TERMINOLOGY:
In this lecture, "landslide" is used as a general term for various mass-movement processes, including debris flows and mud flows (Varnes, 1978). In a majority of cases, coarse and fine sediment flows caused by the storm began as shallow slides, that quickly transformed into rapidly moving flows.
It appears that the movement involved both sliding and flowing.
For simplicity, we have generally used the term "debris flow" for this complex mechanism.

RAINFALL CONDITIONS:
Location map
Portland is located in the northeastern section of Jamaica, on the windward slope of the Blue Mountain Range directly in the path of the moisture laden North East Trade Winds.
This area is the wettest parish in Jamaica.
It is characterized by high annual precipitation, 760 to 6500 mm, and periodic short-duration high-magnitude rainfall from various types of tropical storms which may reach hurricane force.
Map of average annual rainfall in eastern Jamaica
Tropical waves and depressions affect the island during May to November. The rainfall during December to March is due to frontal systems.
Flood conditions on the island are more common in the northern parishes of Portland, St. Mary and St. Ann and the eastern parish of St. Thomas.
The rainfall experienced in Portland during 3-4 January 1998 was above normal and extreme and was due to a frontal trough ( Nat. Met. Service Jamaica, 1998).
The area around Fellowship received some 148.8 mm of precipitation on 4th January. Most of the landslides in the area were triggered by this rainfall.
Isohyetal map