ATL: GORDON - Post-Tropical

Moderator: S2k Moderators

Message
Author
User avatar
Steve
S2K Supporter
S2K Supporter
Posts: 6199
Joined: Sat Apr 05, 2003 11:41 pm
Location: NOT a State-caster

ATL: GORDON - Advisories

#1781 Postby Steve » Thu Sep 06, 2018 10:18 am

Finally getting a taste of Gordon here. The feeder/inflow is cruising SLA and feeding upwards. Hopefully it won't flood, but that remains to be seen whether or not the feeder rain trains or not.
https://radar.weather.gov/ridge/Conus/s ... y_loop.php
0 likes   

User avatar
cycloneye
Storm2k Moderator
Storm2k Moderator
Posts: 116135
Age: 62
Joined: Thu Oct 10, 2002 10:54 am
Location: San Juan, Puerto Rico

Re: ATL: GORDON - Advisories

#1782 Postby cycloneye » Thu Sep 06, 2018 9:35 pm

BULLETIN
Tropical Depression Gordon Advisory Number 19
NWS Weather Prediction Center College Park MD AL072018
1000 PM CDT Thu Sep 06 2018

...GORDON CONTINUES TO DRIFT THROUGH CENTRAL ARKANSAS...


SUMMARY OF 1000 PM CDT...0300 UTC...INFORMATION
-----------------------------------------------
LOCATION...34.6N 92.2W
ABOUT 25 MI...35 KM S OF LITTLE ROCK ARKANSAS
MAXIMUM SUSTAINED WINDS...10 MPH...20 KM/H
PRESENT MOVEMENT...NW OR 321 DEGREES AT 3 MPH...6 KM/H
MINIMUM CENTRAL PRESSURE...1013 MB...29.92 INCHES


WATCHES AND WARNINGS
--------------------
Flash Flood Watches are in effect over portions of Mississippi
and Arkansas.

There are no coastal watches or warnings in effect.

For more information on Gordon, please see products issued by your
local National Weather Service office.


DISCUSSION AND OUTLOOK
----------------------
At 1000 PM CDT (0300 UTC), Tropical Depression Gordon was
located near latitude 34.6 North, longitude 92.2 West. The
depression was moving toward the northwest near 3 mph (6 km/h) and
Gordon is expected to turn towards the north on Friday.

Maximum sustained winds are near 10 mph (20 km/h) with higher gusts.
Little change in strength is forecast during the next 48 hours.

The estimated minimum central pressure is 1013 mb (29.92 inches).


HAZARDS AFFECTING LAND
----------------------
RAINFALL: Gordon is expected to produce total rain accumulations of
3 to 6 inches over northwest Mississippi and much of Arkansas, up
into the Midwest, with possible isolated maximum amounts of 10
inches through Saturday night. This rainfall will likely cause local
flooding and flash flooding.


For more information on rainfall totals please see the Storm Summary
available at www.wpc.ncep.noaa.gov/discussions/nfdscc2.html

NEXT ADVISORY
-------------
Next complete advisory at 400 AM CDT.

$$
Forecaster Petersen

FORECAST POSITIONS AND MAX WINDS

INIT 07/0300Z 34.6N 92.2W 10 KT 10 MPH
12H 07/1200Z 35.0N 92.4W 10 KT 10 MPH...INLAND
24H 08/0000Z 35.9N 92.4W 10 KT 10 MPH...INLAND
36H 08/1200Z 37.3N 91.3W 15 KT 15 MPH...POST-TROP/EXTRATROP
48H 09/0000Z 38.1N 89.9W 15 KT 15 MPH...POST-TROP/EXTRATROP
72H 10/0000Z 40.3N 85.6W 20 KT 25 MPH...POST-TROP/EXTRATROP
96H 11/0000Z 44.4N 77.2W 25 KT 30 MPH...POST-TROP/EXTRATROP
120H 12/0000Z 47.2N 65.8W 25 KT 30 MPH...DISSIPATED
0 likes   
Visit the Caribbean-Central America Weather Thread where you can find at first post web cams,radars
and observations from Caribbean basin members Click Here

User avatar
AJC3
Moderator-Pro Met
Moderator-Pro Met
Posts: 2849
Age: 55
Joined: Tue Aug 31, 2004 7:04 pm
Location: West Melbourne, Florida
Contact:

Re: ATL: GORDON - Advisories

#1783 Postby AJC3 » Fri Sep 07, 2018 6:34 pm

BULLETIN
Tropical Depression Gordon Advisory Number 22
NWS Weather Prediction Center College Park MD AL072018
400 PM CDT Fri Sep 07 2018

...TROPICAL DEPRESSION GORDON MOVING NORTH THROUGH CENTRAL
ARKANSAS...


SUMMARY OF 400 PM CDT...2100 UTC...INFORMATION
----------------------------------------------
LOCATION...35.8N 92.3W
ABOUT 89 MI...143 KM WSW OF JONESBORO, ARKANSAS
MAXIMUM SUSTAINED WINDS...10 MPH...20 KM/H
PRESENT MOVEMENT...N OR 360 DEGREES AT 7 MPH...11 KM/H
MINIMUM CENTRAL PRESSURE...1012 MB...29.89 INCHES


MAXIMUM SUSTAINED WINDS...10 MPH...20 KM/H

:uarrow: :uarrow: :cheesy: :ggreen: :cheesy: :ggreen:
3 likes   

User avatar
galaxy401
Category 5
Category 5
Posts: 1466
Age: 24
Joined: Sat Aug 25, 2012 9:04 pm
Location: Casa Grande, Arizona

Re: ATL: GORDON - Tropical Depression - Discussion

#1784 Postby galaxy401 » Mon Dec 03, 2018 2:35 pm

0 likes   
I don't get hurricanes here but I do get their remnants.

User avatar
ColdMiser123
Professional-Met
Professional-Met
Posts: 279
Joined: Mon Sep 26, 2016 3:26 pm

Re: ATL: GORDON - Post-Tropical

#1785 Postby ColdMiser123 » Sun Dec 16, 2018 2:40 pm

Kind of interesting reading the TCR for Hurricane Cindy in 2005. The primary justification for a post-season upgrade to hurricane was a uniform area of 70-74 KT radial velocities at ~9000 feet AGL.

https://www.nhc.noaa.gov/data/tcr/AL032005_Cindy.pdf

In the NHC discussion for Gordon, they mentioned that Gordon had 65-75 KT radial velocities at ~2500 feet AGL, closer to the ground than the velocities discussed with Hurricane Cindy's TCR. This is likely something they will be looking more into with their final TCR for Gordon.

https://www.nhc.noaa.gov/archive/2018/a ... .011.shtml?
Last edited by ColdMiser123 on Mon Dec 17, 2018 9:59 pm, edited 1 time in total.
0 likes   
B.S. Meteorology and Atmospheric Science, 2018
M.S. Graduate Student, Meteorology and Atmospheric Science

CrazyC83
Professional-Met
Professional-Met
Posts: 27539
Joined: Tue Mar 07, 2006 11:57 pm
Location: Deep South, for the first time!

Re: ATL: GORDON - Post-Tropical

#1786 Postby CrazyC83 » Mon Dec 17, 2018 6:53 pm

ColdMiser123 wrote:Kind of interesting reading the TCR for Hurricane Cindy in 2005. The primary justification for a post-season upgrade to hurricane was a uniform area of 70-74 KT radial velocities at ~9000 feet AGL.

https://www.nhc.noaa.gov/data/tcr/AL032005_Cindy.pdf

In the NHC discussion for Gordon, they mentioned that Gordon had 65-75 KT radial velocities at ~2500 feet AGL, even closer to the ground than the velocities discussed with Hurricane Cindy's TCR. This is likely something they will be looking more into with their final TCR for Gordon.

https://www.nhc.noaa.gov/archive/2018/a ... .011.shtml?


The wind factor at 2,500 feet is lower - winds at the surface are typically about 75-80% of winds at that height. That would support well an intensity of about 55-60 kt. I'm not seeing anything supporting Gordon being a hurricane - that would generously support 60 kt, and come closer to a 55 kt intensity.
0 likes   

User avatar
ColdMiser123
Professional-Met
Professional-Met
Posts: 279
Joined: Mon Sep 26, 2016 3:26 pm

Re: ATL: GORDON - Post-Tropical

#1787 Postby ColdMiser123 » Mon Dec 17, 2018 7:31 pm

CrazyC83 wrote:
ColdMiser123 wrote:Kind of interesting reading the TCR for Hurricane Cindy in 2005. The primary justification for a post-season upgrade to hurricane was a uniform area of 70-74 KT radial velocities at ~9000 feet AGL.

https://www.nhc.noaa.gov/data/tcr/AL032005_Cindy.pdf

In the NHC discussion for Gordon, they mentioned that Gordon had 65-75 KT radial velocities at ~2500 feet AGL, even closer to the ground than the velocities discussed with Hurricane Cindy's TCR. This is likely something they will be looking more into with their final TCR for Gordon.

https://www.nhc.noaa.gov/archive/2018/a ... .011.shtml?


The wind factor at 2,500 feet is lower - winds at the surface are typically about 75-80% of winds at that height. That would support well an intensity of about 55-60 kt. I'm not seeing anything supporting Gordon being a hurricane - that would generously support 60 kt, and come closer to a 55 kt intensity.


I would make the case that it would warrant further investigation into Radar data that wasn't possible during operations, especially since radial velocity only measures the component of the wind perpendicular to the Radar. I would assume that they will also likely investigate differing tilt angles to gauge radial velocities at different heights.

Should note that there were no surface observations indicating that Hurricane Cindy was a hurricane either.

A bit outdated, but I think this is a pretty good resource looking at the wind speed conversions for differing heights for a tropical cyclone.

https://www.nhc.noaa.gov/aboutwindprofile.shtml
0 likes   
B.S. Meteorology and Atmospheric Science, 2018
M.S. Graduate Student, Meteorology and Atmospheric Science

CrazyC83
Professional-Met
Professional-Met
Posts: 27539
Joined: Tue Mar 07, 2006 11:57 pm
Location: Deep South, for the first time!

Re: ATL: GORDON - Post-Tropical

#1788 Postby CrazyC83 » Mon Dec 17, 2018 9:34 pm

ColdMiser123 wrote:
CrazyC83 wrote:
ColdMiser123 wrote:Kind of interesting reading the TCR for Hurricane Cindy in 2005. The primary justification for a post-season upgrade to hurricane was a uniform area of 70-74 KT radial velocities at ~9000 feet AGL.

https://www.nhc.noaa.gov/data/tcr/AL032005_Cindy.pdf

In the NHC discussion for Gordon, they mentioned that Gordon had 65-75 KT radial velocities at ~2500 feet AGL, even closer to the ground than the velocities discussed with Hurricane Cindy's TCR. This is likely something they will be looking more into with their final TCR for Gordon.

https://www.nhc.noaa.gov/archive/2018/a ... .011.shtml?


The wind factor at 2,500 feet is lower - winds at the surface are typically about 75-80% of winds at that height. That would support well an intensity of about 55-60 kt. I'm not seeing anything supporting Gordon being a hurricane - that would generously support 60 kt, and come closer to a 55 kt intensity.


I would make the case that it would warrant further investigation into Radar data that wasn't possible during operations, especially since radial velocity only measures the component of the wind perpendicular to the Radar. I would assume that they will also likely investigate differing tilt angles to gauge radial velocities at different heights.

Should note that there were no surface observations indicating that Hurricane Cindy was a hurricane either.

A bit outdated, but I think this is a pretty good resource looking at the wind speed conversions for differing heights for a tropical cyclone.

https://www.nhc.noaa.gov/aboutwindprofile.shtml


Also, there was no Recon in Cindy at that time right at landfall (the previous flight was about 6 hours before landfall which well supported the 60 kt intensity at that time while some improvement on radar occurred afterward, while the following flight was over the marshes after some filling). There was Recon in Gordon at that time, and no data supported hurricane intensity (Recon ran between 55 and 60). I'd personally keep the operational estimate unchanged (60 kt), but if I had to move it in either direction I'd go on the low end.
0 likes   

User avatar
ColdMiser123
Professional-Met
Professional-Met
Posts: 279
Joined: Mon Sep 26, 2016 3:26 pm

Re: ATL: GORDON - Post-Tropical

#1789 Postby ColdMiser123 » Mon Dec 17, 2018 9:55 pm

CrazyC83 wrote:
ColdMiser123 wrote:
CrazyC83 wrote:
The wind factor at 2,500 feet is lower - winds at the surface are typically about 75-80% of winds at that height. That would support well an intensity of about 55-60 kt. I'm not seeing anything supporting Gordon being a hurricane - that would generously support 60 kt, and come closer to a 55 kt intensity.


I would make the case that it would warrant further investigation into Radar data that wasn't possible during operations, especially since radial velocity only measures the component of the wind perpendicular to the Radar. I would assume that they will also likely investigate differing tilt angles to gauge radial velocities at different heights.

Should note that there were no surface observations indicating that Hurricane Cindy was a hurricane either.

A bit outdated, but I think this is a pretty good resource looking at the wind speed conversions for differing heights for a tropical cyclone.

https://www.nhc.noaa.gov/aboutwindprofile.shtml


Also, there was no Recon in Cindy at that time right at landfall (the previous flight was about 6 hours before landfall which well supported the 60 kt intensity at that time while some improvement on radar occurred afterward, while the following flight was over the marshes after some filling). There was Recon in Gordon at that time, and no data supported hurricane intensity (Recon ran between 55 and 60). I'd personally keep the operational estimate unchanged (60 kt), but if I had to move it in either direction I'd go on the low end.


Good points. Still, the post season upgrade came from a post season analysis of Radar that wasn't possible during operations. Should be interesting to see what they find this time.
0 likes   
B.S. Meteorology and Atmospheric Science, 2018
M.S. Graduate Student, Meteorology and Atmospheric Science

ncforecaster89
Tropical Low
Tropical Low
Posts: 34
Joined: Sat Oct 20, 2018 12:32 pm

Re: ATL: GORDON - Post-Tropical

#1790 Postby ncforecaster89 » Tue Jan 08, 2019 10:14 pm

Very good posts regarding a prospective upgrade to minimal hurricane intensity for tropical storm Gordon. In addition to the points already made, I’d add that the central pressure dropped a full 5 mb in the last two hours prior to landfall; intensifying as it came ashore. The highest FL wind of 63 kt was measured two hours prior to landfall and preceded the subsequent 5 mb pressure drop.

The totality of the available data is most consistent with 60 kt, but it’s conceivable Gordon may have just achieved a 65 kt intensity as it was crossing the coastline. Especially, if one factors in the prospect of any slight undersampling of the max wind, the aforementioned rapid pressure decrease, and the improving satellite presentation in those last two hours prior to landfall.

All things considered, and as others have noted, it will be very interesting to see the NHC TCR.
2 likes   


Return to “2018”

Who is online

Users browsing this forum: No registered users and 2 guests