ATL: GRACE - Remnants - Discussion

[cycloneye]

 https://twitter.com/AndyHazelton/status/1427612900030623744

[cycloneye]

12z Best Track up to 45 kts.

AL, 07, 2021081712, , BEST, 0, 182N, 761W, 45, 1005, TS

[cycloneye]

Strong discussion from the SSD folks.

TXNT22 KNES 171206
TCSNTL

A. 07L (GRACE)

B. 17/1130Z

C. 18.3N

D. 75.9W

E. THREE/GOES-E

F. T3.0/3.0

G. IR/EIR/VIS

H. REMARKS...SYSTEM HAS 6/10 BANDING RESULTING IN A DT OF 3.0. THE
0949Z SSMIS 91 GHZ MW PASS REVEALS THE DISTINCT BANDING STRUCTURE ON
THE EASTERN AND SOUTHEASTERN SIDE OF THE LLCC. THE 37 GHZ ADDITIONALLY
SHOWS INDICATION OF THE BANDING STRUCTURE MAKING EFFORTS TO WRAP AROUND
THE LLCC INDICATING A STRENGTHENING SYSTEM. THE 24 HR DEVELOPING TREND
RESULTS IN DEVELOPING. MET AND PT ARE 3.0. FT IS BASED ON DT.

I. ADDL POSITIONS

NIL


...PATEL

[kevin]

Slowly but surely it seems that Grace is pulling itself north of Jamaica. Jamaica will still get a lot of rain and wind, but I think most of Grace will remain above water which could be unfortunate news down the road for Mexico.

[Hypercane_Kyle]

Certainly generating quite a bit of convection this morning.

Personally, I do think the NHC forecast is a bit on the conservative side. 45 knots is where this system was supposed to be in 24 hours.

[tolakram]

saved loop

[aspen]

Quite a compact circulation seen by recon, as forecast by previous HWRF runs. It’s very close to Jamaica and could make landfall, but I’m not sure how much it would be disrupted; I remember a tweet posted here a few days ago about how Jamaica barely disrupted another Caribbean system despite being stronger than Grace is now; I think it was Gustav but I can’t remember off the top of my head.

If Grace manages to make it past Jamaica unscathed, the combo of its tight core and much better structure — far ahead of previous NHC forecasts — could lead to a phase of RI before it either hits the Yucatán or passes through the Yucatán Channel, most likely the former.

[aspen]

~63kt FL, ~55kt SFMR unflagged, <1005 mbar extrapolated (the barometer stopped recording right at the center). This supports a 50-55 kt TS. We’ll have to see what the dropsonde found for the central pressure, but the center is very compact so it might’ve missed.

The higher level recon mission also recorded 55 kt SFMR in the northern half of the circulation, supporting an intensity of 55 kt for 11am.

[TallyTracker]

~63kt FL, ~55kt SFMR unflagged, <1005 mbar extrapolated (the barometer stopped recording right at the center). This supports a 50-55 kt TS. We’ll have to see what the dropsonde found for the central pressure, but the center is very compact so it might’ve missed.

The higher level recon mission also recorded 55 kt SFMR in the northern half of the circulation, supporting an intensity of 55 kt for 11am.

How close was the SFMR reading to the coast? The flight level winds do line up nicely so I agree with 50-55 kts as long as the reading is over deep water.

[aspen]

~63kt FL, ~55kt SFMR unflagged, <1005 mbar extrapolated (the barometer stopped recording right at the center). This supports a 50-55 kt TS. We’ll have to see what the dropsonde found for the central pressure, but the center is very compact so it might’ve missed.

The higher level recon mission also recorded 55 kt SFMR in the northern half of the circulation, supporting an intensity of 55 kt for 11am.

How close was the SFMR reading to the coast? The flight level winds do line up nicely so I agree with 50-55 kts as long as the reading is over deep water.

Very close to the northern Jamaica coast. The NHC might be conservative and go with 50 kt instead of 55 kt at 11am, or just stick with 45 kt.

[TallyTracker]

~63kt FL, ~55kt SFMR unflagged, <1005 mbar extrapolated (the barometer stopped recording right at the center). This supports a 50-55 kt TS. We’ll have to see what the dropsonde found for the central pressure, but the center is very compact so it might’ve missed.

The higher level recon mission also recorded 55 kt SFMR in the northern half of the circulation, supporting an intensity of 55 kt for 11am.

How close was the SFMR reading to the coast? The flight level winds do line up nicely so I agree with 50-55 kts as long as the reading is over deep water.

Very close to the northern Jamaica coast. The NHC might be conservative and go with 50 kt instead of 55 kt at 11am, or just stick with 45 kt.

50 kts seems like a reasonable blend of the data. Either way Grace is intensifying faster than previously expected. Might need some hurricane watches for the Cayman Islands at this rate.

[GCANE]

Very high rain rate measured at 80 mm/hr.
53 knot max surface wind measured close to the 1006mb CoC.
Very concentrated lightning at the deepest convection.
No doubt this is strengthening.
May ramp to Cat 1 as it approaches the warmer water to the west and CAPE increases during the day.
Biggest inhibitor is the 355K PV streamer to the west which is forecasted to dissipate as Grace gets near Cancun.

[jaguars_22]

We should feel good in Texas now right? I don’t see any reason why it would come north with the mid level high blocking us! What has to happen for it to come more north?

[ThetaE]

Last pass must've been pretty bumpy: hurricane hunters have ascended from 925mb to 850mb, and are turning around for another center pass. Maybe they'll get a better pressure measurement this time.

Dunno why they were flying at 925mb to begin with-- must've been expecting a weaker system. But near land with convection growing just NW of the center, that's pretty low.

[Cat5James]

We should feel good in Texas now right? I don’t see any reason why it would come north with the mid level high blocking us! What has to happen for it to come more north?

The ridge would have to end farther east, or be tilted in a way that would allow a more NW path as it approaches from the bay

[Iceresistance]

We should feel good in Texas now right? I don’t see any reason why it would come north with the mid level high blocking us! What has to happen for it to come more north?

The only reason if Grace goes to Texas is if she gets very strong & the Ridge fails to center in Texas, if the Ridge farther east, the SW quadrant might catch Grace & pull her to Texas, that possibility is unlikely, but I'm not taking any chances . . .

[jaguars_22]

By hour 78 on the gfs it looks like the ridge is gone!

[ThetaE]

The GITMO radar site is a bit far away, but you can definitely make out what looks like a developing inner core/eyewall just off the coast of Jamaica. Lines up well with recon's center fixes.

https://www.metoc.navy.mil/fwcn/animate.html?icao=mugm&type=CMaxZH240

[Iceresistance]

~63kt FL, ~55kt SFMR unflagged, <1005 mbar extrapolated (the barometer stopped recording right at the center). This supports a 50-55 kt TS. We’ll have to see what the dropsonde found for the central pressure, but the center is very compact so it might’ve missed.

The higher level recon mission also recorded 55 kt SFMR in the northern half of the circulation, supporting an intensity of 55 kt for 11am.

I actually get worried about compact centers, because like Delta in 2020, it can spin up much faster than larger centers.

The smaller the center, the more compressed the winds are & the faster the winds can go . . .

[jaguars_22]

Henri looks stronger than the gfs has been indicating… so if that does pull high over to east it opens the possibility for grace. I just feel bad for Mexico!!!