Friday, April 14, 2017

Mid-April Weather Doldrums

The weather doldrums seem to have spread from southern Arizona across much of the CONUS for mid-April. Above map (which is blurry in all versions for unknown reasons) shows severe thunderstorm reports to SPC yesterday - April 13th. There were only two. Weak tornadoes were reported near Bend, Oregon, and Wichita Falls, Texas, and that was it.

The large-scale pattern is dominated by a split flow regime that leaves the Plains under a weak trough in southern branch, below a bent-back ridge that extends from Minnesota northwestward toward Alaska. The pattern has resulted in strange vertical wind profiles that are not supportive of organized thunderstorm systems.

The sounding from Dodge City, Kansas, this morning provides a nice example. There is considerable CAPE above 700 mb, but a strong low-level jet gives way to wind speeds of 15 to 20 kts from 500 to 300 mb. This produces the bizarre hodograph shown below - strongly veering jet below 2 km, topped by weirdness resembling an accordion. Not exactly a classic Plains supercell hodograph.

Locally, not much in sight except for some windy afternoons - rain seems far away in the model forecasts.

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