Page History

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• Example of freezing rain, Canada
• Example of freezing rain, SE Europe
• Example of freezing rain, France
• Example of freezing drizzle, SE England

Note: HRES and Ensemble Control Forecast (ex-HRES) are scientifically, structurally and computationally identical.  With effect from Cy49r1, Ensemble Control Forecast (ex-HRES) output is equivalent to HRES output shown in the diagrams.   At the time of the diagrams, HRES had resolution of 9km and ensemble members had a resolution of 18km.

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Fig8.1.10-10A: HRES forecast (9km resolution) forecasts freezing rain (total over 12hr).  HRES DT 00UTC 23 February 2018, T+72 VT 00UTC 26 February 2018.  Colour scale: Light Blue 0.0-0.2mm, Mid Blue 0.2-0.5mm, Dark Blue 0.5-1.0mm, Dark Red 1.0-2.0mm, Red 2.0-5.0mm, Pink 5.0-10.0mm, Orange >10.0mm.  The pin marks the location of Quebec City with the forecast 12hr total of freezing rain given in the probe information frame.  Freezing rain total values are not the same as accumulation of glaze or glazed ice although some proportional accretion must be expected.  

Note: HRES and Ensemble Control Forecast (ex-HRES) are scientifically, structurally and computationally identical.  With effect from Cy49r1, Ensemble Control Forecast (ex-HRES) output is equivalent to HRES output shown in the diagrams.   At the time of the diagrams, HRES had resolution of 9km and ensemble members had a resolution of 18km.

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Fig8.1.10-10B: The ensemble forecasts freezing rain probability (>1mm over 12hr).  DT 00UTC 23 February 2018, T+72 VT 00UTC 26 February 2018. Colour scale: Yellow 5-35%, Green 35-65%, Darker Green 65-95%, Blue >95%.  The pin marks the location of Quebec City with the forecast probability of >1mm 12hr total of freezing rain given in the probe information frame.  

Note: HRES and Ensemble Control Forecast (ex-HRES) are scientifically, structurally and computationally identical.  With effect from Cy49r1, Ensemble Control Forecast (ex-HRES) output is equivalent to is equivalent to HRES output shown in the diagrams.   At the time of the diagrams, HRES had resolution of 9km and ensemble members had a resolution of 18km.

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Fig:8.1.10-11: ecCharts presentation of HRES forecast (9km resolution) forecast freezing rain accumulations over the previous 6hr, DT 00UTC 16 February 2023, T+42 VT 18UTC 17 February 2023.  The vertical profile at Bangor, Maine, USA shows the classic freezing rain structure of a very moist and precipitating frontal zone overlying the sub-zero layer near the surface.  

Note: HRES and Ensemble Control Forecast (ex-HRES) are scientifically, structurally and computationally identical.  With effect from Cy49r1, Ensemble Control Forecast (ex-HRES) output is equivalent to HRES output shown in the diagrams.   At the time of the diagrams, HRES had resolution of 9km and ensemble members had a resolution of 18km.

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Fig:8.1.10-15: Forecast of freezing rain over Ukraine VT 06UTC 08 January 2024, DT 00UTC 06 January 2024.  Colours show 6hr totals of freezing rain. Arrows show 10m winds. 2m isotherms in red.  Vertical profile and type of precipitation histogram for Odesa, in the warm air.  

Note: HRES and Ensemble Control Forecast (ex-HRES) are scientifically, structurally and computationally identical.  With effect from Cy49r1, Ensemble Control Forecast (ex-HRES) output is equivalent to HRES output shown in the diagrams.   At the time of the diagrams, HRES had resolution of 9km and ensemble members had a resolution of 18km.

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Fig:8.1.10-16: Forecast of freezing rain over Ukraine VT 06UTC 08 January 2024, DT 00UTC 06 January 2024.  Colours show 6hr totals of freezing rain. Arrows show 10m winds. 2m isotherms in red.  Vertical profile and type of precipitation histogram for Kryve Ozero, in the area of freezing rain. The vertical profile shows temperatures above 0°C in a layer about 1000m thick.  

Note: HRES and Ensemble Control Forecast (ex-HRES) are scientifically, structurally and computationally identical.  With effect from Cy49r1, Ensemble Control Forecast (ex-HRES) output is equivalent to HRES output shown in the diagrams.   At the time of the diagrams, HRES had resolution of 9km and ensemble members had a resolution of 18km.

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Fig:8.1.10-17: Forecast of freezing rain over Ukraine VT 06UTC 08 January 2024, DT 00UTC 06 January 2024.  Colours show 6hr totals of freezing rain. Arrows show 10m winds. 2m isotherms in red.  Vertical profile and type of precipitation histogram for Kyiv, in the cold air.  

Note: HRES and Ensemble Control Forecast (ex-HRES) are scientifically, structurally and computationally identical.  With effect from Cy49r1, Ensemble Control Forecast (ex-HRES) output is equivalent to HRES output shown in the diagrams.   At the time of the diagrams, HRES had resolution of 9km and ensemble members had a resolution of 18km.

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Fig:8.1.10-18: Forecast of freezing rain over Ukraine VT 06UTC 08 January 2024, DT 00UTC 06 January 2024.  Colours show 6hr totals of freezing rain. Coloured spots show type of precipitation.  Vertical profile and type of precipitation for a location near Uman, on the northern flank of the area of freezing rain. The vertical profile shows temperatures just above 0°C in a thin layer. Orange spots show ice pellets.  

Note: HRES and Ensemble Control Forecast (ex-HRES) are scientifically, structurally and computationally identical.  With effect from Cy49r1, Ensemble Control Forecast (ex-HRES) output is equivalent to HRES output shown in the diagrams.   At the time of the diagrams, HRES had resolution of 9km and ensemble members had a resolution of 18km.

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Fig:8.1.10-19: Forecast of freezing rain over Ukraine VT 06UTC 08 January 2024, DT 00UTC 06 January 2024.  Blue/purple colours show 6hr totals of freezing rain.  Red/orange colours show precipitation extreme forecast index for precipitation.  Arrows show 10m winds. 2m isotherms in red.  Insets show EFI and CDF for 24hr precipitation for point with pin west of Odesa.  

Note: HRES and Ensemble Control Forecast (ex-HRES) are scientifically, structurally and computationally identical.  With effect from Cy49r1, Ensemble Control Forecast (ex-HRES) output is equivalent to HRES output shown in the diagrams.   At the time of the diagrams, HRES had resolution of 9km and ensemble members had a resolution of 18km.

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Fig:8.1.10-23: Forecast vertical profile at Paris to the north of the surface front with typical zone of positive temperatures above an undercutting sub-zero cold zone. The vertical profiles compare the forecast profile (red) and observed profile (black).  The forecast vertical profile captured the underlying cold dry air and overlying warm air quite well.  

Note: HRES and Ensemble Control Forecast (ex-HRES) are scientifically, structurally and computationally identical.  With effect from Cy49r1, Ensemble Control Forecast (ex-HRES) output is equivalent to HRES output shown in the diagrams.   At the time of the diagrams, HRES had resolution of 9km and ensemble members had a resolution of 18km.

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Fig:8.1.10-24: Forecast vertical profile at Idar-Oberstein to the north of the frontal zone with typical zone of positive temperatures above an undercutting sub-zero cold zone. The vertical profiles compare the forecast profile (red) and observed profile (black).  The forecast vertical profile didn't capture the observed structure completely.  It wasn't cold enough in the lowest layers (observed surface temperature -4°C but forecast 2m temperature -1°C) and the layer with temperatures above 0°C was forecast to be too deep.  Nevertheless the forecast temperature structure was sufficient for the HRES forecast (9km resolution) to produce freezing rain and ice pellets. 

Note: HRES and Ensemble Control Forecast (ex-HRES) are scientifically, structurally and computationally identical.  With effect from Cy49r1, Ensemble Control Forecast (ex-HRES) output is equivalent to HRES output shown in the diagrams.   At the time of the diagrams, HRES had resolution of 9km and ensemble members had a resolution of 18km.

Example of freezing drizzle, SE England

Freezing drizzle can be as much of a hazard as freezing rain.  The "Probability of Freezing Rain" option on ecCharts can show 0% when the default threshold is used.  Freezing drizzle can be seen if a very low threshold (say >0.01mm in previous 6hr) is applied.

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Fig:8.1.10-14 ecCharts presentation of ensemble forecast of probability of freezing rain accumulations, threshold 0.01 mm in previous 6 hr, DT 12UTC 24 January 2023, T+21 VT 09UTC 25 January 2023.  The vertical profile at Reading (located by the pin) shows a saturated layer of stratus at about 950 hPa with temperature above 0°C.  Very slight precipitation produced from the stratus by the model falls through an underlying sub-zero layer near the surface. The model gave above 65% probability of very light freezing precipitation.  Freezing drizzle was observed at Reading during the period.  

Note: HRES and Ensemble Control Forecast (ex-HRES) are scientifically, structurally and computationally identical.  With effect from Cy49r1, Ensemble Control Forecast (ex-HRES) output is equivalent to HRES output shown in the diagrams.   At the time of the diagrams, HRES had resolution of 9km and ensemble members had a resolution of 18km.

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