What is the best weather model? Is it the GFS? Is it the EURO? Is it Naomi Campbell? No, the best weather model can be the “look out the window” model. Observing nature can be an incredibly useful of forecasting the weather. The following weather sayings are not always accurate, but they are accurate enough to be useful.
“Halo around the sun or moon, rain or snow is coming soon.” Using optics to bend light, cirrostratus clouds cause a halo to form around the sun or moon. These clouds are often followed by stratiform rain within 48 hours.
“Rainbow to windward, foul fall the day. Rainbow to leeward, rain run away.” In the mid-latitudes, the prevailing wind is from the west. If you see a rainbow in the same direction that the prevailing wind is coming from, rain is coming towards you, and it usually rains within the hour. If you see a rainbow in the direction the prevailing wind is going to, the rain has passed you, and the rain is over.
“Short notice soon to pass. Long notice, long to last.” Rain or snow systems that move in quickly like squalls or thunderstorms also tend to move out quickly. Systems that move in slowly like hurricanes or noreasters tend to move out slowly.
“Big snowflakes, little snowfall. Little snowflakes, big snowfall.” Snowflakes become big when they clump together. They usually clump together because of some melting layer where the temperature is above freezing. If the above freezing layer is at the surface, the snow will melt on contact. If the layer is aloft, the snow will chngeover to sleet. When snowflakes are small, temperatures are usually below freezing everywhere in the column.
Short term numerical weather prediction is incredibly helpful. However, it can also be coupled with ground observations to provide a more complete picture of our natural world. The ability to forecast when rain has ended by the rainbow is important because it tells people that they can resume their outdoor activities. We all can forecast the clouds without using the Cloud.