September 2021: Hurricane Nicholas

[Stratton20]

Even the 12z CMC has shifted significantly north into N.Mexico compared to keeping it in the BOC, not liking the fact that the GFS is indicating that this 2nd system could be a really slow mover, it just meanders the system in the NW Gulf until heading for the Tx/La border

[Scott747]

That 6z system is independent of 91l and comes from yet another hybrid/pseudo set-up in the Caribbean. I'd have to look a little closer but I can't find the wave that triggers this one plus it originates more off of SA. The GFS has already been hinting at it but was burying it in the southern BoC so it isn't coming out of nowhere and is in a range that can't be immediately dismissed.

We'll see in the subsequent runs today if it was a one off or continues back to the southern end solution.

Well it took one full day of runs for the GFS to swing back to the original idea of the southern solution....

And not quite as buried on the 12Z. What may be happening here - AGAIN - is the tendency for models to initially develop the southern end of the wave axis that is more attached to monsoonal storminess closer to Central America. Where did we see this? With initial Ida guidance, before they correctly forecast development on the northern end of the wave axis. Not that the same scenario plays out here, but we’ll need to see where (if) consolidation occurs AND what ridge orientation is likely to its north late this-coming week.

The problem I'm having is that there is no discernable wave axis that I can find like there was with Ida. I'll go back again and look but yesterday the only axis I could see was way out ahead of any eventual consolidation and almost a totally different entity.

This run also again shows an orientation with the ridge like a few runs yesterday that would allow anything to track towards N Mex and Texas. Even has a trough that pulls it a little bit but misses it fully before another ridge builds back in.

[weatherguy425]

Well it took one full day of runs for the GFS to swing back to the original idea of the southern solution....

And not quite as buried on the 12Z. What may be happening here - AGAIN - is the tendency for models to initially develop the southern end of the wave axis that is more attached to monsoonal storminess closer to Central America. Where did we see this? With initial Ida guidance, before they correctly forecast development on the northern end of the wave axis. Not that the same scenario plays out here, but we’ll need to see where (if) consolidation occurs AND what ridge orientation is likely to its north late this-coming week.

The problem I'm having is that there is no discernable wave axis that I can find like there was with Ida. I'll go back again and look but yesterday the only axis I could see was way out ahead of any eventual consolidation and almost a totally different entity.

This run also again shows an orientation with the ridge like a few runs yesterday that would allow anything to track towards N Mex and Texas. Even has a trough that pulls it a little bit but misses it fully before another ridge builds back in.

True, just a little unusual for this to be purely ITCZ/Monsoonal. It’ll be interesting to watch... once again.

[TexasBreeze]

There is a wave 76 west with some scattered convection down there, but it looks like vorticity comes from northern South America then coalesces further west.
It would be signs of maybe a phantom- if it wasn't modelled to start in a day or two. Interesting!

[Scott747]

And not quite as buried on the 12Z. What may be happening here - AGAIN - is the tendency for models to initially develop the southern end of the wave axis that is more attached to monsoonal storminess closer to Central America. Where did we see this? With initial Ida guidance, before they correctly forecast development on the northern end of the wave axis. Not that the same scenario plays out here, but we’ll need to see where (if) consolidation occurs AND what ridge orientation is likely to its north late this-coming week.

The problem I'm having is that there is no discernable wave axis that I can find like there was with Ida. I'll go back again and look but yesterday the only axis I could see was way out ahead of any eventual consolidation and almost a totally different entity.

This run also again shows an orientation with the ridge like a few runs yesterday that would allow anything to track towards N Mex and Texas. Even has a trough that pulls it a little bit but misses it fully before another ridge builds back in.

True, just a little unusual for this to be purely ITCZ/Monsoonal. It’ll be interesting to watch... once again.

It has been crazy. Almost like a conveyor belt in the modeling world. After season synopsis will have some interesting reads.

Will say that the CMC and GFS are virtually identical with consolidation in the BoC and intermediate ridging. Only spread is when the trough pops up on the GFS allowing enough of a weakness to pull our 'phantom' system n.

[weatherguy425]

The problem I'm having is that there is no discernable wave axis that I can find like there was with Ida. I'll go back again and look but yesterday the only axis I could see was way out ahead of any eventual consolidation and almost a totally different entity.

This run also again shows an orientation with the ridge like a few runs yesterday that would allow anything to track towards N Mex and Texas. Even has a trough that pulls it a little bit but misses it fully before another ridge builds back in.

True, just a little unusual for this to be purely ITCZ/Monsoonal. It’ll be interesting to watch... once again.

It has been crazy. Almost like a conveyor belt in the modeling world. After season synopsis will have some interesting reads.

Will say that the CMC and GFS are virtually identical with consolidation in the BoC and intermediate ridging. Only spread is when the trough pops up on the GFS allowing enough of a weakness to pull our 'phantom' system n.

Even with the CMC; there is a bit of a weakness over Texas allowing a more north or northwesterly trajectory after a landfall in northeast Mexico or Texas border - allowing at least the heavy rain threat to spread into Texas.

[Stratton20]

Well to say the next 7-10 days will be interesting in the tropics , would be a understatement hahaha

[DoctorMu]

91L: NEXT



2nd System: 12Z GFS resembles the paths for the Greek letter storms of last year into LaTx border - we're still a long way off.



CMC brings a depression into the RGV. Not much on Euro and Ensembles.

TBD.

[Stratton20]

Would love to get y’all’s opinion on this as their has always been a debate over the GFS and Euro models ,IMO the Euro is absolutely trash with the tropics and picking up on system, I feel like the Euro is better for other forecasts that dont have to do with tropical systems, ofc it shows nothing, definitely feel like the GFS is a much better model to follow, ofc im not saying the GFS is going to be right everytime, but it’s obvious how significantly the GFS has outperformed the Euro yet again this hurricane season, don really get why the Euro has a hard time with picking up on tropical systems,

[weatherguy425]

IMO the Euro is absolutely trash with the tropics and picking up on system, I feel like the Euro is better for other forecasts that dont have to do with tropical systems, ofc it shows nothing, definitely feel like the GFS is a much better model to follow, ofc im not saying the GFS is going to be right everytime, but it’s obvious how significantly the GFS has outperformed the Euro yet again this hurricane season, don really get why the Euro has a hard time with picking up on tropical systems

It is not trash, but like many models has issues from time to time. It DOES have something; just not a closed low on this particular run.

It was the first operational model to jump eastward with Ida. No development doesn’t make it wrong. The signal for development, while there, is not incredibly strong overall to begin with. It’s just worth watching.

The model has struggled with genesis - as have others to varying degrees - for the past couple seasons.

[Stratton20]

weatherguy425 you make some pretty good points their, and i absolutely am not saying the euro isnt right here and we get no development with the 2nd system, but it just seeks that this model in particular really has a hard time with cyclogenisis

[weatherguy425]

weatherguy425 you make some pretty good points their, and i absolutely am not saying the euro isnt right here and we get no development with the 2nd system, but it just seeks that this model in particular really has a hard time with cyclogenisis

It has for the past couple seasons, but not through its entire lifespan.

[Stratton20]

weatherguy425 ah gotcha! Well we will see if we will have any tropical trouble to deal with around here next week, although if something does form, may it stay far away from Lousiana, thise poor folks dont need any more systems

[DoctorMu]

Welp. Today may be the day for CLL to finally hit the century mark. "Cool" summer. "Hot" meteorological Fall so far.

97° now onto 99 or 100°F. Lots of heat for the week. September and October extreme heat get old around here fast.

[Stratton20]

DoctorMu as someone else who is also in College Station, I cant agree more with this heat getting old fast

[Stormlover2020]

To my understanding.

Less traveling has been messing with it. Vs Gfs & icon get to take over.

Euro doesn’t use all over our weather stations like hrrr/nam/gfs/icon do.

[weatherguy425]

To my understanding.

Less traveling has been messing with it. Vs Gfs & icon get to take over.

Euro doesn’t use all over our weather stations like hrrr/nam/gfs/icon do.

This was a concern very early in the pandemic, but this is really just a social media rumor.

[DoctorMu]

99°F was the high today, Officially, the hottest day of the year in CLL.

What a bizarre weather year it has been. Mega snows in January and February with frozen tundra for a week and single digit lows.

57°F low in June. 7 Days in the 80s for highs in July.

We finally arrive at football season and September, and then are slammed with the hottest week of the year....and another week of searing heat lies ahead.

[jasons2k]

99°F was the high today, Officially, the hottest day of the year in CLL.

What a bizarre weather year it has been. Mega snows in January and February with frozen tundra for a week and single digit lows.

57°F low in June. 7 Days in the 80s for highs in July.

We finally arrive at football season and September, and then are slammed with the hottest week of the year....and another week of searing heat lies ahead.

Hit 101 here. Run of the mill. Had many days hotter than today.

It’s still 90F at 8:55. Reminds me of DFW….

That is so unusual b/c Bryan-C/S should theoretically be hotter. I guess all the concrete is winning out.

[DoctorMu]

There's a back door front sagging through, but almost no energy associated. A broken line of showers fizzled north of here.

Won't be any cooler on the other side.

Chance of rain in our southern counties tomorrow. Expecting nada here, unless some wedging and uplift brings a rogue shower in the wee hours.


Area Forecast Discussion
National Weather Service Houston/Galveston TX
646 PM CDT Sun Sep 5 2021

.AVIATION...

A line of showers and thunderstorms ahead and along a weak cold
front will approach SE TX this evening. The line has begun to
weaken and not sure how far south the line will get this evening.
Still plenty hot and there is decent CAPE and PWATs in advance of
the front so will carry VCTS for northern TAF sites and see how
things evolve. Leaned toward the HRRR which shows the line
weakening and then blossoming again after 09z further south
affecting the Houston terminals for the morning push. Will carry
VCSH after 09z through the morning. Will carry a VCTS for central
and southern TAF sites for Monday afternoon but confidence with
additional development is low as models dry things out quickly
after 18z. 43

&&

.PREV DISCUSSION... /ISSUED 308 PM CDT Sun Sep 5 2021/

DISCUSSION...

Showers have had a hard time getting started so far today, though
that is expected to change for the Houston Metro/I-45 eastward as
a weak front droops into the region. Though the rain setup does
not overall look particularly impressive, the strongest cell or
two may manage some isolated heavy rain.

The deeper we go into the new week, the lower rain chances will go
as some drier air filters into the region and high pressure
attempts to build back. Along with the lower rain chances, we`ll
also see above average temperatures with highs away from the Gulf
looking to rise into the middle to upper 90s multiple days.

Finally, we will continue to keep an eye on Invest 91L and its
potential for development as it lifts northward across the Gulf
over the next several days. Confidence though, is increasing that
this feature will be kept well to our east.

SHORT TERM [Monday Through Monday Night]...

The remainder of this afternoon`s weather pattern will be very
similar to what we saw yesterday. Despite higher PW air along our
eastern counties again today, subsidence still seems to be winning
out and our radar remains quiet inland. With high pressure overhead
and light SW flow, the sea-breeze will begin to push inland over the
next few hours and at most might kick up some isolated showers along
our coastal areas before dissipating around sunset. Meanwhile, a
front currently passing through DFW`s area will sag further south
and is expected to reach our northern counties by late this evening.
Therefore, isolated to scattered showers and storms are expected
along the frontal boundary as it pushes south overnight and reaches
the coast by morning. WPC has placed our eastern and northern
portions of our CWA in a marginal risk for excessive rainfall
tonight, but as the front becomes more E/W oriented, it`s low-level
moisture transport will weaken, so not expecting much of a risk
tonight.

By tomorrow, the frontal boundary will be stalled across our
southern CWA and act as a focus for showers throughout the day. With
daytime heating, coverage and intensity of these showers are
expected to increase throughout the day and peak late afternoon.
Rain chances will also be enhanced by a broad tropical trough in the
Central Gulf expected to migrate north and bring a surge of deep
tropical moisture along the northern Gulf Coast. Forecast soundings
show PWs climbing to 2.1-2.2 inches and CAPE peaking at ~2200 J/kg.
Therefore, WPC has placed our southeastern counties in a marginal
risk for excessive rainfall. Any training storms and slow moving
storms are capable of producing heavy rainfall tomorrow. By the
evening with the frontal boundary still stalled across our southern
counties, PoPs will remain near 30-60% overnight.

Regarding temperatures, tonight will be warm and muggy again with
lows reaching the mid to upper 70s inland and near 80 along the
coast. Tomorrow`s high temperature are expected to reach the lower
to mid 90s, a slight cool down thanks to the FROPA. But for tomorrow
night, optimistically, our northernmost counties will reach the
lower 70s and perhaps even the upper 60s for our most rural sites..
Gasp!

LONG TERM [Tuesday Through Sunday]...

By Tuesday morning, there will likely be precious little left of
the upper trough/weak front that was the story of the short term
forecast. We may have some lingering vorticity left aloft in a big
gap in the subtropical ridge, but it will be entirely cut off from
the main trough heading towards the Canadian Maritimes. We could
still see some showers and storms on Tuesday around the coast,
particularly if the boundary doesn`t make it as far south as
progged in the model guidance.

For the rest of the week and into the weekend, the main story will
be the rebuilding of the subtropical ridge, and the filtering in
of some drier air from the north behind the weak front. Both of
those will allow for afternoon temperatures to shoot up above
seasonal averages and into the middle to upper 90s away from the
coast (and even to around or just above 90 to the Gulf). While the
surface pressure gradient won`t be too tight, we should see enough
onshore flow - especially in the wake of 91L - to keep overnight
lows from falling out of the 70s...so if you like it a bit cooler,
we look to get the worst of both worlds there with both above
average temps overnight and during the day.

This setup should effectively cut off rain chances, at least over
the vast majority of the area late in the week. With high pressure
and precipitable water progged to fall to around or even below an
inch, convection seems a long shot. Depending on how deep the
drier air manages to work, guidance suggests we could still
squeeze out some showers/storms over the nearshore Gulf waters and
maybe, maaaaaaaybe right on the immediate coast, but that should
be about it.

As some deeper Gulf moisture returns to the region late in the
weekend or early next week, we should see higher humidity and
perhaps even some rain chances creeping back into the picture.

The potential fly in the ointment for this forecast? Invest 91L.
My forecast reflects the increasing confidence that the bulk of
the Gulf moisture (and any tropical cyclone, if there is one),
will ride east of the incoming boundary and get caught up in the
last little bit of influence from the passing northern stream
trough and take that break in the subtropical ridge right up into
the North/Northeast Gulf coast and Southeastern states. This seems
pretty clearly the most likely scenario, and the one that the
deterministic guidance strongly favors. But there are a couple
lonely members of the GEFS that really have something against
Freeport/Matagorda, and take 91L as a tropical cyclone over their
way. This very much has "SoYoureTellingMeTheresAChance.gif"
energy, but theoretically, yes, it is still on the table. We will
continue to monitor things and start raising a ruckus if things
change for our area - we just ask you recall that it is peak
hurricane season and are prepared accordingly.

MARINE...

Light to moderate winds are expected through the first half of the
week along with seas below three feet. Showers and thunderstorms
will be possible as a weak front drops into Southeast Texas
tonight and tomorrow, then rain chances will be relatively low for
much of the coming week along with a general land/seabreeze
diurnal pattern. Deeper Gulf moisture pushing back into the area
may start to boost rain chances at the end of next week. Mariners
should closely monitor the forecasts regarding potential tropical
cyclone development in the Gulf of Mexico towards the middle of
the week.

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 75 94 72 96 70 / 30 20 10 10 0
Houston (IAH) 78 94 75 94 74 / 30 50 40 20 10
Galveston (GLS) 80 91 79 90 79 / 30 40 60 30 20