Jack Sillin

Proper resolution of diabatic heat released by convection in the WCB will be critical to accurately predicting the storm's forecast track. Note sensitivity analysis showing strong dependence of both track and intensity on the strength of the downstream ridge: This gives me additional reason to be skeptical of the southerly outliers since they're mostly GFS-based and thus lower-resolution/parameterizing convection But it's also worth noting a model like the NAM has a bias towards overdoing convection so its outlier output on the other end of the spectrum should a

Gmorning friends. 06z Euro substantially more amplified/NW with the ULL which is about what we'd expect given the sensitivity analysis conducted yesterday and subsequent RAOB sampling of the shortwave over Oregon maps via weathermodels.com

Updated blog post exploring the dependence of medium-range track on short-range intensity for those interested: https://blog.weather.us/hurricane-isaias-struggling-with-shear-and-dry-air-in-the-bahamas-this-morning/ TLDR strong storm goes east, gets stronger and vice versa. You probably knew that though! The blog explains why that's the case

Key idea to watch on satellite imagery this AM: to what extent can new hot towers rotate upshear? Zoomed in GOES-East meso sector https://weather.us/satellite/743-w-215-n/satellite-superhd-1min/20200731-124723z.html#play-0-30-10

Rise and shine! Isaias now (allegedly) a hurricane. Not sure latest recon pass still supports that. Biggest task today is fending off dry air and shear from the SW. I see that the 3km NAM is up to its usual antics with a 965mb off FL https://weather.us/model-charts/conus-hd/800-w-320-n/sea-level-pressure/20200802-1800z.html. Don't fall for it! Here's why: https://blog.weather.us/why-does-the-3km-nam-persistently-overforecast-tropical-cyclone-intensities/ All eyes on the medium range forecast should (IMO) be focused on the extent to which Isaias interacts wit

Latest HWRF more bullish on axisymmetrizing convection tomorrow as Isaias treks through the Bahamas. Would improve the odds of a stronger (cat2+) storm in NC greatly. For those curious, I wrote a detailed blog explaining the implications of trends like this (and others important to the storm's future) https://blog.weather.us/tropical-storm-isaias-likely-to-threaten-the-east-coast-as-a-hurricane-this-weekend/

Tis the season... Already had Arthur and Bertha so we're off to a hot start. 92L out in the open Atlantic (https://weather.us/satellite/546-w-263-n/satellite-color-super-hd-15min/20200529-2020z.html) might claim "Cristobal" first but it's no threat to land. Perhaps the first real issue of the season will emerge from the developing Central American Gyre? Some longer musings: https://blog.weather.us/could-we-see-the-third-tropical-cyclone-of-the-2020-season-form-in-the-gulf-of-mexico-next-week/

going.. going... gone was always gonna be tricky but I'm running out of plausible paths to an interesting event SW of Nova Scotia. #WagonsNortheast

Looking for hope that the weekend storm ends up a hit? ECMWF gets us within a rounding error on the lead s/w timing but the GFS offers no such opportunity. Why do I think the ECMWF has a better handle on things? Let's take a trip to Hawaii Thunderstorms. Thursday evening. ECMWF prob better than GFS' efforts to parameterize. Known bias Diabatic enhancement of jet streak. Thursday evening. Sends our secondary s/w digging instead of sliding. and voila, if you can get that lead s/w tucked back into NC/SC you should be in business (ECMWF left panel). We r

00z ecmwf a lot closer to a hit than most prob think IMO. Check out how the Pacific jet buckles and now we have strong NW winds over ND as opposed to W winds just a little shortwave timing off from getting a storm (vs making an impossible connection in Zonal flow) prob explains why more EPS members went for the coastal track last night (though while keeping it on the shallower side until it's in the Maritimes)

ICON kept the storm closer to the coast, but it left 80% of the southern stream disturbance behind over the GOM. Picked up enough for >flurries but if you're lookin for the big one, it's gonna be hard to find in this pattern (I talked a lot more about that https://blog.weather.us/forecast-for-weekend-east-coast-storm-remains-uncertain/ for those interested)

Opening salvo from 12z global guidance comes from the ICON (German) model... Certainly looks promising though man are we leaving some energy behind over TX/Mexico. For those interested, I put some longer form thoughts up on the blog this morning: https://blog.weather.us/forecast-for-weekend-east-coast-storm-remains-uncertain/

focus on the west coast, more ridging there would increase the odds of a phase out east

here's a trend in EPS guidance you probably weren't looking for, but is certainly encouraging

ECMWF deterministic is wide right, but seriously check out what happens after it roars into the Gulf of Saint Lawrence. Its diabatic outflow jet is so strong it puts up a giant Greenland block! Moreover, the immense poleward and upward heat fluxes from that type of event may be enough to split the stratospheric PV (in tandem with the building Alaskan ridge Any of the long range specialists feel free to tell me this is bs, but I'm starting to think there may be a big silver lining if this misses