2024 Hurricane Season Discussion

[Cpv17]

So not only has the named storm number forecast been a bust this season, but the ACE numbers forecast has also been a bust. This is not me poo-pooing the forecasts. Everything was in place. What did they/we not foresee? All the dry air and shear that has been so prevalent. Had this been 2005 or 2020, Beryl and Francine would’ve been Cat 4/5 hurricanes by now.

Thank God for shear and dry air.

I’m sure we’ll find out the real culprit at some point down the line. Just a true head scratcher.

[Stratton20]

Im for once glad both forecasts turned out to be a bust, beryl was enough for me

[tireman4]

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Site logo image The Eyewall
Francine exits as attention shifts to a bunch of middling Atlantic action
By Matt Lanza on September 12, 2024

Headlines
Francine will likely produce flash flooding, particularly in Alabama and Tennessee over the next couple days.
We recap Francine below with info on how AI modeling did and why New Orleans saw worse conditions than expected earlier in the day.
The Atlantic looks more active than it actually is, with two invests that should not develop and one depression that may become a named storm and stay out at sea.
A subtropical or tropical system may form off the Southeast coast next week.
Thanks to folks in Louisiana that followed along with us through Francine, and we hope you'll spread the word and stick with us. We did experiment with a new format yesterday by updating the AM post instead of pushing new posts all day. Any feedback is appreciated.

Francine recap
With Francine down to depression status and dissipating, I want to just point out a couple odds and ends related to the storm.

Current forecast

The rainfall forecast for the rest of the week is pretty stout in the Southeast, with as much as 6 to 8 inches of rain possible across portions of Alabama and Tennessee.


Rainfall over the next 3 days from Francine's remnants could drop as much as 6 to 8 inches or more across Alabama and portions of Tennessee, leading to flash flooding. (NOAA WPC)
Flash flooding and localized severe weather will be the primary impacts of Francine's remnants over the interior. A good idea to remain weather away, particularly between Birmingham and Huntsville due to flooding.

AI modeling & ICON scores a big win

I went through and assessed the 15 model runs leading up to landfall from various models with Francine. Keep in mind that the landfall point is not the only variable that matters, but it's an important one. And one thing you cannot tolerate as a forecaster is a lot of whipping around within the models. Enter the European AI model, the AIFS. Here are the 15 runs leading up to landfall with Francine:


AIFS model 15 runs leading up to landfall with Francine.
This is a remarkable feat of stability. The AIFS showed landfall between Vermilion Bay and Grand Isle run after run after run. Ultimately, it came in on the eastern half of that spread, but the consistency was some of the best I have ever seen with respect to a tropical system. The timing and intensity bounced around a bit, but not so much as to make the tool useless. It had immense value, and it's one of the reasons we were very bullish about this not being a serious Texas concern. This was a lesson learned from Beryl. And not to be outdone, the ICON also showed a healthy amount of stability run to run in terms of track.


ICON model for 15 runs leading up to landfall with Francine.
While the ICON kept western Louisiana in play for a while, it too corrected east in time. This, combined with its performance during Beryl (as well as last week with Invest 90L) made it another valuable tool. Will these models fail in the future? Yes, all models do. And the ICON remains prone to spurious tropical systems that never end up happening. But at this point, I think there's a lesson to be taken from this as a meteorologist. particularly when the models show this sort of stability. The GFS and Euro operational model (and the ensemble guidance) also performed respectably, but those models showed less consistency run to run than did the ICON and AIFS.

Last minute lurch to New Orleans

In yesterday's morning post, we noted the forecast for New Orleans showed maximum wind gusts forecast to be 57 mph. They gusted to 78 mph. The reason was twofold. First, the storm had a quick late burst of intensification (in the face of wind shear no less) on approach to landfall. This led to an eastward shift at the last minute. Instead of coming in right at Atchafalaya Bay, it came in a more of a slanted angle just east of there. This, coupled with the stronger intensity pushed the eyewall into the New Orleans metro area leading to wind gusts of 60 to 80 mph. Hurricane forecasting remains imperfect.

Of note, thus far the highest wind gust I have seen is 96 mph in Dulac, LA. There were two 100 mph gusts south of Burns Point, LA, but those I believe were on elevated oil platforms which would have higher winds than at surface level. The highest rain total was in Mandeville, at just over 9 inches. New Orleans saw over 8 inches in the city. Officially, they reported 7.33 inches at the airport, the 9th wettest day on record there.

Atlantic action amplifies
Turning our attention back to current matters, let's take a look at the Atlantic this afternoon.


It's less busy than it looks, really.
There are two invest, a tropical depression, and an area to watch in the Atlantic today. We'll cover the area to watch below. But in the meantime, Invests 92L and 94L just east of the Caribbean are not really of any concern. Those should dissipate before acquiring the ability to develop. So nothing to see here right now.

Meanwhile, Tropical Depression 7 will probably make an attempt to become Tropical Storm Gordon, which somehow hasn't been retired, despite being used since 1994 in perhaps its most memorable iteration. But Gordo will probably remain out at sea.


TD 7/future Gordon's track.
Otherwise, the Atlantic is quiet for now.

Southeast system next week?
Things may get interesting next week, to an extent, off the Southeast coast as a remnant cold front could help spawn a disturbance off the Florida, Georgia, or South Carolina coast.


This morning's GFS model shows a disturbance off the Carolina coast as early as Friday night.
Exactly how this evolves is a bit tricky since remnant fronts tend to be a little difficult to exactly predict. But in general, watch for a disturbance to form off the Southeast coast. Because it's forming from a front, it would probably be non-tropical or "subtropical" in nature. It may have some time to develop into a tropical system over the Southeast coast's warm waters early next week before likely coming ashore somewhere in the Carolinas. Intensity-wise, it's a bit early to get too cutesy, but this would probably be slow to organize and develop, so it would probably be a tropical storm at most. But regardless, watch for heavy rain risk next week in the Southeast due to this system. More to come.

We will leave it there for now, but tomorrow we'll talk a bit more about the longer-range and why things may start getting busy again by the end of September.

Comment

[Stratton20]

I am pretty confident our season is getting close to being done here. i see at least a couple of weak fronts moving down over the next few weeks, its mid september, not fully ruling out another texas threat, but odds are definitely decreasing on that, good, we don’t need anymore coming this way!

[don]

Im for once glad both forecasts turned out to be a bust, beryl was enough for me

Agreed!

[Pas_Bon]

I am pretty confident our season is getting close to being done here. i see at least a couple of weak fronts moving down over the next few weeks, its mid september, not fully ruling out another texas threat, but odds are definitely decreasing on that, good, we don’t need anymore coming this way!

Agreed. I would be shocked if the Upper Tx Coast had any more threats this year.
Bring on Fall. Please.

[tireman4]

000
WTNT33 KNHC 161451
TCPAT3

BULLETIN
Potential Tropical Cyclone Eight Advisory Number 4
NWS National Hurricane Center Miami FL AL082024
1100 AM EDT Mon Sep 16 2024

...STRONG WINDS AND HEAVY RAINS CONTINUE SPREADING OVER PORTIONS
OF SOUTHEASTERN NORTH CAROLINA...


SUMMARY OF 1100 AM EDT...1500 UTC...INFORMATION
-----------------------------------------------
LOCATION...32.9N 78.3W
ABOUT 70 MI...115 KM SSW OF CAPE FEAR NORTH CAROLINA
ABOUT 95 MI...150 KM E OF CHARLESTON SOUTH CAROLINA
MAXIMUM SUSTAINED WINDS...50 MPH...85 KM/H
PRESENT MOVEMENT...NNW OR 330 DEGREES AT 5 MPH...7 KM/H
MINIMUM CENTRAL PRESSURE...1005 MB...29.68 INCHES


WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY:

The Tropical Storm Warning from Edisto Beach to South Santee River,
South Carolina has been discontinued.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT:

A Tropical Storm Warning is in effect for...
* South Santee River, South Carolina northward to Ocracoke Inlet,
North Carolina

A Tropical Storm Warning means that tropical storm conditions are
expected somewhere within the warning area, in this case within the
next 6 to 12 hours.

For storm information specific to your area, including possible
inland watches and warnings, please monitor products issued by your
local National Weather Service forecast office.


DISCUSSION AND OUTLOOK
----------------------
At 1100 AM EDT (1500 UTC), the disturbance was centered near
latitude 32.9 North, longitude 78.3 West. The system is moving
toward the north-northwest near 5 mph (7 km/h). A northwestward
motion is expected during the next day or two. On the forecast
track, the low will reach the coast of South Carolina this afternoon
and then move inland across the Carolinas tonight through early
Wednesday.

Surface observations indicate that maximum sustained winds are near
50 mph (85 km/h) with higher gusts. Little change in strength is
expected before the system reaches the coast, but steady weakening
is anticipated after the system moves inland. The low is forecast
to dissipate over the Carolinas by early Wednesday.
* Formation chance through 48 hours...medium...40 percent.
* Formation chance through 7 days...medium...40 percent.

Tropical-storm-force winds extend outward up to 175 miles (280 km)
from the center. A National Ocean Service station at Wrightsville
Beach, North Carolina, recently reported a sustained wind of 51 mph
(81 km/h) and a gust of 67 mph (107 km/h).

The estimated minimum central pressure is 1005 mb (29.68 inches).


HAZARDS AFFECTING LAND
----------------------
Key messages for Potential Tropical Cyclone Eight can be found in
the Tropical Cyclone Discussion under AWIPS header MIATCDAT3 and WMO
header WTNT43 KNHC.

WIND: Tropical storm conditions are expected within the warning
area for the next several hours.

STORM SURGE: The combination of a storm surge and the tide will
cause normally dry areas near the coast to be flooded by rising
waters moving inland from the shoreline. The water could reach the
following heights above ground somewhere in the indicated areas if
the peak surge occurs at the time of high tide...

South Santee River, SC to Oregon Inlet, NC... 1-3 ft
Neuse and Bay Rivers, NC... 1-3 ft
Pamlico and Pungo Rivers, NC... 1-3 ft

The deepest water will occur along the immediate coast near and to
the east of the landfall location, where the surge will be
accompanied by large and dangerous waves. Surge-related flooding
depends on the relative timing of the surge and the tidal cycle, and
can vary greatly over short distances. For information specific to
your area, please see products issued by your local National Weather
Service forecast office.

For a complete depiction of areas at risk of storm surge
inundation, please see the National Weather Service Peak
Storm Surge Graphic, available at
hurricanes.gov/graphics_at3.shtml?peakSurge.

RAINFALL: Potential Tropical Cyclone Eight will bring 4 to 8 inches
of rainfall, with isolated totals near 10 inches, across portions of
northeast South Carolina and southeast North Carolina into tonight.
Across the remainder of North Carolina, 2 to 4 inches of rainfall,
with isolated totals near 6 inches, is expected through Tuesday.
Over much of Virginia, 1 to 3 inches of rainfall, with locally
higher amounts, is expected tonight through Wednesday. This rainfall
could lead to a risk of flash and urban flooding and minor river
flooding.

For a complete depiction of forecast rainfall associated with
Potential Tropical Cyclone Eight, please see the National Weather
Service Storm Total Rainfall Graphic, available at
hurricanes.gov/graphics_at3.shtml?rainqpf and the Flash Flood Risk
graphic at hurricanes.gov/graphics_at3.shtml?ero.

TORNADOES: A few tornadoes may occur through this evening across
eastern North Carolina.

SURF: Swells are forecast to affect portions of the coast of the
southeastern United States through Tuesday. These swells are likely
to cause life-threatening surf and rip current conditions. Please
consult products from your local weather office.


NEXT ADVISORY
-------------
Next intermediate advisory at 200 PM EDT.
Next complete advisory at 500 PM EDT.

$$
Forecaster Reinhart

[tireman4]

000
WTNT32 KNHC 161447
TCPAT2

BULLETIN
Tropical Depression Gordon Advisory Number 21
NWS National Hurricane Center Miami FL AL072024
1100 AM AST Mon Sep 16 2024

...GORDON SHOWING LITTLE CHANGE IN STRENGTH...


SUMMARY OF 1100 AM AST...1500 UTC...INFORMATION
-----------------------------------------------
LOCATION...19.1N 48.1W
ABOUT 985 MI...1580 KM E OF THE NORTHERN LEEWARD ISLANDS
MAXIMUM SUSTAINED WINDS...35 MPH...55 KM/H
PRESENT MOVEMENT...W OR 270 DEGREES AT 7 MPH...11 KM/H
MINIMUM CENTRAL PRESSURE...1006 MB...29.71 INCHES


WATCHES AND WARNINGS
--------------------
There are no coastal watches or warnings in effect.


DISCUSSION AND OUTLOOK
----------------------
At 1100 AM AST (1500 UTC), the center of Tropical Depression Gordon
was located near latitude 19.1 North, longitude 48.1 West. The
depression is moving toward the west near 7 mph (11 km/h). A
gradual turn toward the west-northwest and northwest at a slower
forward speed is expected during the next day or so, followed by
a turn toward the north and north-northeast by Wednesday.

Maximum sustained winds remain near 35 mph (55 km/h) with higher
gusts. Little change in strength is forecast during the next 48
hours.

The estimated minimum central pressure is 1006 mb (29.71 inches).


HAZARDS AFFECTING LAND
----------------------
None.


NEXT ADVISORY
-------------
Next complete advisory at 500 PM AST.

$$
Forecaster Pasch

[biggerbyte]

Well, the GFS looks interesting today.

[Ptarmigan]

https://x.com/webberweather/status/1834675543817732353

Eric Webb
@webberweather
Jun-Jul-Aug North Atlantic Oscillation (NAO) index correlation w/ N Atlantic SLP (left), & Jun-Jul-Aug N Atlantic SLP anomalies for non-El Nino hurricane seasons w/ < 100 ACE (n = 14 years) (top right), and this year's N Atlantic SLP anomalies (bottom right).

While this year's Hurricane Season has been unexpectedly quieter than usual basin-wide, the overall circulation pattern we've seen this summer (a very strong +NAO) is pretty consistent w/ most "quieter-than-expected" non-El Nino Atlantic Hurricane Seasons. While the influence of this year's poleward shifted Africa ITCZ, deep-layer tropical stability issues, and AGW to a lesser degree have been garnering most of the attention/blame of late, I'd argue the the influence of "internally" generated variability extratropics, like the +NAO, is just as if not potentially more important here in dictating this season's "unexpected" outcome... (1/2)

The North Atlantic Oscillation (NAO) has been in strong positive territory. That tends to make hurricane season less active. The areas outside of the tropics should be looked at as a factor.

[Ptarmigan]

https://x.com/webberweather/status/1835172468308242652

Eric Webb
@webberweather
Another reason I suspect this year's "busted" Atlantic Hurricane Season forecasts were forced largely by "internal" variability from the extratropics rather than say a poleward shift in the Africa ITCZ (tho that played a role too!):

When I go back and look at climate model forecasts for this Hurricane Season, what really strikes me is they correctly predicted the potential for very (& possibly record) low SLP over NE Africa & Mediterranean, which ultimately helped drag the ITCZ anomalously northward over the Sahel & Sahara.

What about the record low SLP over Greenland/Iceland associated w/ the +NAO? It was grossly underestimated to put it lightly w/ only a slightly higher chance for lower tercile SLP.

Oops.

Eric Webb believes that lower pressure over Northeast Africa and Mediterranean Sea help bring the Inter Tropical Convergence Zone (ITCZ) further north than usual. There was lower pressure over Greenland and Iceland.

[Ptarmigan]

https://x.com/philklotzbach/status/1833992602565361727

Philip Klotzbach
@philklotzbach
#Francine has made landfall as a Category 2 #hurricane in Louisiana - the 3rd continental US hurricane landfall this year (Beryl, Debby). 8 other years since 1900 have had 3+ continental US hurricane landfalls by 9/11: 1915, 1916, 1933, 1934, 1985, 2004, 2005, 2020.

2024 had 3 hurricanes make landfall on American by September 11. Beryl, Debby, and Francine.

[srainhoutx]

Keep a close eye next week for potential Tropical Troubles in the Gulf. All of the Global models are sniffing out possible development.

[DoctorMu]

Keep a close eye next week for potential Tropical Troubles in the Gulf. All of the Global models are sniffing out possible development.

Yep. Euro, Canadian, and GFS all have a CAT 2-4 storm in the eastern Gulf.

[DoctorMu]

We're not out of the woods, because the TS could be drawn toward the FROPA and trough as our mini-Death Ridge breaks down.

Eventually the TS and FROPA would join forces.

[DoctorMu]

Fortunately, Francine hit the sweet spot of the Atchafalaya basin swamp and did less damage than expected. Folks in the NOLA - BR corridor are still shook by Ida which was more destructive than predicted.

[Stratton20]

At this time i see no reason to believe this system would pose a threat to the western gulf, models agree on a trough and associated FROPA sweeping through the central US that should easily keep this away from texas, not concerned about it in the least bit

[Pas_Bon]

At this time i see no reason to believe this system would pose a threat to the western gulf, models agree on a trough and associated FROPA sweeping through the central US that should easily keep this away from texas, not concerned about it in the least bit

I am slightly concerned about any timing of the front, but I think the chances for an impact in SE Tx are pretty low.

[tireman4]

A quiet balance of the week before Caribbean shenanigans next week
September 17, 2024 at 1:47 pm by Matt Lanza
Headlines
After flooding and strong winds in North Carolina, we look at why PTC 8 never became Tropical Storm Helene.
Caribbean mischief is likely next week with details TBD. But it’s clear something is probably going to try and develop.
How does an unnamed storm behave so much like a tropical storm?
Cleanup is underway in North Carolina after yesterday’s deluge from an unnamed potential tropical cyclone. We’ve gotten some questions as to how a storm with very obvious tropical storm conditions goes unnamed? Well, the point of the “Potential Tropical Cyclone” designation is to account for the fact that a certain system may not meet the technical requirements to be classified as tropical in nature or, alternatively, it may be close enough to land and unformed yet that it requires watches and warnings. The Carolinas needed watches and warnings for sure yesterday, and thus the PTC designation met the former definition that it fell short on account of technicalities.


PTC 8 analyzed on a surface map yesterday afternoon with a stationary front to its east and cold front to its south, which is indicative of a storm that is non-tropical in nature. (NOAA WPC)
In this specific case, PTC 8 was a cyclone, but it was not tropical in nature. It had fronts nearby, a rather clear designation of a non-tropical storm. This was more akin to a nor’easter type storm that we frequently see in the fall, winter, and spring months on the East Coast. Still, the impacts were virtually identical to a tropical storm and to most people that is likely what they assume they were hit with yesterday in North Carolina. The PTC products work in that respect as intended. However, there is still some inherent clunkiness in communicating the situation, which is why we tend to focus almost exclusively on impacts. For PTC 8, we had noted even late last week that this was going to probably be a rain and windmaker for the Carolinas, and even though the coverage of total rainfall was a bit surprising, for the most part this played out as expected.


Rain totals and radar estimates from yesterday’s rain in southeast North Carolina.
Rain totals were historic and exceptional across Brunswick County and portions of southern New Hanover County, NC. The gradient between Wilmington Airport (north of Wilmington) and Carolina Beach was remarkable. That’s about 16 inches difference over 16 miles. The isolated nature of some of these rain totals can really make a forecast tough. It’s just as plausible that this could have been closer to Wrightsville Beach than Carolina Beach. It’s just the nature of tropical systems.

Our thoughts are with the folks that were flooded yesterday that can hopefully clean up in a reasonable amount of time. We’ve seen a number of cases of extreme flooding this month: Myanmar, Europe, even parts of Manitoba, North Dakota, and Minnesota yesterday. All this is consistent with more extreme rainfall that is expected in a warming climate, though to what specific extent that is contributing is TBD. Most recently, August was the warmest recorded month in our historical record however.

Caribbean watch on for next week
We’ve been discussing reasons why we expect Atlantic activity to tick up to close September. The most specific example we have of this is what is expected in the Caribbean next week. We’re beginning to see operational models more frequently go a little crazy with development there. But it seems consistent across most operational models. The GFS, Euro, ICON, and AI modeling from ECMWF all show tropical development in the northwest Caribbean with various tracks west or north. There is no consistency in track, but there is consistency in development. This tells me that we’re likely to see something happen next week.


A strong signal on something developing in the NW Caribbean next week, but there are few specifics on details, which leaves uncertainty high.
We see this on the GFS ensemble as well above, which shows a pretty healthy signal for development but also a significant spread in outcomes next Tuesday evening, with potential low pressure centers anywhere from Cuba to the Caribbean to the eastern Gulf of Mexico.

We have a lot of Texas and Louisiana readers here on the site since we’re based in Houston, so I want to make a quick comment about potential here. Right now, with a potential trough off the Southeast coast, no significant westerly steering component available, and the potential for a southward moving front in Texas or the Deep South, the most likely path of least resistance would probably be northward or northeastward.


Upper air pattern supports something likely to come broadly north or northeast out of the Caribbean next week.
That’s not to say folks in Texas and Louisiana should ignore this; you should not. However, sitting here today, I’d be more likely to say the odds of impacts are greater in Florida than the rest of the Gulf Coast. We’ll see this sort of show itself a bit more in the coming days. Notably, given that this is developing off a Central American Gyre type circulation, there is historical precedent for high uncertainty in this setup, which is why I don’t want anyone to write this off yet. But I think Florida needs to watch this more closely than elsewhere, and I want to highlight that for our Florida readers.

Elsewhere, there may be a signal for a new disturbance off Africa to form later next week as well, but that’s days away from any land and is not a concern right now. Gordon has degenerated into an open wave in the Atlantic but could reform at some point this weekend or so. Still, it’s no threat to land. So for now, the only system to concern ourselves with will be next week in the Caribbean.

I’ve generally been against naming winter storms, but considering your comments on PTC8, it made me wonder if maybe people just won’t bother to take any weather event seriously if it hasn’t been given a familiar name.

[DoctorMu]

At this time i see no reason to believe this system would pose a threat to the western gulf, models agree on a trough and associated FROPA sweeping through the central US that should easily keep this away from texas, not concerned about it in the least bit

I am slightly concerned about any timing of the front, but I think the chances for an impact in SE Tx are pretty low.

Yes, Timing is everything. We're well beyond a 5-day sensible forecast.