FIP/FIS (aka IPA) Overview Cory A. Wolff 5 – 7 November 2013

NCAR Icing Research FAA AWRP – Late 1980’s – History of accidents and icing incidents – Observational and Modeling Studies – Field Programs CO, OH, AK, Canada, others – Product Development T & RH Algorithms Added observations, model improvements Anchorage

Resulting in…

IPA Forecast Icing Probability (FIP) – Calibrated likelihood of icing conditions Icing Severity (FIS) – Relative amount of liquid water present Supercooled Large Drop (SLD) Potential – Forecast large drops in and out of precipitation

Membership Functions Used to create interest maps A method to get an algorithm to “think” like a forecaster so large volumes can be covered – The interest in icing varies based on the values of given variables

Cloud Identification Cloud Tops – Requires at least 2 levels w/ RH > 70% – Then looks at vertical gradients where RH > 70% RH VV TotC θ e – Combine using interest maps

Cloud Identification Cloud Bases and Layers Cloud Base: RH > 80% Cloud Layer: At least 3 levels < 50%

Precipitation Identification Where is precipitation falling? – Precipitable condensate Sum of the three condensates in the model that can reach the surface (rain, snow, graupel) at the lowest 3 levels Maximum value is the precipitable condensate – If this value is greater than 0.01 g kg -1 then precipitation is forecast

Precipitation Identification What type of precipitation? – Decision tree scheme from Baldwin et al. (1994) Gives forecasts of RA, SN, FZRA, and PE – Modified to add DZ and FZDZ CTT > -12 °C combined with surface temperature

Icing Probability Initial Calculation – Based on T, RH, and CTT – Interest maps provide a likelihood of icing for a given value Based on cloud physics principles, but adjusted by PIREPs compared with model data – Multiply the 3 maps together

Icing Probability Final Calculation – Adjustments Precipitation type – SN and RA decrease the likelihood while others can increase it VV – Upward motion = boost, downward = decrease SLW – If the model has any SLW then boost the likelihood – Why not just use SLW? Rising Air Sinking Air

Icing Probability The previous slides resulted in an icing potential – Uncalibrated likelihood of icing conditions Probability requires calibration – Study done in 2006 – Based on comparisons with PIREPs in the Great Lakes Lots of reports – For a diagnosis an icing potential of 1 gave an 85% chance of icing 3 hr forecast  74% 12 hr forecast  43%

SLD Potential Supercooled large drops: SLW with a diameter ≥ 50 μm Precipitating clouds – Requires a forecast of DZ, FZDZ, FZRA, or PE – These precipitation types are direct indicators of SLD aloft Non-precipitating clouds – Requires a CTT > -14 °C – Total condensate of at least 0.45 g m -3 (boundary layer) or 0.15 g m -3 (non-boundary layer) – Supercooled rain water also contributes

Icing Severity Scenarios No Precipitation – Cloudy, but no precipitation forecast All Snow – Snow is forecast Cold Rain – Rain is forecast Warm Precipitation – Collision-Coalescence forms the precipitation – CTT ≥ -12 °C and precipitation is DZ or FZDZ Cold Non-Snow/Rain – Precipitation is something other than snow or rain and the CTT < -12 °C Classical Precipitation Above a Melting Layer Classical Precipitation Below a Melting Layer Convection – Certain CAPE, LI, KI, and TT thresholds must be met Each one has different icing properties. None have the same fields applied in the same way.

Icing Severity

SEV = w 1 *i 1 + …. + w n *i n w 1 + …. + w n + (dw1*t_df + dw2*ctt_df + dw3*pcond_df) where w = weight, i = interest, and dw = damping weight Weight – What is the influence of this field for determining SLW production or depletion in this scenario? 1 = very little; 5 = maximum SLW production terms – Moisture, VV, potential condensate, distance from cloud base, total water path, others – Scenario specific SLW depletion terms – T, CTT, precipitation

Simple Map Vertical Velocity Interest Provides the meaning of a field ’ s range of values in terms of icing severity 0 = no interest 1 = maximum interest Scenario Specific Map No Precipitation All Snow Cold Rain Combo Map Moisture 50% RH 30% Liquid Cond. 20% Ice Cond.

Depletion Extra denominator fields give information about the depletion of SLW – Temperature If too cold SLW more likely to become frozen If too warm plane ’ s airspeed will discourage icing Used in all scenarios except below the warm nose and convection – Cloud Top Temperature Cold temperatures  more ice crystals Only applied in top 10,000 ft. of cloud Used in all scenarios except below the warm nose and convection – Amount of Precipitation Indicator of ice production with increasing values Only applied in bottom 5000 ft. of cloud Used in all scenarios except below the warm nose, convection, and no precipitation

Damping Membership Functions Temperature Cloud Top Temperature Precipitable Condensate

Final Severity (0-1) Categorical Severity (None, Trace, Light, Moderate, Heavy) Final Severity (0-1) Categorical Severity (None, Trace, Light, Moderate, Heavy) Thresholds Applied Final Icing Severity

Performance Forecast LeadPODyPODnVolume %# of PIREPs Average Based on PIREPs from February and March 2013 CONUS version is generally similar in performance but with less volume

Plans IPA Forecast – Experimental version finalized: May 2014 – Verification: Summer 2014 – Experimental ADDS: December 2014 – Operational version development: Experimental version of IPA Diagnosis – Experimental version: 2015 Combined product

Cases

18 Sep 2013 UA /OV FAI /TM 2125 /FL070 /TP C208 /TA M01 /IC MOD CLR C

18 Sep 2013 UA /OV FAI /TM 2125 /FL070 /TP C208 /TA M01 /IC MOD CLR C

19 Sep 2013 UA /OV BRW /TM 1814 /FLUNKN /TP B737 /IC MOD RIME /RM ICGIC, RY7 BRAG B

10 Oct 2013 UUA /OV BKA343019/TM 2320/FL050/TP AT72/TA M14/IC SEVER CLEAR /RM DURC ZAN CORRECTION AT

19 Oct 2013 UA /OV TED360016/TM 1647/FL090/TP B737/TA M08/IC LGT RIME UA /OV TED /TM 1656/FL140/TP DH8A/TA M19/IC MOD RIME LGT RIME /RM DURGD

12 August 2013 I looked at IC4D and concentrated on the areas where it was expecting icing. There were two areas: Northwest coastal area to the western Brooks Range. The second area was over the se panhandle. synoptic - A HI PRES ridge over northwest Alaska. The second area had a hi pres extends from cook inlet to southeast ak. FIP - In these two situations FIP was showing significant values (80+). I would not have expected that. Soundings didn't show a moist layer above the freezing layer. Soundings were available on awips but not on the internet. PIREPs JNU UA /OV SSR090040/TM 2012/FL100/TP B737/TA M05 /IC LGT RIME /RM DURD /CWSU ZAN= JNU UA /OV JNU /TM 2221 /FL120 /TP SR22 /SK OVC-TOP012/OVC035- TOP048/OVC078-TOP120 /TA M05 /IC LGT RIME /RM TOP /TA 00-M05= ORT UUA /OV ORT114045/TM 0213/FL120/TP C120/TA M07/RM IC MOD- HEAVY RIME= Convection was occurring in the vicinity of the pirep for ORT/Northway

12 August 2013

31 October 2012 A frontal system is over the gulf of Alaska, lynn Canal, central southeast north of Kake, and coastal waters of AK. FIP Over southeast Alaska (Eastern Gulf Coast, Coastal Southeast Alaska, Central Southeast Alaska, and Lynn Canal zones values of were mainly at FL060. The values improve by 090 over Lynn Canal. FIS values of 50 were over these same areas at the 060 and 090 levels. Attached are the pireps...indicating ICING over SE Alaska. This was so right on the money. I don't know what to say. NICE!

31 October 2012 UA /OV JNU /TM 1443 /FL085 /TP B737 /TA M12 /IC MOD MX /RM DURD RWY 8. MOD MX/RIME ICE TEMP AT 060 M08. AT 085 M12 UA /OV SIT /TM 1536 /FL010 /TP AT72 /SK BKN-OVC010 /TB LGT-MOD /IC NEG /RM LGT-MOD TB DURING DESCENT JNU-SIT/NEG ICE DURING ENTIRE APCH UA /OV SIT /TM 1633 /FL047 /TP AT72 /SK BKN-OVC012 /TA M04 /IC NEG /RM DURC/IMC UA /OV CDV /TM 1640 /FL070 /TP B190 /TA M05 /IC LGT RIME /RM DURD UA /OV BKA/TM 1750/FL050/TP PA31/TA M04/IC LGT-MOD RIME/RM DURC 075 RATE OF ACCUMULATION IS DIMINISHING ZAN UA /OV JNU100010/TM 1824/FL050/TP B737/SK TOP100/IC MOD RIME/RM DURC ICING ZAN UA /OV SIT /TM 1835 /FL070 /TP B734 /TA M10 /IC LGT RIME /RM DURD RWY 11/OVR BASSU UA /OV SSR /TM 1921 /FL080 /TP AT72 /SK OVC020-TOP110 /TA M07 /TB LGT-MOD /IC MOD RIME /RM LGT-MOD TB DURD RY8 JNU. AIS 3MILE FINAL. TOWER DID NOT INDICATE TYPE CLD LAYER UA /OV SIT /TM 1956 /FL040 /TP C130 /IC LGT RIME /RM DURD RWY 11/NO TEMPS UA /OV CDV /TM 1956 /FL200 /TP B190 /SK OVC040-TOP200 /IC LGT RIME /RM DURD RY9 TA UNKN UA /OV JNU /TM 1959 /FL105 /TP AT72 /SK OVC033-TOP105 /TA M15 /IC MOD RIME /RM DURD RY8. TA M01 FL033 UA /OV BKA350040/TM 2000/FL085/TP C130/TA M05/IC LGT RIME /RM DURC ZAN UA /OV CGL210010/TM 2004/FL100/TP AT72/SK OVC030/IC LGT RIME SFC-100/RM DURC ZAN UA /OV SIT350050/TM 2027/FL100/TP PA31/SK TOP090/TA M10/IC CONT LGT RIME /RM DURC ZAN UA /OV SSR035015/TM 2106/FL190/TP B734/TB NEG/IC NEG/RM DURC ZAN UA /OV SSR045025/TM 2141/FL110/TP B737/TB OCNL LGT100/IC NEG/RM DURC ZAN UA /OV BKA/TM 2357/FL090/TP BE20/SK OVC020 TOPS 070/TA M8 AT 6500/IC LGT RIME

Thank you for your time