Convective indexes calculated from HIRLAM output

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Convective indexes calculated from HIRLAM output

• St.Petersburg
• The Russian State Hydrometeorological University
• Faculty of Meteorology
• Meteorological Forecasting Department
• Kanukhina Anna

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Aims

• to estimate possible use of convective indexes
  calculated on HIRLAM outputs for forecasting of
  place, beginning time and type of mesoscale
  convective phenomena

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Initial data are HIRLAM analysis and forecast
files

• - air temperature at surface and heights at
  various periods
• - dew point temperature at surface and heights at
  various periods
• - wind parameters at surface and heights at
  various periods
• - surface pressure tendencies
• - specific humidity at surface and heights at
  various periods

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3 types of indexes

• diagnostic - atmospheric preparedness for
  convection development (?, ?, MOCON)
• index having triggering function (? )
• indexes estimating possible type of arising
  phenomena (CAPE,HEI)

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atmosphere statical stability index ?

• ??
• ?

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moisture convergence

• MOCON
• r specific humidity, kg/kg
• V wind speed at 10 m, m/s

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generalized index indicating possibility of
convective disturbance formation ?

• ?

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convective instability indicator (Falkovichs
index) ?

• ?

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EHI energy helicity index

• EHI CAPEH
• ? relative wind helicity
• CAPE convective available potential energy
• CAP?

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Studied cases divided into 3 groups

• 1 group days with thunderstorms and showers
  indexes indicate high possibility of these
  weather phenomena
• 2 group days without any convective phenomena
  but indexes shows existing possibility of
  phenomena arising( atmospheric instability)
• 3 group days associated with thunderstorms and
  showers atmosphere is stable according to
  indexes consideration

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Used data

• HIRLAM forecast
• HIRLAM analysis
• sounding data
• surface observations (synoptic charts OSCAR,
  registered thunderstorm charts from FMI site
  http//www.ava.fmi.fi/tjt/salark.html).

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Studied cases

• 29.06.200019.06.200121-23.11.200103-06.07.20
  0216-20.07.2003

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23.11.2001 12UTC
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Indexes profiles for Kardla, Estonia
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MOCON, 1/s for Kardla (Estonia) on 23.11.2001 12
UTCanalyse fc12
fc24
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MOCON and ? scattering graph for 6 h forecast
(on base of analisys on 23.11.2001 0600 UTC and
forecast 23.11.2001 0000 UTC)
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? and G scattering graph for 6 h forecast (on
base of analisys on 23.11.2001 0600 UTC and
forecast 23.11.2001 0000 UTC)
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CAPE and HEI scattering graph for 6 h forecast
(on base of analisys on 23.11.2001 0600 UTC and
forecast 23.11.2001 0000 UTC)
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29.06.2000 12UTC
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MOCON, CAPE analysis on 29.06.2000 12 UTC
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• Thunderstorms chat on 29.06.2000
• (http//www.ava.fmi.fi/tjt/salark.html)

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?APE and MOCON scattering graph for 24 h forecast
(on base of analisys on 29.06.2000 1200 UTC and
forecast 28.06.2000 1200 )
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? and G scattering graph for 24 h forecast (on
base of analisys on 29.06.2000 1200 UTC and
forecast 28.06.2000 1200 )
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Indexes correlation coefficients (forecast and
analysis)

• ??? 1 ?
• ??? 2 G
• ??? 3 ?
• ??? 4 ?APE
• ??? 5 MOCON
• ??? 6 HEI

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Conclusions

• ? values defined by forecasts have essential
  distinctions with calculations from analysis and
  ? can not be used for atmospheric state
  estimation when forecasting at period more than
  6h.
• The same could be said for HEI.
• CAPE and MOCON may be used forecasting at period
  no more than 12h.
• ? and G forecasts are close to real situation
  even at 24h forecast period particularly for C
  values.