ICEDAMAGE

INDEX

RADIAL ICEAMOUNT

(inches)

WIND(mph)

DAMAGE AND IMPACTDESCRIPTIONS

1

2

3

4

5

0.10 – 0.25

0.10 – 0.25

0.50 – 0.75

0.10 – 0.25

0.50 – 0.75

0.75 – 1.00

0.50 – 0.75

0.75 – 1.00

1.00 – 1.50

0.75 – 1.00

1.00 – 1.50

> 1.50

15 - 25

25 - 35

15 - 25

< 15

> = 35

15 - 25

< 15

25 - 35

15 - 25

< 15

> = 25

> = 15

Any

Some isolated or localized utility interruptions are possible, typically lasting only a few hours. Roads and bridges may become slick and hazardous.

Scattered utility interruptions expected, typically lasting 12 to 24 hours. Roads and travel conditions may be extremely hazardous due to ice accumulation.

Numerous utility interruptions with some damage to main feeder lines and equipment expected. Tree limb damage is excessive. Outages lasting 1 – 5 days.

Prolonged & widespread utility interruptions with extensive damage to main distribution feeder lines & some high voltage transmission lines/structures. Outages lasting 5 – 10 days.

Catastrophic damage to entire exposed utility systems, including both distribution and transmission networks. Outages could last several weeks in some areas. Shelters needed.

The Sperry-Piltz Ice Accumulation Index, or “SPIA Index” (Copyright – February, 2009)

(Categories of damage are based upon combinations of precipitation totals, temperatures and wind speeds/directions.)

0.25 – 0.50 < 15

0.25 – 0.50

0.25 – 0.50 25 - 35

0.25 – 0.50 > = 35

0.50 – 0.75 > = 35

0 < 0.25 < 15 Minimal risk of damage to exposed utility systems; no alerts or advisories needed for crews, few outages.

Weather Conditions and SPIA Index Levels at a Glance:

Ice and Wind: < 15 15-25 25-35 > = 35

0.10 – 0.25

0.25 – 0.50

0.50 – 0.75

0.75 – 1.00

1.00 – 1.50

> 1.50

Radial Ice in Inches; Wind in Miles per Hour.

0

1

1 2

2

2

3

3

3

3

4

4

4

4

5

5 5

5 5 5

5 5 5 5

mph mph mph mph

inches

inches

inches

inches

inches

inches

Tuesday Jan 27 2009

Additional Ice Forecast 3pm Tuesday to end of the event.

SPIA combining what fell and the 3pm forecast to the

left.

Determining Significance and its Potential Impact

Determining Significance and its Potential Impact

• Standardized AnomaliesN = (X – m) / s

– X: Variable – (X – m) traditional anomaly

– m : the centered-daily mean value– s : the centered-daily standard deviation

Frequency of Anomalies Found Over Eastern North America

Frequency of Anomalies Found Over Eastern North America

The biggest anomaly found over eastern North America

Vertically Integrating Each Variables Value for Event

Vertically Integrating Each Variables Value for Event

• NTemp : absolute value of anomaly at a level for a variable.

• MTemp : average of all anomalies over Pressure surface for a variable – From 1000 to 200 hPa

• Compute MTOTAL:

MTOTAL = (MHEIGHT + MTEMP + MWIND + MMOIST)/4.

• Objectively find big MTOTAL days and events.

Re-analysis Ranking by MTOTAL 1948-2005Rank Date MTOTAL Description References

1 00Z09JAN1956 4.950 "The Great Atlantic Low" Ludlum 1956

2 12Z15JAN1995 4.722 Deep Gulf of Mexico Storm

3 00Z14MAR1993 4.576 Superstorm of 1993 Kocin et al 1995; Dickinson et al 1997

4 12Z11JAN1975 4.566 Severe Minnesota Blizzard

5 12Z08JAN1998 4.536 NE US/SE Canada Ice Storm Gyakum and Sisson 1999; DeGaetano 2000

6 12Z28DEC1980 4.469 Deep Carolina Coastal Low

7 12Z17MAR1983 4.464 Low-latitude intense cyclone Dickinson et al 1997

8 00Z26NOV1953 4.396

9 00Z16OCT1954 4.391 Extratropical Hazel Knox 1955; Palmen 1958

10 12Z08JAN1958 4.356

11 12Z19JAN1977 4.340 Historic Florida Freeze Schwartz 1977

12 12Z19JAN1996 4.307 NE US Flooding/Snowmelt Leathers et al 1998

13 00Z10JAN1978 4.260 Deep NE U.S. Storm

14 12Z31OCT1993 4.232 E. U.S. Elevation Blizzard Grumm and Nicosia 1997

15 00Z04FEB1970 4.201

16 12Z22DEC1972 4.199 Deep Gulf of Mexico Storm

17 12Z11DEC1950 4.192

18 12Z17NOV2002 4.185 Southern/Central New England Ice Storm

19 12Z26JAN1978 4.179 The Cleveland Superbomb Gaza and Bosart 1990; Hakim et al 1995,1996

20 00Z20OCT1989 4.179 SE U.S. Record Cold & Snow

21 12Z22JAN1959 4.176 Severe E. U.S. Snow/Ice Storm Treidl 1959

Interesting sitesInteresting sites

• Reanalysis sites:– Standardized anomalies: http://hart.met.psu.edu/meteo497/mapper.html – http://www.hpc.ncep.noaa.gov/ncepreanal/

• Observed– Blended TPW http://www.osdpd.noaa.gov/bTPW/– Precip type, QPE http://nmq.ou.edu/– Snow and ice analysis http://www.nohrsc.nws.gov/interactive/html/map.html

• Advanced Warning Operations Course – Winter Weather Track– http://www.wdtb.noaa.gov/courses/winterawoc/lessons.html

Interesting sitesInteresting sites

• Models (besides OWL)– Experimental NCEP model site– SREF with standardized anomalies: http://cms.met.psu.edu/sref/ensembles/

• Learning about Standardized anomalies– http://nws.met.psu.edu/

• HPC Winter Weather impact forecasts– http://www.hpc.ncep.noaa.gov/wwd/impactgraphics/

• WRFensemble data– http://wrfensemble.wdtb.noaa.gov/