Evaluation by forecasters at the NESDIS Satellite Analysis Branch during the 20062007 winter with fo

1
Validation

• To highlight areas favorable for highly efficient
  snowfall based on real-time GOES imagery and
  short term numerical weather prediction data
• Identify areas where saturated vertical ascent is
  collocated within a narrow temperature range
  (centered at -15ºC).
• This temperature range is favorable for efficient
  snow production as a result of the preferential
  growth of dendritic ice crystals by deposition.

• Algorithm -15C pressure level was tested by
  comparing RAOBS that were coincident with
  algorithm output at 1115 and/or 2315 UTC. 
• Algorithm pressure level determined by taking
  mean pressure of a 5 x 5 pixel area over each
  RAOB station.
• To ensure that only deep clouds capable of
  producing moderate to heavy precipitation were
  validated, only -15C pressure levels collocated
  with at least -5 µb/sec were included in the
  sample.

for areas with cloud tops lt -15C
for areas with cloud tops lt -15C and upward
motion greater than -5 µb/sec near -15C

• Effective cloud amount, cloud top pressure and
  cloud top temperature from GOES imager cloud
  products
• Determines pressure level of -15C by assuming a
  moist adiabatic lapse rate from cloud top to
  pressure level of -15ºC
• Collocates areas of significant lift (defined as
  -5 µb/sec) from Rapid Update Cycle (RUC) analysis
  with the -15ºC pressure level.

Future Initiatives

• Include results of validation into a more
  accurate determination of the -15C pressure level

RUC analysis
UVV data input into algorithm with vertical
resolution of 25mb to best highlight the
collocation of -15C and the maximum in saturated
vertical ascent

• Evaluation by forecasters at the NESDIS
  Satellite Analysis Branch during the 2006/2007
  winter with follow up testing during the
  2007/2008 winter.
• Algorithm available at
• http//www.nssl.noaa.gov/rabin/dendritic/index1.h
  tml

References
Auer, A. H. Jr., and J. M White, 1982 The
Combined Role of Kinematics, Thermodynamics, and
Cloud Physics Associated with Heavy Snowfall
Episodes, J. Meteor. Soc. Japan, 60,
591-597. Waldstreicher, J.S., 2001 The
Importance of Snow Microphysics for Large
Snowfalls, Preprints, 3rd Northeast Operational
Workshop NOAA/NWS Albany, NY, Available online
at http//www.erh.noaa.gov/er/hq/ssd/snow micro/.

bob.rabin_at_noaa.gov