Transcript Adriatic Snow event of 5 March 2015: Capracotta, Italy Extreme

Heavy snow impacted Italy and the Balkans with record snows on both sides
of the Adriatic.
100.8” of snow fell in 18 hours. Pescocostanzo, Italy – 21 miles away – picked
up 94.5”. The WMO will confirm whether the snowfall did indeed surpass the
current 24 hour snowfall record (75.8” at Silver Lake, Colorado set in 1921).
Capracotta record snowfall setup
• Due to the terrain near Capracotta, this village is
most susceptible to weather coming from the
northeast. As noted in the upper air and surface
pressure, wind, temperature, and precipitable
water (PWAT) patterns attached, this event
provided a near-perfect setup for heavy snow.
The center of the low pressure system formed to
the southwest of the area; resulting in strong
northeast winds over the town. These winds
channeled high PWAT air over Capracotta and
temperatures continued to drop during the
event.
Italy : the terrain and station location
Zoomed In Terrain Near Capracotta
terrain favors upslope and funneled winds from northeast
The Pattern from the CFSRV2
Climate forecast system re-analysis version 2
• 500 hPa heights and anomalies
– Deep cut-off low develops over Italy south of affected
region
• Surface
– Secondary cyclone develops south of the region
– Surge high PWAT air from south and east of region
• 850 hPa
– Temperatures fell -4 to -6C
– Strong northeasterly winds
• Jet
– Strong 250 hPa jet about the close cyclone
500mb Pattern
Localized 500mb Pattern
Surface Pattern
Precipitable Water (PWAT)
250mb Winds
850mb Temps
850 U Winds
850mb V Winds
250mb U Winds
250mb V Winds
The impacts
• Pictures from the web and new outlets
– Deep snow
– Channels for roads between snow banks
– Buried cars
– Snow covered ski slopes til June?
Source: meteoweb.eu
Source: meteoweb.eu
Source: meteoweb.eu
Source: meteoweb.eu
Source: meteoweb.eu
Source: meteoweb.eu
Video – enter slide show mode and click play to view or visit
https://www.youtube.com/watch?v=GjsUgauEzVs
Source: ABC7 WJLA
Video – enter slide show mode and click play to view or visit
https://www.youtube.com/watch?v=9it3Sge13y0
Source: Telemolise
GEFS forecasts
• Indications of potential heavy precipitation
– 24 hours 25 to 75 mm
– Localized in Italy and Balkans
• Pattern well predicted
– 500 hPa
– Winds
– Cold for snow
GEFS Probability 25 mm QPF
24 hour period 6-Forecast cycles
GEFS Probability 25 mm QPF
24 hour period
GEFS mean QPF and each member
75mm or more QPF
500 hPa and anomaly forecasts
18Z 5 March
V-wind forecasts
U-wind forecasts valid 18Z 5 March
850 hPa temeperatures
GEFS forecasts
• Indicated the pattern and potential
• QPF was in the general areas of heavy snowfall
– Regional area of Italy
– Regional area of Balkans
• Strong 850 hPa winds well predicted
– Case model QPF knew where lift was
– Regional scale models likely would have focused the
QPF and refined forecasts of heavy snowfall which is
beyond the skill of a global forecast system.
Snowfall map
7-day snowfall may from March 5th to March 11th, 2015
Source: snow-forecast.com
NASA imagery from 10 March 2015, showing the snowfall impact from the event.
Source: meteoweb.eu
Summary
• Record snow event for city
– Possible but unlikely world record snowfall for 18
hours.
• Cut-off low for late season snow
– Had several signals in the standardized anomaly
fields
– Strong forcing implies some predictability