Report on the Windstorm during the Inauguration Day of the Mayaguez 2010 Central American Games on Saturday, July 17, 2010

During the early afternoon of Saturday, July 17, 2010, a thunderstorm squall line affected the grounds of the Isidoro Garcia Park Olympic Stadium in the city of Mayaguez, where the Opening Ceremony for the Mayaguez 2010 Central American Games was to be held later that afternoon.
The squall line moved across Mayaguez, producing strong gusty winds that downed a scaffold equipped with lighting equipment at the Isidoro Garcia Park, Olympic Stadium near the coast. Several persons were injured and some vehicles were damaged, as the platform fell to the ground. Downed trees and power lines were also reported in several other municipalities of western Puerto Rico. Due to these adverse weather conditions, officials were forced to delay the Games’ Opening Ceremony.
Several ingredients came together for this type of weather event to occur across Puerto Rico on July 17. An upper level low pressure system and its surface reflection were located north of the local area. Deep moisture with precipitable water values up to 2.25 inches, coupled with strong thunderstorms that were generating strong gusty winds.
Initial local and national media reports attributed this event to a tornado or a waterspout that had moved inland. However, most of the evidence examined indicates that it was an outflow boundary that propagated from the east southeast to the west northwest across Puerto Rico at a fast pace. It is very common in mainland USA for this type of squall line to generate tornadoes as it propagates, however, in tropical regions all the conditions for tornado development are not necessarily present. The western and northwest waters of Puerto Rico at times experience isolated but strong waterspouts in association with near severe thunderstorms, and on occasion a few of these waterspouts have moved inland, becoming tornadoes of EF0 or EF1 intensity. 
Reviewing the data available for the different wind sensors, official and non-official, deployed across the island revealed interesting wind gusts as the squall line traversed the island.

Sensor Name
Sensor Location
Wind Speed/Gust MPH
11:15 AM
gust to 43 mph
11:15 AM
gust to 43 mph
11:18 AM
Yabucoa Harbor
25 mph gusting to 43 mph
12:00 PM Approx
La Parguera, Lajas
gust to 46 mph
12:17 PM
gust to 53 mph
12:30 PM
El Maní Mayaguez
gust to 33 mph
12:45 PM
El Maní Mayaguez
gust to 36 mph
1:00 PM
El Maní Mayaguez
gust to 30 mph
1:14 PM
National Wildlife Refuge
Cabo Rojo
gust to 48 mph

The NOS-NWLON sensor at the Penuelas-Guayanilla Bay reported a wind gust to 53 mph at 12:17 pm as the squall line moved through. The Cabo Rojo National Wildlife Refuge sensor recorded a wind gust to 48 mph at 1:14 pm. Data from the Puerto Rico Electric Power Company (PREPA) wind sensor at El Mani site near the Mayaguez airport, indicated wind gusts of 33 mph at 12:30 pm, 36 mph at 12:45 pm, and 30 mph at 1:00 pm. The PREPA net highest wind gust was recorded at La Parguera sensor in Lajas, where a 46 mph gust was recorded around noon. Other locations in Puerto Rico recorded wind gusts that ranged between 35 and 45 mph.
The CARA ICOOS sensor (MAROB 42085) near Caja de Muertos Island south of Ponce recorded wind gusts of 40 mph between 12:20 and 12:30 pm.
The Cabo Rojo National Widlife Refuge RAWS sensor (MCRRP4) recorded sustained winds of 29 mph with gusts to 48 mph from the east southeast at 1:14 pm and 1:43 pm. Followed by a period of sustained winds of 21 to 29 mph with gusts of 42 to 45 mph from the east southeast between 2:34 pm and 3:43 pm. 
At 10:51 am the squall line was located about six miles southeast of Yabucoa and was moving west northwest around 30 mph. It moved rapidly inland producing gusty winds and lightning. NOAA’s NOS NWLON station (YABP4) at the Yabucoa harbor recorded sustained winds of 25 mph with gusts to 43 mph from the east southeast at 11:18 am. The PREPA wind sensors recorded wind gusts of 43 mph in the municipalities of Fajardo and Guayama at 11:15 am. By 11:31 am, the squall line was across southeast Puerto Rico and moving to the northwest at a speed greater than 35 mph. By 11:37 am, the line of thunderstorms was moving across parts of central Puerto Rico with damaging winds of 35 to 45 mph, and it was expected to reach western sections of Puerto Rico before 12:15 pm.

The National Weather Service Forecast Office in San Juan issued a Special Weather Statement for strong and gusty winds at 10:57 am, followed by updated statements at 11:37 am, 11:52 am, and 12:44 pm. See the following special weather statements:

The following picture of the squall line was taken by Dr. Eddie Laboy as he was driving from the municipality of Santa Isabel to Juana Diaz along Highway PR 52. Around noon, he arrived to a location near Cerro Puntas, inland Ponce, where he felt the winds to be remarkably strong.

Squall Line. Image courtesy of Dr. Eddie Laboy

Squall line moving inland between the coastal municipalities of Juana Diaz and Santa Isabel around noon on July 17, 2010. Photo by Dr. Eddie Laboy
Around 12:35 pm, the squall line reached the city of Mayaguez, producing strong gusty winds that downed a scaffold equipped with lighting equipment at the Isidoro Garcia Park Olympic Stadium, along road 102, near the Mayaguez coast. Several persons were injured and some vehicles were damaged as the platform fell to the ground.
The Peñuelas-Guayanilla NOAA NOWS-NWLON (MPLSP4) sensor recorded sustained winds of 41 mph with gusts to 53 mph from the south at 12:17 pm, followed by a period of sustained winds of 33-38 mph with gusts from 38-47 mph from the south and south southeast between 12:27 pm and 1:08 pm.

outflow boundary

The thunderstorm outflow boundary denoted by a band of higher reflectivity values can be seen moving rapidly northwest and into Mayaguez in this 12:16 pm radar image.


Visible Satellite

The thunderstorm outflow boundary or arc cloud is evident on this visible satellite image just off of the west coast of Puerto Rico at 12:45 pm.


MADIS obsevations

MADIS Observations 1501 UTC to 1700 UTC

In conclusion, there were no indications of significant rotation within the thunderstorm that affected the Mayaguez 2010 Central American Games site, nor were there any visual reports or station observations that indicated that a tornado had developed over land or a waterspout had moved ashore. All available meteorological data examined for this wind event, indicate that the series of strong wind gusts and resulting injuries and damage were from a thunderstorm outflow boundary (squall line) or down-rushing, rain-cooled air spreading out along the surface, moving quickly west northwest across Puerto Rico, and eventually affecting the west coast of the island, including Mayaguez.

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