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Major Hurricane Florence: STORM MODE THREAD


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Agree on the Cat 3 intensity. However, the windfield is expanding. This poses an increase in surge potential for a slow-moving landfall or stall near landfall. Greater fetch. Additionally, even with expansion of windfield, favorable environmental conditions can still result in intensification of the core vortex. We still have a long ways to go. It wouldn't be unrealistic for reintensification back to a Cat 4 and then additional weakening trend near landfall.

 

 

 

 

 

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Didn't Harvey intesy to a category 4 just before landfall? 

 

Harvey had exceptional upper atmospheric environmental conditions on approach, a tight vortex and 30-31°C up to the shoreline. Florence is a much larger hurricane. It's not impossible that Florence could make landfall as a Cat 4, it's just not as likely based on slow movement in a less favorable environment.

 

 

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I'm no expert, but the one hour improvement on satellite was pretty impressive, given that the SW side tightened up a bit and the eye is circular and clear now.  Again, just going off of what I read, it is not that odd for a hurricane to struggle a bit coming off an ERC, and people here have noted that pressure falls may precede an increase in wind.  Guess we'll have to see what happens here., but I don't see how people can discount continued weakening or rapid intensification.  We've seen that it does not take a long time for these systems to gain an incredible amount of strength, and that could very well happen here.

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2 minutes ago, Windspeed said:

 

Harvey had exceptional upper atmospheric environmental conditions on approach, a tight vortex and 30-31°C up to the shoreline. Florence is a much larger hurricane. It's not impossible that Florence could make landfall as a Cat 4, it's just not as likely based on slow movement in a less favorable environment.

 

 

I wonder if the NHC will start to acknowledge the less than ideal environment. This storm is undergoing effects beyond the Erc. Im no expert but i l think it's been clear on satellite for much of the day. 

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6 minutes ago, NYCGreg said:

I'm no expert, but the one hour improvement on satellite was pretty impressive, given that the SW side tightened up a bit and the eye is circular and clear now.  Again, just going off of what I read, it is not that odd for a hurricane to struggle a bit coming off an ERC, and people here have noted that pressure falls may precede an increase in wind.  Guess we'll have to see what happens here., but I don't see how people can discount continued weakening or rapid intensification.  We've seen that it does not take a long time for these systems to gain an incredible amount of strength, and that could very well happen here.

That’s exactly why intensity forecasting is so challenging. And the following conflicting factors.

Going for Florence we have increasing SST and higher OHC plus a low shear environment.

Going against Florence we have a relatively dry ascendant airmass.  

Now that Florence has increased in size I think it will Be tough for much strengthening past a low end cat 4 something like 120kts. 

If you want to see what truly perfect conditions and incredible OHC check out mangkhut.  

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The NAM is the NAM but still, it is American so we should look at it.  The NAM has no landfall during the entire run.   Florence wanders the coastline out to "hour 84".

Will it verify just so?  Nope.  Still a few other model runs have had a close brush with the coast but no Carolina LF during the next 96 hours or so.  It is not impossible that LF may be delayed or extra-tropical.

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I can see why they held it at 140 MPH. No need to make knee-jerk down/up revisions. They'll give it another few hours to see if winds start responding back up. If not, they can start reducing winds. Surface pressures are lowering. As I explained last night, the larger wind-field is helping keep the winds from responding upwards for now. As a 'rubber-band effect', the winds could respond upward quite quickly in the next 12-18 hours if the pressure keeps falling. We've seen it in several intense hurricanes after ERWC.

The wind being held at 140 MPH is probably being done for societal reasons versus pure scientific. The post-storm report will undoubtedly revise intensity estimates as needed. 

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58 minutes ago, jayson said:

Harvey happened in August, further south, in 90 degree SSTs.

I don't think its an apples to apples comparison, though....Harvey was in the maturing part of its life cycle. Once they have matured, gone through ERCs etc, it can be tricky as far as seeing extended periods of bonafide intensification.

I think we've seen peak intensity, but just an educated guess.

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When an eyewall is open, the wind field expands and while pressure may stay low the gradient is lessened (and thus the wind field expands while the wind at the eyewall drops). During today's ERC there was a long periods of an open eyewall, and this is one reason why we are seeing the wind field lower than expected for the storm. The result is going to be TS and hurricane force winds at a larger radius, but a less intense eyewall. The eyewall may recover these winds if the central pressure keeps falling, but it's really a wait-and-see state.

Looking at WV loop, it does look like there is some dry air it is ingesting to the SW. This seems to be what is contributing to the ragged appearance:

CODNEXLAB-GOES16-meso-meso1-09-03_33Z-20

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