WxWatcher007

Yeah, it looks like the ERC is finishing up, and this is the best it has looked on satellite yet. That said, we need to see how the winds respond. It looks like they’re gradually coming up, at least at FL, and another center pass is imminent so we’ll see how the pressure trend continues. NHC has ticked the exact track a touch east, with the center expected right over Tallahassee now.

The 96-frame GOES-E loop shows just how much organizational progress has been made in just the last few hours. Deeper convection, much more symmetrical, and a less diffuse look. Will be interesting to see what recon finds as convection looks to finally fully wrap upshear.

If not for the globals, I would’ve repositioned west by now. Will reassess in the morning and early afternoon.

I think it’s ok but only if the inner core can completely close. Otherwise any intensification will remain gradual. Once the eye can permanently close and wrap convection around it, this’ll take off. The runway is still clear, the system just has to put everything together.

IR looks to be improving markedly the last hour or two, but let’s see if it actually holds.

Tropical Storm Isaac. First forecast has it peak near hurricane strength. Basin finally lighting up.

Pre-Helene tracking that was an area I identified as having a shot.

A new high risk (rainfall) for part of the panhandle tomorrow. FFW west of Tallahassee tonight. Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 853 PM EDT Wed Sep 25 2024 Day 2 Valid 12Z Thu Sep 26 2024 - 12Z Fri Sep 27 2024 ...THERE IS A HIGH RISK OF EXCESSIVE RAINFALL IN PORTIONS OF THE SOUTHERN APPALACHIANS AND NORTHEAST GEORGIA... ..LIFE-THREATENING FLASH FLOODING LIKELY OVER THE SOUTHERN APPALACHIANS AND PORTIONS OF THE SOUTHEAST.. The extensive period of heavy rainfall during the D1 period will continue through D2 across portions of the interior Southeast U.S with a primary focus across the Southern Appalachians where the back end of our predecessor rainfall event (PRE) will still be occurring. Further to the south, all eyes turn to Hurricane Helene as the storm continues to move quickly through the Eastern Gulf within the weakness created by the trough to the north. The northern extent of Helene's tropical moisture will begin nosing into the Gulf coast with PWAT anomalies steadily rising from 1-2 deviations above normal to as high as 4 deviations above normal by the time it makes landfall on Thursday evening. Despite a fast forward propagation, copious amounts of rainfall will impact the Florida Panhandle over to the Big Bend with the feeder bands on the eastern flank of the cyclone impacting the coastal areas of the Florida Peninsula. Rainfall amounts between Panama City to Tallahassee will reach between 8-12" with local maxima of up to 15" possible within the axis of Helene's landfall as the storm moves almost due north, perpendicular to the coastal plain. For this reason, a High Risk was added to portions of the Florida Panhandle/Big Bend, including the Tallahassee area, as well as across Apalachicola. By Thursday night into Friday morning, Helene will continue making steady progress northward with a large rain shield capable of dropping 3-6" of rainfall within the core of the cyclone in short periods of time. A swath of 6+ inch totals will progress northward, eventually cascading into the Atlanta metro and surrounding locales generating a higher threat of flash flood potential within the urban corridor. Areas in the path of Helene will undoubtedly see significant flood potential with small rivers and streams likely becoming inundated very quickly to exacerbate the flood threat within the rural areas of Georgia. The recent HREF blended mean QPF footprint is robust for the period with a large areal extent of 5+ inches with the secondary maxima positioned across Northeast GA where the next round of significant rains will approach with Helene's core making an approach. The situation across the Southern Appalachians is becoming increasingly severe with regards to the ongoing flash flood threats from the PRE and eventually with the approach of Helene's core as the cyclone moves up through Western GA. This will place the eastern quadrant of the cyclone across Central and Northern GA with a strong, prevailing east southeast flow expected to bank against the terrain situated over North GA through the Western Carolinas, a mechanism for maximizing ascent within a deep tropical moisture plume that will enhance rainfall rates for several hours moving through late Thursday night into Friday morning. The 12z HREF mean QPF output continued to signal for prospects of 3-6+ inches within a short time frame as the core of higher PWATs advect into the region and douse the Southern Appalachians in another round of significant rainfall with rates generally steady between 1-2"/hr with some small probabilities (10-15%) for hourly rates pushing close to 3"/hr in the stronger convective cores embedded in the precip shield. The HREF neighborhood probability for >5" has peaked at 90+% for the Southern Appalachian front, a signal reserved for only the most impactful events, correlating well with the EAS signal of >90% as well for at least 3". The combination of multiple periods of heavy rainfall with elevated rates likely thanks to Helene will produce significant, life- threatening flash flooding across the area over Northeastern GA through the Blue Ridge of SC and NC, including areas in and around Asheville and to the west of Greenville- Spartanburg in Upstate SC. Several landslides due to the prolific rainfall are very likely with a history of these types of events producing catastrophic damage from both flooding and the prospects of land and mudslides within the complex terrain. For these purposes, and in coordination with the GSP and FFC WFO's, the High Risk was maintained and expanded further southwest to just northeast of the Atlanta metro to account for the most significant signals for flash flood prospects during the period. Considering the scope of Helene's size, the flash flood threat will not be relegated to a small corridor like we see in some tropical events. The trough to the west will play a pivotal role in the steering mechanism for Helene as the storm approaches the latitude of North GA, eventually pulling the cyclone more northwest towards the back end of the forecast period. Due to the progression, there is a growing consensus within the deterministic of the heavy rain threat also shifting into Northern AL with the area in and around Huntsville to the TN state line becoming more favorable for flash flooding potential within the western flank of the cyclone. The signal is not as prolific as the Southern Apps or where Helene makes landfall, but the probability and QPF fields certainly depict a significant amount of rain (3-5") within a time frame generally between 4-8 hrs prior to the end of the forecast period. This swath will extend across Eastern AL and Western GA up through Northern AL, following the western periphery of the cyclone as it moves north then northwest. The heavy rain will expand into Southern TN before the end of the forecast period with more rain anticipated in the Tennessee Valley after D2. Because of the growing consensus in the heavy rainfall across the above areas, the MDT risk was expanded further west and northwest into Alabama and over the southern fringes of TN. A large SLGT and MRGL risk will encompass a large area of the Southeast and Southern Mid Atlantic as well as the outer bands of Helene are forecast to impact the region with locally heavy rainfall possible as is customary with these types of tropical evolutions. Kleebauer

I’d resist the urge to play the over performing/underperforming game. It can’t intensify at a rapid pace (again) until the next stage of the organizational phase is complete. That takes time and is not linear in many cases.

That would be the ultimate…except it’ll be at 11pm in utter darkness.

Spiral band eye in the latest VDM.

I think this is really good consensus, actually. These precise things always come down to a very small movements on final approach.

Very impressive look.

Despite the globals, the consensus hasn’t changed. Makes it hard to bet against. Having been through a lot of these now, it’s almost always coming down to the final hours for precise landfall location. That’s just how it goes. Folks just have to be ready for anything.

Just got our first little rain band from the system. It’s absolutely massive.

Starting to get the first far flung outer rain bands here and across much of Florida. Speaks to how expansive this thing is already.

I think it’s also really important to note that even the NHC hasn’t quite honed in on that final landfall point yet. This is from their 11am discussion: The track guidance remains tightly clustered, and the NHC forecast is generally just an update of the previous prediction. It is still too soon at this point to be overly focused on an exact landfall location and time, since NHC track forecasts can be off by an average of 60 nm at the 36-hour forecast time. Anyone in the cone should be ready for a direct impact. Francine just a few weeks ago with the last minute east trend is a good example of why. Personally, I’m still hedging for a landfall slightly further east.

I’ve recorded 65mph with a Kestrel before. It’s powerful stuff.

That 2pm advisory shows the TS wind field expanding 100 miles since the advisory at 8am.

I know you are—I just mean the pressure at least is a legitimate possibility. I’m more skeptical of the very high end wind depiction but it’s not completely unrealistic imo.

Given what we’re seeing from the hurricane models, and the consistency once it was projected that the center wouldn’t cross the Yucatán land mass, I think they’re absolutely worth taking seriously. That said, how the storm reacts to the pressure fall is key. I think it’s more likely that pressure is very low and the RMW is larger with lower peak winds (still could be car 3/4 to be sure) than it’s an enormous storm with an enormous ring of 125kt winds in addition.

GFS Euro

Yeah, I think a middle ground is probably best and I’m kind of with you on that NNE motion. That may last a bit longer before a northward turn. For center impacts, every wobble “trend” is going to matter, especially considering that this one will be moving fast and may not have a chance to course correct. As the NHC said, 60nm is the 36hr average error. That’s significant.