ATL: IRMA - Post-Tropical - Discussion

[Steve]

Very slow motion at the moment for sure, still drifting westwards again but I think that the lift out is now only a matter of a couple of hours away, can't imagine this will last much longer.

maybe a little ridge pumping...

though you can see the mid to upper low over the lower MS valley dropping south.. only a mater of time..

http://www.ssd.noaa.gov/goes/east/eaus/flash-wv.html

Yeah. It would appear that the push from the Atlantic (east) and the pressure applied from the high coming down behind the retreating trough of low pressure in New England offsets the flow out of the SW from the trough protecting (most of) the Gulf Coast. Only real way it can go is NNW. The upper low is as far south as Central Mississippi and pretty weak. But it should be the nudge.

[fsusurfer]

I think it's still possible for Irma to miss just W of KW and the peninsula up to NE panhandle...

I'm in Destin. That doesn't make me feel great.

[PandaCitrus]

The outer eyewall is becoming dominant. The inner is contracting and dying and then the outer will clean out and be 30 miles in width.

[tolakram]

Here's the latest shear tendency. Look how hostile conditions are north and west of Irma. If it does go further west it will run into that quickly.

http://tropic.ssec.wisc.edu/real-time/w ... oom=&time=

[Michele B]

well radar could be deceiving me but that outer wall has gained very little latitude over the past couple of hours...

I was seeing the same thing. I think Irma is west of the last forecast point but I could be wrong.

Shes turning...add in EWRC. Going to start polward in next 3-6 hrs

Anybody think that's early enough to affect the path - trend it more to the east?

[Blinhart]

Very slow motion at the moment for sure, still drifting westwards again but I think that the lift out is now only a matter of a couple of hours away, can't imagine this will last much longer.

maybe a little ridge pumping...

though you can see the mid to upper low over the lower MS valley dropping south.. only a mater of time..

http://www.ssd.noaa.gov/goes/east/eaus/flash-wv.html

Yeah. It would appear that the push from the Atlantic (east) and the pressure applied from the high coming down behind the retreating trough of low pressure in New England offsets the flow out of the SW from the trough protecting (most of) the Gulf Coast. Only real way it can go is NNW. The upper low is as far south as Central Mississippi and pretty weak. But it should be the nudge.

I don't think the Upper Low is strong enough to do anything that is why this is stalling right now, there really isn't anything to direct her to go anywhere. The front has to lift out for her to move North or she will have to continue West.

[Noles2016]

I think it's still possible for Irma to miss just W of KW and the peninsula up to NE panhandle...

I'm in Destin. That doesn't make me feel great.

We are ready here in Wakulla...

[tallywx]

I think it's still possible for Irma to miss just W of KW and the peninsula up to NE panhandle...

I'm not a meteorologist, but it does occur to me that a storm moving NW paralleling the coast could at a mesoscale level create a standing Kelvin wave between itself and land (due to frictional differentials) that could keep the center just offshore as it rides the coast, as long as the overall mean steering flow is more or less parallel (so as to not disrupt the standing wave). Similar principle to how Irma never went inland in Cuba. Using this "theory," Irma wouldn't go inland until the end of the standing wave, which would be around the apex of Apalachee Bay. That would be a bad situation for Tallahassee.

Not sure these fluid dynamics have been extensively researched just yet, but standing Kelvin waves in oceans were recently researched by COAPS (Center for Ocean-Atmosphere Prediction Studies) subsequent to Hurricane Dennis in 2005 as to why the apex of Apalachee Bay received a 10-foot+ storm surge from a NW-moving storm. Same general principle here but in the atmosphere, which is also a fluid.

[Big Easy Breeze]

Very slow motion at the moment for sure, still drifting westwards again but I think that the lift out is now only a matter of a couple of hours away, can't imagine this will last much longer.

maybe a little ridge pumping...

though you can see the mid to upper low over the lower MS valley dropping south.. only a mater of time..

http://www.ssd.noaa.gov/goes/east/eaus/flash-wv.html

Last evening, around this time, it was written...Irma should begin her move to the WNW to NW motion, in the next 12-18 hours. Now this evening; it is only a matter of time, You are correct!

Here it is, over 24 hours later and Irma still has not made that change in motion.

Irma has moved within the cone of the NHC. The issue is; from a timing standpoint, she has been slow to change direction within the forecast cone.

That said, with time, weather patterns change and the dynamics could change such that she takes a different path. Time will tell and is a huge factor, with being so close to a landfall.

I guess you can say; "Stay tuned folks"!

[Blinhart]

Here's the latest shear tendency. Look how hostile conditions are north and west of Irma. If it does go further west it will run into that quickly.

http://tropic.ssec.wisc.edu/real-time/w ... oom=&time=

I thought a lot of this shear is actually the outflow of her.

[PTPatrick]

Well if shear comes in in 12 hrs, too late for key west but here's hoping for a shear induced last minute desinigration before landfall ala Hurricane Lili(2002)

[ozonepete]

its been cralwing or stalled the last hour.. or so.. we dont need that..

Could very well be starting a clockwise loop? The Euro actually had some indications of that on and off over the last few days. Would be a sensible response to an abruptly forced recurve.

[chaser1]

I think it's still possible for Irma to miss just W of KW and the peninsula up to NE panhandle...

I fully agree with at least the first part of your statement. I'd love to have a chance to glance back at the UK model. Pretty sure it better handled Irma's more southerly and westerly trajectory.

[Steve]

maybe a little ridge pumping...

though you can see the mid to upper low over the lower MS valley dropping south.. only a mater of time..

http://www.ssd.noaa.gov/goes/east/eaus/flash-wv.html

Yeah. It would appear that the push from the Atlantic (east) and the pressure applied from the high coming down behind the retreating trough of low pressure in New England offsets the flow out of the SW from the trough protecting (most of) the Gulf Coast. Only real way it can go is NNW. The upper low is as far south as Central Mississippi and pretty weak. But it should be the nudge.

I don't think the Upper Low is strong enough to do anything that is why this is stalling right now, there really isn't anything to direct her to go anywhere. The front has to lift out for her to move North or she will have to continue West.

It's not quite far enough south yet to combat 2 strong highs in the positions they are in

[PandaCitrus]

A west track with the center not making landfall significantly increases potential storm surge in Tampa Bay. Right now they are forecasting 5-8 feet in Tampa.

The maximum Cat 4 numbers are over 20 feet in many locations. They didn't evacuate for 20 feet.

[WeatherOrKnot]

We are in Lantana. 7 of us are in an interior bathroom.

Lantana? Unless there is a tornado in the area it seems too early for that..

Yes, we like sitting in the bathroom for no reason.

We got an extreme alert of tornado activity and told to go to safe room. So we did.

[dukeblue219]

Last evening, around this time, it was written...Irma should begin her move to the WNW to NW motion, in the next 12-18 hours. Now this evening; it is only a matter of time, You are correct!

I posted the 11PM last night track above. The discussion at 11pm said the following:

Code: Select all

Apparently the ridge to the north of Irma has been stronger than
expected, and the initial motion remains westward, or 280/11 kt.
The track guidance continues to insist on Irma turning
west-northwestward soon, moving along the Cuban Keys adjacent to
the north coast of Cuba during the next 24 hours.  After that time,
Irma is expected to turn sharply north-northwestward

I'm not seeing a major disconnect from those statements yet.

[Raebie]

Meanwhile, Cuba is probably getting torn to bits.

[Hammy]

its been cralwing or stalled the last hour.. or so.. we dont need that..

Could very well be starting a clockwise loop? The Euro actually had some indications of that on and off over the last few days. Would be a sensible response to an abruptly forced recurve.

So Irma could actually stall and then just loop around to the NNW rather than a curve north?

[Bamagirl2408]

I think it's still possible for Irma to miss just W of KW and the peninsula up to NE panhandle...

I said that earliet. Impacting it heavily but eye to the left