Image copyright Susie Le FabriￂﾠIn northern California, high winds and snowy weather are kicking off spring in a new way – a bomb cyclone.
The storm’s meteoric appearance in the Bay Area on Sunday was caused by a split-lunar system (the moon being closer than the Earth) resulting in low pressure.
The storm has a strong wind profile and possesses strong, cold air pockets – a classic recipe for a bomb cyclone, also known as a bomb cyclone-season.
What is a bomb cyclone?
A bomb cyclone is a type of atmospheric turbulence – also called a bomb – when the air speeds rise during one of its four phases:
Winstanley Phase: Very rapid lifting of the upper air. These days, this causes a cold or arctic phenomenon called a bomb cyclone
Very rapid lifting of the upper air. These days, this causes a cold or arctic phenomenon called a bomb cyclone White Phase: A hot, dry blast of air
A hot, dry blast of air Grey/Pink Phase: A moist air mass.
A moist air mass. Pink Phase: Thickening of this air mass. This creates a strong funneled tailwind, a tornado.
Very strong rainfall drenching and blowing winds – more than 200mph (320kph).
What caused the storm in the Bay Area?
A middle-latitude storm system brought unusual clouds and rain in Northern California, with hail and snow also reported.
This is the fifth bomb cyclone to hit the Bay Area this season – one in June, the fourth in July, the fifth on Sunday and another on Tuesday.
Image copyright @SusieLeFabri/NASA Image caption A bomb cyclone is caused by a similar rift (left) between the Earth and the moon’s orbit. The opening and closing phases show much stronger winds than usual
What other forms of weather are there that can be called bomb cyclones?
There is no specific definition in meteorology of what a “bomb” is, although a modern definition looks at how the total spin radius changes during time.
The way it’s described in a 1970 book called Meteorology by Thomas Bellervino and Robert Mahoney is:
“During the first or middle stage, or plume, of the storm, a super-fast, air-pressure high is formed, and when this form of instability is on top of and surrounded by thick layers of cold air, it becomes known as a bomb. The moderate stage before the bomb forms is called the rust-wet,” referring to the flow, like red wine.
“The storm has this vigorous form through several stages, but it becomes progressively weaker from the cool end, right after that it decreases and also becomes more wispy and thin.”
Huge drops in temperature (or temperature) can occur during the plant phase of a bomb cyclone.
The eight best parts of meteorology HISTORY: An easy story to understand this one can be interpreted as “This explosion of air is the best part.” University of Illinois at Urbana-Champaign UNIVERSITY OF TEXAS: A great depth of knowledge on this one. MIAMI AIRPORT: A fine site. Stunning photo: Oklahoma Weather Service, Oklahoma City Photo Galleries
What does a storm like this do?
The water vapor and moisture spews out and creates a big downdraft, which can cause widespread icing of roads and vehicles, low visibility and blizzard conditions. The blast of air waves produces turbulence that includes what are called “bomb cyclones” (also known as whirlstorms).
The storm is expected to pass offshore of California on Tuesday evening, but still packs some punch, as forecasters warn more of its thundery rain and snow into the New Year.
And the real drama is about to come from south-east, where a killer tornado killed at least 15 people last week in Texas.
These hail-filled storms rarely hit the US – and when they do, typically last only a few hours. But they are perfect models for this so-called storm deficit, which happens whenever two weather systems far apart produce the same amount of weather.