTC, Tropical Storm Parma (994 hPa) located at 18.1N 121.0E has 10 minute sustained winds of 40 knots with gusts of 60 knots. The storm is reported as moving south-southeast at 6 knots.

RSMC Dvorak Intensity: T3.5

Gale-Force Winds
==================
180 NM from the center in northeast quadrant
150 NM from the center in southwest quadrant

Forecast and Intensity
=====================
24 HRS: 17.2N 122.2E - 40 kts (CAT 1/Tropical Storm)
48 HRS: 17.0N 121.4E - 35 kts (CAT 1/Tropical Storm)
72 HRS: 17.5N 119.5E - Tropical Depression

--------------
landlover cyclone came back for a visit
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Quoting amd:
before I left for work, I said that 91L looked like crap. I come home from work, and we now have tropical storm Henri. Just goes to show how quickly things can change in the tropics, especially when 84+ degree water is involved.

Even though it will probably not intensify in the next couple of days, the most important observations to make with Henri will be its movement. If it goes south of the forecast track, eventual interaction with Hispaniola will be much less.


actually considering that steering is expected to become weak in a few days and we are unsure of what Henri will even be at that point; it is hard to talk about Henri in terms of chances of impact.

This truly is one of those wait and see situations because everything is so up in the air.
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Quoting FloridaScuba:
ok. i got cornfuzeed cus they stll show 2 firrent systems on the tropical link. maybe someone still having a smoke break or something.

:)

Yeah, I noticed that too..then I looked at the coordinates. That would be a little close for 2 systems. They must have been in a hurry to list it for the bloggers here.
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Wow! What a surprise it was to come home from work and find we have Henri.
Member Since: September 10, 2007 Posts: 0 Comments: 10978
Quoting StSimonsIslandGAGuy:
Count me as surprised! I thought noting would come of 91L, though I wasn't sure. Henri will be interesting to watch--I have no idea what he will do next.
he should pull nw then stall and wane ne of pr and dom. then may drift some of him into ne carb with the rest pulled n ne in about 4 days from now
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ok. i got cornfuzeed cus they stll show 2 diffrent systems on the tropical link. maybe someone still having a smoke break or something.

:)
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29. amd
before I left for work, I said that 91L looked like crap. I come home from work, and we now have tropical storm Henri. Just goes to show how quickly things can change in the tropics, especially when 84+ degree water is involved.

Even though it will probably not intensify in the next couple of days, the most important observations to make with Henri will be its movement. If it goes south of the forecast track, eventual interaction with Hispaniola will be much less.
Member Since: August 29, 2005 Posts: 0 Comments: 1024
wow this is like the season of short lived storms
Danny, Erika, Ana, and Fred all dealt with or died by wind shear. I have to say these storms this year are some of the most disappointing I've ever seen.
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Quoting FloridaScuba:
forgive me for being ignorant of this (s'why aw don't sayz much)

are 91 and henri the same system?

Yes they are. Once 91L's circulation came close, then came Henri.
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Tropical storm Henri
I think it will go north of PR
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Quoting FloridaScuba:
forgive me for being ignorant of this (s'why aw don't sayz much)

are 91 and henri the same system?

Yes, 91L is now TS Henri.
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Some dry air is infiltrating the system. Quite minor but enough to retard development for now but . 98-99% of what will kill Henri is shear. If it does die of course.
Member Since: September 6, 2009 Posts: 2 Comments: 3710
Been very wet today... and it's just getting wetter....
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forgive me for being ignorant of this (s'why aw don't sayz much)

are 91 and henri the same system?
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Herni's interaction with Hisp will be crucial, if it misses it, it may become something very nasty, it not then it will dissipate either again or for the first time.
Member Since: September 6, 2009 Posts: 2 Comments: 3710
Quoting HurricaneSwirl:
huh? henri? when did we have grace?

Did you read the section about the storm that is hitting England?
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Picked from previous blog:
Quoting RitaEvac:


DEADLY sure


Well, that's one way to be sure you're 100% right. If nothing happens, you're right. If a storm does come, someone will likely die... and then you can say you were right too. Way to cover your bases.
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now we wait watch and see
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Shear is high, but dry air is low.
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Thanks, Dr. M. Take some credit for calling it a little better than NHC in this case and for wearing a shirt.
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thanks for update doc
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Quoting jeffs713:
Great satellite image of ex-Grace. I enjoy seeing that kind of high-relief image, especially when a tropical system is involved.

Especially cool with a visible sat image near sunrise/sunset so we can really see a little of the 3-D nature.
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Thanks, Dr. M.

And take some credit for bring right earlier today when you gave the invest a higher percentage of becoming Henri than the NHC.
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Finally something interesting happened this year...
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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.
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Quoting Seastep:


It happened a lot in 2007 too if I remember.



There were quite a few in 2007 and 2008:

2007:

STS Andrea
TS Gabrielle
TS Olga

2008:

TS Arthur
Hurricane Dolly
TS Fay (originally, later made TD6 in post season)
Hurricane Kyle (originally, later made TD11 in post season)
TS Laura
TS Nana (originally, later made TD 14 in post season)
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From the Carribean to out to sea, quite problematic as far as tracking goes
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Quoting HurricaneSwirl:
huh? henri? when did we have grace?


lol you serious. Pull up a sat pick of Ireland.
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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.