No – bomb cyclones are not tropical cyclones. The scientific term for a bomb cyclone is “explosive cyclogenesis,” but they go by many other names: weather bomb, explosive development, bombogenesis, meteorological bomb, etc.
There are time, latitude and pressure requirements that a weather system must meet to gain bomb cyclone status.
To put it simply when a storm is described as “bombing,” it essentially means there’s a massive drop in pressure in a 24-hour period.
A rapid drop in pressure is one of the features of a hurricane, but the term bomb cyclone is generally only used to describe extratropical cyclones, not tropical cyclones (hurricanes, tropical storms and tropical depressions). They’re often especially violent storms since:
All types of weather patterns can undergo bombogenesis, and the high winds generated are a key factor in the effect.
Not exactly – but it’s complicated. Hurricanes, and tropical cyclones more generally, do feature massive fluctuations in pressure. It’s why they generate such high winds. It’s fundamentally the same weather effect that generates winds in bomb cyclones. However, the extratropical version of bombogenesis and the tropical rapid deepening of hurricanes are considered, for meteorological purposes, two separate things.
One of the ways in which hurricanes are ranked is by their fluctuations in millibars in 24-hour periods. Hurricane Wilma holds the record with a massive 97 millibar drop in just 24 hours. Hurricane Maria, although not as intense, still experienced a rapid 55 millibar drop in just 24 hours.
Bomb cyclones do generate winds similar in scope to tropical storms or Category 1 hurricanes. Bomb cyclones can create winds in the 74 mph to 95 mph range, but in the U.S. they’re usually extratropical winter events.
Although bomb cyclones do often gain strength or react to jet streams and pressure changes driven by ocean surface temperatures, they can also form over landlocked areas – which a hurricane can’t do.
And unlike hurricanes, bomb cyclones are not a purely East Coast and Gulf Coast phenomenon. Explosive cyclogenesis is in the news currently because of a record-breaking bomb cyclone on the West Coast.
Moist air over the U.S. West Coast merged with the bomb cyclone for devastating effect, with wind gusts reaching up to 60 mph. In parts of the Pacific Northwest this system generated an almost storm surge-like effect of waves crashing 20 feet higher on Northern California and Oregon coasts.
The San Francisco Bay Area and Oakland were preparing for potentially record-breaking rainfall, which is both a blessing and a curse for that part of the country. The good news is the rains will help with some of the still-raging wildfires. The bad news is places that have been affected by wildfires are prone to severe mudslides.
Yes – just because hurricanes don’t technically undergo bombogenesis in the extratropical sense, it can still happen in Florida. In early January 2018, when Tallahassee received a rare dusting of snow, it was due to a storm that underwent explosive cyclogenesis off the Atlantic coast.
That storm, which even got its own name – Grayson – experienced a 51 millibar drop in less than 24 hours. At its peak, Grayson had 90 mph winds, with peak gusts measured at 125 mph. It dragged blizzard conditions all the way up the east coast, with peak snowfall of 24 inches in Bathurst, New Brunswick in Canada.