Tropical Storm Henri forms

By: Dr. Jeff Masters , 9:37 PM GMT on October 06, 2009

Share this Blog
3
+

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


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: 607 - 557

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14Blog Index

Member Since: Posts: Comments:
606. Skyepony (Mod)
After the short jog left Oct 2-3, I had figured the MJO was going to try one more round about circle in the WPac. Instead it turned back & has tracked toward the Atlantic since.

Member Since: Posts: Comments:
Good Morning Ike, Kman and the rest of you all!

Henri is holding his own against the shear, though the convergent upper level flow that is forecast would tend to decrease convection. It'll be interesting to see how it plays out... By now the LLC is so well developed that even if it decouples, the LLC could regenerate at a later point.

Also, the area of storms to the southeast will continue to find itself in a low shear environment (much more conducive than Henri) over the next several days. It just needs a tug or two to the north and then it would be a Caribbean problem.
Member Since: Posts: Comments:
hmm, so what you guys are saying is yes, i suppose. the reason I ask is b/c on loops it just looks like its going directly for them + 456 isnt here.

Ima noob tho.
Member Since: Posts: Comments:
603. IKE
Henri appears to be moving just north of west.
Member Since: Posts: Comments:
new disturbance, no surface low. there is a mid level circulation near 10N 46W
Member Since: Posts: Comments:
Quoting DookiePBC:
Forgive a completely amateur question here, but which way is Henri moving right now? Looking at the convection it looks to be moving just south of due west. Would that be a temporary jog or a track change? Thanks!


convection is not a good indicator of movement. Looking on visible or microwave imagery, or radar when close to land, is a good way to know movement.
Member Since: Posts: Comments:
Forgive a completely amateur question here, but which way is Henri moving right now? Looking at the convection it looks to be moving just south of due west. Would that be a temporary jog or a track change? Thanks!
Member Since: Posts: Comments:
It looks like unless shear ramps up again the NHC will continue to extend the forecast gone.
Member Since: Posts: Comments:
Oppressive humidity. Feels like August:

Hammond Municipal Airport
Lat: 30.52 Lon: -90.42 Elev: 43
Last Update on Oct 7, 7:22 am CDT

Fog/Mist

82 °F (28 °C)
Humidity: 94 %
Wind Speed: Calm
Barometer: 30.03"
Dewpoint: 81 °F (27 °C)
Heat Index: 93 °F (34 °C)

Visibility: 5.00 mi.
Member Since: Posts: Comments:
597. IKE
Quoting CandiBarr:
Is Henri still expected to go north of the antilles?


Member Since: Posts: Comments:
Member Since: September 10, 2007 Posts: 0 Comments: 11011
Is Henri still expected to go north of the antilles?
Member Since: Posts: Comments:
Shear has been decreasing around Henri and quite significantly so.

This should allow for further improvement today.
Member Since: August 19, 2006 Posts: 0 Comments: 15776
593. IKE
Member Since: Posts: Comments:
Good muggy morning all. I guess it's drier today. Yesterday we had 100% humidity. Lol. Water's rolling down the windows and it's not raining. Come on with the cold front already!


Beaumont, Texas (Airport)
Updated: 32 min 37 sec ago
Clear
80 °F
Clear
Humidity: 96%
Dew Point: 79 °F
Member Since: Posts: Comments:
Back later
Member Since: August 19, 2006 Posts: 0 Comments: 15776
Quoting IKE:
Pre92L looks like a low-runner. Appears to be moving north of west. Moving at a good clip.


And sitting under an anticyclone with low shear levels ahead.

If it can avoid SA this could pose big problems down the road.
Member Since: August 19, 2006 Posts: 0 Comments: 15776
Member Since: September 10, 2007 Posts: 0 Comments: 11011
588. IKE
Pre92L looks like a low-runner. Appears to be moving north of west. Moving at a good clip.
Member Since: Posts: Comments:
Good morning

Well, I see that the bend back to the W has come sooner than forecasted which I posted yesterday morning might well happen. I progged this system to be just SE of PR by Thursday and that may also verify.

Hard to believe it has handled the shear so well.
Member Since: August 19, 2006 Posts: 0 Comments: 15776
with the expected demise of Henri tonight, this will leave room for the disturbance to it;s southeast to flourish, now with such a conducive envtronment i expect the disturbed area ESE of the winwards to be classified as 92L during the course of today. i anticipate this system will form into the next named storm IDA the next few days.
Member Since: Posts: Comments:
584. IKE
Quoting P451:


And a lot of heat to work with. It's a good thing that Henri is fighting shear. If it weren't it would already be a monster IMO.



I agree with you on that.
Member Since: Posts: Comments:
my gosh the names this year are crackin' me up!

My mom used to call my brother ahne-ree when he used his GI-Joe to assassinate my Barbie's and his At-At to stomp on my My-Little-ponies.

where is the origin of Ida?
Member Since: Posts: Comments:
Quoting IKE:
Look for 92L within 24 hours.

Low shear all the way to the Caribbean....

looks like this one will have an excellent shot at developing if it does not interact with any landmasses
Member Since: Posts: Comments:
579. IKE
Look for 92L within 24 hours.

Low shear all the way to the Caribbean....

Member Since: Posts: Comments:
Quoting amd:


same feeling here in Houston. It is more humid now than it has been all summer. Fortunately by Sunday, the forecast for Houston is a high of 76 and a low of 63. Right now, it's 81 degrees and the dew point is 79 degrees.



kprc says 58 for low eeee :D
Member Since: Posts: Comments:
576. amd
Quoting TheCaneWhisperer:
Record heat today in SEFL, when will it end?
Heat indices to reach near 105 this afternoon..


same feeling here in Houston. It is more humid now than it has been all summer. Fortunately by Sunday, the forecast for Houston is a high of 76 and a low of 63. Right now, it's 81 degrees and the dew point is 79 degrees.

Member Since: Posts: Comments:
it appears we may have a another tropical system to contend with in the very near future, i think henri will survive the shear and head towards hispaniola and then dissipate
Member Since: Posts: Comments:
Record heat today in SEFL, when will it end?
Heat indices to reach near 105 this afternoon..
Member Since: Posts: Comments:
there are still tropical waves over africa and one about to exit the coast
Member Since: Posts: Comments:
Morning all.

I see the area I pointed out yesterday to the SE of Henri is showing signs of organizing. Could pose a bigger threat than Henri based on it's forecast dissipation. Looks like an invest is in store today, 92L, as it will ride the north coast of South America, over water and into the Caribbean.
Member Since: Posts: Comments:
sry I shoulda previewed that
Member Since: Posts: Comments:
Quoting IKE:


Cold front is suppose to make it down to the northern gulf-coast this weekend.

From NO,LA..

looks like the coastal car show could get wet, at least we wont feel like a crawfish at a La wedding :)
Member Since: Posts: Comments:
568. IKE
Quoting CandiBarr:


Ive got 81 degrees with 96% humidity...ewwww


Cold front is suppose to make it down to the northern gulf-coast this weekend.

From NO,LA...

"LONG TERM...
MODELS COMING INTO A LITTLE BETTER AGREEMENT ON FRONTAL MOVEMENT
THIS WEEKEND. FRONT WILL ONLY SHIFT THROUGH THE AREA SLOWLY...AND
FINALLY CLEAR THE AREA MONDAY OR TUESDAY. BEST CHANCES FOR
PRECIPITATION WILL BE FRIDAY NIGHT AND SATURDAY. WILL NOT STRAY
TOO FAR FROM GFS SOLUTION...WHICH ONLY COOLS TEMPERATURES DOWN TO
NEAR OR JUST BELOW NORMAL BY THE END OF THE FORECAST PERIOD."
Member Since: Posts: Comments:
BR>
76 degrees outside. Where's fall?


Ive got 81 degrees with 96% humidity...ewwww
Member Since: Posts: Comments:
565. amd
good morning all. Looks like Henri continues to surprise. Despite substantial wind shear, and dry air to its nw, it continues to slowly strengthen (in terms of winds). Also, it is going almost due west, which is not surprising given that the system is still shallow (in terms of pressure).

If the storm can survive the next 36-48 hours, Henri could be a substantial problem. However, according to this water vapor imagery, dry air and shear at Henri's gate, I am not surprised that the NHC is calling for dissipation.
Member Since: Posts: Comments:
564. IKE
Henri is getting whipped with shear.


TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
800 AM EDT WED OCT 7 2009

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

THE NATIONAL HURRICANE CENTER IS ISSUING ADVISORIES ON TROPICAL
STORM HENRI...LOCATED ABOUT 460 MILES EAST OF THE NORTHERN
LEEWARD ISLANDS.

SHOWERS AND THUNDERSTORMS HAVE INCREASED IN ASSOCIATION WITH A
TROPICAL WAVE LOCATED ABOUT 925 MILES EAST-SOUTHEAST OF THE
WINDWARD ISLANDS. DEVELOPMENT...IF ANY...OF THIS SYSTEM SHOULD BE
SLOW TO OCCUR AS IT MOVES TO THE WEST-NORTHWEST AT ABOUT 15 MPH.
THERE IS A LOW CHANCE...LESS THAN 30 PERCENT...OF THIS SYSTEM
BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS.


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

PUBLIC ADVISORIES ON HENRI ARE ISSUED UNDER WMO HEADER WTNT35 KNHC
AND UNDER AWIPS HEADER MIATCPAT5. FORECAST/ADVISORIES ARE ISSUED
UNDER WMO HEADER WTNT25 KNHC AND UNDER AWIPS HEADER MIATCMAT5.

$$
FORECASTER BLAKE/PASCH




Member Since: Posts: Comments:
area of convection southeast of Henri, could be the big player of the 2009 season. Right now it has built convection, under very weak shear ,warm SST and has some cyclonic turning. The system is about 9oo miles ESE of the winward islands amd is gaining a little latitude. the problem is , should it survive and then enters the caribbean. where it is a cimatologically favoured area this time of year.
Member Since: Posts: Comments:
560. IKE 7:33 AM EDT on October 07, 2009

Think AtlantaMET is trying to provoke me. Fortunately I have my shields up.


Yup. He is not smart enough to get to you. Good!
Member Since: Posts: Comments:
561. Relix
Henri is like a dead fish =P
Member Since: Posts: Comments:
560. IKE
Quoting SQUAWK:


Good morning Ike. Glad to see you. I have flagged and reported the jerk.


Good morning.

Think AtlantaMET is trying to provoke me. Fortunately I have my shields up.


Quoting leftovers:
hey there "im in the mood now" have a great day


Good taste in music.

76 degrees outside. Where's fall?
Member Since: Posts: Comments:
Quoting Mikla:
Henri w/ mid and upper shear. He still faces a good deal of shear 20-30 over the next day or two...
OMG, it's going to go over the dreaded (gasps) Hebert Box!!!! J/K, lol.
Member Since: Posts: Comments:
Quoting AtlantaMET:


Good morning Ike. Glad to see you. I have flagged and reported the jerk.
Member Since: Posts: Comments:

Viewing: 607 - 557

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14Blog 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.