WxWatcher007

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.

D1 High Risk (Flooding) added: Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 1144 AM EDT Wed Sep 25 2024 Day 1 Valid 16Z Wed Sep 25 2024 - 12Z Thu Sep 26 2024 ...THERE IS A HIGH RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF NORTHEAST GEORGIA THROUGH FAR WESTERN SOUTH CAROLINA AND SOUTHWEST NORTH CAROLINA... ..LIFE-THREATENING FLASH FLOODING INCREASINGLY LIKELY OVER THE SOUTHERN APPALACHIANS.. Deep layer south to south-southwest flow will allow for the advection of increasingly moist, unstable air to funnel poleward ahead of Helene thanks to a closed upper low/trough centered over the Mid-Mississippi Valley. Afternoon destabilization within the budding warm sector along with sufficient left-exit region (LER) jet dynamics from the trough will translate to more widespread convective coverage across the Southeastern U.S into the Central/Southern Appalachians as we move into the late-afternoon and evening time frame. Areas across the Escarpment located over far Northeast GA into the Western SC/NC border have seen 2" to as much as 5" of rainfall in the last 24-36 hrs leading to a priming of the top soil layer as indicated by the latest NASA SPoRT soil moisture percentiles approaching 60-70% over the areas affected. Recent CAMs and ensemble output have increased the QPF signal across the Southeast with the axis of heaviest rainfall bisecting Eastern AL up through Western GA into North GA and the Southern Apps/Smokies bordering TN/SC/NC. HREF blended mean QPF indicates widespread 3-6" of rainfall from this predecessor rainfall event (PRE) that correlates with the strong upper forcing and deep tropical connection to north of Helene as it wanders into the Eastern Gulf. Probability fields are also very aggressive with the signature for enhanced rainfall rates and totals with the EAS signal for 3" settling at 50-80% within the Escarpment area into Northeast GA. Neighborhood probabilities of >5" between 70-90+% and >8" between 20-35% are more than sufficient for a very impactful event expecting to unfold across the complex terrain in-of the Southern Appalachians. Given the signals expressed via the hi-res ensemble, along with ample support from the various ML output for the heaviest rainfall, as well as coordination with the local Greenville-Spartanburg WFO, a targeted High Risk was added for the D1 period.

27 was fine and my guess is 98 was good too. The difference here is the wind field is likely to be so much bigger that I think it’s going to be tough on state roads. Ideally for me, I’d end up closer to I-10. If the models hold that would be the case, and with the forward speed we’d still get big winds inland.

We have our first VDM with data on a nascent eyewall trying to form, along with FL winds slightly above 64kt. Product: Air Force Vortex Message (URNT12 KNHC)Transmitted: 25th day of the month at 13:54ZAgency: United States Air ForceAircraft: Lockheed WC-130J Hercules with reg. number AF99-5309Storm Name: HeleneStorm Number & Year: 09 in 2024 (flight in the North Atlantic basin)Mission Number: 11Observation Number: 11 ( See all messages of this type for this mission. )A. Time of Center Fix: 25th day of the month at 13:12:50ZB. Center Fix Coordinates: 21.33N 86.16WB. Center Fix Location: 46 statute miles (74 km) to the ENE (75°) from Cancún, Quintana Roo, Mexico.C. Minimum Height at Standard Level: 2,941m (9,649ft) at 700mbD. Minimum Sea Level Pressure: 982mb (29.00 inHg)E. Dropsonde Surface Wind at Center: From 360° at 22kts (From the N at 25mph)F. Eye Character: Open from the northeast to the southeastG. Eye Shape: Elliptical (oval shaped)G. Orientation of Major Axis in Elliptical Eye: 360° to 180° (N to S)G. Length of Major Axis in Elliptical Eye: 50 nautical miles (58 statute miles)G. Length of Minor Axis in Elliptical Eye: 30 nautical miles (35 statute miles)H. Estimated (by SFMR or visually) Maximum Surface Wind Inbound: 47kts (54.1mph)I. Location & Time of the Estimated Maximum Surface Wind Inbound: 46 nautical miles (53 statute miles) to the NE (36°) of center fix at 13:00:00ZJ. Maximum Flight Level Wind Inbound: From 128° at 51kts (From the SE at 58.7mph)K. Location & Time of the Maximum Flight Level Wind Inbound: 94 nautical miles (108 statute miles) to the NE (42°) of center fix at 12:46:30ZL. Estimated (by SFMR or visually) Maximum Surface Wind Outbound: 60kts (69.0mph)M. Location & Time of the Estimated Maximum Surface Wind Outbound: 29 nautical miles (33 statute miles) to the SSW (204°) of center fix at 13:21:30ZN. Maximum Flight Level Wind Outbound: From 284° at 68kts (From the WNW at 78.3mph)O. Location & Time of the Maximum Flight Level Wind Outbound: 39 nautical miles (45 statute miles) to the SSW (205°) of center fix at 13:24:30ZP. Maximum Flight Level Temp & Pressure Altitude Outside Eye: 10°C (50°F) at a pressure alt. of 3,049m (10,003ft)Q. Maximum Flight Level Temp & Pressure Altitude Inside Eye: 16°C (61°F) at a pressure alt. of 3,049m (10,003ft)R. Dewpoint Temp (collected at same location as temp inside eye): 6°C (43°F)R. Sea Surface Temp (collected at same location as temp inside eye): Not AvailableS. Fix Determined By: Penetration, Radar, Wind, Pressure and TemperatureS. Fix Level: 700mbT. Navigational Fix Accuracy: 0.02 nautical milesT. Meteorological Accuracy: 2 nautical milesRemarks Section: Maximum Flight Level Wind: 68kts (~ 78.3mph) which was observed 39 nautical miles (45 statute miles) to the SSW (205°) from the flight level center at 13:24:30Z

I’d wait to see more longer term motion/center fixes. That’s a better way to characterize it, thanks. Here’s the illustration for others. Will try to add those in future posts. 18z yesterday 00z 06z

The west trend has continued on the globals, with the 06z Euro and 06z GEFS ticking west. More in line with the spaghetti models.

Long post looking at the various hazards.

First light is beginning to reveal a much more organized TC near the Yucatán Channel, a harbinger of things to come. Recon, radar, and satellite all show a modestly organizing and gradually intensifying TC that will likely be a hurricane by the 11am full advisory. With shear reduced over the system itself and dry air most likely out of the way as an inner core forms in the next 12-18 hours, it looks like the runway is primed for Helene to take off in intensity late tonight into Thursday provided the center does not traverse the Yucatán. You can tell dry air—something that has plagued systems across the basin all season—is not a factor at this time because of the expansive outflow and deep CDO convection that has persisted all night. I would watch the SE quadrant in case some of the drier air to the south wraps in. We have a system that’s already sub-980mb as a result, but that’s only part of the story. Generally speaking, the wind field is still broad. A smaller system would be a hurricane by now with a tighter center. Helene is poised to become one of the largest named storms since 2000. This will have tremendous implications for the forecast and scale of region wide impacts. First, the wind. This is extraordinary to look at—tropical storm warnings from the Keys to coastal GA for a Gulf storm and hurricane warnings well into southern GA. The storm already has TS winds expanding 175 miles out and that’ll grow substantially over the next day. In fact, you can already see how large Helene is using zoomed out satellite. It’s going to take time for the RMW to tighten enough for major hurricane wind speeds to be found. What we’ll likely see are very low pressures with an expansive area of “modest” hurricane force FL then surface winds before RI takes place and tightens the inner core at that point. That said, I don’t believe the HAFS depictions of a small core and large TS field. This may limit peak wind potential some. That’s not to say the potential for something on the order of a category four isn’t there because it is, but we’ll just have to see how the storm reacts to falling pressure. Second, the surge. What may be lost in peak wind potential will likely be more than made up for in surge, which may be catastrophic in the Big Bend region and major in other locations. The difference in category will matter little given the surge potential. While a stronger or weaker peak wind could do significant damage inland, the coastal impacts are already baked in. Third, the rain. If wind and surge weren’t enough—and both have the potential to be high end—rainfall looks to be a major concern well inland. A Predecessor Rain Event looks likely, and a HIGH risk for excessive rainfall has been issued. Extreme rainfall is possible and inland folks should not let their guard down just because Helene is currently well south. Fourth, severe potential. Finally, we have severe potential on the east side of Helene. I think we need to see how banding sets up tomorrow and Friday, but a D2 enhanced risk is pretty significant for a TC. This is a long post that didn’t even go into track (though I’m closely watching potential shifts west, possibly worsening wind impacts into the Panhandle and southern GA) But for the general public the center will matter less than usual given the size of the wind field and surge potential all along the coast.

Spaghetti models are a touch west too. I do think there’s a limit to how west it can go given the steering pattern and how deep I think this’ll get, but TLH could be the bullseye.

Thanks. Ominous and maybe a touch west too. This is going to be an extraordinarily impactful storm for the region, and it’d actually be a bit easier for me if it did force me into the panhandle—easier highway access.

This is an absolutely exhausted WxWatcher007 reporting live from Perry, FL. I just got here so I can’t give much of a lay of the land, but I know from the logistical challenges already that this is a serious one. I may need to reposition, as it’s unclear what, if any, places will be open here in the region Thursday. In a sturdy ride out spot at the moment. The goal this time is (hopefully) no need to move (I’m hedging east) and a very good pressure trace of the center. Will be reporting on conditions too of course. For now though, first food of the day and a little rest. Wish us all luck down here.

New D2 SPC outlook highlights a pretty significant tornado risk in coastal GA. @GaWx Off to bed. Long day of travel to the Big Bend region. May need to reposition tomorrow.

The 18z hurricane models (HWRF, HMON, HAFS-A&B) show just how critical the next few 12-18 hours may be with the track of the LLC near the Yucatan. Each run misses the landmass and all develop a formidable major hurricane as a result.

Good stuff, @40/70 Benchmark. Our thoughts are aligned. If there is a legitimate inner core completed or near completion at the Yucatán Channel, I think it’ll be all systems go for a high end wind and surge system, even if an ERC levels things off later. If not, it may just slow walk its way along in terms of intensification until Thursday. I do think this will end up a large system and will be much more resistant to shear and/or dry air as a result, with the increasing forward speed being a secondary factor in limiting any window for weakening. I think the floor is probably around 100mph and the ceiling is still fairly high, around 140mph. Right now I think LF is probably around 120 imo.