Hurricane Idalia

[WxWatcher007]

There are probably some folks in this thread saying "woah woah slow down this hasn't even developed yet", and wondering why the thread is starting to take off after the early 12z guidance. There are a few reasons. 

First, although we don't have a well defined low yet, there's increasingly high confidence that one will form. You see that in the NHC outlook at 2pm but let's talk about why. 

With the latest satellite image above, you can see a clear, but broad circulation that is already in place. It's less broad than 18 hours ago, however. This is why the NHC has designated Invest 93L--with a viable area of focus we can get additional model guidance. 

The first thing you may hear a lot of people say is that the exceptionally warm waters in the western Caribbean and Gulf are the reason this has a higher ceiling. It's more complicated than that. In order to get a sense of the ceiling for a tropical system, you need to look at the entire environment, which consists of a few major elements. 

1. Thermodynamic environment (SSTs, OHC)

This is the easiest one to look at. Anomalies matter, but for in-situ analysis it's most helpful to examine current sea surface temperatures and oceanic heat content IMO. Both are exceptionally high. 

You can have boiling water, but if you don't have thunderstorms that can fire consistently without getting blown away, you won't have any kind of strong tropical system. We're currently seeing this with Tropical Storm Franklin in the Atlantic. 

2. Wind Shear

Shear can be complicated, because there are a number of ways it can be imparted and it can happen at various levels of the atmosphere. With shear, thunderstorms cannot organize efficiently, if at all, around a low pressure. An upper level low is producing a ribbon of shear just to the north of the invest, but that ULL has pulled west in the last 24 hours. 

Even more significant, there is an upper level anticyclone (ULAC) that promotes ideal low shear conditions and thunderstorm development. I believe this is why we're seeing the organization we have thus far. 

The guidance in the last 24 hours has trended away from higher shear, which would allow for modest to significant organization even if there is some land interaction with the Yucatan, which the guidance thus far has shown. With more shear, this could remain a more messy system, with convection unable to wrap around a low allowing it to develop an inner core. An inner core is key to significant intensification, and while it is unclear whether 93L attains that level of organization in the Gulf, it's something worth watching given the shear trends. 

On other flag is looking at the vorticity here. I posted it earlier, but look at how aligned the 850mb and 925mb areas of vorticity are. Having that kind of alignment allows for more efficient thunderstorm and low pressure organization. 

I would watch that ULL closely. While it could influence 93L negatively if closer, it could also allow for ventilation of an outflow channel as it heads north or NNE. 

4. Dry Air

Anytime you are talking about a US landfall, you have to watch for continental dry air entrainment. Dry air is like putting water in a gas tank. It'll cause problems with the engine. On the guidance we see dry air lurking, which could arrest development. However, if there's no shear to impart the dry air it won't slow organization down. 

The 00z Euro had the dry air lurking while today's GFS did not. 

The bottom line is that this is something worth watching if you are in the eastern Gulf and SE coast. No one is locking in a hurricane, but given the signals in the environment, any faster organizational pace increases the ceiling for 93L. At this time, it looks like a minimal tropical storm is the floor, which could happen if this hangs up over the Yucatan and finds a more sheared environment in the Gulf. That looks less likely given the current environmental analysis. 

It's also important to note that while everyone will be talking about wind, the potential track of this could bring storm surge into surge prone areas. That's something to watch closely as well for folks along the coast.

[mob1]

12Z Euro has it coming in near Crystal Springs. This thing really hauls once it clears the Yucatan, which might limit its potential. 

[WxWatcher007]

Right off the GA/SC border at 132. 

Not really worth opining much on right now, but I've noticed that the steering trend has kind of been all over the place with regard to the NE trough.  

[WxWatcher007]

Euro has the low head offshore eventually, but it's left behind by the trough, similar to 12z yesterday. That tells me there's some uncertainty with the long term track, though I'd favor OTS with either the original trough or a future one. 

72 to 192 on the 12z Euro

[Kevin Reilly]

Just now, WxWatcher007 said:

Euro has the low head offshore eventually, but it's left behind by the trough, similar to 12z yesterday. That tells me there's some uncertainty with the long term track, though I'd favor OTS with either the original trough or a future one. 

72 to 192 on the 12z Euro

I am sure it will get to about the latitude of say Cape Hatteras and head out that's been the pattern for a few months now along the East Coast. 

[nycwinter]

loving all the troughs summer is ending..

[MJO812]

1 hour ago, nycwinter said:

loving all the troughs summer is ending..

It's beautiful 

[WxWatcher007]

Here’s the first super ensemble 

The big caveat early is that until we have a well defined LLC this can shift.

The caveat for the Atlantic is that we still don’t know what will happen with late period troughing and Atlantic ridging—though I’d strongly favor OTS off the Carolina coast even at this stage due to climo.

[WxWatcher007]

No surprise, but the GFS is a little tighter with vorticity at 24 given the organizational trend we’ve seen today. 

[WxWatcher007]

Maybe a little more lopsided verbatim at 90 & 96, but it’s probably going to end up another relatively strong run. 

[cptcatz]

The convection is quite impressive and much further east than models had been showing. Watching these trends closely here in south Florida. 

[WxWatcher007]

Somewhat divergent steering pattern that needs to be worked out. 

[Windspeed]

We currently do not have a flight plan for Invest 93L tomorrow. They do mention 93L in the outlook for Sunday.

    2. OUTLOOK FOR SUCCEEDING DAY:
       A. CONTINUE 12-HRLY FIXES ON FRANKLIN.
       B. A POSSIBLE LOW LEVEL INVEST IN THE NORTHWEST CARIBBEAN SEA
          NEAR 20.0N 86.2W FOR 27/1800Z.
       C. A POSSIBLE NOAA G-IV SYNOPTIC SURVEILLANCE MISSION OVER
          THE GULF OF MEXICO DEPARTING KLAL AT 27/1730Z.

 

They may however have to move something up to tomorrow. I'm a little surprised at how quickly convection is consolidating and maintaining persistence. I think this disturbance may be ahead of modeling in organization. No we do not yet have an LLC. Still, if deep convection does persist in the same general location, it may not take that long to tighten the broader circulation into something. Both the GFS and ECMWF show the disturbance hanging around the Yucatan for several days before it lifts north. Neither really close a low until Sunday. The ECMWF meanders that low inland over the Yucatan for some time as well. Yet here we are with all this convection focusing pretty far east of those modeling trends. Intriguing to watch unfold.

[TheGhostOfJohnBolaris]

18z HWRF is a pretty dramatic change in intensity 

[Normandy]

Looking at trends tonight I’m upping my original call to a strong to major hurricane.  Convection is already expansive and cyclonic turning is very robust.  Further east development of convection leads me to think interaction with the Yucatan will be minimal.   This is developing in the same manner Harold did except it has more time over water.  I Like 110 mph into FL near Tampa. 

[hlcater]

Don’t feel confident enough to commit to a major hurricane until we get a better idea of what shear will look like as this transits the gulf. With a very dry continental airmass lurking just west of the storm impacts of any shear could be exacerbated 

[WxWatcher007]

Right. Having a higher ceiling doesn’t mean it gets reached. Land interaction and sneaky shear imparting dry air, along with limited time over the Gulf could easily hold this back. 

Also, it takes time to organize an inner core, which is an absolute essential for higher end development. It’s too early to say exactly where this is headed. 

[Normandy]

It’s not unreasonable.  Guidance that keeps this away from the Yucatan have a strong system hitting land.  If the low stays offshore and has 90 hours over water, getting a strong to major hurricane isn’t even a high ceiling.  Let’s see how it plays out though I staked my claim and the crow may come!

[Kmlwx]

6 minutes ago, Normandy said:

It’s not unreasonable.  Guidance that keeps this away from the Yucatan have a strong system hitting land.  If the low stays offshore and has 90 hours over water, getting a strong to major hurricane isn’t even a high ceiling.  Let’s see how it plays out though I staked my claim and the crow may come!

I don't think anybody said "unreasonable" 

It's simply too early to start making calls like "110mph into Tampa" 

[NorthHillsWx]

A high ceiling means very little in the grand scheme of things and that is totally off the assumption this gets a coherent core together about the time it enters the gulf. Without engaging in hyperbole, this system needs to be watched with extreme caution because the ingredients are present for a strong hurricane to impact the gulf coast without the usual week-long buildup 

[BooneWX]

Someone correct me if I’m wrong but is the synoptic setup eerily similar to Ian? If I remember correctly, we spent a day or two projecting a modest storm with Ian at best and then it became clear that it would tap into a jet streak and warm waters. 

[WxWatcher007]

18z EPS
 

[GaWx]

11 minutes ago, BooneWX said:

Someone correct me if I’m wrong but is the synoptic setup eerily similar to Ian? If I remember correctly, we spent a day or two projecting a modest storm with Ian at best and then it became clear that it would tap into a jet streak and warm waters. 

Ian formed in the C Caribbean and became a H way down below the Caymans 2.5 and a MH 1.5 days before SW FL landfall.

[BooneWX]

1 minute ago, GaWx said:

Ian formed in the C Caribbean and became a H way down below the Caymans 2.5 days before SW FL landfall.

Yea not sure which storm I’m thinking of. The setup is giving me deja vu and not in a good way for some reason. 

[cptcatz]

12 minutes ago, BooneWX said:

Someone correct me if I’m wrong but is the synoptic setup eerily similar to Ian? If I remember correctly, we spent a day or two projecting a modest storm with Ian at best and then it became clear that it would tap into a jet streak and warm waters. 

Ian had the biggest lead up since Irma.  Go check out the Ian thread again... we were discussing a major hurricane in the Gulf while it was still an invest over a week before landfall.

[cptcatz]

2 minutes ago, BooneWX said:

Yea not sure which storm I’m thinking of. The setup is giving me deja vu and not in a good way for some reason. 

Michael?

[BooneWX]

2 minutes ago, cptcatz said:

Michael?

Thank you. That’s it. The forgotten 5. I recall Michael not earning much attention early on and then absolutely going nuclear in the last 24 hrs when the shear was in a more favorable orientation. 

[yoda]

 

[cptcatz]

2 minutes ago, BooneWX said:

Thank you. That’s it. The forgotten 5. I recall Michael not earning much attention early on and then absolutely going nuclear in the last 24 hrs when things the shear was in a more favorable orientation. 

Yep, modeling totally blew the initial intensity forecast...

[CheeselandSkies]

2 hours ago, TheGhostOfJohnBolaris said:

18z HWRF is a pretty dramatic change in intensity 

Even has it down to 959MB right on the coast at FH111...too bad there's not a sim IR frame for that FH.