Hundreds of millimeters of rain fell on Honduras as slow-moving tropical storm Sara moves across coastal regions of Central America.

Sara will likely become one of the region’s most prolific rainstorms in recent memory, joining last September’s Hurricane Helen in making flash flooding the storm’s primary calamity.

Here’s a look at how the prolific rains from Tropical Storm Sara and Hurricane Helen each played out in their own way.

DON’T MISS: How Hurricane Helene produced more than 700 mm of rain in three days

Tropical Storm Sara causes extreme flooding

Tropical Storm Sara is a classic late-season storm in the western Caribbean Sea. Warm water temperatures and favorable atmospheric conditions make this region of the Atlantic the most common place for storms to form this late in the hurricane season, which ends on November 30.

THE the system crashed approaching northern Honduras. A ridge of high pressure over the northern Caribbean cut winds around the storm, and this feature acted as a barrier to prevent Sara from moving northward out of the region.

As a result, the storm tracked just offshore and brought persistent torrential rain to the coast.

Northern Honduras is a very mountainous region. These precipitation rates were increased by a process known as orographic uplift: winds rising up mountain slopes, wringing out their moisture along the way in the form of torrential rains.

La Ceiba, home to a quarter of a million people, reported 552.0 mm of rain in 24 hours between November 14 and 15 at noon. The rain is not expected to stop anytime soon, and parts of Honduras could see 700 to 1,000 mm of rain by the time the storm finally ends this weekend.

This caused widespread flash flooding and mudslides across the country. The extent of the damage will not be known for several days.

Helen’s rains began well before the storm arrived

The pattern that produced the extensive flash flooding of Tropical Storm Sara is very different from the scenario we saw unfold during Hurricane Helene.

Helene crossed the eastern Gulf of Mexico in late September as a powerful major hurricane that would hit Florida with maximum sustained winds of 140 mph.

Long before Helen reached Florida, torrential rains began falling hundreds of miles inland. This phenomenon is known as a predecessor rain event (PRE).

A deep plume of tropical moisture flowing ahead of Hurricane Helene collided with a parked boundary over the interior of the southeastern United States. This boundary expelled tropical moisture from the air like a sponge, leading to heavy rainy days through the mountainous terrain of North Carolina and Tennessee.

Only after several days of rain did Helen’s core arrive, hitting the region with a second wave of additional heavy rain that overflowed local waterways well beyond their banks. Some communities received more than 700 mm of rain over several days, pushing rivers so high that they swept away entire cities.

The two events each highlight how tropical systems pose multifaceted threats that can create a unique set of hazards. No matter how strong the stormflash floods from heavy rains are almost always the most deadly hazard to any landing system.

WATCH: Comparing Hurricane Helene to 2021 British Columbia Floods

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