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Hurricane Ian


Scott747
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1 minute ago, TradeWinds said:

HMON looks like it is doing as well as GFS and better at 72 hrs. Interesting that the tracks for several days were consistent with GFS to panhandle/big bend and jumped way south at 6z (TPA to Jax).

AL092022_models.png

With all the grief it gets, the GFS has done fairly well given the track chaos thus far. 

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Regarding the doom and gloom posts, a storm moving slowly 100 miles off the coast will not drive catastrophic surge into the coast. Water rise and wave buildup? Sure. Major surge? No. You need the wind energy driving the water inland. I’m not mitigating the threat, but if that Euro run verifies, everyone should breathe a sigh of relief in Tampa. 
 

Other good news, a major system slowing down is usually the worst case for rainfall. In this case, Ian is slowing down while being shredded by shear and dry air. This looks to rip most of the moisture north of the circulation. This is not a prime setup for flooding at least in Florida there will likely be a large dry slot east of the center as the circulation injects dry air from the west.

Lastly, as far as windfield goes, I’m not seeing a massive system. This looks to be modeled as a pretty tight core. HWRF, HMON, EURO, GFS all barely skim the west coast of Florida with TS force winds. As it weakens, those winds do expand from the center but by that time I’m really not thinking a large fetch of 35-50 kt winds would be devastating.

Once again, I am not downplaying this system or it’s potential destruction. However, overnight the modeling trend would shed the core of destructive winds and surge west of the peninsula. We need to temper our doom and gloom for this storm if that scenario plays out, which thankfully would spare millions of people a very destructive hit. Still a lot of variables at play but to see the major modeling push west, the current position being SW of where the models that pushed this near or over the Tampa area yesterday, and continued hostile to extreme hostile conditions modeled across the northern GOM, it looks like we may have an “out” to avoid a destructive impact 

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11 minutes ago, Ed, snow and hurricane fan said:

OTWH, Euro ensemble eyeball mean is towards TPA, OTOH it has initialized as a weak system and the ones that head further N towards the shear and dry air are the stronger members

IanEurEnsemblesfronWeatherNerds..PNG

That is really old. The 9/26 6Z is way west. Like...way...WAY...big cave to the GFS and even further kind of west.

391KKuI.png

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As far as flooding goes, the western Carolina’s may actually have the higher risk as an overrunning event sets up with moisture from Ian being sheared north. The easterly flow from the circulation against the mountains would further enhance rainfall for east facing slopes. These can be very significant events for that part of the south especially with a tropical system interacting with a boundary providing increased lift over a large area. 

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9 minutes ago, NorthHillsWx said:

Regarding the doom and gloom posts, a storm moving slowly 100 miles off the coast will not drive catastrophic surge into the coast. Water rise and wave buildup? Sure. Major surge? No. You need the wind energy driving the water inland. I’m not mitigating the threat, but if that Euro run verifies, everyone should breathe a sigh of relief in Tampa. 
 

Other good news, a major system slowing down is usually the worst case for rainfall. In this case, Ian is slowing down while being shredded by shear and dry air. This looks to rip most of the moisture north of the circulation. This is not a prime setup for flooding at least in Florida there will likely be a large dry slot east of the center as the circulation injects dry air from the west.

Lastly, as far as windfield goes, I’m not seeing a massive system. This looks to be modeled as a pretty tight core. HWRF, HMON, EURO, GFS all barely skim the west coast of Florida with TS force winds. As it weakens, those winds do expand from the center but by that time I’m really not thinking a large fetch of 35-50 kt winds would be devastating.

Once again, I am not downplaying this system or it’s potential destruction. However, overnight the modeling trend would shed the core of destructive winds and surge west of the peninsula. We need to temper our doom and gloom for this storm if that scenario plays out, which thankfully would spare millions of people a very destructive hit. Still a lot of variables at play but to see the major modeling push west, the current position being SW of where the models that pushed this near or over the Tampa area yesterday, and continued hostile to extreme hostile conditions modeled across the northern GOM, it looks like we may have an “out” to avoid a destructive impact 

 

This is a good post. 

One big factor too is that Florida has some of the best building codes around. You literally had Hurricane Irma's Category 3 eyewall move over downtown Naples, the Naples Airport recorded a wind gust to 142 mph, and then the backside was dry and weak. People literally were taking their dogs to poop like a thunderstorm had moved in a few minutes after the eyewall of this "monster" storm struck. Those building codes are amazing.

To be fair though, Irma's strange angle approach to the coast caused a reverse surge along much of the west coast. Charley's small size limited his surge along the coast. We have yet to see a major hurricane dragging up the western side of the peninsula yet. I'm curious how the surge would be. 

 

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This is now a bit a old. I'm posting the 0Z big 3 ensemble so that it can be compared with the 6Z cycle that should be available in about 30 minutes. The 0Z cycle was showing the head fake toward the coast but ultimately held firm with the landfall near the big bend area of FL. I suspect the 6Z will be a tick west of the 0Z due to the big shift from the ECMWF suite.

IYgu9Vm.png

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3 minutes ago, TradeWinds said:

Probably why the NHC kept track closer to GFS mean than Euro at times.

Maybe. Blending is the way to go usually, and I think that holds true here so far. There is a lot of medium range spread in track, which translates into intensity and obviously impacts. This one seems to be a mess for emergency managers along the coast that need to start getting people ready now. 

This is where I think Tomer's super ensemble is especially helpful, and at five days 00z you still have significant spread. 

yQwmVEk.png

I think we're still in the stage where we're trying to figure out the real envelope of possibilities. A Tampa LF vs Panama City LF is a big spread. What happens inland is a big spread too and will have impacts on GA/SC. I don't have to make a forecast so it's easy for me to say, but I'm more in watch/collect data mode because I'm not sure any model has this evolution under control yet. 

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The full 6z Euro run has the crawl/stall WSW/W of Tampa Bay, and it’s pushing a ton of energy up the coast and in the bays.  Not certain how this equates to total surge potential, but it remains an impactful solution and we still have margin of error with the track at this stage.

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3 minutes ago, WxWatcher007 said:

This one seems to be a mess for emergency managers along the coast that need to start getting people ready now. 

Couldn’t agree more. A sharp angle of approach, a major city, uncertain intensity at Landfall, and a major hurricane sitting a stones throw off the beach. The destructive potential is extremely high but the bust potential especially in the public eye is as high as it gets. Glad I’m not making those decisions 

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8 minutes ago, WxWatcher007 said:

This is where I think Tomer's super ensemble is especially helpful, and at five days 00z you still have significant spread. 

If it's not obvious yet I'm big fan of ensembles. There is a proven a record of superior forecast skill when using ensembles. I do like Tomer's super ensemble as well. My only complaint is that I *think* it only includes the deterministic UKMET run and not the actual ensemble suite. The only place I've found to get the UKMET ensemble is the RAMMB site.

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3 minutes ago, bdgwx said:

If it's not obvious yet I'm big fan of ensembles. There is a proven a record of superior forecast skill when using ensembles. I do like Tomer's super ensemble as well. My only complaint is that I *think* it only includes the deterministic UKMET run and not the actual ensemble suite. The only place I've found to get the UKMET ensemble is the RAMMB site.

Originally it had the UKMET ensembles, but they ran so late it kind of made the super ensemble obsolete as it was significantly delayed. 

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23 minutes ago, NorthHillsWx said:

Couldn’t agree more. A sharp angle of approach, a major city, uncertain intensity at Landfall, and a major hurricane sitting a stones throw off the beach. The destructive potential is extremely high but the bust potential especially in the public eye is as high as it gets. Glad I’m not making those decisions 

Yeah it is very delicate given the night and day difference from small deviations in tracks. A mildly aggressive approach seems the most prudent? Post evacuation orders for the most vulnerable? Always better safe than sorry. 

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53 minutes ago, cptcatz said:

It will still have huge surge though. Surge isn't correlated with the intensity at landfall but is a function of the size, intensity, and time over water of the entire history of the storm. All the water that the storm was pushing out in front of it will still be there. Similar situation as Sandy which was a massive storm over water for a very long time and even though it made landfall with only cat 1 winds, those other factors caused 14 foot storm surges.

This is not true.  With all other things being equal, once a storm starts to weaken, the surge potential starts going down.  Those waves need energy (wind) to continue to push it, as soon as that energy is reduced, the amount of water being pushed by it starts to get reduced as well.  What you're saying would only be true in a vacuum. 

 

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41 minutes ago, NorthHillsWx said:

As far as flooding goes, the western Carolina’s may actually have the higher risk as an overrunning event sets up with moisture from Ian being sheared north. The easterly flow from the circulation against the mountains would further enhance rainfall for east facing slopes. These can be very significant events for that part of the south especially with a tropical system interacting with a boundary providing increased lift over a large area. 

That’s actually a really good point. The “PRE” is no joke when it verifies WNC/SVA 

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The 6Z cycle of the big 3 ensembles is in. As expected the EPS took a big leap toward the GEFS and so now the uncertainty rings line up pretty well. Unexpectedly MOGREPS shifted slightly east showing a landfall near Tampa. The mean of the 3 is still well offshore, but the intersection points of the rings gets Ian very close to the coast at HR96 and parallels it for either a very oblique landfall angle or an eventual landfall in the big bend area. I wonder if MOGREPS will cave to the GEFS and EPS on the 12Z cycle?

 

oiMRIm3.png

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The ensembles are great, but the mean actually has a larger track MAE than the operational model. For example, the GFS ensemble had 20 NM greater error than the GFS at 120 hours in the 2021 NHC verification report. They're a tool to see different solutions, model spreads, and sensitivities to the overall weather pattern. 

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1 hour ago, cptcatz said:

It will still have huge surge though. Surge isn't correlated with the intensity at landfall but is a function of the size, intensity, and time over water of the entire history of the storm. All the water that the storm was pushing out in front of it will still be there. Similar situation as Sandy which was a massive storm over water for a very long time and even though it made landfall with only cat 1 winds, those other factors caused 14 foot storm surges.

But Sandy had  a FAR lower pressure than this will have at  landfall plus Sandy was  very  large. I saw  2 other examples given. Katrina and Fiona. Fiona was undergoing  intensification while  Ian will be literally getting stripped. Ian will not  be setting  low  pressure records anywhere on land. As far as  Katrina it weakened windwise  but  it still came  onshore with a  pressure  around  923 mb which could  be a weak cat 5 pressure. To sum up Ian, its  going to be rapidly weakening and going rather  slow. that will give alot  of the  surge alot  of time to dissipate.

 

From Wikipedia:

 

"Sandy briefly re-intensified to Category 2 intensity on the morning of October 29, around which time it had become an extremely large hurricane, with a record gale-force wind diameter of over 1,150 miles (1,850 km),[6][30] and an unusually low central barometric pressure of 940 mbar, possibly due to the very large size of the system.[5] This pressure set records for many cities across the Northeastern United States for the lowest pressures ever observed."

 

 

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