Hurricane Idalia

[USCG RS]

22 minutes ago, Amped said:

The GFS on the other hand, just randomly decided to take it west of 18z for no apparent reason

NARRATOR: The GFS was acting normally.... 

[TPAwx]

So the 4-7 for TB includes +1-2 from king tide

[negative-nao]

Makes second Land Fall at Brunswick Georgia @ hr 240 on 0ZGFS

 

[GaWx]

0Z UKMET: after the 12Z UKMET had a 65 mile NW shift to Apalachee Bay, the 0Z is similar with no more than a slight E adjustment. So, most of the 12Z 65 mile NW shift is retained on the 0Z:

TROPICAL STORM IDALIA ANALYSED POSITION : 21.8N 85.1W

ATCF IDENTIFIER : AL102023

LEAD CENTRAL MAXIMUM WIND
VERIFYING TIME TIME POSITION PRESSURE (MB) SPEED (KNOTS)
-------------- ---- -------- ------------- -------------
0000UTC 29.08.2023 0 21.8N 85.1W 994 50
1200UTC 29.08.2023 12 23.6N 84.8W 993 51
0000UTC 30.08.2023 24 26.4N 85.1W 991 43
1200UTC 30.08.2023 36 29.2N 84.4W 987 47
0000UTC 31.08.2023 48 32.1N 82.5W 989 41
1200UTC 31.08.2023 60 34.0N 79.7W 994 40
0000UTC 01.09.2023 72 34.4N 76.0W 999 38
1200UTC 01.09.2023 84 34.2N 73.4W 1003 43
0000UTC 02.09.2023 96 33.4N 71.2W 1006 37
1200UTC 02.09.2023 108 30.8N 71.2W 1007 34
0000UTC 03.09.2023 120 30.9N 70.6W 1007 30
1200UTC 03.09.2023 132 30.3N 71.6W 1008 27
0000UTC 04.09.2023 144 30.2N 72.0W 1008 26
1200UTC 04.09.2023 156 CEASED TRACKING

[TriPol]

18 minutes ago, RU848789 said:

Can you elaborate on the physics of why a cyclone would be pulled east, relative to track forecasts, while approaching the west coast of FL?  Obviously the track moved east relative to the forecast track with Ian, especially in the last 1-2 days before landfall (which is where we are now), but one could imagine many reasons for such shifts.  Thanks.  

The trajectory of a tropical cyclone is predominantly governed by the ambient steering flow, a term that encapsulates the mean environmental wind field in which the cyclone is embedded. Deviations in this steering flow, such as an anomalously robust westerly component, can induce a corresponding easterly shift in the cyclone's track. Synoptic-scale anticyclonic systems also exert a significant influence on cyclone trajectory. The spatial orientation and dynamical strength of a high-pressure system situated to the north or northeast of a cyclone can act as a steering mechanism, directing the cyclone on a more westerly course. Conversely, a weakening or lateral displacement of the anticyclonic system may permit a more easterly trajectory for the cyclone. Upper-level atmospheric features, including troughs and ridges, further modulate cyclone tracks. An approaching trough from the westerly direction can effectively "capture" the cyclone, inducing a poleward and often eastward deflection from the originally forecasted path. It's imperative to acknowledge the inherent uncertainties associated with numerical weather prediction models. These uncertainties stem from various sources, including but not limited to, initial condition errors, approximations in the model's physical parameterizations, and the intrinsically chaotic nature of the atmosphere. While the fidelity of these models generally improves as the temporal proximity to the event decreases, unforeseen deviations in the cyclone's track can still manifest. Oceanic parameters, such as sea surface temperatures and underlying currents, can also exert an indirect influence on cyclone trajectory by modulating its intensity. An intensifying cyclone may interact differently with the ambient steering flow and other synoptic to mesoscale features, thereby altering its anticipated path. As the cyclone nears a landmass, the increased surface friction can induce structural changes in the cyclone's inner core, which may, in turn, result in last-minute alterations to its track. Additionally, microscale geographical features, such as bays, inlets, and even expansive urban areas, can impart localized effects on the cyclone's trajectory, although these influences are generally subordinate to the aforementioned larger-scale dynamical factors.

[Amped]

HAFS A now 933mb 131kts at landfall, at landfall close to a cat 5

[so_whats_happening]

26 minutes ago, RU848789 said:

Can you elaborate on the physics of why a cyclone would be pulled east, relative to track forecasts, while approaching the west coast of FL?  Obviously the track moved east relative to the forecast track with Ian, especially in the last 1-2 days before landfall (which is where we are now), but one could imagine many reasons for such shifts.  Thanks.  

 

5 minutes ago, TriPol said:

The trajectory of a tropical cyclone is predominantly governed by the ambient steering flow, a term that encapsulates the mean environmental wind field in which the cyclone is embedded. Deviations in this steering flow, such as an anomalously robust westerly component, can induce a corresponding easterly shift in the cyclone's track. Synoptic-scale anticyclonic systems also exert a significant influence on cyclone trajectory. The spatial orientation and dynamical strength of a high-pressure system situated to the north or northeast of a cyclone can act as a steering mechanism, directing the cyclone on a more westerly course. Conversely, a weakening or lateral displacement of the anticyclonic system may permit a more easterly trajectory for the cyclone. Upper-level atmospheric features, including troughs and ridges, further modulate cyclone tracks. An approaching trough from the westerly direction can effectively "capture" the cyclone, inducing a poleward and often eastward deflection from the originally forecasted path. It's imperative to acknowledge the inherent uncertainties associated with numerical weather prediction models. These uncertainties stem from various sources, including but not limited to, initial condition errors, approximations in the model's physical parameterizations, and the intrinsically chaotic nature of the atmosphere. While the fidelity of these models generally improves as the temporal proximity to the event decreases, unforeseen deviations in the cyclone's track can still manifest. Oceanic parameters, such as sea surface temperatures and underlying currents, can also exert an indirect influence on cyclone trajectory by modulating its intensity. An intensifying cyclone may interact differently with the ambient steering flow and other synoptic to mesoscale features, thereby altering its anticipated path. As the cyclone nears a landmass, the increased surface friction can induce structural changes in the cyclone's inner core, which may, in turn, result in last-minute alterations to its track. Additionally, microscale geographical features, such as bays, inlets, and even expansive urban areas, can impart localized effects on the cyclone's trajectory, although these influences are generally subordinate to the aforementioned larger-scale dynamical factors.

This! lol It has to do with pressures and land can produce lower pressures dayside than at night which will cause a low pressure to form over land versus over the ocean even on a small scale. Think of like a fujiwara type of effect interaction of two low pressure areas will cause them to spin around each other and landmasses can often act as the other low pressure to help this until upper levels become too much. Interaction of friction from land mass will also play a role in dragging the system in a certain direction. Remember the main goal is for the atmosphere to balance out so the usual negligible effects of friction become more prevalent in certain situations.

Thanks for taking the time to write this Tripol.

[CoralRed]

11 minutes ago, Amped said:

HAFS A now 933mb 131kts at landfall, at landfall close to a cat 5

Wow! I looked this HAFS A up and it is new, which most of you probably already knew. 

What do you all think about this prediction? It sure isn't what people down there want.

[WxSynopsisDavid]

22 minutes ago, CoralRed said:

Wow! I looked this HAFS A up and it is new, which most of you probably already knew. 

What do you all think about this prediction? It sure isn't what people down there want.

It’s plausible but this hinges on Idalia taking full advantage of the pristine environment ahead. This would indicate lack of shear upon landfall and minimal hindrance from the trough. Lastly, it would suggest Idalia does not have any eyewall replacement cycles before landfall which is plausible if forward speed increases.

[turtlehurricane]

26 minutes ago, CoralRed said:

Wow! I looked this HAFS A up and it is new, which most of you probably already knew. 

What do you all think about this prediction? It sure isn't what people down there want.

I think it's very likely to hit Category 4-5 intensity. The waters are just absolutely rocket fuel like never before, which is why the convection has been firing non-stop at full power. -- Also it got past Cuba without disruption and actually got way more organized, so now it has a solid 48 hours to rapidly intensify, when all it needs is 24 hours to hit Cat 4-5....

It's not even the best upper level environment ever. It would take alot of wind shear to stop it from going all the way though.

Eye popping out on satellite now. By the morning we will probably have a nice and big drilled-down eye https://weather.cod.edu/satrad/?parms=meso-meso1-13-24-1-50-1&checked=map&colorbar=undefined

[WxWatcher007]

34 minutes ago, CoralRed said:

Wow! I looked this HAFS A up and it is new, which most of you probably already knew. 

What do you all think about this prediction? It sure isn't what people down there want.

I think it shows what the absolute ceiling is should everything just take off between now and landfall, but it’s an outlier. 

I think it’s becoming extremely important as we get inside ~36 hours of landfall to analyze the structure and organizational pace of the system, and the inevitable wobbles that come with landfalling TCs. 

I like the NHC forecast and a landfall intensity between 105-115kt. 

[so_whats_happening]

12 minutes ago, turtlehurricane said:

I think it's very likely to hit Category 4-5 intensity. The waters are just absolutely rocket fuel like never before, which is why the convection has been firing non-stop at full power. -- Also it got past Cuba without disruption and actually got way more organized, so now it has a solid 48 hours to rapidly intensify, when all it needs is 24 hours to hit Cat 4-5....

It's not even the best upper level environment ever. It would take alot of wind shear to stop it from going all the way though.

Eye popping out on satellite now. By the morning we will probably have a nice and big drilled-down eye https://weather.cod.edu/satrad/?parms=meso-meso1-13-24-1-50-1&checked=map&colorbar=undefined

It really depends on how well the core can organize itself vertically. Definitely still some slanting going on aloft from the ULL along the Gulf coast. This should weaken a bit in the next day and I believe even some models showed it setting up a jet streak as we get close to landfall. We should know by tomorrow afternoon how well the core is stacked up. I would say cat 3 seems reasonable but if things set up just right cat 4 is attainable (cat 5 intensity is pretty difficult to attain)  with the amount energy in place.

Either way fun one to watch and really hope folks do take it serious down in Florida.

[beanskip]

Coarse maps on Euro annoyingly hard to extrapolate when the 36-hour mark is the key window. 

[GaWx]

33 minutes ago, turtlehurricane said:

I think it's very likely to hit Category 4-5 intensity. The waters are just absolutely rocket fuel like never before, which is why the convection has been firing non-stop at full power. -- Also it got past Cuba without disruption and actually got way more organized, so now it has a solid 48 hours to rapidly intensify, when all it needs is 24 hours to hit Cat 4-5....

It's not even the best upper level environment ever. It would take alot of wind shear to stop it from going all the way though.

Eye popping out on satellite now. By the morning we will probably have a nice and big drilled-down eye https://weather.cod.edu/satrad/?parms=meso-meso1-13-24-1-50-1&checked=map&colorbar=undefined

Isn't it more like 32 hours from now til landfall rather than 48 hours?

[Floydbuster]

6 minutes ago, GaWx said:

Isn't it more like 32 hours from now til landfall rather than 48 hours?

Probably a little less. I'm thinking 8-10am Wednesday. 

[RU848789]

30 minutes ago, beanskip said:

Coarse maps on Euro annoyingly hard to extrapolate when the 36-hour mark is the key window. 

This might help - the 0Z Euro moved landfall about 15-20 miles NW vs. 12Z today (was 976 mbar, 3 hours earlier)...

[Roger Smith]

I hope the model consensus proves accurate and this doesn't do a Charley-2004 style swerve towards Tampa Bay; in any case the impact there will be considerable given (a) we are closing in on full moon, (b) the track is close enough to permit strong TS level winds to blow for many hours from the south, all pointing to a considerable storm surge into the Bay. 

Even if the track was along the eastern edge of the cone, it would be bad news for the TBSP metro and any further east could be disastrous. An eastward jog means a considerably earlier landfall also. Instead of Wednesday morning near Cedar Key it would be closer to Tuesday midnight around Dunedin FL. Let's hope this does not happen. 

[SluggerWx]

Lighting in the core of Idalia now in last 4 frames from GOES. You can also see some towers going up.

Sent from my Pixel 6 using Tapatalk

[HillsdaleMIWeather]

Officially a Hurricane 

Nice blowup going on rn

[WxSynopsisDavid]

Finally appears that the centers are aligned and stacked. Vertical column significantly healthier and less tilted. Idalia now into the southern Gulf…and rapidly getting symmetrical. Idalia has that look now, as soon as the eye clears this thing bombs. Hopefully it’s when we have recon inside the storm.

[LovintheWhiteFluff]

000
WTNT45 KNHC 290859
TCDAT5

Hurricane Idalia Discussion Number  11
NWS National Hurricane Center Miami FL       AL102023
400 AM CDT Tue Aug 29 2023

Radar data from western Cuba indicates that Idalia is becoming 
better organized.  Most of an eyewall has formed, with much more 
curvature in the banding features and overall radar pattern.  
Satellite imagery also shows the center of Idalia firmly within the 
central dense overcast.  Thus, the initial wind speed is raised to 
65 kt, in accordance with the latest TAFB satellite classification.

The hurricane is accelerating northward this morning, now moving at 
about 9 kt.  Idalia should move faster to the north or 
north-northeast through landfall on Wednesday between mid-level 
ridging over Florida and a trough dropping into the western Gulf of 
Mexico.  There has been a westward shift in the model guidance 
overnight, perhaps due to the trough tugging Idalia more 
northward before taking a north-northeast turn.  It should be 
noted that the ECMWF ensemble shows many of its strongest members 
on the eastern side of its guidance envelope, which is a 
reasonable place to be given the synoptic pattern.  The new NHC 
forecast is adjusted a little to the west but is now east of the 
model consensus on the eastern side of the reliable model guidance. 
After Idalia leaves the eastern United States coastline, the track 
forecast becomes highly uncertain and little change was made to the 
previous forecast.  

With an inner core now present, the stage is set for Idalia to 
rapidly intensify before landfall. Shear should continue to lower 
over the cyclone as an upper-level trough departs the northeastern 
Gulf of Mexico and ridging builds closer to the cyclone.  These 
changes, combined with extremely warm and deep waters the hurricane 
will be traversing, all strongly point to rapid intensification.  
The new forecast is similar to the previous one, and confidence is 
increasing in an extremely dangerous major hurricane making landfall 
Wednesday along the west coast or Big Bend region of Florida.

KEY MESSAGES:

1. There is a danger of life-threatening storm surge inundation
along portions of the Florida Gulf Coast where a Storm Surge Warning
is in effect, including Tampa Bay and the Big Bend region of
Florida. Inundation of 8 to 12 feet above ground level is expected
somewhere between Chassahowitzka and Aucilla River.  Residents in
these areas should follow any advice given by local officials.

2. Hurricane conditions are expected within portions of the
Hurricane Warning area along the Florida Gulf Coast, with the
potential for destructive winds where the core of Idalia moves
onshore. Strong winds will also spread inland across portions of
northern Florida near the track of the center of Idalia.

3. Heavy rainfall is expected across portions of western Cuba and 
may produce areas of flash and urban flooding as well as landslides. 
Areas of flash and urban flooding, some of which may be locally 
significant, are expected across portions of the west coast of 
Florida, the Florida Panhandle, and southern Georgia beginning today 
into Wednesday, spreading into portions of the eastern Carolinas 
Wednesday into Thursday.


FORECAST POSITIONS AND MAX WINDS

INIT  29/0900Z 23.1N  85.0W   65 KT  75 MPH
 12H  29/1800Z 24.9N  84.8W   85 KT 100 MPH
 24H  30/0600Z 27.8N  84.3W  105 KT 120 MPH
 36H  30/1800Z 30.6N  82.9W   70 KT  80 MPH...INLAND
 48H  31/0600Z 32.7N  80.5W   50 KT  60 MPH...INLAND
 60H  31/1800Z 33.8N  77.5W   50 KT  60 MPH...OVER WATER
 72H  01/0600Z 33.9N  74.4W   50 KT  60 MPH
 96H  02/0600Z 33.3N  71.5W   45 KT  50 MPH
120H  03/0600Z 32.5N  70.5W   40 KT  45 MPH

$$
Forecaster Blake

[LovintheWhiteFluff]

[TriPol]

I'd wager a hefty sum that the likelihood of a landfall event in the Florida Panhandle is rather minimal, a hypothesis that I find somewhat at odds with the current projections from the National Hurricane Center. Since the case of Hurricane Charlie, Gulf-originating hurricanes to veer westward in their tracks, particularly when their initial trajectories are not aimed at Texas, Louisiana, or the Mississippi/Alabama coastline. This westward bias is often less pronounced when a robust anticyclonic system is situated over Florida, effectively serving as a protective barrier for the state's western coastline. One could argue that the NHC's forecasting methodology could benefit from a reevaluation of these recurrent patterns, especially in the context of recent advancements in ensemble forecasting and data assimilation techniques.

[Hotair]

Cuban weather radar indicates the eyewall of Idalia has closed off. Some RI is expected now.  Storm is moving at a healthy 14 mph which is nearly 2x as fast as day prior.  This is good as it limits the amount of uncertainty in the cone. 

[WxSynopsisDavid]

Just now, Hotair said:

Cuban weather radar indicates the eyewall of Idalia has closed off. Some RI is expected now.  Storm is moving at a healthy 14 mph which is nearly 2x as fast as day prior.  This is good as it limits the amount of uncertainty in the cone. 

Faster forward speed also limits the likelihood of eyewall replacement cycles being induced. This means the chances are increasing that Idalia rolls in at peak intensity on landfall.

[dan11295]

Tbh anything within 20 miles or so of current forecast is probably a best case scenario as far as damage. less surge for Tampa, but keeps it E of Apalachee Bay.

[WxWatcher007]

Recon is in the air and will soon provide critical structural and heading data on a strengthening Hurricane Idalia. 

Idalia has remained resilient in the face of moderate shear the last few days, gradually organizing and attempting to fire convection consistent enough to establish an inner core. This morning satellite and radar show that with shear decreasing Idalia is beginning to develop an inner core, with deep convection rotating around the center in the image above and an eye feature evident on radar. 

Recon will be important in assessing just how far along this inner core process has progressed, and whether there is still significant vortex tilting, which can still be possible if there's enough shear still present. My guess looking at the radar however, is that the vortex tilting that was an issue 24 hours ago is no longer enough to keep this from increasing its rate of intensification. 

According to CMISS analysis, shear is now in the favorable zone and expected to remain so until landfall.

As the trough sets up during Idalia's final approach, upper diffluence combined with increasing OHC and SSTs will almost certainly allow for rapid intensification. 

(SST image courtesy of Brian McNoldy)

Once rapid intensification occurs, and it is explicitly forecast by the NHC, we don't know where it'll stop. Time will be a limiting factor, but it cuts both ways. On on hand, there may not be enough time for the very high ceiling for Idalia to be reached. On the other, the lack of time means that a structural change, such as an Eyewall Replacement Cycle (ERC) is less likely. 

There is also modest but meaningful divergence in track.

The consensus among most guidance is to bring this further north, while the European Model and stronger members of the EPS have a further east landfall. It's been talked about around here but we will need to watch for deviations closely, as there are almost always small changes that have a substantial impact on sensible weather.

To be clear--nobody living in the region should merely look at the center track. Heavy rain, storm surge, and strong to destructive winds will be possible far outside the center. Given the parallel run up the west coast of Florida however, where the center landfalls is obviously important for surge and strongest wind impacts. The 06z GFS ticked ever so slightly east relative to 00z. 

Watch the organizational trends, pace of intensification, and the wobbles relative to long term heading.

It should be an active day.

[WxWatcher007]

Didn't add to the post, but recent microwave imagery suggests a nearly completed eyewall. 

[NorthHillsWx]

The only silver lining from the trends this morning is, if the current track holds, the storm could not have found a much more sparsely populated area than where it’s currently forecast to make landfall 

[Eskimo Joe]