WxWatcher007

I think the early development of an eye surprised everyone, but the current issues are not surprising. It’s important to remember that despite the exceptionally high level RI systems we’ve seen since 2017, for most TCs development and intensification are not linear, and development and intensification can be two separate things. Nascent eyes are just that—yeah they can herald taking off or intensification, but they’re fragile because developing a mid and then fully developed eye is part of the development stage. When convection started declining from the peak earlier that was a flag that intensification was likely to slow. Dry air is going to be nearby because of both the boundary to the north and the continental dry air that’s often accompanying TCs in the Gulf. I think the key thing to watch is organization not intensity (read: wind). Are pressures continuing to drop? Is the eye ragged, or becoming wrapped fully with convection? Is the RMW tightening and are we seeing greater temperature contrasts in the eye? That’s going to tell us what direction things are going. Tonight the signals are mixed, not uncommon of systems at this stage of development.

Yeah I think it’s one of those things where the broader circulation isn’t quite aligned with whatever lower level center wants to become the primary. I think given recon and radar that the area seeing significant pressure drops NW of the original low level spin is the leader in the clubhouse, but there’s still some organizational work to do before this can really go. The big pressure drop and visible appearance are eye opening to me though.

For now at least, there’s a nascent eyewall. Product: Air Force Vortex Message (URNT12 KNHC)Transmitted: 9th day of the month at 17:22ZAgency: United States Air ForceAircraft: Lockheed WC-130J Hercules with reg. number AF98-5308Tropical Depression: Six (flight in the North Atlantic basin)Mission Number: 3Observation Number: 08 ( See all messages of this type for this mission. )A. Time of Center Fix: 9th day of the month at 16:45:10ZB. Center Fix Coordinates: 23.69N 95.85WB. Center Fix Location: 186 statute miles (299 km) to the SE (146°) from Brownsville, TX, USA.C. Minimum Height at Standard Level: 1,387m (4,551ft) at 850mbD. Minimum Sea Level Pressure: 996mb (29.42 inHg)E. Dropsonde Surface Wind at Center: From 140° at 5kts (From the SE at 6mph)F. Eye Character: Open in the westG. Eye Shape & Diameter: Circular with a diameter of 20 nautical miles (23 statute miles)H. Estimated (by SFMR or visually) Maximum Surface Wind Inbound: Not AvailableI. Location & Time of the Estimated Maximum Surface Wind Inbound (Undecoded): NAJ. Maximum Flight Level Wind Inbound: From 308° at 31kts (From the NW at 35.7mph)K. Location & Time of the Maximum Flight Level Wind Inbound: 6 nautical miles to the SW (219°) of center fix at 16:43:30ZL. Estimated (by SFMR or visually) Maximum Surface Wind Outbound: 47kts (54.1mph)M. Location & Time of the Estimated Maximum Surface Wind Outbound: 55 nautical miles (63 statute miles) to the NE (47°) of center fix at 17:02:00ZN. Maximum Flight Level Wind Outbound: From 133° at 58kts (From the SE at 66.7mph)O. Location & Time of the Maximum Flight Level Wind Outbound: 12 nautical miles (14 statute miles) to the NE (44°) of center fix at 16:49:00ZP. Maximum Flight Level Temp & Pressure Altitude Outside Eye: 16°C (61°F) at a pressure alt. of 1,523m (4,997ft)Q. Maximum Flight Level Temp & Pressure Altitude Inside Eye: 20°C (68°F) at a pressure alt. of 1,524m (5,000ft)R. Dewpoint Temp (collected at same location as temp inside eye): 18°C (64°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 Levels (surface & flight level centers within 5nm of each other): Surface and 850mbT. Navigational Fix Accuracy: 0.02 nautical milesT. Meteorological Accuracy: 1 nautical mileRemarks Section: Maximum Flight Level Wind: 58kts (~ 66.7mph) which was observed 12 nautical miles (14 statute miles) to the NE (44°) from the flight level center at 16:49:00Z

Very true. There’s always a lot to learn. Turning closer to home, the 12z GFS isn’t as exotic as that happy hour run, but I think it’s more “realistic” in how we’d get something up here. A spin up off the SE coast as the ridge builds in over the top and has no escape route as the ridge slides east. Obviously fantasy range, but I’ve highlighted the SE window for a while now.

A substantial drop in extrapolated pressure between passes on that new apparent center under the deep convection. From just over 1001mb to 995.6mb. Again this extrapolated, so more of an estimate. Still, that’s very impressive.

I’ll be interested in seeing 18z more because I think the recon data will be included, but as the NHC notes the SHIPS output is quite robust.

Not sure when we’ll get a VDM, but recon is finding a much tighter and more organized center in that deep convection. Winds aren’t terribly strong, but it’s the organization that matters.

Maybe a touch more NE, but the real critical factor imo will be how strong an inner core the system has as it’s approaching the coast. If it’s a weak inner core, shear could cause last second weakening as the vortex gets tilted and drier air gets imparted. You can see on the HWRF how the core is only half complete. Other models are closer to closed but not quite there and as a result pressures are lower. I’d just caution that we don’t have a well defined center yet, so both final track and especially intensity are far from settled matters. Shear and dry air lurk, but on the other side of the equation we see very strong convection and western Caribbean like OHC along the the projected track of the system that should favor continued deep convection.

That’s the kind of signal where the right track could cause extremely efficient ventilation. Or, any deviation from that “ideal” track blasts the system right before landfall. Things look like they’re a go for intensification later, and it’s kind of impressive we’re getting this with the rest of the Gulf under high shear. ULAC saves the day I guess.

Still some uncertainty on the trough interaction so that’s not surprising

Everything that’s developed has hit land. Even Ernesto somehow found Bermuda. Just an odd quirk of a season that started hot but then had a historically inactive period during peak season. Recon just starting and already finding 40-45kt winds, consistent with earlier ASCAT partial pass.

Recon has entered the system, so we’ll get a good sense soon of whether we have a well defined center.

How does the historic +NAO that we’ve seen this summer factor into your winter thoughts, if at all?

I think it depends largely on what you said, is the trough interaction going to be ideal with a further NE turn like the GFS/Euro, or a little flatter and thus more hostile like the Canadian. I lean toward the former, but I don’t think it’s a lock.

Not much time to write but this morning we’re likely seeing 91L begin to organize at a more deliberate pace. For the first time in a while given the stability issues we’ve had across the basin, this invest is producing deep and persistent convection, a critical element for future development and structural organization. The residual energy from 90L continues to dive down into the BoC and is merging with what was the weak Caribbean wave we were tracking for a week. https://tropic.ssec.wisc.edu/real-time/atlantic/movies/wg8vor5/wg8vor5_loop.html Although it is trying to organize, I’m not sure we have a TC quite yet. Recon is scheduled for later and by then we may have something if the convective trends continue. I would caution however, that this system while currently in a conducive environment will need to battle more potentially hostile conditions including shear and dry air at some point. For now, however, in the race with 92L to break the historic inactive streak, 91L is closest to getting a name. NHC telegraphing that advisories are coming at some point today.

Posted in the main forum but pasting here too Just quickly, my areas of interest: 1. BoC low/Invest 91L—80% Looks most likely to break our NS drought. Like I said before, it’s hard to bet against the BoC topography, though I’m not sure we’d have this area as likely to pop without old 90L and the boundary assisting what was an anemic wave. Western Gulf should watch closely. 2. Invest 92L—50% I won’t lie. I’m still nervous that this next iteration of the MT breakdown will fail to immediately produce, but like Windspeed said the tropical Atlantic portion of the MDR is looking substantially better than it did even a week ago. The apparent organization tonight gives me a little more confidence something is developing here. 3. MT Part II—40% This is the eastern end of the trough that will take more time to organize, if at all. A future AEW coming off Africa may help give the area the kick it needs to develop. Models are waffling on which part of the MT develops first, but it looks like 92L is in the lead. This is the easternmost NHC orange. 4. SE Coast—20% There’s still a signal late next week for a low to develop along a stalled boundary, and this may factor in the eventual track of 92L. What has my interest here is 1) the further south potential for development in a more tropical genesis favored zone, and 2) the possibility of a ridge developing over the top, potentially cutting off a quick exit. Two things 99L didn’t have. Long way away so not worth much attention. I’m not going to declare anything until it happens, but I do wonder if the lid is starting to come off…from west to east.

Just quickly, my areas of interest: 1. BoC low/Invest 91L—80% Looks most likely to break our NS drought. Like I said before, it’s hard to bet against the BoC topography, though I’m not sure we’d have this area as likely to pop without old 90L and the boundary assisting what was an anemic wave. Western Gulf should watch closely. 2. Invest 92L—50% I won’t lie. I’m still nervous that this next iteration of the MT breakdown will fail to immediately produce, but like Windspeed said the tropical Atlantic portion of the MDR is looking substantially better than it did even a week ago. The apparent organization tonight gives me a little more confidence something is developing here. 3. MT Part II—40% This is the eastern end of the trough that will take more time to organize, if at all. A future AEW coming off Africa may help give the area the kick it needs to develop. Models are waffling on which part of the MT develops first, but it looks like 92L is in the lead. This is the easternmost NHC orange. 4. SE Coast—20% There’s still a signal late next week for a low to develop along a stalled boundary, and this may factor in the eventual track of 92L. What has my interest here is 1) the further south potential for development in a more tropical genesis favored zone, and 2) the possibility of a ridge developing over the top, potentially cutting off a quick exit. Two things 99L didn’t have. Long way away so not worth much attention. I’m not going to declare anything until it happens, but I do wonder if the lid is starting to come off…from west to east.

happy hour GFS indeed

Sitting currently with .24”.

I do wonder how much room there is for an eastward trend or sharper hook. The track forecast looks like it could be pretty sensitive until we have a well defined system. I’d imagine faster/stronger will get carried more efficiently, which could also make the upper air conditions more favorable as well.

12z Euro is weaker, but finally in line with other guidance. Doesn’t matter as much at this point, but it has intensification through landfall.