ATL: HARVEY - Post-Tropical - Discussion

[Dave C]

I remember Bob Sheets saying how storms will drop pressure quickly then level off before next big pressure drop. Next few hrs will be something to watch.

[Kingarabian]

Looks like shear is increasing a bit, not sure if it's enough to keep strength down or not. Very little outflow on the SW side of the storm.

https://weather.msfc.nasa.gov/cgi-bin/get-abi?satellite=GOESEastconusband02&lat=25&lon=-94&width=1000&height=800&zoom=2&type=Animation&numframes=20&quality=92

Yeah it had that problem from earlier today when the RI began.

Also if it wants to become a major, the eyewall needs to do better.

[Langinbang187]

Is there a chance that this will drop down to the 880 pressure range, or will it stay above 900? I know a pressure of 900 would be catastrophic and could cause this system to bomb out even more than expected, but if somehow it drops below 900 I think this will be the most costly storm in history.

Can't see it. Pressure has already strangely leveled off.

[Cuda]

Is there a chance that this will drop down to the 880 pressure range, or will it stay above 900? I know a pressure of 900 would be catastrophic and could cause this system to bomb out even more than expected, but if somehow it drops below 900 I think this will be the most costly storm in history.

I haven't seen any model runs or predictions that pressure would get THAT low, have you?

[MaineWeatherNut]

And all this explosive development is taking place during the day... Usually these kinds of explosive development takes place at night so just watch it does come the over night hours unless something unexpected comes up to disrupt it.

[MaineWeatherNut]

Is there a chance that this will drop down to the 880 pressure range, or will it stay above 900? I know a pressure of 900 would be catastrophic and could cause this system to bomb out even more than expected, but if somehow it drops below 900 I think this will be the most costly storm in history.

I haven't seen any model runs or predictions that pressure would get THAT low, have you?

Latest NAM i believe had it down to like 878mb or something like that.

[davidiowx]

Is there a chance that this will drop down to the 880 pressure range, or will it stay above 900? I know a pressure of 900 would be catastrophic and could cause this system to bomb out even more than expected, but if somehow it drops below 900 I think this will be the most costly storm in history.

I haven't seen any model runs or predictions that pressure would get THAT low, have you?

Latest NAM i believe had it down to like 878mb or something like that.

It's the NAM...

[ronjon]

12z NAVGEM - essentially Euro but with further inland penetration in Tx.

https://www.tropicaltidbits.com/analysis/models/?model=navgem&region=us&pkg=mslp_pcpn_frzn&runtime=2017082412&fh=6&xpos=0&ypos=0

[Kingarabian]

You need time and near perfect conditions to get a Cat.5 and a sub 900mb pressure. Harvey has neither.

[davidiowx]

You need time and near perfect conditions to get a Cat.5 and a sub 900mb pressure. Harvey has neither.

Time? Probably not.... Perfect Conditions? Absolutely. It is in a really good environment for RI.

[Dave C]

Looks like shear is increasing a bit, not sure if it's enough to keep strength down or not. Very little outflow on the SW side of the storm.

https://weather.msfc.nasa.gov/cgi-bin/get-abi?satellite=GOESEastconusband02&lat=25&lon=-94&width=1000&height=800&zoom=2&type=Animation&numframes=20&quality=92

Look at the infrared loop, its outflow shows up better on the sw flank but is a little less robust there agreed.

[KWT]

I remember Bob Sheets saying how storms will drop pressure quickly then level off before next big pressure drop. Next few hrs will be something to watch.

Yeah I wouldn't be surprised if that happens, typically once they open their eyes you'll see a decent pressure drop with these systems.

With that being said it hasn't got the greatest IR presentation on that southern side, looking a little squished.

[KWT]

Is there a chance that this will drop down to the 880 pressure range, or will it stay above 900? I know a pressure of 900 would be catastrophic and could cause this system to bomb out even more than expected, but if somehow it drops below 900 I think this will be the most costly storm in history.

I haven't seen any model runs or predictions that pressure would get THAT low, have you?

Latest NAM i believe had it down to like 878mb or something like that.

NAM shouldn't be used for tropical cyclones, and I'd be surprised if it goes anywhere close to sub 900mbs, this neck of the Gulf tends to bottom out in the 920-935mbs range usually, but who knows!

[Kingarabian]

You need time and near perfect conditions to get a Cat.5 and a sub 900mb pressure. Harvey has neither.

Time? Probably not.... Perfect Conditions? Absolutely. It is in a really good environment for RI.

There are some dry air issues and outflow is restricted to the S/SW. Take a look at past Pacific cat.5 hurricanes and compare them with Harvey. Or just look at the bad boys from 2005.

[GCANE]

Another new tower firing up.

[Cunxi Huang]

Is there a chance that this will drop down to the 880 pressure range, or will it stay above 900? I know a pressure of 900 would be catastrophic and could cause this system to bomb out even more than expected, but if somehow it drops below 900 I think this will be the most costly storm in history.

I haven't seen any model runs or predictions that pressure would get THAT low, have you?

This happens sometimes in West Pacific.
I remember ECMWF run onetime while forecasting typhoon Muifa in 2011. And it's the 1st time EC got a pressure lower than 900mb in my mind.
GFS happened a lot...i mean not a lot, but few times.
I have a screenshot that GFS run a 858 mb for cyclone Winston in South Pacific. But i can't find that screenshot.

[txwatcher91]

I remember Bob Sheets saying how storms will drop pressure quickly then level off before next big pressure drop. Next few hrs will be something to watch.

Yeah I wouldn't be surprised if that happens, typically once they open their eyes you'll see a decent pressure drop with these systems.

With that being said it hasn't got the greatest IR presentation on that southern side, looking a little squished.

Give it some time, we are at DMIN right now which is slowing things down a bit. Tonight will be a different story, pressure leveling off as expected before a big sudden drop occurs. I wouldn't be surprised to see this sub 920 by tomorrow morning and cat 4/5 winds.

[Kingarabian]

Fairly shallow from the south GCANE. CDO needs to expand and outflow to the south has to establish itself or else dry air will poke its nose.

[MaineWeatherNut]

You need time and near perfect conditions to get a Cat.5 and a sub 900mb pressure. Harvey has neither.

lol Time? Wilma went from like a cat 1/2 in the evening to a Cat 5 in like 12 hours.

[KWT]

You need time and near perfect conditions to get a Cat.5 and a sub 900mb pressure. Harvey has neither.

Time? Probably not.... Perfect Conditions? Absolutely. It is in a really good environment for RI.

There are some dry air issues and outflow is restricted to the S/SW. Take a look at past Pacific cat.5 hurricane and compare them with Harvey. Or just look at the bad boys from 2005.

Yeah I don't think conditions are perfect, very good but not perfect. Still it has got a decent amount of time left and given the steering currents to the north, its not going to be dragging in huge amounts of dry air from the USA even near landfall so could see strengthening right into landfall with this one.