Windspeed

A good example of why satellite can sometimes be deceiving. Roslyn is still an intense hurricane. Despite the eye being overcast with cloud debris, the eyewall is still very much intact and should have destructive impacts through landfall. Note the extreme lightning GLM data. Structure is still solid.

That's nearly a pattern flip. Notice the WAR appear out if nowhere versus previous runs. New Foundland low gone. May be a flook or something to watch for upcoming runs.

Yes. There may also be an outer band consolidating into an outer eyewall, but it apparently is not organized enough to prevent Rosslyn's small eyewall from continued rapid intensification. Most likely a Cat 4, perhaps upper Cat 4 at the moment with an impressive satellite presentation. Inevitably there will be weakening prior to landfall either due to structural changes or increasing shear but at least for the moment, Rosslyn is a beast.

Long range 12z GFS op is up to some Caribbean shenanigans...

Yeah I busted on this one big time though clearly the potential was there, the thing just took forever and a day to get the low-level structure aligned with the prolonged intense mid-level vortex / convective pulses. A lot of this was probably due to the duration of land interaction with Venezuela as the broad low was organizing. But fortunately for Nicaragua, the RMW did not tighten until just prior to landfall. Additionally, though globals were slow to intensify and suggested intensification only just prior to landfall, I lack much enthusiasm that it was due to detailed modeling of the low-level structure and land interaction, and they would have failed to show RI beyond if or if not structural issues persisted. Again, the ingredients were there, sometimes loose structure of a broad low-level envelope with multiple vorticy maximums gets in the way.

Seems to be the case. Shear is just being too much of a deterrent for allowing Julia to resolve surface structural issues. Gonna bust hard on this one it seems. Would need RI to be occurring now. Starting to look unlikely.

Still expecting Julia to rapidly intensify today. Despite its initial structural issues at the surface, I do not think it will take long for intensity to ramp up quickly once the eyewall is established. There are hints of this on radar. Again, sure, time is limited over water, but it may have just enough time to peak at a high intensity prior to any first ERC. I think Julia landfalls as a major and depending on how rapidly, even a Cat 4 is still possible once rapid intensification is underway. I think we tend to be conservative and for good measure, as intensity forecasting remains difficult. But ventilation is certainly good enough to get the job done despite 10 kts of shear. I'm going to call 105-110 kts into the Nicaraguan coastline in the early AM hours of Sunday.

Recon is funky. It's as if the LLC is repositioning again.

Boy how things can rapidly change. Unfortunately, Julia is going to be an intense hurricane before it reaches Nicaragua. Two major changes: 1) Recon has found that the LLC has relocated under the very dense/deep -80°C formative CDO. 2) The mid-level circulation is now stacking with a slight tilt, but shear has abated significantly in the past 9 hours. With these developments and the quickly organizing core, I fully expect Julia to become a major hurricane, and perhaps even peaking at Category 4 prior to landfall. Too much time left over 29-30°C SSTs and fast enough motion to get the most out of available OHC.

Missfired into the seasonal thread. Shear vector is pivoting easterly. New strong convection should now wrap the LLC. At any rate, BOOOM!!!

Nice thread...

Agree with Andy here that bands holding position north of the exposed center indicates shear is dropping fast, perhaps to around 10 kts. So the exposed center may be temporary as a remnant region of suppression where higher shear values earlier blew off/broke down mid level vorticity. Likely slow restructuring today and then as soon as a core is built this evening, more significant intensification should ensue.

Hilarious, no sooner than I posted that impressive hot tower above that did look like an eye band (core) forming... *splOOOOpF* The entire column collapses due to some northerly mid level shear. So this is likely to be a gradual process unless a core can establish sooner than later.

Per 12z ATCF Best Track, this is now TS Julia, pending NHC following suite at the 11AM package.

This should be Julia on the next advisory package. Very intense hot tower going up right adjacent to the center that looks to be a formative eastern eyeband. You can make the outline based on GLM lightning data, which is pretty neat. This thing is about to go off.

It is tighter and more consolidated than a trough. That's a sharp wind shift and there is a circulation there, it's just weak. The promixity to the SA coastline may inhibit it from organizing into a TC however.

This thing is pulling a Bonnie. It did not consolidate at a high enough latitude as I thought it would. Therefore unless the axis lifts/folds north, land interaction with SA will keep it in check until it clears Colombia. May still become a hurricane / develop rapidly then, but significantly limits developmental time.

Trough interaction is still very difficult to forecast and model. That being said, there were some strong TC model runs. But overall, it's still a science that still cannot be considered a mature discipline. Much research is still in its infancy.

We are scheduled for recon this afternoon. If something is organizing under the convective canopy, we'll know then. There is presently good low-level convergence into that suspicious area of the northern dense blob. The old vort has been kicked out to the NW.

Despite the drop in %/color code for TCG potential, I'm sticking to favoring development of 91L sooner than later. Current convective activity may look anemic, however, these semi-permanent clusters of storms will aid in organizing a low level vorticity maximum if they can persist beyond diurnal maximum and into the day tomorrow. Sure, global op modeling remains meh, but visually 91L remains a vigorous wave with turning, albeit weak, that appears to have the ingredients for genesis. I still favor this becoming a hurricane in the Caribbean that will threaten CA.

Very evident mid-level rotation. There does appear to be low-level westerlies on the southside of the wave axis. Really nice moist envelope. Despite lack of early enthusiastic modeling, I'm still on the TCG train. Just needs to fire and sustain convection near the nascent center. The positioning of the axis folding is far enough south of the ULL/upper trough to avoid hinderance as far as strong shear. There may still be shear in the eastern Caribbean for a short window to deal with, but I really like this system to take off in the short term, then perhaps a steady state until the TC gets south of the Greater Antilles. Hopefully we'll get a recon flight out there in the next day or so.

Carribean runner. I actually like development of this system and a hurricane landfall somewhere from the Rivera Maya, Yucatan, down to Nicaragua. Outflow looks really great. There will be some enhancement by an ULL to the north that may aid TCG. But then may impart a window of shear. By the time the system is south of the DR, however, conditions will support a strong hurricane all the way into CA.

The pattern flipped late, but it flipped. We may be facing an active October. We aren't going to reach hyperactive for the season, but active/above normal is looking like a lock. We are now in a +AMO setup. If this had occurred in August as was previously forecasted by seasonal outlooks, the year probably would have ended up hyperactive. Wave breaking issues aside, this is a classic look...