ATL: GRACE - Remnants - Discussion

[cheezyWXguy]

https://i.postimg.cc/5yGBd1vn/2-F5-D3-D73-5-D75-43-D5-B1-D1-10-C27329-DDB5.png
993mb

That is a faster drop than I expected

[kevin]

https://i.postimg.cc/5yGBd1vn/2-F5-D3-D73-5-D75-43-D5-B1-D1-10-C27329-DDB5.png
993mb

Looks like we may have spoken a bit too soon, guess the plane wasn't at the center yet. Just measured 993 mbar. Could be an indication that HMON is closer to short-term reality than HWRF. HWRF doesn't have this reaching hurricane strength until about 20 hours from now (keeps it at 1000 - 1005 mbar for now), while HMON has it within a few hours. For reference, HWRF has a cat 1 Yucatan landfall and HMON a cat 3.

[GCANE]

Lots of subsidence in that PVS.
Seeing very low CAPE.
Appears that it was trying to form convection along a dry-line front but got washed out.

[aspen]

Yeah looks like the first plane missed the exact center, or the pressure discrepancy is due to an altitude difference.

I wonder why the PVS is as stubborn as Linda. I’m guessing this is what the HWRF sees that keeps a lid on Grace prior to its Yucatán landfall.

[ChrisH-UK]

Looks like there has been some strengthening overnight, if these surface measurements are to be believed. Also, recon missed the center to the west, so pressure is probably a little lower than indicated on this first pass.

Another weather station had 57 mph winds and a pressure of 999mb. Interestingly they also had a spike in solar radiation which is a bit weird unless they was am eye but it was 6am.

https://www.wunderground.com/dashboard/pws/IBODDE1

Another station had the same pressure and 50 mph winds, no solar radiation spike.

https://www.wunderground.com/dashboard/pws/IGEORG45

[tolakram]

Floater visible loop
https://weather.cod.edu/satrad/?parms=meso-meso1-02-24-0-100-1&checked=map&colorbar=undefined

[GCANE]

Looks like down to about 993mb.
Very tight wind field and warm core.

[Owasso]

Dropsonde confirming 993mb extrap

[kevin]

Will be interesting to see what wind speeds recon finds in a NE to SW pass.

[ElectricStorm]

Nice to see the PVS stronger this morning as that's probably gonna hold it back and prevent it from becoming a major before the Yucatan. Should still be a solid Cat 1/2 coming in though but luckily it shouldn't explode. Although it's still the WCAR so a major wouldn't surprise me much. Might blow up in the BOC though but we'll have to see what it looks like when it gets back over water.

[GCANE]

NOAA3 reported a 80+ mm/hr rain rate right where an eyewall would be.
Due to the fact Grace is so compact, the PVS may not have a great influence on this.
Grace seems to be able to pull heat out of the water at very close distances from the CoC.

[GCANE]

It has that cirrus stacking pattern on VIS Sat with some radial fingers.
Being a small TC, it may take off.

[Chris90]

I would guess that Grace just started strengthening in the past couple hours. That microwave image from a couple hours ago showed that she was very lopsided to the east and was having trouble wrapping bands through the west quadrant into the south quad. On satellite/IR imagery she appears to have started wrapping convection into her west quad more efficiently recently, so if she maintains I would expect more significant pressure drops to start.

How fast she can build a core will probably be the deciding factor in how strong of a TC the Yucatán receives. If she was moving slower she would have more time to really ramp up over the WCar waters.

[Nuno]

Do we have any word or obs from the Cayman Islands?

[ElectricStorm]

I will say though the last few frames of IR have been looking much more ominous...

[kevin]

It's starting to get that shrimp look.

[Owasso]

...GRACE NEAR GRAND CAYMAN...
...HEAVY RAINS AND STRONG WINDS CONTINUING ACROSS THE CAYMAN
ISLANDS...


SUMMARY OF 800 AM EDT...1200 UTC...INFORMATION
----------------------------------------------
LOCATION...19.1N 81.4W
ABOUT 20 MI...30 KM SW OF GRAND CAYMAN
ABOUT 405 MI...650 KM ESE OF TULUM MEXICO
MAXIMUM SUSTAINED WINDS...65 MPH...100 KM/H
PRESENT MOVEMENT...WNW OR 285 DEGREES AT 16 MPH...26 KM/H
MINIMUM CENTRAL PRESSURE...993 MB...29.32 INCHES

Looks like they went with 993/65

[ElectricStorm]

BULLETIN
Tropical Storm Grace Intermediate Advisory Number 20A
NWS National Hurricane Center Miami FL AL072021
800 AM EDT Wed Aug 18 2021

...GRACE NEAR GRAND CAYMAN...
...HEAVY RAINS AND STRONG WINDS CONTINUING ACROSS THE CAYMAN
ISLANDS...


SUMMARY OF 800 AM EDT...1200 UTC...INFORMATION
----------------------------------------------
LOCATION...19.1N 81.4W
ABOUT 20 MI...30 KM SW OF GRAND CAYMAN
ABOUT 405 MI...650 KM ESE OF TULUM MEXICO
MAXIMUM SUSTAINED WINDS...65 MPH...100 KM/H
PRESENT MOVEMENT...WNW OR 285 DEGREES AT 16 MPH...26 KM/H
MINIMUM CENTRAL PRESSURE...993 MB...29.32 INCHES

[Owasso]

It’s closed now.

[tolakram]

Non decoded, which I find easier to read (but I appreciate the decoded version!)

989
URNT12 KNHC 181154
VORTEX DATA MESSAGE AL072021
A. 18/11:29:30Z
B. 19.10 deg N 081.30 deg W
C. 850 mb 1375 m
D. 994 mb
E. 255 deg 8 kt
F. CLOSED
G. E02/20/12
H. 40 kt
I. 295 deg 52 nm 11:06:00Z
J. 283 deg 60 kt
K. 190 deg 4 nm 11:24:30Z
L. 56 kt
M. 117 deg 4 nm 11:31:00Z
N. 240 deg 64 kt
O. 122 deg 6 nm 11:31:30Z
P. 16 C / 1538 m
Q. 24 C / 1522 m
R. 14 C / NA
S. 12345 / 08
T. 0.02 / 1.5 nm
U. AF307 1307A GRACE OB 05
MAX FL WIND 64 KT 122 / 6 NM 11:31:30Z