Why be a Cloud Spotter
Any mariner who ventures offshore will appreciate visual signs assisting the wonderful technology available for forecasting. No matter the amount of information one has, the more confirmation the less stress, keeping a weather eye out is de riguer at sea. Jet streams in the upper atmosphere can have major influences on our weather and sometimes we are lucky enough to be in the right place and time to capture jet stream cloud. Such an occasion was last week when a jet passed over us. Jets range from 80 kts to over 150 kts usually but can be more. This one last Friday was on the lower end of the scale. My usual sequence of observation begins with spotting the jet cloud and hopefully obtaining a picture. Thence to the BOM site for a 200mb map and a 500 mb map. A jet can be anywhere between these levels and the wonderful qualities of the human brain can allow us to create a three dimensional concept. Lastly, to an aircraft Australia Significant Weather (SIGWX) map for a schematic diagram. Do you know what FL370 means? Can you interpret the wind strength symbols? All subject matter in our weather course Module 4.
Next I keep an eye on the following weather maps to confirm suspicions.
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Jet Stream picture from the 5th June 2020 |
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200hpa Height Wind the arrow point to the Jet Stream |
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Australia Significant Weather (SIGWX) Chart Valid 10:00 5th June 2020 Flight Level 250-630 |
A better example of the cloud-spotting usefulness
I have a sequence of pics from 4th April 2019, this was a quite strong jet and the follow-up weather was of a deep low well south with a strong cold front which created dust storms, and blew off roofs etc.
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Picture of the Jet stream Cloud from the 4th April 2019 |
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Note the lag from the cloud, the 200hpa jet map with progression, 500mb lagging 200mb and eventually the MSLP. The 850mb map gives an indication of the disturbance |
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200hpa wind map Valid at 10:00 10kms above the earth surface 30 000 feet |
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200hpa wind map Valid at 22:00 showing the 120 knot Jet Stream
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500hpa Wind Map it is around 5.5km in height
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Australia Significant Weather (SIGWX) Chart Valid 22:00 4th April 2020 Flight Level 250-630
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MLSP for the 4th April showing the strong front
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850hpa Wind Map 1.5 km above sea level, usually just above the boundary layer showing the intense low
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Article by Robin Hewitt. |
