Windspeed

The mid-level vortex isn't decoupled from the low-level center, but it sure is tilted southward to the max.

Perhaps 5-6 hours at most from landfall. Another convective burst right over the center. Previous ones have relented including several healthy looking CDO features at times today. RI just isn't on the menu for the NW Caribbean this time. Some continued slow strengthening into landfall perhaps. The Cat 2 lock call I made this morning isn't looking so good. Probably going to end up a bust on my part unless.... Nope. Good night.

Sheesh, tired and totally looked at an older timestamp recon flight. At any rate, recon is in there right now:

A hectic day but a significant change in Grace since my last post. Grace not only has evolved a tight core, it has multiple CBs rotating around its eyewall. This is a visual sign that intensification is ramping up. Anxious to see new recon data. Grace being slow to evolve structurally today is going to be a blessing for the communities and resorts along the Riveria Maya. It may still begin a period of significant intensification prior to landfall.

SAL outburst is crossing the MDR. This should help suppress any AEWs during a period of limited activity following Grace and Henri. The next potential CCKW should be here around the first week of Sept. leading into peak. So we should have a quiet week or two at least barring any subtropical development or an overly strong AEW off the West African Monsoonal region.

Waiting on convection to pop on the SW side of the circulation. The VDMs have showed robust instability but so far it's been lacking coverage. Any delay this evening will be good for the Yucatán as that limits time for rapid intensification to kick in but of course this could change in short order.

Good thing we'll have recon. Despite the moderate shear values, Henri appears to be intensifying.

That's an anomaly map though. Yes, SSTs off the New England and Mid-Atlantic coasts are running above climatological mean. However, that doesn't mean they're warm enough to sustain a slow moving Tropical Cyclone. There is a reason notorious New England strikes are generally associated with mid-to-upper trough interactions, phases and swift motion. They're carrying convective momentum and some baroclinic assistance while traversing that cold current. A hurricane strike for New England, even a strong one is quite possible, but we need the right setup scenario to unfold.

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.

CDO developing over the LLC. Looks like this is a go...

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.

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.

Nice article explaining how radar rates and dbz can be deceiving in tropical systems. https://radarlab.wordpress.com/2015/06/22/whats-so-special-about-tropical-rainfall/

000 WTNT42 KNHC 171452 TCDAT2 Tropical Storm Grace Discussion Number 17 NWS National Hurricane Center Miami FL AL072021 1100 AM EDT Tue Aug 17 2021 The cloud pattern of Grace is gradually becoming better organized on satellite images, but the system still lacks distinct banding features over the eastern semicircle. Cirrus-level outflow from the system appears to be well defined. Flight-level and SFMR-observed surface winds, as well as dropsonde measurements, support an intensity of 45 kt for this advisory. Not much change in intensity is likely through this afternoon while the circulation of Grace interacts with the island of Jamaica. Thereafter, since the cyclone will be over the very high heat content waters of the northwestern Caribbean Sea with modestly low vertical shear tonight and Wednesday, strengthening is anticipated. Grace will likely become a hurricane tomorrow and continue to intensify before moving over the Yucatan Peninsula. The interaction with that land mass is expected to temporarily interrupt strengthening, with some reintensification over the Bay of Campeche in 3-4 days. The official intensity forecast is near the model consensus for the first half of the forecast period, but below the consensus for the latter part of the period owing to the inherent uncertainties for that extended time frame. Grace continues to move just a little north of due west, or at about 280/13 kt. A well-defined 500 mb ridge should remain entrenched to the north of the tropical cyclone for the next several days. Therefore, a continued west to west-northwestward track is likely to continue for most, if not all, of the forecast period. The official forecast is close to the previous one through 72 hours and just slightly south of it at 4-5 days. This is very similar to the latest multi-model consensus prediction. Key Messages: 1. Heavy rainfall across Haiti, Cuba, Jamaica, the Cayman Islands, and the northern Yucatan Peninsula may lead to flash, urban, and small stream flooding, with the potential for mudslides highest in Haiti and Jamaica. 2. Tropical storm conditions are expected over portions of Jamaica today, and over the Cayman Islands later today and tonight. Tropical storm conditions are expected over portions of the southern coast of Cuba today in the warning area, spreading westward to possibly other portions of the southern coast of Cuba this evening through Wednesday morning. 3. There is an increasing risk of wind, rainfall, and storm surge impacts on the Yucatan Peninsula of Mexico Wednesday night and Thursday, and a Hurricane Warning will likely be needed for that area later today. FORECAST POSITIONS AND MAX WINDS INIT 17/1500Z 18.3N 76.8W 45 KT 50 MPH 12H 18/0000Z 18.8N 79.0W 55 KT 65 MPH 24H 18/1200Z 19.2N 82.2W 65 KT 75 MPH 36H 19/0000Z 19.7N 85.3W 70 KT 80 MPH 48H 19/1200Z 20.4N 88.3W 65 KT 75 MPH...INLAND 60H 20/0000Z 20.9N 91.3W 60 KT 70 MPH...OVER WATER 72H 20/1200Z 21.1N 94.0W 65 KT 75 MPH 96H 21/1200Z 21.5N 98.5W 65 KT 75 MPH...INLAND 120H 22/1200Z 21.5N 103.0W 30 KT 35 MPH...POST-TROP/INLAND $$ Forecaster Pasch

Grace is now forecasted to become a hurricane in the NW Caribbean prior to landfall along the Riviera Maya coastline, Yucatán.

Yeah I hope you've got a boat. Looks like Chattanooga area totals are going to exceed forecast.

A common trait of tropical system rainfall. It's steady moderate rain here at my location south of Bristol but the radar dbz echoes aren't really that impressive.

Latest HRRR..

Going to resurrect this thread for the Fred and frontal related heavy rains over the eastern Tennessee Valley this week and weekend. Looks like it's going to be a mess for some folks despite a much-needed soaker.

I-75 corridor is getting pummeled right now as coverage continues to increase. I-81 coverage is beginning to increase as well. Should we make a new thread specifically for a heavy rain event as to not clutter up the medium/long range too much going forward?