Scott Dennstaedt, PhD Posted December 23, 2018 Report Share Posted December 23, 2018 What does this satellite image tell you about the icing threat in the Chicago area? Quote Link to comment Share on other sites More sharing options...
carusoam Posted December 23, 2018 Report Share Posted December 23, 2018 Two wags... 1) The warmth of the lake is having an effect on the air above it? 2) water evaporating is showing a temp drop over the lake? Color matched with -8? Best regards, -a- Quote Link to comment Share on other sites More sharing options...
Yetti Posted December 23, 2018 Report Share Posted December 23, 2018 I see an eagle. 1 1 Quote Link to comment Share on other sites More sharing options...
exM20K Posted December 23, 2018 Report Share Posted December 23, 2018 cloud tops just below freezing? Did my IFR currency approaches this afternoon, and there was moderate clear icing in the tops (3000') between Chicago and Rockford. Quote Link to comment Share on other sites More sharing options...
FloridaMan Posted December 23, 2018 Report Share Posted December 23, 2018 Cooler temps can be correlated with winds and temperatures aloft to give you a picture of the where the tops are with visible moisture. Cross-reference the temps with the temps aloft for the cloud tops. I assume the temps are Celsius so anything yellow to orange carries a high risk of icing; I assume those are all low level clouds with the highest risk. Those clouds with the cooler temperatures are likely just thicker, but still likely carry the same risks of icing down low. Quote Link to comment Share on other sites More sharing options...
M016576 Posted December 23, 2018 Report Share Posted December 23, 2018 This is a gimme- It’s Chicago in the winter time- If there’s a cloud out there, it definitely contains icing! 1 1 Quote Link to comment Share on other sites More sharing options...
moodychief Posted December 23, 2018 Report Share Posted December 23, 2018 Spend your time looking at the upper air soundings Skew-T chart. Not only does it show the freezing level when the balloon was launched but also shows where the clouds/layers are. Downfall is they only launch the balloons twice a day. At least it will give you a better idea of what to expect. Quote Link to comment Share on other sites More sharing options...
bradp Posted December 23, 2018 Report Share Posted December 23, 2018 I don’t have the data from last night but ... this morning is probably not to dissimilar. Ground temps just above freezing. Low level clouds with some ice in em. ? SLD threat yellow and pale green. Safe and clear skies locally above. Got a skew-t or temps aloft plot to compare for that timeframe? Scott has a good fore flight blog post about using the color IR to help with icing threat analysis. Quote Link to comment Share on other sites More sharing options...
Scott Dennstaedt, PhD Posted December 23, 2018 Author Report Share Posted December 23, 2018 The cloud top temperatures in this image tell you a lot about the phase of the moisture in the cloud. Clouds with tops that are warmer than about -15°C are likely to dominated by supercooled liquid water. I can also tell these clouds are highly capped by an inversion without knowing the temperature profile. Moreover, depending on the environment, it also may be dominated by SLD. This SLD Potential analysis from the WeatherSpork app shows a high likelihood of SLD in this region. This is an environment that will also typically produce freezing drizzle KRFD 222337Z 2300/2324 VRB03KT P6SM OVC015 TEMPO 2300/2302 5SM -FZDZ BR OVC009 FM231200 27009KT P6SM OVC020 FM231900 27009KT P6SM SCT025 BKN035 And, the NWS forecast was right on the money with FZDZ reported at the surface. This was a forecast that was issued at 2333Z. KRFD 230254Z 29009KT 6SM BR OVC012 M01/M03 A3004 RMK AO2 FZDZE31 SLP181 P0000 60000 I1000 I3000 T10111033 51016 KRFD 230237Z 29007KT 6SM BR OVC012 M01/M03 A3004 RMK AO2 FZDZE31 P0000 I1000 T10111033 KRFD 230154Z 29008KT 6SM -FZDZ BR OVC013 M01/M03 A3003 RMK AO2 FZDZB54 SLP178 P0000 I1000 T10111028 KRFD 230141Z 28006KT 6SM BR BKN014 OVC022 M01/M03 A3003 RMK AO2 T10111028 The RFD sounding analysis shows the unstable cloud structure that is capped by the temperature inversion. Quote Link to comment Share on other sites More sharing options...
Scott Dennstaedt, PhD Posted December 23, 2018 Author Report Share Posted December 23, 2018 3 hours ago, moodychief said: Spend your time looking at the upper air soundings Skew-T chart. Not only does it show the freezing level when the balloon was launched but also shows where the clouds/layers are. Downfall is they only launch the balloons twice a day. At least it will give you a better idea of what to expect. That's a great suggestion given that this time was right around the 23Z launch time...however, the closest radiosonde is DVN which is 120 miles away from Chicago or GRB which is 150 nm from Chicago. Unfortunately, neither one of these will be a good representation of what's happening in Chicago. Quote Link to comment Share on other sites More sharing options...
Scott Dennstaedt, PhD Posted December 23, 2018 Author Report Share Posted December 23, 2018 12 hours ago, Antares said: Cooler temps can be correlated with winds and temperatures aloft to give you a picture of the where the tops are with visible moisture. Cross-reference the temps with the temps aloft for the cloud tops. I assume the temps are Celsius so anything yellow to orange carries a high risk of icing; I assume those are all low level clouds with the highest risk. Those clouds with the cooler temperatures are likely just thicker, but still likely carry the same risks of icing down low. Nice observations. Actually the pale greens will also tell you that the cloud is likely dominated by supercooled liquid water. Colder tops don't really tell you much about what's happening below, but often these higher clouds will be mostly ice crystals. Those tend to fall into the lower clouds and will often "seed" the clouds below turning lower clouds into a more mixed phase variety (and maybe lessening the icing risk). In this case, there are no higher clouds, so the ability to seed them isn't there. Another reason I'm confident these clouds are nasty ice makers. Quote Link to comment Share on other sites More sharing options...
smccray Posted December 23, 2018 Report Share Posted December 23, 2018 16 hours ago, scottd said: What does this satellite image tell you about the icing threat in the Chicago area? It tells me 1) I need to keep learning about weather, and 2) I’m glad I’m in Texas... 1 Quote Link to comment Share on other sites More sharing options...
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