Typhoon Roke bears down on Japan; 98L continues to grow more organized

By: Dr. Jeff Masters , 6:48 PM GMT on September 20, 2011

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Powerful Category 3 Typhoon Roke is bearing down on Japan, and is expected to hit the main island of Honshu on Wednesday morning, local time. Roke is on a dangerous track for Japan, one that would take the storm over some of the most heavily populated areas of the country. Heavy rains from Roke have already reached the coast of Japan, as seen on Japanese radar. However, Roke is starting to weaken, as seen in latest satellite imagery. The eye is no longer apparent, the cloud tops have warmed, and a slot of dry air has gotten wrapped into the storm's northwest side. Wind shear should continue to weaken Roke as it approaches landfall; shear is currently a high 20 knots, and will increase to 30 knots by Wednesday morning. Given the current weakening trend, I expect Roke is most likely to be a Category 2 typhoon at landfall.

Typhoon's Roke's storm surge, winds, and heavy rains will all be a concern. A damaging storm surge is likely to the right of where the center makes landfall, since Roke is a large storm whose winds are spread out over a wide area. If Roke tracks farther to the east than expected, a large storm surge may affect Tokyo Bay. Perhaps the biggest concern from the storm is heavy rain. The soils over much of Japan are saturated from the passage of Tropical Storm Talas during the first week of September. Talas was a very slow moving storm, and brought extreme rainfall amounts of over six feet to some portions of Japan. Roke is expected to bring up to 20 more inches of rain along its path. Roke could bring winds of 30 - 40 mph and heavy rains of 3 - 5 inches to the damaged Fukishima-Dai-Iche nuclear plant northeast of Tokyo.


Figure 1. MODIS image of Typhoon Roke taken at 1:45 pm local time (4:45 UTC) on Tuesday, September 20, 2011. At the time, Roke was a Category 2 storm with 110 mph winds. Image credit: NASA Earth Observatory.

Invest 98L continues to grow more organized
A tropical wave midway between Africa and the Lesser Antilles (Invest 98L) has increased in organization this afternoon, but still lacks a well-defined surface circulation. Satellite imagery shows a number of curved spiral bands have formed this afternoon, and the area covered by heavy thunderstorms has steadily increased. An ASCAT pass from 8:21 am EDT this morning did not capture the full circulation of the storm, but did show winds of 30 mph on the east side of the center. Wind shear as diagnosed by the SHIPS model has increased to a moderate 10 - 15 knots, and is predicted to stay moderate through Friday. Ocean temperatures are 28 - 28.5°C, well above the threshold typically needed for a tropical storm to spin up. Water vapor satellite images show 98L is embedded in a moist environment, but there is dry air to the system's northwest. Given that the shear has now increased to the moderate level, this dry air may begin to hinder development on Wednesday. An analysis of upper level winds from the University of Wisconsin CIMMS group shows a pattern favorable for development, with an outflow channel open to both the north and south available to ventilate the storm and allow 98L to efficiently lift plenty of moisture to high levels.


Figure 2. Afternoon satellite image of 98L.

The latest 8 am EDT (12Z) runs of the computer models show either no development of 98L, or development of 98L into a tropical depression or weak tropical storm by Saturday. 98L's westward motion of 5 - 10 mph should bring the storm into the Lesser Antilles Islands by Saturday, though the models are not in strong agreement about the forward speed of the storm. The GFDL model brings 98L into the islands on Friday, while the HWRF model keeps the storm east of the islands through Sunday. If 98L takes a more west-northwesterly path through northern Lesser Antilles, which has been the preferred track for tropical systems this year, the disturbance should encounter high wind shear in excess of 20 knots due to strong upper-level winds out of the west. This shear should make it difficult for 98L to intensify as it moves though the islands. However, if 98L takes a more southerly path across Barbados, as predicted by the GFDL model, the storm will miss seeing the high shear area that lies over the northern islands, and the storm would have more opportunity to strengthen. The most likely scenario I see at this point is for 98L to be a weak tropical storm on Saturday as it moves through the Lesser Antilles--but there is more than the usual amount of uncertainty in both the track and intensity forecast. NHC gave the disturbance a 70% chance of developing into a tropical depression by Thursday in their 2 pm Tropical Weather Outlook.

September temperatures return to normal over the U.S.
The summer of 2011 was the second hottest in U.S. history, but September of 2011 is so far shaping up to be an average one for temperature. A series of cold fronts and cold-cored low pressure systems have moved southwards out of Canada this month, bringing typical amounts of cool air to the country. If you want to select dates for the start and end of the U.S. heat wave of 2011, the dates to pick would be May 20 - September 4. During the period May 20 - September 4, 2011, the number of daily record high temperatures at the 515 major airports in the U.S. exceeded the number of daily low temperature records every day but one. That's an astonishing 107 out of 108 days! Only July 15 had more record daily lows than highs during that 108-day period. I doubt one could find a similar stretch of days anytime in U.S. weather history where such a lopsided ratio of high temperature to low temperature records existed. For the 3-month summer period of June, July, and August, 2703 daily high temperature records were set, compared to 300 daily low temperature records--a ratio of 9-to-1. Not surprisingly, the summer of 2011 wound up as the hottest summer in 75 years in the U.S., and was only 0.1°F cooler than the all-time record hottest summer, during the Dust Bowl year of 1936. But so far this September, the ratio of high temperature records to low temperature records has been close to 1-to-1. There were 283 daily high temperature records set during the first sixteen days of September, and 246 low temperature records. Eight of the first sixteen days of September have seen the lows outnumber the highs, and eight have seen the highs outnumber the lows. The latest 2-week forecast from the GFS model shows a continuation of pretty normal weather over the U.S. for the rest of the month, and September temperatures will end up close to average.

Jeff Masters

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Quoting JLPR2:


Sure.





I wouldn't call that closed.

It's elongated, and open to the SW. Note the lack of any westerly, northwesterly, or southwesterly wind vectors. All I see is SSW-N winds.

Not enough to call it closed, imo.

Quoting Tazmanian:




thats old

regardless, it still looks open.
Member Since: Posts: Comments:
Quoting beell:
GFS showing good consistency in developing 96E (Hilary) in the EPAC then bringing it NNW along the coast of MX and finally very near or into southern CA/AZ. At least one deep trough passing to the north may keep it closer to the coast. September is the favored month for systems to bring some weather to SOCAL.

SST's are a bit warmer than usual so it may hold together a bit farther north than most storms that develop in the EPAC. A strong trough either phases with the storm or picks it up and out to the NE over the desert SW. Probably moving pretty quick at that point so the flash flood risk could be minimized.

Nothing but a curiosity at this point.

click for big
SST's Valid 09/17



SST Anomaly



09/20 18Z GFS 850mb Vort
Valid @ 240 hrs
Nice to see you back Beell! I thought you had closed shop!
Member Since: May 26, 2011 Posts: 0 Comments: 1193
513. JLPR2
Quoting DiddyVort:
Until the low-level vorticity breaks out of the ITCZ this system will not develop.
The only reason there is any stronger low-level vorticity is because it is still tangled up down there.
The shear to the North of the system is not allowing a Northward migration yet.





That is not right, the only problem the ITCZ is causing 98L is that it is stealing the focus of the lower level convergence, limiting 98L's ability to fire up strong convection over its center.
Member Since: September 4, 2007 Posts: 7 Comments: 8747
Quoting TomTaylor:
agreed.

If this is the ASCAT pass everyone is so excited about, it does not constitute a well defined closed circulation.




It may be there now, but it is certainly not in this pass.




thats old
Member Since: May 21, 2006 Posts: 5091 Comments: 115456
I am sure someone posted/commented on this earlier but I did not notice it. This is too far out to have any reality yet but this is line with what Levi was saying a few days ago.


Member Since: June 2, 2007 Posts: 0 Comments: 619
I say that 98L is very close to a TD now, but will not be classified for at least 12 hours. Im going to say 2pm or 5pm on Wednesday.
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Quoting BDADUDE:
I may try it. Maybe tonight if i get a chance to see what the fuss is all about.





you dont no what you been missing all your life
Member Since: May 21, 2006 Posts: 5091 Comments: 115456
507. JLPR2
Quoting TomTaylor:
agreed.

If this is the ASCAT pass everyone is excited about, that does not constitute a well defined closed circulation



Old.
Member Since: September 4, 2007 Posts: 7 Comments: 8747
98L is still rather broad and this is partly why it's taking so long to close of a single circulation. It has to pull all of that energy into a mean center. Based on sat imagery and the voticity readings, it looks like a center is trying to develop to the south-west of the original low pressure center (nearest the deep convection). Separation from the monsoon trof would be beneficicial because it's only hindering its ability to tighten up.
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505. JLPR2
Quoting CybrTeddy:
ASCAT still looks a little elongated from NE to SW.


Yep, similar to the Windsat pass.
Member Since: September 4, 2007 Posts: 7 Comments: 8747
Quoting Chicklit:

it's spinning counterclockwise with spiral banding with definite organization.
Any time a system resembles a buzz saw I sit up and wonder.
LinkCATLoop
While it may not meet your expectations of a developing system it has enough characteristics of one to watch for development. Basically all 98L needs right now is to tighten up.
[ ].

I agree with him about the monsoon trough, though. Until 98L gets organized enough to pull out of it, it's not likely to get classified.

I find it interesting that TAFB has been analysing that monsoon trough all the way across the ATL at times, with little genuine ITCZ action. I'm wondering how much that difference is impacting our ability to accurately forecast storm cyclogenesis with African waves this year.
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Quoting CybrTeddy:
ASCAT still looks a little elongated from NE to SW.
agreed.

If this is the ASCAT pass everyone is so excited about, it does not constitute a well defined closed circulation.




It may be there now, but it is certainly not in this pass.
Member Since: Posts: Comments:
deleted: again misposted some coordinates I meant to temporarily store in the NewComment box.
Member Since: Posts: Comments:
501. beell
GFS showing good consistency in developing 96E (Hilary) in the EPAC then bringing it NNW along the coast of MX and finally very near or into southern CA/AZ. At least one deep trough passing to the north may keep it closer to the coast. September is the favored month for systems to bring some weather to SOCAL.

SST's are a bit warmer than usual so it may hold together a bit farther north than most storms that develop in the EPAC. A strong trough either phases with the storm or picks it up and out to the NE over the desert SW. Probably moving pretty quick at that point so the flash flood risk could be minimized.

Nothing but a curiosity at this point.

click for big
SST's Valid 09/17



SST Anomaly



09/20 18Z GFS 850mb Vort
Valid @ 240 hrs
Member Since: Posts: Comments:
Quoting interstatelover7165:
http://rammb.cira.colostate.edu/products/tc_realt im e/image_mpsatwnd.asp?storm_identifier=AL982011& ;pro duct_filename=2011AL98

Defintally Closed Circ.
multiplatform analysis at RAMMB is very unreliable when it comes to weak tropical disturbances, depressions, and storms.
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None of the respectacle models develop 98. Some thing to consedere
Member Since: May 26, 2011 Posts: 0 Comments: 1193
ASCAT still looks a little elongated from NE to SW.
Member Since: July 8, 2005 Posts: 259 Comments: 24580
Quoting Tazmanian:



no its not its still dead in other words 99L is still EX 99L
I reminds me a lot of the little swirl that was name Jose,, a very define circulation but on this case can't hold convection long enough to be call something do to the strong shear...
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496. JLPR2
Quoting TomTaylor:
yea I changed the CIMSS part, since the new maps came out. The old one looked like this




and that was the basis of that statement.

Could you post the ASCAT pass, please? thanks


Sure.
Member Since: September 4, 2007 Posts: 7 Comments: 8747
http://rammb.cira.colostate.edu/products/tc_realtim e/image_mpsatwnd.asp?storm_identifier=AL982011&pro duct_filename=2011AL98

Defintally Closed Circ.
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Quoting CaicosRetiredSailor:
Mon soon come...
Hey.... do u have internet back at ur house yet?
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Quoting JLPR2:


Don't agree with those two since ASCAT showed half of a nice LLC and Windsat showed a closed LLC. CIMMS updated their image and bam! vort reflecting all the way to 200mb.
yea I changed the CIMSS part, since the new maps came out. The old one looked like this




and that was the basis of that statement.

Could you post the ASCAT pass, please? thanks
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Quoting DiddyVort:
it's spinning counterclockwise with spiral banding with definite organization


Yep...it sure is Chicklit.
Lots of stuff spins.


That's a pretty cavalier remark.
Member Since: July 11, 2006 Posts: 14 Comments: 11424
I am thinking that we will not see any more major hurricanes in the Atl Basin this year. Agree?
Member Since: May 26, 2011 Posts: 0 Comments: 1193
Quoting Tazmanian:




why not you bump IE and go with googl chorm
I may try it. Maybe tonight if i get a chance to see what the fuss is all about.
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Quoting BDADUDE:
IE comes with a home button as default.




why not you bump IE and go with googl chorm
Member Since: May 21, 2006 Posts: 5091 Comments: 115456
IE comes with a home button as default.
Member Since: Posts: Comments:
Quoting DiddyVort:
All of that low-level vorticity is still tangled up in the monsoon trough...so it's gotta break free of that before any development can happen.
This system looks more like 40% to me right now.


it's spinning counterclockwise with spiral banding with definite organization.
Any time a system resembles a buzz saw I sit up and wonder.
LinkCATLoop
While it may not meet your expectations of a developing system it has enough characteristics of one to watch for development. Basically all 98L needs right now is to tighten up.
Member Since: July 11, 2006 Posts: 14 Comments: 11424
Quoting AvidWeatherHound:


Thanks Taz!I now have a home button :)



your welcome
Member Since: May 21, 2006 Posts: 5091 Comments: 115456
Quoting Tazmanian:
for the ones that are uesing google chorm 14 if you still dont no how too get your Home button too show up here how go too option-Basics go down too Toolbar then the 1st one you see Show Home button and hit that check box and there you go you now have your Home button


Show Home button


Thanks Taz!I now have a home button :)
Member Since: Posts: Comments:
482. JLPR2
Quoting TomTaylor:
Not really. Convection intensity is there, it's just that this disturbance spun up out of the monsoon trough. As a result, it's had trouble focusing that energy and vorticity over one area. In other words, surface convergence is lacking, which can be seen on satellite imagery (noted by the convection being spread out across a large area rather than focused like 99L has) or CIMSS analysis. This explains why we have a very broad system, with a poor vorticity signature on CIMSS analysis, lacking a defined closed surface circulation.


Don't agree with those two since ASCAT showed half of a nice LLC and Windsat showed a closed LLC. CIMMS updated their image and bam! vort reflecting all the way to 200mb.
Member Since: September 4, 2007 Posts: 7 Comments: 8747
evening everyone
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Quoting TropicalAnalystwx13:


Thank you Taz, I was wondering why there wasn't one :P



your vary welcome
Member Since: May 21, 2006 Posts: 5091 Comments: 115456
479. JLPR2
Quoting TropicalAnalystwx13:


Wow, that's contradictory.

I would've upgraded at 11PM, but I don't know if they will or not.


Well it's nice to have contradictory opinions, thinking the same is boring. xD
Member Since: September 4, 2007 Posts: 7 Comments: 8747
Mon soon come...
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Quoting JLPR2:
This will probably be 16L by 11pm, 5am the latest.


Just needs stronger convection.
Not really. Convection intensity is there, it's just that this disturbance spun up out of the monsoon trough. As a result, it's had trouble focusing that energy and vorticity over one area. In other words, surface convergence is lacking, which can be seen on satellite imagery (noted by the convection being spread out across a large area rather than being focused over one area like 99L has) or CIMSS analysis. This explains why we have a very broad system lacking a defined closed surface circulation.

I do expect this will eventually become a TD, I'm just noting its issues.
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476. JLPR2
Winds are steadily picking up at buoy:
41041 (14.1N 45.9w)

Up to 20mph, with gusts to 30mph.


Interesting considering the system is so far away.
Member Since: September 4, 2007 Posts: 7 Comments: 8747
Back soon.
Member Since: July 6, 2010 Posts: 113 Comments: 32865
Quoting Tazmanian:
for the ones that are uesing google chorm 14 if you still dont no how too get your Home button too show up here how go too option-Basics go down too Toolbar then the 1st one you see Show Home button and hit that check box and there you go you now have your Home button


Show Home button


Thank you Taz, I was wondering why there wasn't one :P
Member Since: July 6, 2010 Posts: 113 Comments: 32865
850 mb vorticity is up.


she be cruisin'
Member Since: July 11, 2006 Posts: 14 Comments: 11424
for the ones that are uesing google chorm 14 if you still dont no how too get your Home button too show up here how go too option-Basics go down too Toolbar then the 1st one you see Show Home button and hit that check box and there you go you now have your Home button


Show Home button
Member Since: May 21, 2006 Posts: 5091 Comments: 115456
Quoting MississippiWx:
98L has continued to become better organized throughout the day. Personally, I would have raised the percentage to at least 80%, if not 90. However, it's obviously not my call. The issue remains with the broad structure of the invest and the lack of one dominant area of circulation. I mentioned earlier in the day how we seemed to have at least a couple vort maxes spinning around a common center of circulation. This is a common issue with monsoonal systems and the main reason why they take longer to be classified.
Seems like we've had quite a few of these monsoonal systems this year. I've been saying 2011 will go down as "the year of the twin centres"....
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Quoting JLPR2:
This will probably be 16L by 11pm, 5am the latest.


Just needs stronger convection.
Quoting TropicalAnalystwx13:


By morning?

5AM at the earliest, IMO.


Wow, that's contradictory.

I would've upgraded at 11PM, but I don't know if they will or not.
Member Since: July 6, 2010 Posts: 113 Comments: 32865
I think 98L is finally starting to move.
Member Since: July 11, 2006 Posts: 14 Comments: 11424
Quoting Neapolitan:

Unless it fades away overnight, I'd say it'll be classified within the next 12 hours.


By morning?

5AM at the earliest, IMO.
Member Since: July 6, 2010 Posts: 113 Comments: 32865
467. JLPR2
This will probably be 16L by 11pm, 5am the latest.


Just needs stronger convection over the center.
Member Since: September 4, 2007 Posts: 7 Comments: 8747
Quoting TropicalAnalystwx13:


Its a nice pinhole eye too! Good eye!




LOL LOL LOL


Member Since: May 21, 2006 Posts: 5091 Comments: 115456
Quoting MiamiHurricanes09:
Dvorak satellite estimates still yield the classification of 16L.

Unless it fades away overnight, I'd say it'll be classified within the next 12 hours.
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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.

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