Day 1 Diagnosis

1
Day 1 Diagnosis Forecast methodology

• J. LaDue
• Winter Wx workshop 2003
• Boulder, CO

2
A miniscenario

• It is 05 UTC
• Its Tuesday night and the first arctic outbreak
  of the season has arrived
• A large scale upper-level trough lies to the
  west.
• An passing shortwave failed to produce expected
  snow the previous afternoon
• The ETA is out and its time to start thinking of
  a forecast.

3
A miniscenario

• You could just use model Omega and forecast
  precip
• This could result in meteorological cancer
• To avoid that, we will look at real data and
  conceptual models.

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850 mb 00 UTC
5
700 mb 00 UTC
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500 mb 00 UTC
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300 mb 00 UTC
DCVA
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A short-term forecast methodology

• Check accuracy of model analysis
• Diagnose model analysis for winter precipitation
  ingredients
• Planview maps and cross-sections
• Adjust model-based ingredients with real data
• Make the forecast
• Further adjustments with real data into forecast
  period

9
Check the sanity of model analysis

• For example with ETA analysis, compare these
  parameters to raobs, profilers
• SFC T, Td, wind, pressure
• 925 - 500 mb T, T-Td, wind, height
• 300 mb and up T, wind, height
• These offer direct comparisons to check validity
  of model analysis
• WV/IR imagery can be used to qualitatively
  evaluate strength of systems

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Diagnosing ingredients for winter precip

• Forcing
• Stability (response to forcing)
• Moisture
• Precip efficiency
• Precip type
• Also helps to figure out where that dang precip
  came from

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Diagnosing ingredients for winter precip

• Forcing What type, where and how strong will it
  be?
• Stability What will be the response to the
  forcing?
• Moisture Will there be saturation (RH) and how
  much moisture (q) will there be?
• Precip efficiency How will forcing,
  instability, and saturation coincide with the
  dendrite formation layer?
• Precip type Top down approach

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Forcing

• Start with synoptics first QG
• DCVA (differential cyclonic vort advection,
• ?2WAA (local max in warm advection),
• QG frontogenesis
• Diagnostics
• Isentropic
• Q-vectors

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850 mb 00 UTC
Frntgenesis
14
700 mb 00 UTC
Frntgenesis
WAA
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500 mb 00 UTC
DCVA
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300 mb 00 UTC
DCVA
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Forcing

• Q-vectors
• Exist when geostrophic wind alters the thickness
  gradient vectors
• Anytime the thickness gradient changes the
  thermal wind goes out of balance
• Secondary ageostrophic circulations attempt to
  restore balance
• Ageostrophic winds keep us employed
• ?Q-vector

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Forcing Flow inflections
Qs Q component parallel to isotherms
?T3
T
?
T?T
?T2
Q2
?T1
???
Q1
?T2
?T3
Q2
?T2
?T1
Q1
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Forcing QG frontogenesis
Qn Q component parallel to isotherms
?
?T1
T
Q1
?T2
???
T?T
?2??
Q2
?T3
?T3
T2?T
?T1
?T2
Q1
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Forcing QG
Qn Qs total Q vector
T
T?T
?
T2?T
???
?2??
(??Qn ?? Qs) 21
Q-vectors
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Forcing
Best convergence means strongest QG forcing for
vertical motion
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Forcing ??Q
650 mb 00 UTC ETA
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Forcing

• If QG cannot explain the vertical motion (fcst or
  real)
• Then go downscale to mesoscale
• Next is 2-D full wind frontogenesis

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Frontogenesis (definition)

• The 2-D frontogenesis function (F) quantifies
  the change in (potential) horizontal temperature
  gradient following air parcel motion
• F0 frontogenesis, F
• Refer to Banacos presentation

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Forcing Frontogenesis
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Forcing Frontogenesis
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Forcing

• If 2-D frontogenesis fails to explain ascent,
  then
• Externally forced mesoscale lifting?
• Orographic ascent
• Frictional convergence
• Shoreline
• Cyclonic sfc flow
• Local diabatic heating
• Water land thermal differences
• Land cover thermal gradients
• Outflow boundaries

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Forcing

• Orographic ascent

Weak cross-barrier winds or high stability KE PE Fr
Strong cross-barrier winds or low stability KE
PE Fr 1
http//www.meted.ucar.edu/mesoprim/flowtopo/
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Forcing

• Diabatic heating gradients

In this case, lake effect enhancement due to land
breeze circulations
http//www.meted.ucar.edu/mesoprim/seabreez/
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Forcing

• Frictional convergence

fr
f
f
?P
?P
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Stability response
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Stability response
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Stability response
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Stability response
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Stability response
You can get away with Looking at only EPV
to Evaluate CSI and CI
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Stability response
Courtesy Pete Banacos
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Stability response
http//www.nssl.noaa.gov/schultz/csi.shtml
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Stability response
This is where MPVg http//www.nssl.noaa.gov/schultz/csi.shtml
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Combined forcing and stability

• PVQ (??Q) (MPVg) for negative MPVg and
  negative ??Q
• 0 for positive MPVg and
  positive ??Q

• Negative PVQ means both Q-vector convergence and
  CSI, CI or both are occurring in the same layer
• This will not occur often as the best instability
  lies on a different layer than the best forcing

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PVQ
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Moisture

• Relative Humidity
• Mixing Ratio

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Precipitation efficiency

• See Dan Baumgardts talk
• http//www.crh.noaa.gov/arx/micrope.html

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Precipitation efficiency
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Precipitation efficiency

• See Dan
• Baumgardts talk
• http//www.crh.noaa.gov/arx/micrope.html

46
Precipitation type

• Refer to the top-down approach in Dan Baumgardts
  presentation
• http//www.cira.colostate.edu/ramm/visit/ptype/tit
  le.asp

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Model Forecast

• Add to typical displays
• 4-panel ingredients for 600-650mb, 650-700mb,
  700-750mb with 80 km model
• Ingredients cross-sections across thickness
  gradients in areas of forcing
• Full frontogenesis
• Ensembles

48
Adjust model forecast

• How will analysis errors affect the ingredients?
• Does the current data agree with model forecasts?
• If not, then how will you adjust model forecasts?

49
A short-term forecast methodology

• Check accuracy of model analysis
• Diagnose model analysis for winter precipitation
  ingredients
• Planview maps and cross-sections
• Adjust model-based ingredients with real data
• Make the forecast
• Further adjustments with real data into forecast
  period

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Related links

• Ingredients-based methodology
• http//cimss.ssec.wisc.edu/goes/visit/ingredients.
  html
• CSI, mesoscale circulations online training
• http//www.meted.ucar.edu/topics_meso.php
• Precipitation type and efficiency
• http//www.cira.colostate.edu/ramm/visit/ptype.htm
  l
• This workshop linked to
• http//www.wdtb.noaa.gov

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Precipitation efficiency