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Hurricane Hermine

Typhoon Tip

By Typhoon Tip,
in New England

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Typhoon Tip

Typhoon Tip

Posted
Posted 
LOCATION...25.5N 87.4W
ABOUT 330 MI...535 KM SSW OF APALACHICOLA FLORIDA
ABOUT 330 MI...535 KM SW OF TAMPA FLORIDA
MAXIMUM SUSTAINED WINDS...50 MPH...85 KM/H
PRESENT MOVEMENT...NNE OR 30 DEGREES AT 8 MPH...13 KM/H
MINIMUM CENTRAL PRESSURE...1001 MB...29.56 INCHES

http://www.nhc.noaa.gov/graphics_at4.shtml?5-daynl#contents

 

Guidance et al are reasonably well clustered around a track that brings Hermine across the Florida Panhandle then essentially up along the coastal plain of the SE. TPC's track guidance and infamous cone of uncertainty appears to mimic that mean rather nicely. 

Unfortunately, that leaves room for a few possibilities in the way the TC could affect SNE.  In short,

if Hermine passes along the left hand side of the guidance mean, the TC will weaken substantially and exhaust its self as a smear out along the quasi-stationary boundary that in time, will be settling into a parallel position along or astride the present track guidance.  If the TC passes to the right ... it's proximity along that path may not be far enough displaced from the warm oceanic heat sources to weaken quite as fast.  

There other concerns regarding what 'form' Hermine take as it moves further NE up the coast.  It should lose tropical characteristics as it eventually and inevitablly interacts with said boundary... but the rate of that absorption would likely depend on Hermine's ability to remind 'tropically intact' - namely, ...a right-ish track may prolong that transition.  At this time of the year, warm waters extend about as far up the coast as they do, annually.  Additionally, the handling of the polar jet is in question.  The models have been behaving reasonably consistency for the time range in question (nearing D4).  However, subtle increases in the amount of dynamics punching S out of the OV along the southern arc of the progressive trough will be important in the evolution of Hermine as it nears the latitudes of the Del Marva - assuming the track guidance verifies reasonably well.  

 

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Typhoon Tip

Typhoon Tip

Posted
  • Author
Posted 
...HERMINE CONTINUES TO STRENGTHEN OVER THE EASTERN GULF OF
MEXICO...
...HURRICANE WARNING ISSUED FOR PORTION OF NORTHWESTERN FLORIDA...


SUMMARY OF 1000 PM CDT...0300 UTC...INFORMATION
-----------------------------------------------
LOCATION...25.8N 87.0W
ABOUT 295 MI...475 KM SSW OF APALACHICOLA FLORIDA
ABOUT 315 MI...510 KM WSW OF TAMPA FLORIDA
MAXIMUM SUSTAINED WINDS...60 MPH...95 KM/H
PRESENT MOVEMENT...NNE OR 25 DEGREES AT 10 MPH...17 KM/H
MINIMUM CENTRAL PRESSURE...998 MB...29.47 INCHES

---------------------------------------------------------------------------------------------------

 

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HoarfrostHubb

HoarfrostHubb

Posted
Posted

From this morning's AFD...just to keep it for posterity:

Model guidance is in generally good agreement on the overall
synoptic pattern.  High pressure will bring quiet, dry, seasonable
weather to the region Saturday. Main concern remains with the track
and intensity of Tropical Storm Hermine and what effect this may
have on southern New England. Whatever effect it has on this region
will likely be felt Sunday and Monday. 01/00Z guidance has shifted
the track of Hermine a bit back to the east. There are several
factors that are contributing to the low confidence forecast with
Hermine:

* The potential phasing of the storm with a shortwave moving out of
  the Great Lakes and to what extent this plays out in the further
  development of the storm
* A strong, blocking ridge developing to our north that may suppress
  Hermine to the south of southern New England
* The fact that this is still a day 4/5 forecast where uncertainty
  reigns supreme

All of this leads to some uncertainty with what impact Hermine will
have on this region.  At this point, the GFS brings Hermine a bit
farther north to just east of New Jersey and takes it out to sea
more quickly (Tuesday) than the ECMWF. The ECMWF develops that
blocking ridge a bit farther to the south, keeping Hermine just off
the DelMarVa peninsula and not really pushing it out to sea until
Thursday.

Reasonable worst case scenario at this point is 2-4" of rain across
portions of southern New England and strong, gusty winds up to 40-50
mph.  But if the storm is suppressed to the south, we could end up
with little to no rain and a few gusty winds.  As mentioned before,
astronomical tides are low so no coastal flooding is expected.  At
worst case, should the ECMWF solution prove true and Hermine lingers
south of the region for several days, some coastal erosion may occur.

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Typhoon Tip

Typhoon Tip

Posted
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Posted
26 minutes ago, HoarfrostHubb said:

From this morning's AFD...just to keep it for posterity:

Model guidance is in generally good agreement on the overall
synoptic pattern.  High pressure will bring quiet, dry, seasonable
weather to the region Saturday. Main concern remains with the track
and intensity of Tropical Storm Hermine and what effect this may
have on southern New England. Whatever effect it has on this region
will likely be felt Sunday and Monday. 01/00Z guidance has shifted
the track of Hermine a bit back to the east. There are several
factors that are contributing to the low confidence forecast with
Hermine:

* The potential phasing of the storm with a shortwave moving out of
  the Great Lakes and to what extent this plays out in the further
  development of the storm
* A strong, blocking ridge developing to our north that may suppress
  Hermine to the south of southern New England
* The fact that this is still a day 4/5 forecast where uncertainty
  reigns supreme

All of this leads to some uncertainty with what impact Hermine will
have on this region.  At this point, the GFS brings Hermine a bit
farther north to just east of New Jersey and takes it out to sea
more quickly (Tuesday) than the ECMWF. The ECMWF develops that
blocking ridge a bit farther to the south, keeping Hermine just off
the DelMarVa peninsula and not really pushing it out to sea until
Thursday.

Reasonable worst case scenario at this point is 2-4" of rain across
portions of southern New England and strong, gusty winds up to 40-50
mph.  But if the storm is suppressed to the south, we could end up
with little to no rain and a few gusty winds.  As mentioned before,
astronomical tides are low so no coastal flooding is expected.  At
worst case, should the ECMWF solution prove true and Hermine lingers
south of the region for several days, some coastal erosion may occur.

 

it all still echoes the original sentiments ... blah blah uncertainties in how the phasing will effect course, timing, intensities... 

but i'll also add ...we're not likely looking at 'a huge deal' as it will affect here.   there is (yes) a lower probability that something more substantial as far as wind and rain is concerned, but we don't actually have any guidance right now that physically shows that.  the GFS's recent runs may in fact be decent normalized perspective considering all; and having light to moderate gradient cyclonic curvature swash through with light to moderate rain shield.  

i agree, however, there is a 'vibe' of this thing as a high surf generator.  the idea of a 20 + mb gradient retrograding and/or stalling abeam of NJ, with a long distant curvi-linear flow design over the NE/E/SE arc of the low,... is a good recipe for seas that feature short and long duration swells occasionally - constructively interfering and making for some serious beach punishment issues... ... erosion and all those headaches that come along with that, regardless of other storm related physicalities.  not to mention, if the system stays sort of right side of track guidance and is stronger as it tucks in up along the MA, this could turn into a multiple tide-cycle surge issue...

... it's an unusual situation really...  the TC is actually tunneling through the mid/UA ridging because that's the course of least resistance that TC's will always mathematically take.  but, that means a slow mover compared to climo for systems gain latitude along the EC.  there's a few offset details either way; slow moving should mean more weakening prior to getting N, but with all this happening at the warm water apex of the year, that may add back some ... particularly as originally discussed, Hermine takes the eastern edge of the proverbial cone of uncertainty.  contrasting, a track more on the left side/over land could make much of this moot. 

one thing that is there in all guidance, however, is at least partial phasing... some mid level dynamics gets somehow entwined in this thing in the MA... and that seems to send it through a kind of sinusoidal phase change:  warm core --> hybrid --> ...hinting back to (warm core + hybrid)/2 before succumbing to entirely and losing identity way out in time.  this is all evidence, but in differing amount per phase, depending on which guidance.   it may not matter much sensibly... but, that does open one's imaginative up to a few possibilities for what could happen. 

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