RU848789

One never wants to "wish" a major hurricane on anyone, but if one thinks about the greater good, it's a bit lucky that this storm looks like it will hit the Big Bend area, the least populated coastal section of Florida, as per the graphic below. Still sucks for them, obviously.

This might help - the 0Z Euro moved landfall about 15-20 miles NW vs. 12Z today (was 976 mbar, 3 hours earlier)...

Can you elaborate on the physics of why a cyclone would be pulled east, relative to track forecasts, while approaching the west coast of FL? Obviously the track moved east relative to the forecast track with Ian, especially in the last 1-2 days before landfall (which is where we are now), but one could imagine many reasons for such shifts. Thanks.

Idalia really looking much healthier over the last several hours - much more concentric convection around the center, as the shear has obviously eased somewhat. But still a TS... Tropical Storm Idalia Discussion Number 10 NWS National Hurricane Center Miami FL AL102023 1000 PM CDT Mon Aug 28 2023 Idalia is producing intense bursts of convection near the center, with an overall comma-shaped cloud pattern along with a dry slot over the western part of the circulation. Upper-level outflow is restricted over the northwestern quadrant. Radar images from the Meteorological Service of Cuba show a partial eyewall forming. Flight-level and dropwindsonde data from NOAA and Air Force aircraft indicate that Idalia is very near hurricane strength. The maximum winds are set again to 60 kt for this advisory. The system has moved a bit slower than earlier today with an initial motion estimate of just slightly east of due north at around 7 kt. Idalia should be steered northward along the western side of a mid-level ridge and then turn north-northeastward due to a trough to its northwest. This track will take the center across the northeastern Gulf coast on Wednesday morning, and over northern Florida and southeastern Georgia thereafter. In 2 to 3 days, a mid-tropospheric trough moving off the eastern U.S. coast will likely cause the tropical cyclone to turn northeastward to eastward off the coast of the Carolinas. The official track forecast for this advisory is essentially the same as the previous one. This is near the middle of the track guidance, which are fairly tightly clustered, with the GFS on the left side and the ECMWF on the right side. Although Idalia is currently experiencing some moderate northwesterly vertical wind shear, the dynamical guidance indicates that the shear will lessen while the system is over the eastern Gulf of Mexico. This, along with a conducive thermodynamic atmospheric environment and high oceanic heat content, should cause Idalia to strengthen rapidly in the 12- to 36-hour time frame. The official intensity forecast, like the previous one, shows the system becoming a major hurricane before landfall along the Florida Gulf coast. This is in general agreement with the regional hurricane hurricane models, HAFS and HWRF, but above much of the other intensity guidance. Idalia is forecast to move into an area that is highly susceptible to storm surge, and regardless of the cyclone's specific landfall intensity, there is increasing confidence that a significant storm surge event will occur. KEY MESSAGES: 1. There is a danger of life-threatening storm surge inundation along portions of the Florida Gulf Coast where a Storm Surge Warning is in effect, including Tampa Bay and the Big Bend region of Florida. Inundation of 8 to 12 feet above ground level is expected somewhere between Chassahowitzka and Aucilla River. Residents in these areas should follow any advice given by local officials. 2. Hurricane conditions are expected within portions of the Hurricane Warning area along the Florida Gulf Coast, with the potential for destructive winds where the core of Idalia moves onshore. Strong winds will also spread inland across portions of northern Florida near the track of the center of Idalia. 3. Heavy rainfall from Tropical Storm Idalia is expected across portions of western Cuba and may produce areas of flash and urban flooding as well as landslides. Areas of flash and urban flooding, some of which may be locally significant, are expected across portions of the west coast of Florida, the Florida Panhandle, and southern Georgia Tuesday into Wednesday, spreading into portions of the eastern Carolinas Wednesday into Thursday. FORECAST POSITIONS AND MAX WINDS INIT 29/0300Z 22.0N 85.0W 60 KT 70 MPH 12H 29/1200Z 23.7N 85.0W 75 KT 85 MPH 24H 30/0000Z 26.2N 84.6W 90 KT 105 MPH 36H 30/1200Z 29.0N 83.7W 105 KT 120 MPH 48H 31/0000Z 31.5N 81.6W 50 KT 60 MPH...INLAND 60H 31/1200Z 33.2N 78.8W 50 KT 60 MPH...OVER WATER 72H 01/0000Z 34.0N 76.0W 50 KT 60 MPH 96H 02/0000Z 33.5N 72.0W 45 KT 50 MPH 120H 03/0000Z 33.0N 70.0W 45 KT 50 MPH

I see the HRRR near surface smoke forecast graphics on Pivotal, but they only go out to 48 hours (every 6 hrs); is there any decent smoke forecast model that goes out maybe 5-7 days that is available on-line? Thanks.

Fairly late-in-the-season cold snap with freeze warnings (dark blue) up for the Poconos, Sussex, W. Passaic and the Hudson Valley N of the Tappan Zee (and almost everywhere N/W of there) and frost advisories (light blue) up for Morris, Hunterdon, Warren, and much of the rest of NE PA. Strong high pressure, clear skies and diminishing winds, allowing for strong radiational cooling will send temps plummeting below 32F in the warning areas and near 32F in the advisory areas. Could also possibly see scattered frost in areas like NW Somerset and N Bergen. Bring in any tender vegetation. Fortunately, the red flag warnings for fire risk for much of SNJ/Pine Barrens come down at 8 pm tonight, as winds die down. Apart from some showers on Saturday, our stretch of fantastic weather looks to continue through the end of next week.

Why wouldn't I have wiped the board after 6 hours? One is supposed to do that and combine measurements.

Hey - did you measure at all? I'm not 100% sure what to do. We had about 0.6" on the board and most of the grass and the 1" on the car I took a pic of (and not much on some other lawns that were likely more in the sun), when I left around 5:15 pm to go to the RU game and got back around 9:30 pm and checked the board, which I had wiped before I left, and had another 0.4" on it, so I'm thinking of calling it an even 1.0". I was monitoring the radar after I left and it looks like Metuchen stayed pretty well under that band for a few hours after I left. I also see a report of 1.4" from Edison, so 1.0" seems reasonable. Thoughts?

here's the pic of 1" on the car. So odd. Still at 1/2" on the board, as intensity has let up a little, so some melting while falling. About to head to the bar and then the RU NIT game, so y'all are on your own...have fun...

We're up to 1/2" on the board on the lawn and the trees have about 1/2", while my undisturbed car in the shade has almost 1" on it and nada on pavement. I'm recording 1/2" right now, since the car is definitely an outlier - I've almost never seen this kind of difference before and I'm sure it's due to the car top being just slightly colder than the ground/board. Still 32F and coming down moderately, so we could get to 1" if that band stays over us (we'll be right on the eastern edge of it). Most years I wouldn't care much about every 1/4" but this winter is different.

If you're getting the moderate to close to heavy bands we're in now and others who also have had little snow this winter appear to be in, get yourself outside and walk around in it. It's a beautiful day - yeah it sucks that most of it has melted, but even falling snow with big flakes is very cool to see and we might not see any more flakes until next winter. Or 2026.

After about 4 hours of light to moderate snow at 33-34F, with a few light dustings established and then melted quickly as intensity lessened, just now we're finally getting sustained moderate snow (maybe 3/8 of a mile visibility (maybe 600-700 yards) at 32F and we now officially have a "full dusting" or "light coating" (whatever that is, lol) on the colder surfaces (and a good 1/4" on trees, but that doesn't count, lol) which translates to about 0.1". My guess is now that we're 2.5 hours past the full height of the sun and a little cooler, the snow will accumulate at least a little now. Radar looks good for me for the next 30 min or so. If we can hold onto this intensity once we have a cold layer on the ground, maybe we can pull off a whole 1/4-1/2". My other guess is that we've probably had 1/4-3/8" per hour snow "falling" rates for ~4 hours (I always think of 1/4" per hour as light with 3/8"/hr as getting moderate), so that's about the melting rate - could've had 1-1.5" over those 4 hours, but it's midday at March and it's been 33-34F until right now. Anyway, that's probably TMI for most, lol, but I get excited about this stuff, lol.

Just woke up from a decent nap and it's been snowing light to almost moderate and just trying to accumulate a little and then I was rooting around on the interwebz and a few minutes later, without having looked back outside, I checked the radar and basically said, OMG that should be close to heavy snow and looked up and it was, lol - almost a dusting! Down to 34F.

Just posted this elsewhere as a reality check, but damn if this verifies or even close to it, it makes our winter, given what we've gotten so far. The modeling gods wouldn't take this away from us now, would they? :>) This is not a forecast - it's just one model run, but it's a doozy... We've officially been NAM-ed, as the 12Z NAM which just came out shows the potential of this highly complex, very powerful nor'easter. This snowfall map is crazy and the snow falls after almost everyone gets an inch of rain on Monday (the transition to snow is by about 1-3 am Tuesday for most and is over by late Tuesday night). This kind of possibility is why so many have been following this so closely. We could still mostly whiff and get mostly rain for CNJ/NENJ/NYC and even much of NNJ/EPA, but this model run shows what is possible in this kind of explosive setup. Also, we're not 5 days out, we're 24-30 hours from the start of the event late Monday morning. Reminds me of the NAM for Jan 2016's blizzard, where it was the first model to sniff out the huge potential (about 48 hrs before the event, iirc). Stay tuned folks.

They're wrong, at least for what the NAM is showing, with great growth, heavy rates and surface temps dropping to around freezing (Kuchera only looks at the max column temp)...

It'll be at least 10:1 with good growth in the DGZ with the incredible lift and supersaturation we're going to have up there and surface temps now down to 31-32F during the height of the storm - CCB FTW!

Holy...

Comparison of 6Z/0Z Euro snowfall through 15Z Tuesday (10 am EST/11 am EDT), showing significant improvements for CNJ, NENJ, NYC/LI, which is key since before 15Z has better rates and is before the sun is too high (especially before 12Z), so accumulations are less likely to be melted.

The NWS in Mt. Holly upped their snowfall totals at 4 am relative to 4 pm yesterday, which is a good sign, as they're usually slow to respond to increases in modeled snowfall, but you can see that the NWS-Upton did not, given the discontinuities at the county interfaces (from 1-2" in Morris/Somerset/Middlesex to <1" across the magical border into Essex/Union/SI. I think the Mt. Holly numbers are much more reasonable, even if still conservative at this point, which I get, since 0" of snow and all rain are still on the table for these locations.

Best CMC run in 2 days...

Kuchera is an awful algorithm, though and often quite wrong, especially in moderate to heavy snowfall rate scenarios, where the ratios are largely set by the crystal formation in the DGZ, which can be fantastic regardless of the warmest temp in the column, which is the only variable Kuchera looks at - and assumes ratios get lower when that temp is above 32F, regardless of where in the column. So one could have fantastic growth rates/high ratio snow falling and Kuchera might still calculate a low ratio if the surface is at 34F, which is nonsense, since the surface goes from 34F to 32F once rates exceed melting and a frozen layer is established on the ground. Wrote a far longer post on Kuchera's suckage a couple of years ago - might try to dig it up. Having said all that, with modest to low rates and surface temps above 32F, Kuchera is better than 10:1 for guesstimating accumulation, but I also like the 10:1 maps, since they indirectly also always provide the QPF, whereas Kuchera doesn't.

Huge difference for NYC Metro/NENJ/LI at 60 hrs on the NAM3K vs. the NAM12K with respect to snowfall...

Thanks so much for the clear, detailed explanation, although it took me a little more time to digest it and looking at the 12Z Euro maps at 500 mbar and 700 mbar and comparing them to the ones you showed really helped. At 78 hr one can see how much further east the CMC closed off 500 mbar low is vs. the Euro and at 78 hr. Now let's see if I remember this for more than 2-3 model cycles, lol. And at 78 hr one can easily see how much further NE the CMC 700 mbar low is vs. the Euro, such that NW of the CMC 700 mbar low is New England and for the Euro that's far NNJ/NYC/LHV.

Definitely true, as the 12Z has the 6" line roughly around 80 and 18Z has it roughly around 78, a difference of ~20 miles and 20 miles is ginormous to those of us on the fringes of good snowfall, i.e., anyone south of 78. Still doesn't explain the discrepancy between SV and Pivotal snowfall maps, though.

Have seen moderately large discrepancies several times in the past week between snowfall amounts on SV vs those on Pivotal, with SV amouts being much higher and we're seeing it again. Does anyone know the difference between their snowfall estimation algrithms to know if one or the other is more accurate?