*Cyclone* Dora in SWIO

[Margie Kieper]

After a quiet January, Dora reached typhoon / severe tropical storm status today; by 1800Z, JTWC, AFWA, and SAB all determined satellite intensity estimates at T4.0. Slow steady intensification is forecast by both JTWC and Meteo France La Reunion over the next couple days.

 

[Margie Kieper]

Dora's eye has now cleared out on IR, and microwave shows continuing organization and consolidation (here is an earlier microwave as well). The links on the NRL home page continue to be more jumbled than usual the last couple days, but the most recent image can be found by selecting "previous." I find it confusing that Dora has had a hybrid-y look and some clockwise circulation above the TC (upper level winds), and recently convection appears to be a little removed from the center, yet the circulation appears deep looking at cloud top temps.

Fri lunchtime update: this is what was cooking, and it makes sense now. Wow.

Fri evng update: Intensity estimates indicate Dora has strengthened to the equivalent of a strong Category 3 hurricane today. While another crazy busy day at work left me with hardly any time to take a look, just now I got a little caught up, and saw that it looks like while the SAB intensity estimates showed a steady increase, the CIMSS ADT went from 3.7 at 0630Z to 5.8 at 1430Z (inbetween data points are missing from the history file), and JTWC advisories went from 85 to 110 kt. The eye has been clearing out and warming. It'll be interesting to see the first visual images tonight! The evolution to annular was interesting, and I'll have to go back and take a look this weekend, as I missed most of it happening in real time.

The first visual images remind me even more of a hybrid TC (wv and ir also seem reminiscent of 2005's Epsilon, although that TC only made it to the threshold of hurricane strength), and it appears Dora likely peaked overnight.


Sat morning: JTWC nudged the intensity up from 110 to 115 kt, but earlier this morning the SAB 0830Z satellite intensity estimate noted, "REMARKS...DORA APPEARS TO HAVE PEAKED ABOUT 12 HOURS AGO WITH COLDEST SURROUNDING TEMPERATURES. IT HAS REMAINED ABOUT STEADY STATE PAST 6 HOURS OR SO. DT=6.0..." The very large eye (30 nmi) has started to reduce in size. Satellite imagery of the TC remains remarkably beautiful.

 

[Peter Kirk]

Pretty big eye on this, been looking rather impressive recently hence the 100kt (930hPa) classification. The remarks from the latest warnings are as follows.

2.B OTHER INFORMATIONS:
SYMMETRIC SYSTEM WITH A RATHER LARGE EYE. MICRO-WAVES IMAGERY SHOW THAT
THE RING OF DEEP CONVECTION STARTS TO BE ERODATED BY THE WEST.
DORA SHOULD KEEP ON GENERALLY TRACKING SOUTHWESTWARDS UNDER THE STEERING
INFLUENCE IN A MID LEVEL OF A BUILDING SUBTROPICAL RIDGE IN THE WEST.
INFLUENCE OF THIS RIDGE SHOULD BE HINDERED BY SUCCESSIVE TROUGHS.
ENVIRONMENTAL CONDITIONS SHOULD NOT BRUTALLY BECOME UNFAVOURABLE AND THE
SYTEM SHOULD GRADU
ALLY WEAKEN.

No way this is a typhoon by the way, wrong part of the world.

 

[Margie Kieper]

No way this is a typhoon by the way, wrong part of the world.

Well then you had better provide the "proper" name.

 

[MJ Poore]

Thanks for keeping the SWIO theatre up to date Margie. I always watch with interest. It gets going for us down here when these systems enter the Moz Channel.

Mungo

 

[Jim Leonard]

Tropical cyclones in the southern hemisphere are just simply called "Cyclones". The term "Typhoon" is used only in the northwest pacific basin.

 

[MJ Poore]

More correctly a Tropical Cyclone

But I hear the word hurricane being used more and more.

 

[Margie Kieper]

Tropical cyclones in the southern hemisphere are just simply called "Cyclones". The term "Typhoon" is used only in the northwest pacific basin.

I knew, when he mentioned it and I went back and looked at the title to the post. I just wanted to make a point and see if PK would come back to actually be "helpful." Wink, wink...

I think I had typhoon on the brain as I spent the last couple days before that post putting together a data set for a met doing a reanalysis of the western North Pacific. I will see if I can still change the title for the post or if an admin can do so...and figure out where the links to those images got off to.

Besides Isabel and now Dora, what other tropical cyclones in recent years have been annular?

 

[Jim Southard]

As far as annular storms similar to Dora go... how about Hurricane Epsilon in 2005?

 

[Margie Kieper]

I was not sure about Epsilon because NHC had only referred to it as having an annular look. I queried a met that has the largest collection of satellite imagery I have ever seen, and he said that since Isabel that there was no significant annular hurricane. But there is one good microwave image of Epsilon that has the annular look to the clouds and convection, so maybe there are other factors that are considered such as intensity, structure, or dynamics. Mainly I was hoping to find something else on the NRL web site to look at, to compare with images of Dora and Isabel to help understand the steady state a little better. It's very interesting (and there is a good article from last October BAMS on Isabel and MPI), and now I see why after initially learning about annular hurricanes I was confused about whether intense hurricanes with large eyes (such as Katrina) had annular characteristics or not.

I went back and reviewed imagery of Daniel (2006 East Pacific) and now I am wondering if that would also qualify...it will take awhile but I'll put together some images comparing these TC this week, and post (I'm guessing microwave imagery would be the best for this?). I heard back from the same met again and he said yes Daniel was annular...he thought I was only asking about the Atlantic basin.

 

[Jim Southard]

OK, gotcha. When you mentioned the word "annular," Epsilon immediately popped into my head. I think it certainly qualifies as steady state too, defiantly maintaining its strength for a few days in hostile conditions.

But you're right, Epsilon certainly pales in comparison to the others in the intensity department, and I apologize for not reading your previous post more closely. It did have the annular appearance, but Epsilon was a very unique and complex storm, and it probably wouldn't be a very straightforward or helpful case to study.

Thanks for the good discussion, and good luck in your investigations!

 

[Peter Kirk]

I knew, when he mentioned it and I went back and looked at the title to the post. I just wanted to make a point and see if PK would come back to actually be "helpful." Wink, wink...

I think I had typhoon on the brain as I spent the last couple days before that post putting together a data set for a met doing a reanalysis of the western North Pacific. I will see if I can still change the title for the post or if an admin can do so...and figure out where the links to those images got off to.

This was called Intense Tropical Cyclone Dora as its peak. Sorry I assumed you'd look at the RSMC La Reunion page to see what it said on there after I made the comment.

Sounds fun that other thing. Been going through the RSMC Tokyo BT recently myself.