🚨PolarWx Update🚨 The website is now back up again. Over the next 1-2 weeks some model suites will be down for underlying restructuring. Due to ongoing tropics activity, disruptions to the real-time tropical cyclone page will be as minimal as possible. polarwx.com/tropical/

While I could just leave this up and laugh that Google AI missed a major game tomorrow, I’ll use this as an example to highlight the probabilistic nature of LLMs. As I’m in NYC, searching “game tomorrow” 100 times showed: - 53 times both FIFA & Yankees - 43 times only Yankees - 5 times only FIFA

Found it! What do I win

One of those days where flash flooding risks outweigh the severe risks in the NYC metro — parts of NYC are going to end up in the 2-3” ballpark when this round moves out, almost all in the span of an hour

Another implication of the smoke plume - in addition to weak forcing for ascent, sufficient instability and elevation over northeast PA, the differential heating gradient near its south edge likely provided a boundary for convective initiation:

With how thick the smoke plume is today, it also had an impact on temperatures by reducing sunlight at the surface. Most weather models don't factor in smoke plumes - and those models were as much as 10-15 degrees too warm today where the smoke concentration was most dense.

While the record-breaking ridge has already decayed a lingering cutoff low stalled over southeast Canada will lead to a strong northwesterly low-level jet lingering through Friday. This will continue to direct thick plumes of near-surface smoke into the Mid Atlantic & Northeast into Friday.

Indeed, it was right around the peak of this hot, dry and windy airmass in SW Ontario on Monday afternoon that the most significant fires initiated with a massive smoke plume rapidly being transported to the east by the strong westerly winds aloft:

Strong southwesterly flow to the west of this ridge led to strong downslope flow off the Rockies into the upper Midwest. This led to very hot, dry and windy conditions - ripe for fire initiation+growth - spreading across the upper Midwest & southern Ontario/Manitoba.

The precursor to these fires is a massive upper-level ridge last weekend into early this week - sending temperatures in Montana soaring into record territory in the 110s - with the ridge itself the strongest in that region since reliable ERA5 reanalysis data began in 1950.

Parts of the Northeast US have been under a thick plume of smoke today overspreading the region from fires across south-central Canada - the worst smoke plume to affect the region since the infamous 2023 NYC smoke plume. Thread for the meteorology associated with this:

Already over 2-3” in spots with additional convective rain bands from the south appearing likely to merge into the dominant quasi-stationary rain band… this isn’t going to end well for localized areas

We are already seeing the beginnings of this unfold, both from near-stationary convection along a moisture flux convergence boundary in NE PA/NW NJ/SE NY (expanding to CT later tonight), and from slightly faster but torrential rain bands over SE PA headed towards the Philly-NYC metros.

There's a real risk of compounding hazards in parts of SE NY & Connecticut - some of the same areas hit by destructive storms yesterday are at risk of localized rain totals over 4-8" tonight through Tuesday with a slow-moving system. This could well prolong the recovery time for parts of the area.

“Well actually…”

Not that close to 2 feet of rain over 4 days is insignificant by any means — yet it still manages to pale in comparison to an isolated portion of Louisiana that received over 2 feet of rain in **12 hours alone** today:

When using radar-derived rain totals, keep in mind that not only are these estimates at best, but their durations also vary. Take this example from the Mobile, AL radar — max estimate over 25”, but the label on the bottom left shows it’s a 4-day total estimate, not just today.

Extreme flash flooding occurred in Louisiana today, where localized but prolonged training convection led to over 2 feet of rain per MRMS estimates. While isolated, this was supported by synoptic-scale moisture flux convergence from a slow-moving mid level vortex moving onshore.

Worcester, MA has been around 37/38 degrees with a strong N to NNE wind through the afternoon so far. Airport obs show rain but with scattered mPING reports of snow/sleet mixing. This is an unusual wind & temp combo for any time of day in May, let alone midday at the end of May.

This is the last storm anyone in the northeast US will get NAM’d. An era comes to an end

Yes, this airmass is cold enough that snow is in the forecast for some in the region. The question is just how low snow levels will fall, as models differ on this depending on how they resolve PBL profiles during wetbulbing.

As is typical for unusually chilly air masses for this time of year, this event is associated with a tropopause polar vortex (TPV) rapidly transported SSE from northern Canada, keeping airmass modification relatively muted, while associated with a locally enhanced cold pool.

Indeed, using IEM to plot the wind rose for temps below 45F in the month of May (regardless of time of day) in Worcester, MA, northerly/NNE wind is less common than NE or west. I’d imagine this is more dominated by overnight hours in the latter part of the month.

Not only is it impressive to see midday temperatures below 50F across southeast New England at the end of May, it is even more unusual to have it occur with predominantly northerly wind and not ENE onshore flow off the chilly waters.

When I saw someone share this I knew I had to reproduce it myself and the results did not disappoint

I was… mentally impacted by these storms (As anyone at SUNY Albany in the CSTAR program on May 15, 2018 recalls)

The Middle East is about to get extremely stormy - from a weather perspective, that is. A deep trough over Egypt & Saudi Arabia is expected to force a severe weather outbreak & torrential rain capable of extreme flooding over UAE, parts of Iran, and the Strait of Hormuz.

It’s the 5 year anniversary of this thing happening

One of the wildest 24-hour loops you'll see in the Mid Atlantic - from mid-upper 80s and tornado warnings to 33F and heavy snow

On the left: 4pm today, with 85-90 degrees across Virginia into Washington DC On the right: 4pm tomorrow, with widespread snow across Virginia into Washington DC Going straight from summer to winter in just 24 hours