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Major Hurricane Grace

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16 minutes ago, andyhb said:

SHIPS RI probs starting to take off with Grace especially beyond 24 hours.

 SHIPS Prob RI for 20kt/ 12hr RI threshold=  10% is   2.1 times climatological mean ( 4.9%)
 SHIPS Prob RI for 25kt/ 24hr RI threshold=  33% is   3.0 times climatological mean (10.9%)
 SHIPS Prob RI for 30kt/ 24hr RI threshold=  22% is   3.2 times climatological mean ( 6.8%)
 SHIPS Prob RI for 35kt/ 24hr RI threshold=  11% is   2.9 times climatological mean ( 3.9%)
 SHIPS Prob RI for 40kt/ 24hr RI threshold=   8% is   3.3 times climatological mean ( 2.4%)
 SHIPS Prob RI for 45kt/ 36hr RI threshold=  21% is   4.5 times climatological mean ( 4.6%)
 SHIPS Prob RI for 55kt/ 48hr RI threshold=  27% is   5.8 times climatological mean ( 4.7%)
 SHIPS Prob RI for 65kt/ 72hr RI threshold=  33% is   6.2 times climatological mean ( 5.3%)

Yeah, but it is SHIPS. 

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Yes, it has evolved from a classic "9" low, to a more symmetric cyclone, with good outflow in the western semicircle. Most of the core is still over land, and although Jamaica is a bit rugged, the highest peaks are in the eastern portion of the island. It probably still has around 6 hours over land before exiting fully over water. Shear is low, less than 15 knots, and since structure seems to be improving, at least steady strengthening should be expected until landfall in the Yucatan. I don't discard RI, but we will have more info this evening.

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28 minutes ago, Windspeed said:

Yeah, clearly Grace's convective envelope is evolving right before our eyes here. Despite its young core and its interaction with Jamaica, convection around the western periphery within mid-level cyclonic flow is expanding and increasing pretty fast now.258d06276f747186c77b4a9153cb6ec7.gif

Nice poleward outflow channel developing too as seen on the GFS frame below. However, this may get impinged upon by that upper level ridge as soon as tomorrow. Will have to see how it evolves


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A little bit anemic on satellite, no doubt having just emerged off of Jamaica, but that is at least a well defined mid-level vortex signature on radar. I suppose all Grace needs now is to kick the convection up over that core as it pulls away from land. May take a little time tonight, but I suspect it will be undergoing intensification all throughout Wednesday.

Grace was plagued all of its life cycle up to this point not being able to develop a core. Convection was never the issue. Now it has a core, let's see what it will do.

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5 minutes ago, SnowenOutThere said:

46AE94A6-1F57-4622-B297-1F90063F014A.thumb.jpeg.d75bdb9703dfdef65315c4e02e49d3c6.jpegThink I’m crazy but this feature has been here for 30 minutes with convection wrapping around so think this might be a legit eye? 

Based on the vortex data message (VDM) from 30 minutes ago, it’s not an eye. Definitely more organized than its ever been as a system though. 

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No update from the NHC at 8am, but Grace is clearly on its way to hurricane status, if it isn't there already. Recon is impressive so far and the northern side hasn't been sampled. It has a closed eye on recon! 


Product: Air Force Vortex Message (URNT12 KNHC)
Transmitted: 18th day of the month at 11:54Z
Agency: United States Air Force
Aircraft: Lockheed WC-130J Hercules with reg. number AF98-5307
Storm Name: Grace
Storm Number & Year: 07 in 2021 (flight in the North Atlantic basin)
Mission Number: 13
Observation Number: 05

A. Time of Center Fix: 18th day of the month at 11:29:30Z
B. Center Fix Coordinates: 19.10N 81.30W
B. Center Fix Location: 14 statute miles (22 km) to the SSE (161°) from George Town, Cayman Islands (U.K.).
C. Minimum Height at Standard Level: 1,375m (4,511ft) at 850mb
D. Minimum Sea Level Pressure: 994mb (29.36 inHg)
E. Dropsonde Surface Wind at Center: From 255° at 8kts (From the WSW at 9mph)
F. Eye Character: Closed
G. Eye Shape: Elliptical (oval shaped)
G. Orientation of Major Axis in Elliptical Eye: 20° to 200° (NNE to SSW)
G. Length of Major Axis in Elliptical Eye: 20 nautical miles (23 statute miles)
G. Length of Minor Axis in Elliptical Eye: 12 nautical miles (14 statute miles)
H. Estimated (by SFMR or visually) Maximum Surface Wind Inbound: 40kts (46.0mph)
I. Location & Time of the Estimated Maximum Surface Wind Inbound: 52 nautical miles (60 statute miles) to the WNW (295°) of center fix at 11:06:00Z
J. Maximum Flight Level Wind Inbound: From 283° at 60kts (From the WNW at 69.0mph)
K. Location & Time of the Maximum Flight Level Wind Inbound: 4 nautical miles to the S (190°) of center fix at 11:24:30Z
L. Estimated (by SFMR or visually) Maximum Surface Wind Outbound: 56kts (64.4mph)
M. Location & Time of the Estimated Maximum Surface Wind Outbound: 4 nautical miles to the ESE (117°) of center fix at 11:31:00Z
N. Maximum Flight Level Wind Outbound: From 240° at 64kts (From the WSW at 73.6mph)
O. Location & Time of the Maximum Flight Level Wind Outbound: 6 nautical miles to the ESE (122°) of center fix at 11:31:30Z
P. Maximum Flight Level Temp & Pressure Altitude Outside Eye: 16°C (61°F) at a pressure alt. of 1,538m (5,046ft)
Q. Maximum Flight Level Temp & Pressure Altitude Inside Eye: 24°C (75°F) at a pressure alt. of 1,522m (4,993ft)
R. Dewpoint Temp (collected at same location as temp inside eye): 14°C (57°F)
R. Sea Surface Temp (collected at same location as temp inside eye): Not Available
S. Fix Determined By: Penetration, Radar, Wind, Pressure and Temperature
S. Fix Levels (surface & flight level centers within 5nm of each other): Surface and 850mb
T. Navigational Fix Accuracy: 0.02 nautical miles
T. Meteorological Accuracy: 1.5 nautical miles

Remarks Section:

Maximum Flight Level Wind: 64kts (~ 73.6mph) which was observed 6 nautical miles to the ESE (122°) from the flight level center at 11:31:30Z
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Grace just has that look now. That last VDM did have a nice temperature spike in the core with a robust vertical column developing. Should see some steady strengthening throughout the day. Obviously if we get an eye to clear out then RI becomes pretty much an expectation at that point. Starting to lean towards a Cat 2 lock at landfall and a major could be knocking on the door.

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18 minutes ago, OhioWX said:

The typically aggressive HWRF on its latest run is a far cry from reality.


HWRF is all discombobulated its *two* forecast MH landfalls on SE Florida failed to materialize and now it just doesn't know what to do.

*Although in all seriousness, given the way the HWRF over-reacts to favorable conditions, is it possible that it also at times over-reacts to unfavorable or at least sub-optimal conditions, such as a certain amount of PVS-induced shear?

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2 minutes ago, wxmx said:

Recon supports an upgrade to at least 60 kts, with FL around 74kts and several SFMR obs 60-67 kts.

Agreed. I’d think this warrants an upgrade, especially with increasing organization at this time. Not sure if NHC will bite or wait for next flight to confirm. This by all means is on the cusp 

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The intense blowup of convection over the center quickly knocked the pressure down several mb first thing this morning, but the core convection has waned since then and the pressure has plateaued.  The overall organization continues to improve, though.  At some point today or tonight we should see more intense convection fire over the center again.

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  • WxWatcher007 changed the title to Major Hurricane Grace

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