Puerto Rico and U.S. Virgin Islands Severe Rainfall 

November 12-14, 2003

 

Heavy rains over Puerto Rico and the U.S. Virgin Islands during the week of November 10-15 2003, led to widespread flash flooding, and numerous mud, land and rock slides. In Puerto Rico, 19 municipalities were declared a federal disaster area, with total damages estimated around 45 million. The U.S. Virgin Islands were also declared a federal disaster area, with damages estimates around 25-30 million.

On November 10, 2003, an active tropical wave approached the U.S. Virgin Islands and Puerto Rico as a mid to upper level low pressure trough advanced towards Eastern Hispaniola from the Bahamas. All ingredients for heavy rains were beginning to come together across the U.S. Virgin Islands and Puerto Rio. As the strong tropical wave crossed the area from east to west, it set up a south to southeast wind flow over the Northeast Caribbean that allowed for abundant low level moisture to slide into the U.S. Virgin Islands and Puerto Rico. By Tuesday November 11, 2003, the strong tropical wave evolved into a broad area of low pressure which developed across the Caribbean Sea southwest of Puerto Rico. This low pressure at the surface extended from Hispaniola eastward into the Leeward Islands and was expected to slowly strengthen through Wednesday, and to eventually move northeast.  A reconnaissance aircraft flew into the suspect low pressure area on Tuesday, but was unable to find a closed circulation center at the surface. However, it did find that the lowest sea level pressure was just east of the Eastern tip of Hispaniola. The combination of all these factors, an almost stationary broad low pressure, a  mid to upper level trough to the west, southeast low level winds, and a plume of moist mid to high level air stream from northern South America, led to a  period of widespread and continuous heavy rains across all of the U.S. Virgin Islands and Puerto Rico, resulting in generalized flash floods and river floods. The heaviest rains affected Puerto Rico through Friday November 14, and the U.S. Virgin Islands through early Saturday morning, November 15.

The period of widespread and heavy rainfall tapered off after November 15, but it was followed by a three day stretch of occasional showers associated to a cold front, from November 15-18, for both the U.S. Virgin Islands and Puerto Rico.  The cold front approached from the northwest, moving southeast across the local area Saturday, and reaching into the Leeward Islands.  By late Sunday into Monday, November 16, the low level trade  winds became southeast across the Northeast Caribbean,  forcing the remnants of the cold front, to move back over the U.S. Virgin Islands and Puerto Rico. Although rainfall amounts were not significant across the U.S. Virgin Islands, the ground was so saturated, that even small amounts of rain resulted in additional flooding, and landslides. In Puerto Rico, many parts of the island received heavy rainfall amounts, and the highest was again, in the municipality of Naguabo, where over 10 inches were recorded at the Rio Icacos USGS sensor. 

 

The greatest rainfall amounts across Puerto Rico for the period from November 12-14, varied from 10 to 20 inches, although the eastern Puerto Rico municipality of Naguabo received 21.01 inches.

The highest 4-day rainfall accumulation, ending @ 0800AM  November 14th, were recorded at : Naguabo - 22.70 in, Sabana Grande - 19.73 in, Ponce - 17.77 in, Rio Grande - 17.13 in,      Guayama - 17.09 in, and Aibonito - 15.79 in  ( Tables 1- 4 ). 

The highest rainfall intensity occurred in the upper part of Naguabo. Comparison with TP- 42 charts indicated:  the 50 yr - 4 day rainfall was exceeded in Naguabo and Aibonito, and the 25 yr - 4 day rainfall was exceeded in the south and eastern coastal plains from Juana Diaz to Naguabo as well as in the northern parts of Yauco, Aibonito and Guayama.

 

The highest 1 hour, 2 hour, and 3 hour rainfall totals of 2.95 inches, 3.97 inches, and 4.73 inches were recorded at Salinas, Sabana Grande and Naguabo,  respectively. The highest 6 hour and 12 hour rainfall totals of 5.83 inches and 8.19 inches were recorded at Sabana Grande.

 

Extreme river rises were observed during the event. These were widespread around the island. Gaged sites that exceeded 15 feet rise were:

            Rio Grande de Loiza below Damsite                      - 26 feet

            Rio Grande de Manati at Hwy 2 near Manati         - 22 feet

            Rio Gurabo at Gurabo                                              - 21 feet

            Rio Jacaguas at Juana Diaz                                   - 20 feet

            Rio de La Plata at Hwy 2 at Toa Alta                      - 19 feet

            Rio de La Plata below La Plata Damsite  - 18 feet

            Rio de La Plata at Comerio                                     - 16 feet

            Rio Caonillas at Paso Palma                                  - 15 feet

            Rio Guanajibo at Hwy 119 at San German            - 15 feet

            Rio Culebrinas at Hwy 404 near Moca                   - 15 feet

           

The highest reservoir water levels rises were observed at:

            Lago Cerrillos at Damsite near Ponce                    - 39 feet

            Lago Toa Vaca at Damsite                                      - 16 feet

 

Rainfall amount across the U.S. Virgin Islands for the period from November 10-15, varied from 10 to 15 inches. The recorded rainfall intensity for St. Croix during the period from November 10-14, exceeded the one hundred year return period. For St. John approached the one hundred year return period, and for St. Thomas it was below the 25 year return period.  Cumulative rainfall for the three day period beginning Saturday November 16 at 8 am, and ending Tuesday November 18 at 8 am, reflected rainfall amounts ranging from 8-10 inches in the area of Naguabo to 4 to 6 inches in many other places of east and central Puerto Rico. (See table   )

In the U.S. Virgin Islands, rainfall varied from 2.6 inches in St. Thomas to 3.65 inches in St. John.  This additional rainfall exacerbated the pre existent flood situation even more, since not much rainfall was needed to cause flooding.  

In Puerto Rico, flood effects on the population were considerable. A total of 19 municipalities were declared a federal disaster, Arroyo, Cabo Rojo, Canovanas, Fajardo, Guanica, Guayama, Juana Diaz, Loiza, Luquillo, Maunabo, Naguabo, Patillas, Rio Grande, Salinas, Santa Isabel, Toa Baja, Yabucoa, and Yauco. The most seriously affected were Guanica, Santa Isabel, Salinas, Juana Diaz, Yabucoa and Maunabo.  Infrastructure and personal losses were estimated at 8 million.  Agricultural losses accounted for approximately $ 31 million. The greatest crop loss was coffee, followed by plantains, oranges, and sugar cane.  Total damages amounted to around 45 million. There were two deaths in Puerto Rico, one in Aibonito by drowning and another in Ciales.  The highest rainfall fell in Naguabo. Approximately 860 people across the island were forced from their homes into shelters due to flooding. Many bridges and roads sustained damages.

There were many livestock lost due to the flooding.

 

The rains were heavy in St Croix on November 11 where around 8 inches accumulated. There were landslides from the hills above Charlotte Amalie. Roads and culverts flooded. Water and mud covered the streets. The commercial district in Christiansted was flooded with debris and mud. Some roads in St Thomas were closed due to damage. The U.S. Virgin Islands government estimated the losses at 25.5 million, St Croix 8.8M, St Thomas 10.6M and St John 6.1M.