WxWatcher007

That ridge is legit. Either it’d have to get poleward before te Greater Antilles to get steered into the SE or round the ridge in the Gulf and get lifted northeast by a trough like the GFS showed IMO.

Tropical Storm Grace Discussion Number 5 NWS National Hurricane Center Miami FL AL072021 1100 AM AST Sat Aug 14 2021 Grace is sending mixed signals on its intensity this morning. The storm has been producing persistent convective bursting since overnight, which would suggest that some strengthening has occurred. The latest subjective data-T numbers are 2.5 (35 kt) from TAFB and SAB, while objective satellite estimates are higher, roughly between 45-50 kt. Then, an ASCAT pass from 1302 UTC showed winds between 35-40 kt. Given these data, the initial intensity is set at 40 kt. A NOAA Hurricane Hunter aircraft is scheduled to investigate Grace this afternoon to provide a better estimate of the storm's intensity. Grace is speeding along toward the west (280 degrees) at 19 kt. Mid-level ridging, entrenched over the western Atlantic, is expected to weaken slightly during the next couple of days. This evolution should cause Grace to slow down to 10-15 kt by Sunday night and Monday and take on a west-northwestward heading. That general trajectory should continue through the end of the forecast period. The track guidance is tightly clustered during the first 48-60 hours or so, showing Grace moving near or across the Leeward Islands, Puerto Rico, and the Dominican Republic. On days 3-5, there is a little more spread, with a few models keeping the system on a southern track across Cuba while others show tracks across the Bahamas. The NHC track forecast splits this difference and continues to show a track running between Cuba and the Bahamas, very close to the HCCA consensus solution. Deep-layer shear is forecast to be 10 kt or less for the next 36 hours or so while Grace is approaching the islands of the Greater Antilles. The thermodynamic environment also appears conducive for strengthening, but the system's continued fast motion is likely to be an inhibiting factor on the rate of intensification. The NHC intensity forecast remains on the conservative side, bringing Grace's intensity up to 50 kt by the time the storm reaches the Virgin Islands and Puerto Rico, but it should be noted that this forecast is on the lower side of the guidance. Only one model, the HWRF, brings Grace to hurricane strength, but it does this by having the storm move farther north and avoid land interaction altogether. The intensity forecast is highly uncertain on days 3-5 since it depends on exactly how much Grace moves over the Greater Antilles, and there is some model signal that increasing northeasterly upper-level winds over the Bahamas and Florida could become a negative factor. Key Messages: 1. Tropical storm conditions are expected in portions of the Leeward Islands tonight and early Sunday, and the Virgin Islands and Puerto Rico on Sunday. Tropical storm conditions are possible over eastern parts of the Dominican Republic by early Monday. 2. Heavy rainfall could lead to flash and urban flooding over the Leeward and Virgin Islands. Across Puerto Rico and the Dominican Republic, heavy rainfall may lead to flash, urban and small stream flooding, along with the potential for mudslides. 3. There is a risk of wind and rainfall impacts across the rest of the Dominican Republic, Haiti, the Turks and Caicos Islands, the Bahamas, and Florida next week, and interests in those areas should monitor the progress of Grace and updates to the forecast. FORECAST POSITIONS AND MAX WINDS INIT 14/1500Z 16.2N 57.9W 40 KT 45 MPH 12H 15/0000Z 16.8N 60.6W 45 KT 50 MPH 24H 15/1200Z 17.5N 63.8W 50 KT 60 MPH 36H 16/0000Z 18.1N 66.4W 50 KT 60 MPH...OVER PUERTO RICO 48H 16/1200Z 18.6N 68.6W 50 KT 60 MPH...OVER DOMINICAN REP. 60H 17/0000Z 19.4N 70.7W 45 KT 50 MPH...OVER DOMINICAN REP. 72H 17/1200Z 20.5N 72.8W 45 KT 50 MPH...OVER WATER 96H 18/1200Z 22.8N 77.3W 45 KT 50 MPH 120H 19/1200Z 25.4N 81.2W 45 KT 50 MPH $$ Forecaster Berg

Fred is dead. For now.

It should be early afternoon from what I saw online. Here's the link to find recon plans, but sometimes it's easiest to just follow on Twitter (I follow the official recon page and @TheAstroNick) in case there are flight changes. I believe today's flight will have both low level recon and high level environmental sampling that'll go into the models. https://www.nhc.noaa.gov/recon.php

Good point. Probably still a bit tilted, so it'll be helpful to see what kind of organization there actually is when recon gets there. Early morning microwave images showed strong convection, but not much in the way or banding or the kind of organization you'd see with a TC putting up an inner core. The last few hours have looked good from the satellite view however, and I'm starting to think the models that showed a weaker system into the Greater Antilles are going to be way off. Note how both the GFS and Euro show some organization right before PR. As this slows down and aligns it could ramp up a good bit given where it is right now and the favorable environment ahead.

Let's talk about the latest named storm in what has been a very active season so far, Grace. After struggling through the day, last night the system started producing more vigorous convection, although it wasn't necessarily reflective of organization. This (early) morning's microwave imagery revealed a little more organization, but nothing particularly impressive. I believe this is because although Grace has been in a warm SST environment a combination of fast forward motion, shear, and dry air was inhibiting the kind of robust and consistent convection to allow for faster organization. This morning has looked a little different, though. Although there is some shear still present, the overall presentation of Grace has improved markedly, with deep and persistent convection near the center and improved outflow (which may be important later in the forecast period). This image shows me that favorable conditions are likely until it reaches the Greater Antilles. SSTs/TCHP certainly aren't an issue at this time. That said, although it looks good on satellite, we need to see what the structure inside is. Sometimes you see these satellite improvements but the internal improvements, which are what matter the most, are lagging. Recon should be investigating later, and that will be critical to understanding what happens next. For now though, we have a tropical storm that at least from afar is trying to organize in a favorable environment. Let's talk about the guidance. First, I think it should be noted that the guidance has struggled to initialize Grace well. As you can see here, the Euro doesn't have grace looking as robust as it currently looks in reality. That can have downstream impacts as specific track matters a lot here. But, for the purposes of illustrating the possibilities let's look at it. The Euro has Grace developing on approach to PR, and then has it skirt the northern coast of DR/Haiti as it rounds a strong ridge which has been the dominant feature of the summer in the Atlantic. What you don't necessarily see is there's likely to be an increase of shear as a TUTT/PV streamer sits over the southwest Atlantic. You can already see the shear in the image below. Grace should avoid the worst of it, but it doesn't take much to be very disruptive. These can be very difficult to forecast, especially if a system is stronger than anticipated when reaching it. Eventually though, on this run the combination of shear and land interaction is too much, and Grace fades into the sunset after reaching Florida. Now here's the GFS, which has bounced around between nothing and something more significant. Here, the GFS is more or less on top of the trend toward something stronger at the start, and note the organization that happens right before PR. That's definitely something to watch for folks down there, as it signals that a favorable environment is likely. The GFS threads the needle here, with Grace staying just south of PR, and then heading through the Mona Pass and safely avoiding DR/Haiti. While shear is still present (and watch that little subtropical critter near Bermuda) Grace never gets truly disrupted, and is able to handle whatever shear there is as it gets toward even warmer waters. That Sets the stage for something more robust for Florida and potentially the East Coast. There's a lot to sort out, but my opinion remains the same--Grace looks like a threat to the US, and has a high ceiling, if it can avoid taking a Fred like track. We need to watch for two things, I believe, in the next 24-48 hours. 1) Does the ridge over the SW Atlantic allow for a further south/westward track over the Greater Antilles, or will the current organization of Grace allow for enough of a poleward push to avoid the islands? 2) Does Grace take advantage of the most favorable environment for a TC so far this season to outperform expectations in the short term? The current IR images are compelling, and I am inclined to say that Grace is organizing underneath the convection, but we need to wait on recon to examine the organization that may or may not be taking place. With a small storm like Grace, things can ramp up quickly, so if there is an inner core developing, rapid intensification odds increase significantly in this environment.

It's not THAT bad We think it's worse than it actually is because weenies here toss it around like it's a global. That's like trying to sub a kicker in at middle linebacker. Won't work. If you have a system that has a closed and relatively stable LLC, it's the best intensity guidance in the toolbox.

Wow. That’s impressive. Look at this track shift in 24 hours. Quite unusual for the NHC. Should be noted that the end point is still inside the original cone. last night tonight

Some will still be calling for a hurricane No doubt. To be clear that’s not what I’m calling for. If I were making an intensity call at landfall I’d probably go 60mph/1004mb or something in that ballpark. Still sheared, with most of the rain (and a lot of it) on the eastern side as usual. Moderate strength TS.

It’s not surprising that Fred looks awful. Virtually all the guidance keeps this system struggling about 36 more hours. I don’t think its current appearance is indicative of what it’ll look like in a more favorable environment. Not saying it’ll be a hurricane lol, but it’ll have a good chance to reorganize in the Gulf.

Absolutely. Love me some HWRF, but when it’s not in its wheelhouse it can be hot garbage.

The op looked like a carbon copy of Fred. Don’t see that often.

This. A stronger system with better outflow should also be able to push back against the PV streamer that would otherwise shear the heck out of it. That’s why these trends in the next 1-2 days are so important.

This is a very good presentation of TD 7 going into sunset. If it can keep that convection going near the center it’ll be a TS in short order.

I can’t see the tweet, but I saw today that this is about as strong a long range signal for US threats as I’ve ever seen for the peak of a hurricane season.

Tropical Depression Fred Discussion Number 17 NWS National Hurricane Center Miami FL AL062021 500 PM EDT Fri Aug 13 2021 Although there has been a general increase in convection associated with Fred since this morning, the system remains disorganized with the low-level center moving farther inland over central Cuba. Earlier ASCAT data detected an area of 25-27 kt winds over water to the northeast of the center, and based on that data, the initial intensity is held at 30 kt, which could be a little generous. Since the previous advisory, Fred has been moving nearly due westward, but the longer-term motion is estimated to be 280/10 kt. The cyclone is nearing the western periphery of a subtropical ridge that is centered over the western Atlantic. This should cause Fred to turn west-northwestward tonight, and then northwestward on Saturday. The latest interpolated guidance that was initialized with the more southward and westward 18Z initial position shows a wider or more gradual northwestward turn, and therefore has shifted significantly westward, especially in the short term. However, the global models fields track the 850-mb vorticity center more along the northern coast of Cuba and some of those models suggest a center re-formation could occur on Saturday near the north coast of Cuba or over the Straits of Florida. As a result, the first 24-36 hours of the track forecast has been adjusted about a degree westward, but it is not as far west as the trackers, leaving open the possibility that a center re-formation could occur. After that time, the NHC forecast lies along the eastern side of the guidance envelope in best agreement with the 12Z GFS. Some additional westward adjustments may be necessary until the track guidance stabilizes. It is worth noting that it isn't too surprising to see these type of models shifts with a system that remains quite disorganized. Fred remains within an area of moderate southwesterly vertical wind shear, and the model guidance generally indicates that this shear will continue during the next day or so. Since it will also take time for the system to recover after its passage over Cuba, only gradual strengthening is indicated during the next day or two. After that time, the system could be in a somewhat more favorable environment, and the NHC intensity forecast calls for some strengthening until Fred reaches the northern Gulf Coast, which now doesn't occur until around 72 hours with the wider turn shown in the track forecast. The NHC intensity forecast lies between the various consensus aids, the statistical guidance, and the HWRF model, which all generally show the system peaking in 60-72 hours. The intensity forecast remains of lower-than-normal confidence due to Fred's continued interaction with land. Users are reminded to not focus on the exact forecast track as heavy rainfall, gusty winds, and a chance of tornadoes will extend far to northeast and east of the center, and those hazards are likely to still affect portions of the Florida peninsula, despite the recent shift in the forecast track. KEY MESSAGES: 1. Today through Monday, heavy rainfall could lead to areal, urban, small stream, and exacerbated river flooding across southern and central Florida into the Big Bend. From Sunday onward, heavy rain and flood impacts could extend into other portions of the Southeast and into the southern and central Appalachians and Piedmont as Fred interacts with a front in that area. 2. Tropical storm conditions are expected in portions of the Florida Keys on Saturday, where a Tropical Storm Warning is in effect. 3. Tropical storm conditions are possible late Saturday and early Sunday across portions of the west coast of Florida in the Tropical Storm Watch area. The risk of tropical storm conditions will spread northward along the Florida west coast and to the Florida Panhandle Sunday and Monday. FORECAST POSITIONS AND MAX WINDS INIT 13/2100Z 22.3N 79.6W 30 KT 35 MPH...INLAND 12H 14/0600Z 23.0N 81.0W 30 KT 35 MPH...INLAND 24H 14/1800Z 24.2N 82.6W 35 KT 40 MPH...OVER WATER 36H 15/0600Z 25.4N 83.7W 35 KT 40 MPH 48H 15/1800Z 27.0N 84.8W 40 KT 45 MPH 60H 16/0600Z 28.8N 85.7W 45 KT 50 MPH 72H 16/1800Z 30.2N 86.2W 50 KT 60 MPH 96H 17/1800Z 33.5N 86.5W 25 KT 30 MPH...INLAND 120H 18/1800Z 37.0N 85.0W 20 KT 25 MPH...POST-TROP/INLAND $$ Forecaster Brown

I’m not convinced yet the steering pattern will be there to slingshot this up the coast. That trough could just as easily be timed or oriented to be a kicker or too shallow to allow anything north of the Outer Banks. If I had to speculate at this range, I’d go with the latter. Of course, it has to miss the Greater Antilles first guys

I remember. I chiseled a lot of tombstones in my day.

I think the guidance handles the sparse data area fine—it’s really a question IMO of can they handle a developing wave because errors grow exponentially when initialization is wrong.

Keep in mind that TC intensity is not static. This could lose its LLC and become an open wave, but a robust wave with strong mid level spin could still regenerate in a more favorable environment. It’s not surprising Fred looks terrible now, but the eastern Gulf looks more conducive for organization and/or intensification with a reduced shear environment. Hadn’t looked until now but I don’t think anything comes of that. Too much wind shear to the north and sometimes convection blows up and collapses after a few hours.

Toss the op guidance

When PTC 7 organized itself further north, it put itself at greater peril for a greater Antilles strike, but also increased the odds for an East Coast impact. I think this one has a high ceiling somewhere if it avoids the Fred path. A lot to sort out. Toss the operational guidance for now.

LOL NHC must have heard me