Hurricane Irma

[Timmytour]

Is there more agreement among the models now about the path?

I thought the eastward trend of the path from a couple of days ago would continue which some models seemed to show then, and was thinking Irma might stay offshore before hitting the Carolinas.

But seems this can be discounted now?

 

[summer blizzard]

Irma looks a lot more symetrical on satellite today but convection is not as strong as it has been in recent days. Hopefully once the ERC completes we can see another round of strengthening. 

[summer blizzard]

3 minutes ago, Timmytour said:

Is there more agreement among the models now about the path?

I thought the eastward trend of the path from a couple of days ago would continue which some models seemed to show then, and was thinking Irma might stay offshore before hitting the Carolinas.

But seems this can be discounted now?

 

Looks to me as if the NHC have backed the Euro operational although the UKMO is even west with with the Euro ensemble mean so don't rule that out.

Edited September 8, 2017 by summer blizzard

[knocker]

3 minutes ago, Timmytour said:

Is there more agreement among the models now about the path?

I thought the eastward trend of the path from a couple of days ago would continue which some models seemed to show then, and was thinking Irma might stay offshore before hitting the Carolinas.

But seems this can be discounted now?

 

[Iceberg]

The path looks pretty nailed to me. Fully supported by the models if it deviates more than 50 miles from the nhc I'll be amazed. 

[joggs]

Does the time of day matter as to when a hurricane strengthens and weakens?.

Edited September 8, 2017 by joggs

[Singularity]

Hurricane Katia, now up to 90 mph and with room for further strengthening before landfall in Mexico, is complicating matters as its outflow may impact the southern portion of the trough that's expected to turn Irma north, but the extent and nature of that impact seems to show little agreement between models, with this not being helped by the fact that Katia has been exceeding projected model intensities. 

Given recent trends, the overall signal appears to be that a stronger Katia affects the trough in a manner that delays the turn north of Irma, but I can't be entirely sure of this so please take it as just a suggestion rather than statement of fact.

[Timmytour]

13 minutes ago, knocker said:

Cheers Knocker..... I must be a NAMI fan I think!   

[Yarmy]

 

The HWRF (which I believe is derived from the GFS?) has been similarly erratic. Somewhat embarrassing given that it is dedicated to tropical storms.

[FetchCB]

5 minutes ago, Yarmy said:

 

The HWRF (which I believe is derived from the GFS?) has been similarly erratic. Somewhat embarrassing given that it is dedicated to tropical storms.

I have a question which hopefully someone can answer

In the UK it is often said that the more severe the depression/Storm then the more it curves poleward. is it the same with Hurricanes? If so then maybe if GFS is overdoing the depth of pressure within Irma then it would want to curve it poleward ?

[Nick F]

25 minutes ago, Singularity said:

Typical... the moment Irma is taken a whisker below category 4 strength, deep convection wraps neatly right around the eye... as if in angry retort!

NHC forecast discussion mentioning that Irma is undergoing an eyewall replacement. With it continuing to move over warm waters of 30C and weak shear, likely it only slightly weaken and will maintain as cat 4 before Florida landfall, risk it could strengthen again, hopefully not for the sake of northern Cuba, SE Bahamas and ultimately Florida in its path.

Some interesting facts about Irma tweeted yesterday:

 

[Polar Bear]

2 hours ago, pip22 said:

A

Andrew left. Irma right.

wow... frightening ...can I use this photo on my FB post? No worries if not...

[Timmytour]

For the "sustained wind" record...how far back in time does this go?   ie From when was the technonlogy available to conduct these measurements?

[Nick F]

11 minutes ago, FetchCB said:

I have a question which hopefully someone can answer

In the UK it is often said that the more severe the depression/Storm then the more it curves poleward. is it the same with Hurricanes? If so then maybe if GFS is overdoing the depth of pressure within Irma then it would want to curve it poleward ?

This may partly answer your question http://www.aoml.noaa.gov/hrd/tcfaq/G5.html

In a nutshell, the semi-permanent sub-tropical ridge steers the hurricanes, easterlies on the equator side steer storms that form mid-Atlantic westwards towards Caribbean, as we've seen with Irma and Jose. But when they reach the western edge of the sub-trop ridge the flow swings southeasterly and southerly, the western periphery of the ridge currently over SE U.S. and Bahamas, so when a hurricane reaches here - they tend to head NW then N. 

Now, differences between model tracks may lie over how much influence or weakness there is in the sub-top ridge on its western edge, as a slacker flow or trough digging SE over eastern U.S. will tend to pull a hurricane poleward, GFS perhaps doing this too soon with slight miscalculations in the steering flow on western edge of sub-trop ridge?

[FetchCB]

1 minute ago, Nick F said:

This may partly answer your question http://www.aoml.noaa.gov/hrd/tcfaq/G5.html

In a nutshell, the semi-permanent sub-tropical ridge steers the hurricanes, easterlies on the equator side steer storms that form mid-Atlantic westwards towards Caribbean, as we've seen with Irma and Jose. But when they reach the western edge of the sub-trop ridge the flow swings southeasterly and southerly, the western periphery of the ridge currently over SE U.S. and Bahamas, so when a hurricane reaches here - they tend to head NW then N. 

Now, differences between model tracks may lie over how much influence or weakness there is in the sub-top ridge on its western edge, as a slacker flow or trough digging SE over eastern U.S. will tend to pull a hurricane poleward, GFS perhaps doing this too soon with slight miscalculations in the steering flow on western edge of sub-trop ridge?

Thanks Nick

I guess my thought was if the GFS was progging a lower pressure then it may be able to push a little harder against the ridge hence its more northerly projected track compared to the EC

[Barking_Mad]

What you can say about Cuba is that they are really well organised about moving people out of harms way.

[JeffC]

3 hours ago, Love Snow said:

Scary sight...

Looks like an Al Gore doodle pad!

 

[summer blizzard]

38 minutes ago, Singularity said:

Hurricane Katia, now up to 90 mph and with room for further strengthening before landfall in Mexico, is complicating matters as its outflow may impact the southern portion of the trough that's expected to turn Irma north, but the extent and nature of that impact seems to show little agreement between models, with this not being helped by the fact that Katia has been exceeding projected model intensities. 

Given recent trends, the overall signal appears to be that a stronger Katia affects the trough in a manner that delays the turn north of Irma, but I can't be entirely sure of this so please take it as just a suggestion rather than statement of fact.

One imagines that the stronger Katia is, the more it feels Katia rather than the upper low over the US (since Katia will have a stronger atmospheric impact.

23 minutes ago, FetchCB said:

I have a question which hopefully someone can answer

In the UK it is often said that the more severe the depression/Storm then the more it curves poleward. is it the same with Hurricanes? If so then maybe if GFS is overdoing the depth of pressure within Irma then it would want to curve it poleward ?

The beta effect will always try pull a system NW.

[Singularity]

4 minutes ago, summer blizzard said:

One imagines that the stronger Katia is, the more it feels Katia rather than the upper low over the US (since Katia will have a stronger atmospheric impact.

The beta effect will always try pull a system NW.

I did consider that too, but over the Category 6 WU blog there's been a lot of comments stating that they're too far apart for the relatively small Katia to have much direct impact on the movement of Irma. 

One other thing I've been wondering - given the potential for the storm surge to coincide with a spring high tide - is whether the sheer mass of Irma might slow the onset of northerly motion following the stall-and-turn, but I expect if so, the models are already factoring this in to the timing of events. 

[Iceberg]

Irma eye is not the clear spec that you can see as per latest recon. 

Pressure has risen to 926mb or so. 

The eye is actually 40miles so aloft double the size it was early. 

On the picture below is roughly he circular red area. The eye needs to clear out and much larger eye wall strengthen vertically for more intensification. 

The signs in the last couple of hrs are that Irma might be doing this very quickly. If done sub 900 is not unreasonable. 

With the inner wall now a memory highest surface winds are probably down to 130-135 kts down from the 160. 

However their is plenty of time for these values to be reached again even before Cuba starts to have much affect. 

[crimsone]

NOAA2 going for another pass through the eye, taking SSTs as she goes, unusually. 29.3 degrees C as she moves towards cuba.

Edited September 8, 2017 by crimsone

[FetchCB]

2 minutes ago, crimsone said:

NOAA2 going for another pass through the eye, taking SSTs as she goes, unusually. 90.3 degrees C as she moves towards cuba.

90.3F?

[crimsone]

Just now, FetchCB said:

90.3F?

Yeaaah. Oops. I don't know how in the hell I mistyped that. Hell of a big difference.

29.3 C

[wellington boot]

Just now, crimsone said:

Yeaaah. Oops. I don't know how in the hell I mistyped that. Hell of a big difference.

29.3 C

Can you imagine Irma's intensity over 90C water?!

[FetchCB]

 

1 minute ago, crimsone said:

Yeaaah. Oops. I don't know how in the hell I mistyped that. Hell of a big difference.

29.3 C

well its often said the sea in a hurricane represent a boiling sea