H4 Clouds: Cirrus (Ci) progressively H4 Clouds Symbol = – invading the sky Cirrus Clouds with Hooks or Filaments Invading the Sky Cirrus clouds that seem to get denser H4 and invade the sky are known as H4 clouds. Cirrus in the form of filaments, strands or National Weather Service hooks, progressively invading the sky and generally becoming dense While invading high cirrus clouds often indicate a frontal system approaching, there may also be no impending weather Notes: These are the same clouds as H1 but changes. The clouds will often form and they progressively invade the sky and seem to fuse together to make generally become denser as a whole. They progressively larger and more invasive often seem to fuse together in the direction clouds. The appearance of H4 clouds is from which they come. The forward edge almost exactly the same as H1 clouds. If moves towards the opposite part of the the wispy nature of high cirrus clouds horizon. The clouds occur most frequently in appear to be progressively invading the form of strands trailing from a small hook or sky, then they are H4 clouds rather than tuft and less frequently in the form of straight H1 clouds. or irregularly curved filaments. Source: Source: National Weather Service JetStream - Online School for Weather
H4 Clouds: Cirrus (Ci) progressively invading the sky H4 Cirrus in the form of filaments, strands or hooks, progressively invading the sky and generally becoming dense Notes: These are the same clouds as H1 but they progressively invade the sky and generally become denser as a whole. They often seem to fuse together in the direction from which they come. The forward edge moves towards the opposite part of the horizon. The clouds occur most frequently in form of strands trailing from a small hook or tuft and less frequently in the form of straight or irregularly curved filaments. Source: National Weather Service JetStream - Online School for Weather H4 Clouds – Symbol = Cirrus Clouds with Hooks or Filaments Invading the Sky Cirrus clouds that seem to get denser and invade the sky are known as H4 clouds. National Weather Service While invading high cirrus clouds often indicate a frontal system approaching, there may also be no impending weather changes. The clouds will often form and seem to fuse together to make progressively larger and more invasive clouds. The appearance of H4 clouds is almost exactly the same as H1 clouds. If the wispy nature of high cirrus clouds appear to be progressively invading the sky, then they are H4 clouds rather than H1 clouds. Source:
APPENDICES-2.docx