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WINTER WEATHER

WINTER WEATHER. FORECAST PROBLEMS INCLUDE: SNOW ICE STRONG WINDS. Scenes from a massive pile-up. Scenes from a massive pile-up. Deaths, injuries …. Destruction. Blame it on the ….….

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WINTER WEATHER

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  1. WINTER WEATHER • FORECAST PROBLEMS INCLUDE: • SNOW • ICE • STRONG WINDS

  2. Scenes from a massive pile-up

  3. Scenes from a massive pile-up

  4. Deaths, injuries …

  5. Destruction

  6. Blame it on the ….…

  7. 01-07-04The number of people dead in a massive pileup of more than 50 cars on Interstate 80 rose to six Wednesday as police and rescue crews finished combing through about 3,000 feet of wreckage. The accident -- involving at least 50 vehicles, 30 of which were tractor-trailers -- happened around 11 a.m. Tuesday. A snow squall caused a whiteout on I-80 near the Milesburg exit, just east of Bald Eagle Creek.

  8. At least six people were killed and dozens injured Friday in a massive pileup snarling miles of I-80 during a heavy snow squall.State police at Lamar said the accident occurred shortly before 1 p.m. when whiteout conditions apparently caused more than 50 vehicles to rear-end one another in the westbound lanes at mile marker 186 near Loganton."You couldn't see in front of you, it was a whole mess of cars," Frank Valley of Massachusetts, who was involved in the wreck here, told the Williamsport Sun-Gazette. "You couldn't avoid it, you just had to get into the pile." 12-29-01

  9. WINTER WEATHER SNOW CLIMATOLOGY

  10. WINTER WEATHER SNOW CLIMATOLOGY

  11. WINTER WEATHER SNOW CLIMATOLOGY

  12. TERRAIN AND PRECIPITATION 80” 60” 40” 20”

  13. WINTER WEATHER SNOW CLIMATOLOGY

  14. WINTER WEATHER • TYPES OF SNOW STORMS • SYNOPTIC-SCALE • Classic Cold Conveyor (i.e. ‘Noreaster) • Overrunning (Strong cyclone, Alberta clipper) • Jet streak • MESO-SCALE • Lake-effect • Oragraphic • Convective

  15. WINTER WEATHER The “Classic” Cold Conveyor Snowstorm

  16. WINTER WEATHER The “Classic” Cold Conveyor Snowstorm • ->>> Northwest of sfc/850mb low About 150 miles NW of surface low About 50 miles NW of 850mb low

  17. WINTER WEATHER The “Classic” Cold Conveyor Snowstorm Often yields widespread/ heavy snow CSI banding - model bias: underdoes amounts - model bias: not far enough to NW Duration

  18. WINTER WEATHER The “Classic” Cold Conveyor Snowstorm Narrower FZRA/PE zone In Cold conveyor area

  19. SNOW STORMS: TYPES • Classic Cold Conveyor • Northwest of sfc/850mb low • Often yields widespread/ heavy snow • These are the 1 to 3’ storms • Impressive snowfall rates • Often have 1-3”/hr rates • Narrow FZRA/PE zone • Can yield blizzards

  20. SNOW STORMS: TYPES • Overrunning • Less accumulation • Typically 2-6”, can be more • Shorter-lived snows • Snowfall rates can be impressive • Can reach 1-3”/hr rates • Followed by PE/FZRA/RN (Large cyclones)

  21. WINTER WEATHER Overrunning snowstorm (Strong cyclone)

  22. WINTER WEATHER Overrunning snowstorm (Alberta Clipper)

  23. WINTER WEATHER • FORECASTING AMOUNTS: • THREE FACTORS • QPF … How much liquid will fall? • Temperature … Will it be cold enough to snow? • Critical thickness … 850 0C … soundings • What will the liquid-to-solid ratio be? COOL WX website EWALL

  24. WINTER WEATHER • FORECASTING AMOUNTS: • QPF: • Consider CSI if ‘rip roaring cyclone • If max VV occurs where T near -15C … expect higher QPF • Temperature: • When its precipitating hard, models likely too warm • For coastal cities, model low-level T’s too slow to transition to colder values when surface flow turns offshore (after being onshore) • Ratios: • Temperature dependent • Cold conveyor: 8:1 to 20:1 • Warm advection (strong cyclone): 7:1 to 15:1 • Warm advection (Alberta clipper): 15:1 to 25:1

  25. WINTER WEATHER

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