nice one ken, good to learn something new.....

i found htis on wiki prompted by your post. in future i'll be looking for mares tails.
The random, isolated cirrus cloud does not have any particular significance. A cirrus castellanus cloud indicates that there is instability at the cirrus level.[23] However, a large number of cirrus clouds may be a sign of an approaching frontal system or upper air disturbance. This usually signals a change in weather in the near future, usually becoming increasingly stormy.[24] When the cirrus clouds deepen and spread, especially when they are of the cirrus radiatus or cirrus fibratus forms, this usually indicates an approaching weather front. When the weather front is a warm front, the cirrus clouds spread out into cirrostratus clouds, which then thicken and lower into altocumulus and altostratus clouds. The next set of clouds are the rain-laden nimbostratus clouds.[23][4][25] When cirrus clouds precede a cold front, it is because they are blown off the anvil, and the next clouds to arrive are the thunderstorm clouds, cumulonimbus.[25] Kelvin-Helmholtz waves indicate extreme wind shear at high levels.[23] Within the tropics, 36 hours prior to the center passage of a tropical cyclone, a veil of white cirrus clouds approaches from the direction of the cyclone.[26]
In the mid to late 1800s, forecasters used these cirrus veils to predict the arrival of hurricanes. In the early 1870s, the president of Belen College (located in Havana, Cuba), Benito Vines, developed the first hurricane forecasting system, and he mainly used the motion of these clouds in formulating his predictions.[27] He would observe the clouds hourly from 4:00 AM to 10:00 PM. After accumulating enough information, Vines began accurately predicting the paths of hurricanes, and he eventually published his book, Apuntes Relativos a los Huracanes de las Antilles.[28]