Hurricane Katia

[Juliancolton]

I really wish you would stay out of the NYC subforum, nevertheless, I was simply stating that the GEFS ensembles appear to favor lower pressures near the SE coast around the 10-14 day range. I'm not taking it too seriously, just attempting to make a case as to why this might not be a fish, even though the odds are for a fish.

The best argument for not locking into a fish solution right now is that we have something like a week and a half before that would come into play.

[Ed Lizard]

Hurricane Irene --> TD 10 --> Tropical Storm Jose --> "K" storm. Sound familiar?

Simple observation, not comparing Katia to Katrina by any means, etc...

You should go to the track and wait for a horse named Seattle Sue or Alley Door to run, and bet your entire bank account on it.

Anway, sure most models scream fish, but natural born optimist, I am at least 1/8th glass full of future Katia being this year's Earl. Maybe more.

[am19psu]

I'm not taking it too seriously, just attempting to make a case as to why this might not be a fish, even though the odds are for a fish.

But using the 300hr GFS ensembles doesn't really make your case legitimate.

[Ed Lizard]

Anyway, Northeast shear, Phil's mention of apparent multiple 850 mb vortices that have to consolidate, and noting future Katia itself is responsible for the apparent erosion of the West side of the ridge, this takes an extra couple of days to get strong, so the future Katia is farther South, not to mention if that trough is a little too strong on the model, it isn't impossible it comes further West and doesn't fish.

[k***]

Maybe GaWx can fact check this statement

[Bob Chill]

Tidbit from 11am NHC adv:

LATER IN THE FORECAST PERIOD...GLOBAL MODELS SHOW THE

WEAKNESS IN THE RIDGE SHIFTING WESTWARD AND THIS SHOULD PREVENT THE

CYCLONE FROM MOVING SIGNIFICANTLY POLEWARD DURING THE FORECAST

PERIOD. THE OFFICIAL TRACK FORECAST IS SIMILAR TO THE PREVIOUS ONE

AND ON THE SOUTHERN SIDE OF THE GUIDANCE ENVELOPE.

Odds of US landfall will obviously increase the longer the cyclone can keep from gaining latitude.

Probably a good 4-5 days before fish forecasts carry a lot of weight.

[Cheeznado]

Two keys here: If this goes exactly on the NHC track it will probably have gained too much latitude for a US landfall according to climo for storms at their forecast position in five days. So it probably needs to stay left of NHCs forecast. Second, how much will the eastern trough dig in the mid-latitudes? There is some ensemble support for a weaker trough than the Op Euro and Op GFS show, this trough must be weaker and/or farther west for a threat to materialize. So there a lot of things that have to go right for a future Katia impact along the eastern seaboard, the odds favor a fish right now but this is not totally a certainty.

[am19psu]

Two keys here: If this goes exactly on the NHC track it will probably have gained too much latitude for a US landfall according to climo for storms at their forecast position in five days. So it probably needs to stay left of NHCs forecast. Second, how much will the eastern trough dig in the mid-latitudes? There is some ensemble support for a weaker trough than the Op Euro and Op GFS show, this trough must be weaker and/or farther west for a threat to materialize. So there a lot of things that have to go right for a future Katia impact along the eastern seaboard, the odds favor a fish right now but this is not totally a certainty.

Wouldn't the recurving WPAC storm favor a stronger than modeled trough in 8-10 days along the Atlantic Seaboard?

[wxsmwhrms]

Maybe GaWx can fact check this statement

Not exactly what is stated in the FB post, but along the same lines:

Just looking at climo on systems developing at this low a latitude and this far east, a good benchmark seems to be 25N, 60W. Since 1950, 16 systems in August/September that started within 300 nm of where NHC has the TD this morning went on to become major hurricanes. Of the 7 that went SW of 25N 60W, 5 hit the CONUS, 1 hit Nova Scotia, and 1 hit Newfoundland. All of the 9 that went NE of 25N 60W were fish. (Of course, this assumes that this TD goes on to become a major as the models seem to imply.)

[blazess556]

COmparing the 12z Euro and 12z GFS, the Euro is much faster with TD 12 than the GFS and extends the subtropical ridge a tad further west than the GFS at 144 hrs.

[wxsmwhrms]

Wouldn't the recurving WPAC storm favor a stronger than modeled trough in 8-10 days along the Atlantic Seaboard?

Probably. But this is where to me all of the speculating about TCs at this timeframe is such a crapshoot. When you look at the GFS ensemble spaghetti diagrams out around days 10-11, some of the ones that show a threat to the East Coast do so because they have a stronger trough than the op run, but the TC also makes it farther SW before it makes the turn, so it uses that stronger trough to pick the TC up and slam it due N into SNE. There are so many factors that come into play, in some ways when you are that far out, I think climo and just a general feel for the means will give one the best "guess" as to what may happen. I know you and many posters on here already know this, just stating for the record.

BTW, I know what you were saying about GFS ensembles and agree with that, but I am not talking here about using them for the forecast - just to illustrate my point.

[donsutherland1]

Some quick thoughts on TD 12/Future Katia:

1. Odds currently favor recurvature. One example of a storm that recurved after forming in the general region where TD 12 developed is TS Anna (1960). That storm came as far west as 74.7W longitude, but safely avoided the U.S./Canada.

2. Odds of U.S. landfall are higher than typical for the region in which TD 12 formed. In the region bounded by 9.0N-15.0W/20.0W-32.0W, 51 tropical storms/hurricanes formed since 1950. 13 (25.5%) eventually made landfall somewhere in the U.S., while 15 (29.4%) made landfall either in the U.S. or Canada.

3. Some prominent storms making at least one landfall along the U.S. East Coast that formed in that general region (1851-2011) included Hurricane #9 (1893), Hurricane #3 (1899), Hurricane #4--"Long Island Express" (1938), Hurricane #4 (1947), Donna (1960), Gloria (1985), Hugo (1980), Fran (1996), and Isabel (2003). Some prominent storms making at least on landfall in the Gulf of Mexico region included Hurricane #2--"Galveston Hurricane" (1915), Hurricane #4 (1947), Donna (1960), Frederic (1979), Allen (1980), and Ivan (2004).

4. The 8/29 12z GFS tracks TD 12 toward Canada landfall. However, toward and just after that landfall, the system is headed north-northwestward (it had bent back to the left). A small delay in TD 12's turn and/or an earlier turn back to the left could suggest an increased threat to the East Coast.

5. A number of the storms that formed in the region in which TD 12 developed have gone on to become major hurricanes. Odds of TD 12's eventually attaining Category 3 or greater status are probably higher than the climatological norm.

[Cheeznado]

Not exactly what is stated in the FB post, but along the same lines:

Just looking at climo on systems developing at this low a latitude and this far east, a good benchmark seems to be 25N, 60W. Since 1950, 16 systems in August/September that started within 300 nm of where NHC has the TD this morning went on to become major hurricanes. Of the 7 that went SW of 25N 60W, 5 hit the CONUS, 1 hit Nova Scotia, and 1 hit Newfoundland. All of the 9 that went NE of 25N 60W were fish. (Of course, this assumes that this TD goes on to become a major as the models seem to imply.)

Interestingly enough, the new Euro op has shifted SW considerably and has Katia at 23.5N 65W at 192 hours....

[IsentropicLift]

By hr 168 on the 12z EC the trough is already lifting out, and ridging is building to the west

[IsentropicLift]

hr 216, she misses the weakness in the ridge, and new ridging builds to the north, looks like a nice threat taking shape, if she manages to miss the weakness

[Typhoon Tip]

Some quick thoughts on TD 12/Future Katia:

1. Odds currently favor recurvature. One example of a storm that recurved after forming in the general region where TD 12 developed is TS Anna (1960). That storm came as far west as 74.7W longitude, but safely avoided the U.S./Canada.

2. Odds of U.S. landfall are higher than typical for the region in which TD 12 formed. In the region bounded by 9.0N-15.0W/20.0W-32.0W, 51 tropical storms/hurricanes formed since 1950. 13 (25.5%) eventually made landfall somewhere in the U.S., while 15 (29.4%) made landfall either in the U.S. or Canada.

3. Some prominent storms making at least one landfall along the U.S. East Coast that formed in that general region (1851-2011) included Hurricane #9 (1893), Hurricane #3 (1899), Hurricane #4--"Long Island Express" (1938), Hurricane #4 (1947), Donna (1960), Gloria (1985), Hugo (1980), Fran (1996), and Isabel (2003). Some prominent storms making at least on landfall in the Gulf of Mexico region included Hurricane #2--"Galveston Hurricane" (1915), Hurricane #4 (1947), Donna (1960), Frederic (1979), Allen (1980), and Ivan (2004).

4. The 8/29 12z GFS tracks TD 12 toward Canada landfall. However, toward and just after that landfall, the system is headed north-northwestward (it had bent back to the left). A small delay in TD 12's turn and/or an earlier turn back to the left could suggest an increased threat to the East Coast.

5. A number of the storms that formed in the region in which TD 12 developed have gone on to become major hurricanes. Odds of TD 12's eventually attaining Category 3 or greater status are probably higher than the climatological norm.

Interesting statistics Don! THx for these. Yeah, I was reading along and knew the Long Island Express would show up there - goose bumples. I was looking at TD12's orgin and noting Hugo, Gloria and that one are quite close. Of course, I am sure there are others that developed there that didn't impact the EC, but it is still interesting - wasn't there a couple of them 4 or so years ago that went from roughly this position into the Caribbean?

Regarding #1 I think it is always a good idea to start off with an expectation (1) because systems starting off this far away are just exposed to too many plausible reasons to interupt an unalter 4.5 thousand mile trek. Heh, when you think about it, it's kinda astounding any ever do.

[IsentropicLift]

hr 240 looks fantasitc, except for possible interaction with low pressure over the eastern gulf

[am19psu]

hr 240 looks fantasitc, except for possible interaction with low pressure over the eastern gulf

Not sure why you think that... it would be a goal post splitter extrapolating from 240.

[IsentropicLift]

Not sure why you think that... it would be a goal post splitter extrapolating from 240.

because it managed to make it all the way to the Bahamas without recurving, and there is plently of time to work out the details. All that we can really ask for right now is a chance, and thats what it shows.

[k***]

because it managed to make it all the way to the Bahamas without recurving, and there is plently of time to work out the details. All that we can really ask for right now is a chance, and thats what it shows.

looks north and east of the bahamas to me

[am19psu]

because it managed to make it all the way to the Bahamas without recurving, and there is plently of time to work out the details. All that we can really ask for right now is a chance, and thats what it shows.

It's moving due north at 28N 70W... that's not at the Bahamas and would not affect the US extrapolating from there. This definitely has a chance to affect the US, but the 12z Euro does not support your hypothesis.

[MarkSC]

Not sure why you think that... it would be a goal post splitter extrapolating from 240.

Not sure about that. The Bermuda high is strengthening and the Gulf low could pinwheel it in, a la Hugo. The main thing to draw from it is that the models haven't locked in the strength of the Bermuda high.

[Juliancolton]

It's moving due north at 28N 70W... that's not at the Bahamas and would not affect the US extrapolating from there. This definitely has a chance to affect the US, but the 12z Euro does not support your hypothesis.

How can you see that it's moving due north?

[am19psu]

Not sure about that. The Bermuda high is strengthening and the Gulf low could pinwheel it in, a la Hugo. The main thing to draw from it is that the models haven't locked in the strength of the Bermuda high.

There is a cold front draped off the Atlantic Seaboard from Nova Scotia to Miami. If you believe the European verbatim, this is not a US threat. People need to stop wishcasting off a 240hr Euro prog.

[am19psu]

How can you see that it's moving due north?

I have 6hr increments from Earthsat.

[MarkSC]

There is a cold front draped off the Atlantic Seaboard from Nova Scotia to Miami. If you believe the European verbatim, this is not a US threat. People need to stop wishcasting off a 240hr Euro prog.

lol, ok how about the 12Z UKMET? It shows building high pressure off the east coast and is well west of yesterday's run. The trend is your friend.

[Juliancolton]

I have 6hr increments from Earthsat.

Ah, alright, thanks.

[am19psu]

I know that arguing over details at 240 hours is ridiculous, but I am an anal you know what, so I do feel compelled to point out that it is definitely not moving due N at 240 hours, unless you can see it in finer temporal detail than I can on the web. The 216 hour position is about 25N 67.5W, and the 240 hour position is about 27.5N, 70W, a 24 hour motion of pretty much due NW.

It's moving due north from 228-240. I have 6 hour increments.

[PSUBlizzicane2007]

Not sure about that. The Bermuda high is strengthening and the Gulf low could pinwheel it in, a la Hugo. The main thing to draw from it is that the models haven't locked in the strength of the Bermuda high.

Could you stop trying to mold every tropical cyclone as a vague threat to South Carolina? It's very transparent.

[am19psu]

lol, ok how about the 12Z UKMET? It shows building high pressure off the east coast and is well west of yesterday's run. The trend is your friend.

Stop with this right now.