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Question
I'm trying to learn how to read weather maps. On the NOAA site
http://www.goes.noaa.gov/goes-w/goes-hi-ir.html
Do you know how to read satellite weather maps? I can't find any help button to explain how to interpret anything like what does the color purple mean? Is it cold or hot? If you run the Hawaii colored loop there is an area, presumably over an island which turns purple then fades, but maybe it won't be there when you view it as it's run daily. UTV time I don't know. Any help here or referral I'ld appreciate it. Thanks

This is a satellite image that ignores visible light and only recognises infra-red (the same reason you can feel the warmth from an electric fire even without seeing it). The general rule of thumb is "the closer to white something is, the hotter it is". Therefore the hurricane spinning off the coast is red and yellows (indicating it is very hot) whereas the sea is blue (indicating that it is cold). The reason for the purple patch on the big island (indicating a cooler patch than most) is really very simple. Hawaii is UTC -10 (so when that first image in the loop is taken the local time in Hawaii is 2.00pm). The big island is home to the Mauna Loa volcano (which stands at a height of 4,169m above sea level. At 2.00pm Hawaii time on October 12th 2015, the temperature at sea level was 29°C (84°F).

For every 1,000m you climb from sea level the temperature drops by 6°C (11°F) so using that formula it is possible to say at at the top of the volcano at 2.00pm on October 12th 2015, the temperature was 4°C (39°F) in other words much colder than the surrounding sea and therefore that's why it appeared purple. As the temperature at sea level continued to warm (the maximum temperature yesterday was 31°C (88°F)) the temperature at the top of the volcano went out of the purple range and into the blue range)
Questioner's Rating
 Rating(1-10) Knowledgeability = 10 Clarity of Response = 10 Politeness = 10 Comment It's so easy once we know how rt? Thank you,it was explained simply enough even a layperson like me could understand it. Terrific job Harry!

Meteorology (Weather)

Volunteer

#### Harry Hayfield

##### Expertise

If given any US zipcode I can give you a forecast (detailed for the next 24 hours and summarised for the next five to ten days) and explain what precisely is likely to happen

##### Experience

I've been interested in weather since the early 1980's and regulary watch global weather forecasts on CNN and Fox News