Tropical Weather Briefing #6, Week of September 18  

GEORGE KASICA - 9/23/2006 12:14 PM
 

Tropical Weather Briefing #6, Week of September 18 

Forecaster: Kasica

Basin: Atlantic

Storm: Hurricane Helene

At 15Z Hurricane Helene is currently located at 37.7N 46.4W and has mostly maintained its speed and direction since yesterdays briefing and is moving at 065 degrees at 20kts with maximum sustained winds of 80kts.

As stated in the discussion http://www.nhc.noaa.gov/text/refresh/MIATCDAT3+shtml/231226.shtml (limited shelf life warning applies) only a small area of convection remains just north of the center of the storm. (1km IR and Visible Image attached)

In the NHC Discussion they mention the latest Quickscat pass only showed winds of 80kts. I have attached the latest Quickscat image from 0916Z for reference, however in looking at the image you can see that the highest winds on this image are just 60 kts not the 80 mentioned in the discussion.

Given that Helene is well on its way to being extra tropical, and based on the later statements of track uncertainty in the NHC discussion, I think a good avenue to follow up would be Helenís future track as they state there are significant differences in the model outputs not far into the future.

Have a great Saturday, 

George 

1_2006-09-23_1545Z_1KM_VIS_08LHELENE.80kts-NAmb-373N-475W.jpg
 
 
2_2006-09-23_1545Z_1KM_COLOR_IR_08LHELENE.80kts-NAmb-373N-475W.jpg
 
 
3_2006-09-23_0916Z_QSCAT_08LHELENE.80kts-970mb-373N-475W.jpg
 
 
re: Tropical Weather Briefing #6, Week of September 18
BRANDON JONES - 9/23/2006 08:15 PM
The track of Helene is a more uncertain after 48 hours. As of 5 PM the NHC notes that the models are in a little better agreement on the track than they were before. I have attached an image of some computer models track for Helene.

On the e-wall the GFS shows Helene slowing down around 72 hours. NOGAPS shows the storm slowing significantly in 72 hours and turning southward while weakening. The CMC however keeps Helene moving east-northeast. I think the track will remain generally east-northeast with some slow down in forward speed in 72 hours. Then it looks that Helene will resume a quicker east-northeast motion. 

A reason for the slower motion in forward speed is that Helene will be out of reach of stronger westerlies to its north. This will also mean that Helene will lose quite a bit of its baroclinic energy. The NHC also mentions the loss of some baroclinic energy in their 5 PM discussion.

There is an interesting water vapor loop at: (http://wwwghcc.msfc.nasa.gov/GOES/goeseastfullwv.html). In the loop you can see Helene's increased interaction with the trough, and its extratropical transition.
Model_forecasts.gif
 
re: Tropical Weather Briefing #6, Week of September 18
PHILIP LUTZAK - Edited 9/23/2006 09:29 PM
Nice obs, Brandon. Since the models are coming into better consensus, looks like Ireland and the British Isles may get a big gale on Wednesday. I attached forecasts for Wednesday morning from the CMC for Europe (from our wonderful e-wall), and one from the Meteorological Office of the UK. Here's a link to the UK office's complete prog maps out to 132 hours: 
http://www.weathercharts.org/ukmomslp.htm

Pretty cool stuff.

CMC_forecast_for_2006-09-27_1200_Europe.gif    
fcst_for_2006-09-27_1200_from_MetOfficeUK.JPG
 

 
re: Tropical Weather Briefing #6, Week of September 18
BRANDON JONES - 9/23/2006 11:43 PM
Thanks Philip!

The latest from the NHC indicates that Helene is hanging on to tropical characteristics. We can see this on an ASMU image from CIMMS (attachment), the image shows that the system still has a warm core. The NHC also notes that they have slowed their track slightly along with a slight southward shift. The NHC set the intensity at 75 knots. The QUIKSCAT image (attached) show some vectors near 70 knots which supports the intensity, but be careful about the black barbs on the image.
Helene_amsua_ch7.gif    
Helene_QuikScat.bmp
 
 
re: Tropical Weather Briefing #6, Week of September 18
LEE GRENCI - 9/24/2006 09:48 AM
Nice use of AMSU, Brandon.
 
re: Tropical Weather Briefing #6, Week of September 18
LEE GRENCI - 9/24/2006 09:50 AM
You know, when I see so many black-flagged observations on QuikSCAT images, I think of an insecticide with the same name.  :-)
 
re: Tropical Weather Briefing #6, Week of September 18
GEORGE KASICA - 9/24/2006 10:19 AM
LOL...not a Nayscar fan eh Lee :)
 
re: Tropical Weather Briefing #6, Week of September 18
LEE GRENCI - 9/24/2006 09:51 AM
Thanks for using Penn State's European e-wall, Phil.  I really like that site.
 
re: Tropical Weather Briefing #6, Week of September 18
PHILIP LUTZAK - 9/24/2006 04:29 PM
Oh you're welcome Lee. I liked it from the moment I saw it. The graphics and satellite presentations are beautiful - very nicely done.
 
re: Tropical Weather Briefing #6, Week of September 18
LEE GRENCI - 9/24/2006 09:54 AM
Thanks Brandon.  I think the model tracks at Colorado State (see attached) are superior to Weather Underground, which is where I'm guessing you got your attachment.
early2.png  
 
re: Tropical Weather Briefing #6, Week of September 18
BRANDON JONES - 9/24/2006 07:08 PM
Hi Lee. I did get those tracks from Weather Underground. I agree with you that model tracks from Colorado State are better.
 
re: Tropical Weather Briefing #6, Week of September 18
LEE GRENCI - 9/24/2006 07:10 PM
No biggie.