Hi Folks,
I got inspired again with using the Skew t/Log P charts as a part of flight planning and deciphering cloud layers, bases and tops, convective activity and icing. So I thought I would post a sample here for KSEA Seattle International and correlate the sounding with the METAR and FA as well as the IR satellite. Some things are still unclear to me as well, so here we go.
First of lets start with the METAR and TAF for KSEA and some other surrounding airports
KSEA 141753Z 22004KT 10SM BKN048 OVC065 08/04 A3023 RMK AO2 RAB36E50 SLP244 P0000 60000 T00830044 10083 20072 53002
KSEA 141720Z 1418/1524 16008KT P6SM SCT045 OVC080 FM150000 14010KT P6SM -RA BKN045 OVC080 FM150900 16015KT P6SM -RA BKN030 OVC045 WS020/20040KT FM151800 18012KT 5SM -RA BR BKN015 OVC030 KRNT 141753Z 18004KT 10SM FEW075 08/05 A3024 RMK AO2 SLP243 T00830050 10089 20072 55000
KBFI 141753Z 15005KT 10SM BKN070 10/04 A3023 RMK AO2 SLP237 T01000044 10100 20078 53001
KBFI 141720Z 1418/1518 15006KT P6SM SCT050 OVC080 FM150000 13010KT P6SM -RA BKN050 OVC080 FM150900 13010KT P6SM -RA BKN035 OVC045 WS020/20035KT
Looks like we have an average first cloud layer at 4800 to 7000 broken to overcast layers, the TAF’s also reflect this w/o much change over time. Now lets look at the top down view from the IR Sat, this one is kind of old 1500Z but is the latest I could find:
http://www.nrlmry.navy.mil/sat-bin/....ir.cloudtop.conus.nogaps.jpg&MOSAIC_SCALE=15
Looks like we have the tops of the uppermost cloud layer at approx 210 to 270, the 270 being possible scattered cirrus and the 210 being possible altostratus (being in the warm sector???) Now let’s look at the Skew T/Log P Plot:
http://rucsoundings.noaa.gov/plot_s...a-based plots;hydrometeors=false&start=latest
click on 1800Z box
We can readily see Convergence of the Temp and DP at 5,000 with a moist surface layer and a dry slot at about 2,500. This correlates with the METAR’s. Could we also infer the tops of this layer at 9,000 where they diverge again? Now the big question I have is that since the Temp and Dp for the most part parallel each other all the way up to 34,000 feet, how would you infer all the other cloud layers? The average Relative Humidity in the stage of the atmosphere is about 75%. This seems low for having cloud layers but we know they are there, at least the ones observed on the IR Sat in the 20,s.
Let’s look at the FA:
WA CASCDS WWDCSTL SXNS...BKN015 LYRD FL220. OCNL -RA. 22Z OCNL VIS 3-5SM -RABR. WND SE G25KT. OTLK...MVFR CIG RA BR WND.OLYMPICS...BKN030-040 LYRD FL220. OCNL VIS 3-5SM -RA. VIS 3SM -SNABV 060. OTLK...IFR CIG RA SN BR.PUGET SOUND...OVC100 LYRD FL220. 22Z BKN045. OCNL -RA. OTLK...VFRRA.INTR VLY...BKN030 LYRD FL220. 20Z OCNL -RA. OTLK...MVFR CIG RA.CASCDS...BKN070 LYRD FL220. 19Z OVC050-060. VIS 3-5SM -SN.OTLK...IFR SN.
Basically we see for Puget Sound, Overcast at 10,000 and Layered to 220. The top correlates with the IR Sat. After 22Z we see the broken layer we have been talking about at 4,500. This could have come in early since it is only 1820Z at the time of this writing. There could still be a layer at 10,000. Since it is day time we can also look at the Visible:
http://adds.aviationweather.gov/satellite/displaySat.php?region=LWS&isingle=single&itype=vis
We can see the top layer of Cirrostratus and Infer that there is very little in the way of thick layers below due to the lack of reported rain. So to summarize, would the biggest area of clear air be between say 15,000 and 21,000? Assuming that the 10,000 foot layer could also be part of the lower 4,500 foot layer (could be all on cloud deck). And you could be on top at 22,000. Also is there any trick to determining cloud decks on the Skew T along that area above 9,000 feet where the air is relatively dry but we know there are clouds? I think that getting the best possible 3D view of the atmosphere is invaluable.
I got inspired again with using the Skew t/Log P charts as a part of flight planning and deciphering cloud layers, bases and tops, convective activity and icing. So I thought I would post a sample here for KSEA Seattle International and correlate the sounding with the METAR and FA as well as the IR satellite. Some things are still unclear to me as well, so here we go.
First of lets start with the METAR and TAF for KSEA and some other surrounding airports
KSEA 141753Z 22004KT 10SM BKN048 OVC065 08/04 A3023 RMK AO2 RAB36E50 SLP244 P0000 60000 T00830044 10083 20072 53002
KSEA 141720Z 1418/1524 16008KT P6SM SCT045 OVC080 FM150000 14010KT P6SM -RA BKN045 OVC080 FM150900 16015KT P6SM -RA BKN030 OVC045 WS020/20040KT FM151800 18012KT 5SM -RA BR BKN015 OVC030 KRNT 141753Z 18004KT 10SM FEW075 08/05 A3024 RMK AO2 SLP243 T00830050 10089 20072 55000
KBFI 141753Z 15005KT 10SM BKN070 10/04 A3023 RMK AO2 SLP237 T01000044 10100 20078 53001
KBFI 141720Z 1418/1518 15006KT P6SM SCT050 OVC080 FM150000 13010KT P6SM -RA BKN050 OVC080 FM150900 13010KT P6SM -RA BKN035 OVC045 WS020/20035KT
Looks like we have an average first cloud layer at 4800 to 7000 broken to overcast layers, the TAF’s also reflect this w/o much change over time. Now lets look at the top down view from the IR Sat, this one is kind of old 1500Z but is the latest I could find:
http://www.nrlmry.navy.mil/sat-bin/....ir.cloudtop.conus.nogaps.jpg&MOSAIC_SCALE=15
Looks like we have the tops of the uppermost cloud layer at approx 210 to 270, the 270 being possible scattered cirrus and the 210 being possible altostratus (being in the warm sector???) Now let’s look at the Skew T/Log P Plot:
http://rucsoundings.noaa.gov/plot_s...a-based plots;hydrometeors=false&start=latest
click on 1800Z box
We can readily see Convergence of the Temp and DP at 5,000 with a moist surface layer and a dry slot at about 2,500. This correlates with the METAR’s. Could we also infer the tops of this layer at 9,000 where they diverge again? Now the big question I have is that since the Temp and Dp for the most part parallel each other all the way up to 34,000 feet, how would you infer all the other cloud layers? The average Relative Humidity in the stage of the atmosphere is about 75%. This seems low for having cloud layers but we know they are there, at least the ones observed on the IR Sat in the 20,s.
Let’s look at the FA:
WA CASCDS WWDCSTL SXNS...BKN015 LYRD FL220. OCNL -RA. 22Z OCNL VIS 3-5SM -RABR. WND SE G25KT. OTLK...MVFR CIG RA BR WND.OLYMPICS...BKN030-040 LYRD FL220. OCNL VIS 3-5SM -RA. VIS 3SM -SNABV 060. OTLK...IFR CIG RA SN BR.PUGET SOUND...OVC100 LYRD FL220. 22Z BKN045. OCNL -RA. OTLK...VFRRA.INTR VLY...BKN030 LYRD FL220. 20Z OCNL -RA. OTLK...MVFR CIG RA.CASCDS...BKN070 LYRD FL220. 19Z OVC050-060. VIS 3-5SM -SN.OTLK...IFR SN.
Basically we see for Puget Sound, Overcast at 10,000 and Layered to 220. The top correlates with the IR Sat. After 22Z we see the broken layer we have been talking about at 4,500. This could have come in early since it is only 1820Z at the time of this writing. There could still be a layer at 10,000. Since it is day time we can also look at the Visible:
http://adds.aviationweather.gov/satellite/displaySat.php?region=LWS&isingle=single&itype=vis
We can see the top layer of Cirrostratus and Infer that there is very little in the way of thick layers below due to the lack of reported rain. So to summarize, would the biggest area of clear air be between say 15,000 and 21,000? Assuming that the 10,000 foot layer could also be part of the lower 4,500 foot layer (could be all on cloud deck). And you could be on top at 22,000. Also is there any trick to determining cloud decks on the Skew T along that area above 9,000 feet where the air is relatively dry but we know there are clouds? I think that getting the best possible 3D view of the atmosphere is invaluable.
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