May 2019 High Sierra Storm Activity to Recharge High Sierra Snow Pack


Alex Wierbinski's picture

By Alex Wierbinski - Posted on 14 May 2019

 

HIGH SIERRA WEATHER PROSPECTS

A, "Spring Recharge," is Underway...

Highly Unusual Sequence of Winter-Like Storms Headed for California (In late May!),
Weather West, May 14, 2019.

MAIN POINTS

End of Dry-Warm Strecth
"A very warm April and relatively warm start to May–coupled with rather dry conditions throughout the state during that period–will come crashing to an end tomorrow."

"...perhaps even downright stormy, conditions are expected across most of California over the next 10 days or so."

PCT & Widespread Effects
"...highly unusual nature of widespread significant rainfall (and mountain snowfall) this late in the season will likely catch a lot of folks by surprise, and will have some substantial impacts for the agricultural sector and those traveling (not to mention those poor souls just starting out on the Pacific Crest Trail)."

Get Ready to Rumble
"Widespread soaking rains will arrive across the northern half of California tomorrow, and will continue on and off for the next 10-12 days. Significant rainfall is also possible across much of southern California, although that will more likely come from subsequent systems."

Rain & Cold
"Total rainfall of 2-3 inches is likely *across most of NorCal,* including the lowlands; orographically favored mountain areas could see 5-6 inches or even more locally. 10-day rainfall totals will greatly exceed May monthly averages nearly everywhere; this storm sequence could easily set numerous daily rainfall records, and could singlehandedly push many NorCal sites into their top-10 wettest Mays on record. Needless to say: temperatures over the next 10 days should be well below mid-May averages throughout California."

Fire Season Delay Early
"...widespread rainfall of 2+ inches will likely delay the start of peak fire season by at least a few weeks, and could actually delay the vegetation “curing” (browning/drying) of seasonal grasses and brush across portions of the state."

Bigger Later?
"Long-term implications are less clear, though, since wet springs have historically been linked toward more severe fires late in the season (as the added moisture allows for increased vegetation growth, which inevitably dries out completely during California’s always dry summers)."

T-Storms Possible
"...at least a couple of these incoming storm systems will yield a decent chance of convective activity in the form of thunderstorms."

"(For you storm chasers out there: I would not be too surprised to see some rotating mini-supercells at some point, given the presence of cyclonically curved jet overhead and other favorable parameters)."

"...there will probably be at least 2-3 distinct periods of convective activity over the next ~10 days."

Strong Winds, Too!
"Strong winds from a Pacific storm system are quite rare in May, yet that’s exactly what some models are suggesting for early next week."

Why?
Screwed Up Arctic Weather
"It’s pretty clear that at least a partial cause of this wild winter pattern was the temporary disruption of the usually-robust circumpolar vortex…"

"In such cases, the Arctic itself tends to experience dramatic warming as its “cold air reservoir” is depleted."
"...extremely warm air temperatures and record/near-record low sea ice extent are occurring, with an unusually wavy (wavenumber 6) atmospheric pressure pattern across the Northern Hemisphere. As was the case this past winter, California once again appears to be the beneficiary of an unusually active North Pacific jet stream (especially for the time of year). "

MJO Behavior
"...noting that the Madden-Julian Oscillation has been very active for the time of year, and this too is likely contributing to the dramatic and unseasonable re-restrengthening of the east Asian jet (which extends across the Pacific toward California). As the MJO signal slowly propagates, it will eventually move into a position unfavorable for the continuation of active weather across California."

 

The Bottom Line

See my April 2 Evaluation of the last few years Winters, with my assessment of this year's status & potential, Esp. my Forecast for how this Spring plays out through extremes. I anticipated there would be further Tropical Transport Mechanism activity during May.

 

Tracking the High Sierra Spring Thaw of 2019

 

Forecasting Tropical Moisture & Heat Flows
North & Northeast Pacific Tropical Transport Mechanisms

 

 

Related

High Altitude Look at the Polar Vortex

This Thing is Freaking Out Right Now
EARTH

It is rotating clockwise as a High, rather than spinning in, as a Low. I can never remember seeing anything like this...

10 hPa, roughly 84,998.2 feet of elevation.

A rough table of pressures and altitudes.

 

 

Current Conditions

High Sierra Backpacker's Weather

High Sierra Backpacker's Calendar, May 12-18

 

 

MJO

The Madden-Julian Oscillation Changing in Warming World

 

Rossby Waves

Rossby Waves Tie Together Extreme Rainfall Events Around the World

 

Freak Arctic Warming

Alaska Skips Mid-Winter to Experience Late Spring Conditions in March

Abrupt Permafrost Thaw Underway Right Now

 

Earlier
The Polar Vortex

Polar Vortex Sliding off Top of Planet, Arctic Weather Plunges into North America

 

Polar Vortex Splits Under Warming Stratosphere

 

What Happens when You Grow Too Big for your Britches? The Arctic Vortex Weakens!

 

 

 

Trail News Forum

May 2019 Trail News

 

 

 

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