Hurricane Katia

[k***]

continued organization

[donsutherland1]

Katia is nearing hurricane strength. Some of the satellite data indicate that it has reached hurricane status for a third time. However, the National Hurricane Center held its intensity at 70 mph. I suspect that if the satellite guidance does not deteriorate overnight, the 5 am advisory will upgrade Katia to hurricane status.

As per Katia's latest position, its track, and the synoptic situation forecast by the GFS ensembles, there has been some change in my 10 analogs. That change reflects some of the trends among the modeling to take the storm farther west.

In terms of Katia's westernmost position, the percentages from that analog set are:

At least:

70.0W: 100%

72.5W: 80%

75.0W: 50%

77.5W: 10%

Right now, I'm still comfortable with the idea that Katia could get as far west as 72W-74W, but the analog set is a little more aggressive: mean: 74.4W and median 74.7W. Considering that the early part of my estimated track has verified reasonably well and the possibility that Lee's future will have a potentially significant impact on Katia's track, I'll leave my guess unchanged until at least after the 9/4 0z guidance. The latter parts of the estimate might need to be revised somewhat to the west.

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

20.0N 56.8W; Actual: 20.0N 57.0W; Error: 13 miles--33.0 hours in advance

25.0N 63.9W

30.0N 72.0W

35.0N 69.6W

40.0N 63.5W

Finally, the new analog set continues to back my thinking that Katia will ultimatey become a major hurricane. All 10 analog storms reached at least Category 3. 60% peaked at Category 4.

[isnice]

Not bad for the GFS...it only shifted about 200 miles to the southwest.

Or maybe it's just a good bit slower...

[SnowGoose69]

GFS still indicating a 1993 Emily esque hard right turn, albeit more off the NC Coast than the 1993 Emily was.

[yoda]

GFS still indicating a 1993 Emily esque hard right turn, albeit more off the NC Coast than the 1993 Emily was.

Wasn't that the hurricane NC and the Mid-Atlantic were sweating out as a Cat 3/4?

[AlexD]

Wasn't that the hurricane NC and the Mid-Atlantic were sweating out as a Cat 3/4?

Sure seems so: http://en.wikipedia.org/wiki/Hurricane_Emily_(1993)

[WeSuck]

I have EURO out to 144 and it is DAMN close to NC. Waiting for next frame to see if landfall occurs

[CooL]

00z Euro is pretty close to a landfall in the outer banks at 162, although its hard to see. But man that is very close.

[ezweather]

00z Euro continues to make things very interesting with Katia. In fact on the 156 hour panel, the center is very close to Cape Hatteras. So, the threat of Katia to portions of North Carolina and points north is still on the table.

[atownwxwatcher]

FWIW 00z NOGAPS shows landfall in the southeast...

[Bob Chill]

00z Euro continues to make things very interesting with Katia. In fact on the 156 hour panel, the center is very close to Cape Hatteras. So, the threat of Katia to portions of North Carolina and points north is still on the table.

What does the Euro show for the remnants of Lee? Is the interaction causing the solution to bring Katia closer?

Such an odd combination. Just a week ago Lee was a maybe and Katia was a probable fish.

[phil882]

00z Euro continues to make things very interesting with Katia. In fact on the 156 hour panel, the center is very close to Cape Hatteras. So, the threat of Katia to portions of North Carolina and points north is still on the table.

I can't discount the major shift west the ECWMF has made in the past 3 runs... although given the 500mb pattern, it still appears to be a miss as the ridge is flatter and we should see an even sharper turn to the east despite the further west track intially.

[ezweather]

Looks like on the upper air, remnants of Lee would shift further off the west. Also, some of the ridging north Katia kind of hangs in there a bit longer. I think thats what brings her closer to North Carolina. The other thing that struck me in looking at the panels is its slow movement near North Carolina and then back offshore. Still have to see if the other guidance begins to follow what the Euro is showing. Well, we have some time to watch.

What does the Euro show for the remnants of Lee? Is the interaction causing the solution to bring Katia closer?

Such an odd combination. Just a week ago Lee was a maybe and Katia was a probable fish.

[ezweather]

Yeh, were gonna have to see how this goes down. Like to see several more runs to see how this plays out. From what your seeing, do you see more riding taking place with each run of the Euro. It almost seems thats what I'm seeing. Well, its getting late and we'll see what tomorrow's run bring. Something tells me that this will not be a clear cut recurve out to see. I just wonder if the pattern favors more than one landfalling hurricane for North Carolina and poirnts north. I know Florida had that several years ago. I hold off any additional comments on this until we get additional data that supports my concern.

I can't discount the major shift west the ECWMF has made in the past 3 runs... although given the 500mb pattern, it still appears to be a miss as the ridge is flatter and we should see an even sharper turn to the east despite the further west track intially.

[SnowGoose69]

Count the NOGAPS of course to bury a cane into one of the quadrants of the East Coast that is least likely to see one make landfall.

[thewxmann]

Count the NOGAPS of course to bury a cane into one of the quadrants of the East Coast that is least likely to see one make landfall.

It actually does a Floyd and makes landfall further north near Cape Fear.

[phil882]

There are reasons why the ECWMF has been showing a further west solution the last few runs, and its important to note why, because it will give us the tools to investigate further in the runs to come.

Looped below is the last three consecutive runs of the ECWMF for Saturday at 12z (about 6 days from now). While I normally hate looking out beyond 6 days, I think its important to see the players that will influence Katia's track.

First, I want to note that the Westerlies are very far north for this time of the year, quite unseasonably far north. This is not surprising when you investigate further and find that the Arctic Oscillation is currently positive, and forecast to become even more positive in the near future. This indicates a stronger polar vortex than normal and higher height anomalies across the mid-latitudes. Thus, strong westerlies are not as likely to take Katia out to sea at this time frame.

Next, lets look at the mid-level ridging in place. Note that we have an interesting pattern. We have a strong mid-level ridge over the Atlantic Basin, while we have another strong ridge out across the upper Rockies and Western Canada. The only feature bridging the gap between these two strong ridges is the remnants of Lee that have combined with a weak upper level feature. Were this feature not to exist we would have a large ridge extending from the Rockies all the way to the Atlantic. However, with Lee in place over the Ohio Valley this ridge bridge is broken.

But look at the evolution of the last three runs. Each run of the ECWMF has weakened the remains of Lee from originally a triple contoured cutoff low to now a single contoured feature. The weaker the feature becomes, the smaller of an influence it can have on the steering currents, and the more ridging can build to allow Katia to make it all the way to the United States, in particular the Southeast. Thus, the strength of Lee in the long range is absolutely crucial to the track of Katia. Of secondary importance is the upper level westerly flow, although if the current +AO transpires, this will likely be less of an influence than that of the cutoff low formed by Lee.

[phil882]

A couple of caveats to the animation above.

1. If Katia Makes landfall in the United States, it will likely be south of 35N. The current forecast orientation of the mid-level ridge remains very narrow, and that should be illustrated in the image above. If this ridging continues to build in as the model runs progress, it may only allow for a continued westward motion and not a path further north. If Katia does track too far north, the ridge will break down and the storm will quickly find itself on the north side of the mid-level ridge which will move Katia eastward. This is why we are seeing such a sharp turn in a lot of the modeling currently.

2. This is a very anomalous pattern. You don't often see these type of ridge formations that allow for a tropical cyclone to track nearly due west when they get up to 25-30N. Thus they are also very fragile. The westerlies could be far enough north to allow such a configuration to take place, but you can see in the loop above that these westerlies are highly variable, and even the 12z run earlier today showed a deep enough trough to likely interfere with the potential ridge formation. So even if the forecast cutoff associated with Lee continues to weaken and allows a strong ridge to build in place, of secondary concern is a piece of the upper level westerly flow getting far enough south to erode the ridge enough for re-curvature.

So at this point its a wait and see like always. I'm a little less confident in my out to sea solution now that I've had a chance to analyze the ECWMF a bit more fully, but there are still quite a few things that could allow for this system to be steered out to sea.

[phil882]

In other news... Katia is certainly becoming better organized.

[LovintheWhiteFluff]

There are reasons why the ECWMF has been showing a further west solution the last few runs, and its important to note why, because it will give us the tools to investigate further in the runs to come.

Looped below is the last three consecutive runs of the ECWMF for Saturday at 12z (about 6 days from now). While I normally hate looking out beyond 6 days, I think its important to see the players that will influence Katia's track.

First, I want to note that the Westerlies are very far north for this time of the year, quite unseasonably far north. This is not surprising when you investigate further and find that the Arctic Oscillation is currently positive, and forecast to become even more positive in the near future. This indicates a stronger polar vortex than normal and higher height anomalies across the mid-latitudes. Thus, strong westerlies are not as likely to take Katia out to sea at this time frame.

Next, lets look at the mid-level ridging in place. Note that we have an interesting pattern. We have a strong mid-level ridge over the Atlantic Basin, while we have another strong ridge out across the upper Rockies and Western Canada. The only feature bridging the gap between these two strong ridges is the remnants of Lee that have combined with a weak upper level feature. Were this feature not to exist we would have a large ridge extending from the Rockies all the way to the Atlantic. However, with Lee in place over the Ohio Valley this ridge bridge is broken.

But look at the evolution of the last three runs. Each run of the ECWMF has weakened the remains of Lee from originally a triple contoured cutoff low to now a single contoured feature. The weaker the feature becomes, the smaller of an influence it can have on the steering currents, and the more ridging can build to allow Katia to make it all the way to the United States, in particular the Southeast. Thus, the strength of Lee in the long range is absolutely crucial to the track of Katia. Of secondary importance is the upper level westerly flow, although if the current +AO transpires, this will likely be less of an influence than that of the cutoff low formed by Lee.

Would you mind telling me what the question marks represent? Thanks...

[phil882]

Would you mind telling me what the question marks represent? Thanks...

The question mark is how much ridging will be in place... the weaker the 500mb reflection of Lee is or the further south and west it is located, the stronger the ridging will be in place to allow a continued westward motion.

I guess an image might illustrate it better... the 00z ECWMF actually does bridge the two ridges at 120 hours, but its only temporary as the 500mb cutoff associated with Lee is still strong enough to break this 588dm ridge in the longer range. You can imagine that if the 500mb cutoff is weaker how the ridge would be able to build in stronger over the Eastern United States.

[HurricaneJosh]

So the Euro and the NOGAPS are showing USA landfall?

Overall, it looks to me that there's less agreement between the models in the post-72-hr timeframe. Some of these recent runs are certainly a it thought-provoking.

[Dsnowx53]

See, I would have thought that the ULL being stronger and also further west would help to raise the heights downstream and around the Newfoundland area. I think if this ULL is too weak, then yeah, you might have more ridging initially via the connection of the ridges just illustrated above, but then once Katia sniffs any sort of westerlies, and is on the wrong side of the W ATL ridge, it will very very quickly run away to the east--especially considering there really aren't any positive anomalies downstream. But with a stronger ULL helping to pump the heights downstream, and also perhaps help turn the steering flow more northerly as opposed to easterly, that could allow Katia to hit the US.

This is why although the 0z Euro was much closer to Hatteras than the 12z Euro was, it was also much further away from New England, whereas the 12z Euro was a very close call. The 0z Euro allows Katia to very quickly escape to the east, whereas in the 12z Euro, there were more positive anomalies downstream and a more favorable steering pattern via a stronger ULL.

[thewxmann]

Euro does an Emily 1993... don't think it officially makes landfall but it comes super close.

Great analysis Phil. I agree that if it makes landfall at all it won't be further north. A small change in latitude and the westerlies catch Katia. That is by no means a strong ridge at all.

[HurricaneJosh]

So if we get a USA landfall it's more likely to be a FL-to-NC deal than a NC-to-ME deal. Cool.

[phil882]

So the Euro and the NOGAPS are showing USA landfall?

Overall, it looks to me that there's less agreement between the models in the post-72-hr timeframe. Some of these recent runs are certainly a it thought-provoking.

Euro is close but no landfall... so only the NOGAPS is showing landfall at this point. The UKMET at 120 hours is also a huge west outlier, but most have been discounting the UKMET for a while now.

See, I would have thought that the ULL being stronger and also further west would help to raise the heights downstream and around the Newfoundland area. I think if this ULL is too weak, then yeah, you might have more ridging initially via the connection of the ridges just illustrated above, but then once Katia sniffs any sort of westerlies, and is on the wrong side of the W ATL ridge, it will very very quickly run away to the east--especially considering there really aren't any positive anomalies downstream. But with a stronger ULL helping to pump the heights downstream, and also perhaps help turn the steering flow more northerly as opposed to easterly, that could allow Katia to hit the US.

This is why although the 0z Euro was much closer to Hatteras than the 12z Euro was, it was also much further away from New England, whereas the 12z Euro was a very close call. The 0z Euro allows Katia to very quickly escape to the east, whereas in the 12z Euro, there were more positive anomalies downstream and a more favorable steering pattern via a stronger ULL.

The ULL won't raise the heights enough if we have a strong +NAO and +AO combo, which is forecasted. As alluded to before, there is little chance this storm will be able to make LF above 35N because of the narrow ridge that won't be able to stretch further northward due to powerful toughing over Greenland. Thus, yes, your second statement bolded is correct, this looks like a slightly higher probability impact for the Outer Banks, but even a lower probability for a landfall further north such as New England. The only chance this system has of making landfall in the United States is if the ULL is weaker or displaced further west, allowing the ridge bridge to hang on longer.

Great analysis Phil. I agree that if it makes landfall at all it won't be further north. A small change in latitude and the westerlies catch Katia. That is by no means a strong ridge at all.

Well a 588dm ridge is actually pretty significant for the latitude its being depicted at, but yes I'd agree that it won't take much of a weakness to erode the ridge to the point the Katia recurves. Right now though it might be up to the cutoff low associated with Lee, rather than the westerlies displaced so far north.

[phil882]

So if we get a USA landfall it's more likely to be a FL-to-NC deal than a NC-to-ME deal. Cool.

Yep . Adam was way ahead of the game talking about this days ago, but that skinny ridge won't really allow for a NNW or N movement for any significant length of time before the system is steered out to sea.

[A-L-E-X]

Yep . Adam was way ahead of the game talking about this days ago, but that skinny ridge won't really allow for a NNW or N movement for any significant length of time before the system is steered out to sea.

At the same time though, if this does make it far enough west between NC and FL, wouldn't the moisture end up here with the remnants even if it recurved? If it gets far enough west, even a recurving storm would get us on its way out..... and we really dont need anymore rain at all.... and that's an understatement!

[phil882]

At the same time though, if this does make it far enough west between NC and FL, wouldn't the moisture end up here with the remnants even if it recurved? If it gets far enough west, even a recurving storm would get us on its way out..... and we really dont need anymore rain at all.... and that's an understatement!

Oh yea, no more rain for the northeast. Unfortunately, it already looks like we have some of that on the way with Lee interacting with this first trough swinging through.

I did a little bit more digging, and the synoptic pattern actually isn't that far off from Fran 1996. Just look at the 500mb setup and you can see the similarities. The thing that I'm particularly interested in is the fact that the ridging with Katia on the 00z ECWMF is actually stronger than the ridging that was in place for Fran.

[phil882]

And to bring this thread back in the present... nice tropical storm! I know the NHC doesn't like to stray away from Dvorak intensity estimates but I think they are going to have to increase the intensity at least a little at 11am.