Hurricane Katia

[Amped]

Lee now has a lower central pressure than Katia.

[wxsmwhrms]

Lee now has a lower central pressure than Katia.

The ECMWF actually nailed that a couple of days ago, LOL.

[dan88]

Nice recent burst of convection, and Microwave from 5:39 shows the structure is responding

Though still looks tilted with height

[blazess556]

18z GFS looks like it has a couple of members who take Katia close to the northeast Bahamas.

[donsutherland1]

Great write up Don. Family and I got into Orlando this morning, and I must say, I can't be happier with sitting between these two vacation busters! (Lee and Katia). However, the return home next Friday (flying) just became a tad more interesting. Models having all sorts of issues with Lee....if he weren't around, I thing the model spread word certainly be narrower. Still over a 50% recurve, but each day seems to shave a few percent off that scenario.

Have a great vacation, LEK.

I agree with you about the wrinkle that Lee is adding to the mix. It will be interesting to see how all this resolves itself.

[bluewave]

18z GFS looks like it has a couple of members who take Katia close to the northeast Bahamas.

The OP forecasts have been too fast compared to the ensembles and other guidance the last few days.

[Edge Weather]

The Canadian model has the best accuracy ratings so far for Katia and the 18z run of the CMC brings Katia due north to a point about 75 miles off the coast of NJ at 18z on Friday and two other models, the GFDI and GFTI bring her to the almost exact same location about 100 miles off the NJ coast. All three of these models do not turn her to the northeast and extrapolated out would bring her to a landfall on eastern Long Island or Rhode Island. These are all the 18z model runs.

[LakeEffectKing]

Have a great vacation, LEK.

I agree with you about the wrinkle that Lee is adding to the mix. It will be interesting to see how all this resolves itself.

Thanks Don. Between riding roller coasters and eating (kids favorites) I hope to post a little on my Droid re: Katia and Lee....

[donsutherland1]

So far, Katia is passing very close to the track that I outlined. Its 5 pm position of 19.9N 56.8W was just 7 miles off my estimate of 20.0N 56.8W from yesterday morning. The big challenge concerning Katia's track remains how far west the storm will come and how quickly will it be turned more sharply to the east once it reaches its farthest position west. A farther north Lee and/or more impressive Bermuda high could delay the eastward turn. The 12z GGEM and ECMWF and 18z GFS now have a slower turn to the east. That increases prospects that the latter idea concerning my track, especially from 35N and northward will need to be adjusted to the left. Considering the Lee-related complexities, I'll hold off on doing that until I have at least seen the 9/4 0z guidance.

Hence, my guess concerning Katia's track remains:

17.5N 52.8W; Actual: 17.5N 52.4; Error: 26 miles--1.5 hours in advance

20.0N 56.8W

25.0N 63.9W

30.0N 72.0W

35.0N 69.6W

40.0N 63.5W

The intensity idea remains a difficult issue. Given that there is a strong analog for some of Katia's difficulties (Gladys in 1975) and limitations of computer guidance intensity forecasts, my thinking remains tied to historic climatology on Katia's peak strength. In other words, I still expect Katia to eventually grow into a major hurricane and possibly peak at Category 4. With its present difficulties, that seems like an idea for the realm of fiction. It may well verify as such, but the book on that idea remains open. In the meantime a closer look at Gladys' struggles offers perhaps some insight:

Gladys (1975):

18.8N 55.1W 990 mb 65 Knots

19.4N 56.4W 992 mb 65 Knots

19.6N 57.4W 992 mb 65 Knots

19.8N 58.2W 1000 mb 65 Knots (IMO the 1000 mb reading suggests Gladys might have fallen below hurricane strength)

20.3N 59.3W 998 mb 65 Knots

21.2N 60.3W 995 mb 65 Knots

22.1N 61.4W 990 mb 65 Knots

23.0N 62.6W 990 mb 70 Knots

23.6N 63.9W 985 mb 75 Knots

24.1N 65.2W 975 mb 80 Knots (Steady state through 27.9N 72.4W)

29.4N 73.0W 969 mb 90 Knots

31.0N 73.0W 954 mb 100 Knots

32.9N 72.1W 942 mb 110 Knots

35.3N 69.8W 939 mb 120 Knots (Steady state through 37.8N 67.0W)

The 12z Euro deepens Katia to 933 mb at about 35N, not far from where Gladys peaked. In stark contrast, the 18z GFS only brings it to 992 mb. The hurricane model consensus is for a weaker storm (probably peaking at Category 2). Nonetheless, given the model performance to date, my guess is that historic climatology probably offers at least as good a solution as the latest model runs.

[Bannor]

NHC advisories 1 - 23:

[wxsniss]

NHC advisories 1 - 23:

awesome! i've been meaning to do this myself... great job, keep this coming, i think trending the trend so to speak is informative in itself as models digest new data closer to the event

[ApacheTrout]

NHC advisories 1 - 23:

That's a really nice graphic. I'm assuming the orange dot represents the actual position of Kaita. The storm stays well within the cone (not particularly hard to do) and consistently moves along the left edge of the forecast track as the track gets updated. Kaita moved south of forecast tracks 4 through 8, then moved back to the general forecast path, and now looks again to be on the left side of the track.

Is there a way to add the 3-day error distance for each actual position fix?

Again, well done. Fascinating to watch.

[phil882]

NHC advisories 1 - 23:

Nice graphic... looks like their forecast thus far have actually been quite excellent

I'm once again quite against the NHC on forecast intensity for the next 120 hours. I think the worst of the upper level shearing is behind us, as evidence in the improving outflow and more circular appearance of the CDO. Just a glance at the 12z ECWMF shows that we should enter a very favorable upper level pattern beyond 48 hours, with a very well developed outflow channel to the system's east that should help to continue to ventilate the system in a low shear environment.

I'm working on a blog update that will hopefully clear up some of my thoughts.

[ApacheTrout]

Nice graphic... looks like their forecast thus far have actually been quite excellent

I'm once again quite against the NHC on forecast intensity for the next 120 hours. I think the worst of the upper level shearing is behind us, as evidence in the improving outflow and more circular appearance of the CDO. Just a glance at the 12z ECWMF shows that we should enter a very favorable upper level pattern beyond 48 hours, with a very well developed outflow channel to the system's east that should help to continue to ventilate the system in a low shear environment.

This kind of consistency makes me wonder if NHC is thinking of shrinking the size of the 3 and 5 day cones. This is also impressive given the sudden appearance of an area of shear, which seemed to make little difference in the track, but all the difference in the strength.

[phil882]

This kind of consistency makes me wonder if NHC is thinking of shrinking the size of the 3 and 5 day cones. This is also impressive given the sudden appearance of an area of shear, which seemed to make little difference in the track, but all the difference in the strength.

The National Hurricane Center forecast cone size is based on their average track error they have experienced with TCs during the last five years... with the estimate being that there is a 67% chance that in each given forecast that the tropical cyclone will remain within the cone of uncertainty.

[Bannor]

Thanks for the comments wxsniss, ApacheTrout & phil882.

Yes, the orange dot is the position of Katia as marked by NHC at the time of their advisory. I can compile these images pretty quickly, but adding additional info such as error metrics is a different ballgame.

There's also the issue of file size. The image posted is 578 x 407 giving a size of 500K. This was reduced from an original 770 x 543 which is 827K. Katia's track is a fair bit clearer on the larger image, but I'm not sure it's worth the extra download time.

[WishingForWarmWeather]

NHC advisories 1 - 23:

Amazing graphic; Thank you so much! Really makes it easy to see the westward trend, as well as the error of the forecasting. I hope you continue to make these for future storms, this was very helpful.

[OSUmetstud]

I'm thinking about a 75% chance for recurve...20% chance SE US hit and a 5% chance of a SNE hit. Models coming farther south and west in the past few days increase the probability of SE US hit. However, the strong 500mb vortex found south of Greenland with low heights extending into Labrador and Nova Scotia has excellent ensemble and index support which would make a SNE hit nearly impossible.

Katia should strengthen pretty readily in the 2 to 5 day range. I think the chances are excellent that Katia becomes at least a category three hurricane as shear drops under 10 kt.

[k***]

nice evolution is evident when you put the last several hours of microwave shots in order

[gil888]

nice evolution is evident when you put the last several hours of microwave shots in order

Looks as good as it ever did really. I'm interested to see if the inner core region, under the moderate sw shear now, can maintain itself-- if it does, the environment

should only get more favorable early next week. The track forecast is as convoluted as ever-- I'd like to see one more ECMWF run on that westward course again

before I seriously consider a US threat. Hard to see how Lee doesn't help recurve Katia, but we all know how this goes...

[phil882]

My updated thoughts on Katia... I'm much more aggressive on intensity than the NHC is, mainly because the ECWMF depicts a very favorable upper level pattern beyond 48 hours. This is not shared by the GFS, but the ECWMF was one of the few models earlier this week that depicted the unfavorable upper level pattern in Katia's future, so I'm more likely to believe it over the GFS at this point. Track is a little bit tricky as well, but ultimately I think the weakness created by lee interacting with a mid-latitude trough will be enough to steer Katia out to sea before making an East Coast landfall.

http://philstropicalweatherblog.wordpress.com/2011/09/03/katia-continues-to-battle-shear-but-has-a-bright-future-tropical-storm-lee-making-landfall-in-louisiana/

Here is the very favorable pattern shown by the ECWMF in the mid-range, featuring two well defined outflow channels.

[donsutherland1]

Very nice discussion, Phil882. I agree with you concerning the intensity idea.

Already, it appears to have regained hurricane strength. It will be interesting to see how things work out in the end.

[HurricaneJosh]

NHC advisories 1 - 23:

Awesome animation-- thanks for posting it.

There's clearly been a slow but sure rightward trend.

[HurricaneJosh]

I've been out and about all day-- hiking in the desert-- so I'm a bit out of the loop. What's up with the models today? The Euro trended left?

[phil882]

Very nice discussion, Phil882. I agree with you concerning the intensity idea.

Already, it appears to have regained hurricane strength. It will be interesting to see how things work out in the end.

Thanks The ECWMF does cause me some pause when you see it bend the track significantly leftward in the 72-120 hour period, but when you also see the orientation of the cutoff low that develops in association with Lee and a digging trough, its unlikely to let the ridge continue building westward beyond 96 hours, and indeed you start to the ridge break down by 120 hours. I think we might end up seeing a much sharper turn than the ECWMF is suggesting between 120 and 168 hours given the orientation of the cutoff low to Katia's west. The cutoff feature would have to be significantly further south and west in order to allow Katia to make an east coast landfall.

[Thunder Road]

Please don't delete because this is priceless!

JB on Twitter says...

"forecast position for Thur night at 30.5 N and 72.0 west, cat 3 . JMA has 892 mb hurricane Fri am 28 n 75 w"

http://twitter.com/#!/BigJoeBastardi/status/110165803185340416/photo/1

LOLZ

Put it in the banter thread and it probably won't be deleted.

[SnowGoose69]

Its too bad the ETAxx no longer exists as far as I know. That model used to blow up everything, that would probably put the JMA's MSLP to shame.

[thewxmann]

This kind of consistency makes me wonder if NHC is thinking of shrinking the size of the 3 and 5 day cones. This is also impressive given the sudden appearance of an area of shear, which seemed to make little difference in the track, but all the difference in the strength.

As Phil alluded to earlier, the cone is based off of average track errors in past years. The NHC tracks have gotten very good in the past few years due to improvements in modeling and what-not, and as such the cone has, in fact, shrunk.

[WeSuck]

Its too bad the ETAxx no longer exists as far as I know. That model used to blow up everything, that would probably put the JMA's MSLP to shame.

Put 892mb to shame?! It is interesting to see so many computer models in existence yet only a few are of use.

[Edge Weather]

The 0z CMC2, I guess that is the Canadian hurricane model, continues to NOT curve this to the east after turning north and brings it due north, making landfall on Central Long Island on Friday night. The 18z run did the same thing. The National Hurricane Center had also said that the Canadian model was verifying the best with Katia so far, so i find this interesting to say the least. Some of the other models are also continuing the trend to either not curve to the east as much, or to do it later. This seems to be the trend.