David Roth

16h

In the recent renovation of the TC/non-TC heavy rain event websites, I ran back across this hybrid beauty from late August 2000 that had somehow escaped a rainfall graphic. At least one NC WFO considered it a tropical storm. Subtropical seems a better description than tropical.

Not hating how this turned out, though the Northeast needs more work

A cyclone forming off the Southeast Sat onward has a good chance to be convective as -18C 500 hPa air moves over 28-29C SSTs. It’s by itself and should have periods of deep convection near the center while it lingers near/south of the Gulf Stream for days. Canadian output shown. 🐻⌚️

Hello, Josephine

Josephine currently

Josephine & Vance

Tropical Storm Vance is forecast to strengthen rapidly. Since the tropical eastern Pacific is not known for abundant couches, one of the favorability requirements is lacking. 🤣

The circulation of the convective nor’easter has again split from the warm conveyor belt to its east. There’s still stratus/cool air to its west. Convective lows are warm core, by definition. In theory, that would isolate them from nearby baroclinicity Likely enough for Sub TC. NHC is at 50/50.

The 12z UKMET, slightly asymmetric and moderately deep warm core.

NHC up to 70/70

Deep convection flared up nicely after sunset near and west of the center.

A broader convective increase is ongoing. 🐻⌚️

Lowell’s preliminary rainfall graphic

Moke’s preliminary rainfall graphic, such as it is

The storm force low starts to convect. The earlier tropical weather outlook increased odds to 40%.

Shallow convection remains near the nor’easter’s center. We’ll see if it can deepen tonight.

The cyclone starts to take shape

Guidance has a consensus on the low/nor’easter offshore the Southeast developing a moderately deep warm core. A few show a bursting pattern of deep convection starting tomorrow/Monday near its occlusion, which occurs over the following 2+ days. 🐻⌚️

The 17/00z GFS solution. More of the guidance shows a symmetric, moderate warm core with the nor’easter in 4-5 days. 🐻⌚️

It appears on the tropical weather outlook

Oct record high MSLPs possible Fri AM. But beware. Model MSLP is computed by forecast profiles, not standard. This tends to lead to 3-5 hPa positive pressure differences in the GFS/ECMWF west of 100W. Sometimes Canadian too. Not sure AI is designed to handle this issue.

Record high October sea level pressures appear to have been set broadly over WY, CO, & the Central High Plains. I’ll compile a list tonight. The 3-5 hPa difference between obs & models didn’t occur. This likely means that standard atmos vertical profiles are similar to model soundings currently.

The list of new October Record High Sea Level Pressures is preliminary

David Roth reposted

Tim Supinie

@plustssn.autumnsky.us

This morning's 12Z OUN sounding has a higher precipitable water than any other sounding taken outside the June 26-September 23 period. Hence the swath of very heavy rainfall in western OK overnight.

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Serious competition for candy corn @climatologist49.bsky.social

The first attempt to generate TC rainfall graphics via python solely. For Lala.

These seem better. :p

Nolo’s trip across the Pacific. It finally dissipated as a tropical cyclone on October 11.

The convective frontal hybrid slop is taking shape in the Gulf. There have been some truly hideous early October Gulf hybrids in the past. Sometimes they’ve been named, other times they have not. 🤞🐻⌚️

Simon, elongating Isaias near a front, and the Caribbean disturbance. Isaias continues to resist the shear, but its synoptic environment is adapting/evolving towards its destination as a purely extratropical cyclone. We’ll see when the dry slot forms, which would be the next step in ET.

Extratropical transition completed rapidly last night, with a sting jet bringing high winds to its west after sunset. Post-T.C. Isaias continues inland, and high winds remain possible in the southern Appalachians.

An array of convective lows in the western part of the North Atlantic presently, all experiencing vertical wind shear. Both the Caribbean and subtropical Atlantic systems appear well defined and non-frontal. Stratus and outflow restriction is seen on the NNW/NW side of Isaias.

After intensifying and looking more tropical during the day, there’s been a recent trend towards convective distortion and greater asymmetry. I’d say it’s starting extratropical transition, but it’s been near a frontal zone the whole time. ¯\_(ツ)_/¯

It’s a 2-for-1 sale near the Isthmus of Tehuantepec this morning as frontal progression, coastal curvature, & divergence aloft have led to disturbances on both sides, likely with surface lows. Expect them to diverge with time as the frontal hybrid lifts E/ENE and the Pacific disturbance moves W.

Compare and contrast the current situation (“compact” TD 9 & its neighboring convective frontal wave) to the situation two years ago today with a more tropical-looking Milton and its companion convective frontal wave.

Looks like Nolo switched from EP5 to CP2, which headed off the bin issue sooner. As CPHC has merged in with NHC, there’s a renewed effort to go to 10 bins in the northeast Pacific. It’s been needed since at least 1988, not long after the Eastern Pacific Hurricane Center was absorbed by NHC.

There are basic rules to follow concerning their movement. If there’s even a smidge of convection near the cyclone center, it will move parallel to 1000-500 hPa thickness lines. Model guidance still fails and tries to occlude convective lows unrealistically.

The 22nd of Nolo quickly becomes the 23rd as it transits the International Dateline, shifting its title from major hurricane to typhoon. It remains 15E. It’s been advised upon or outlooked since September 8th. Nolo is forecast to approach Asia in five days or so. 🐻⌚️

So true, @climatologist49.bsky.social

wpc.ncep.noaa.govMonthly sea level pressure records for the United States & Canada

There’s been a redesign of the Monthly Sea Level Pressure Records web page and the included maps. See what you think. www.wpc.ncep.noaa.gov/research/rot...

Post-TCs Fay, Hanna, & Gonzalo. On its 12th day, Fay is the most convective. Such a show off.

Good day, Hanna & Fay

The buoy 215 miles southwest of Hilo has seen its pressure fall a bit as Nolo passes by. It eclipsed its September record by 5 hPa, the previous record wasset during Iniki. The period of record is since 1984.