Description

Time: 2021-04-11 1:10 PM

Location: Rio Piedras, Puerto Rico

observer statement: I was doing ce5 whole week. Then during my break from work I walked to my balcony with my dog and saw this metalic object with my HDR-CX440 video camera.

Sorry for the background noise, that was my dog playing with some water bottle.

Weather report:
5 m/s east northeast wind (70°) up to 2000m. Above, a strong westerly wind (280°) (up to 25m/s)

Timetables and movement of weather balloons:
A weather balloon is launched twice a day (07:00 and 19:00 locat time) at the NOAA station located 7800m northeast of the observation site.
First weather balloon launch 11:04 UTC
First weather balloon burst 12:43:45 UTC
Second weather balloon launch 23:03 UTC
Second weather balloon burst 00:47:56 UTC

Description of the observation:
The observed object reflected the sunlight with a metallic sheen. It was elongated (ratio of 1/4), probably cylindrical. Both ends were brighter than the rest of the object, possibly emispheric in shape.
It was in slow rotation

Apparent size of the object:
The apparent size of the object was 110 pixels in length at maximum zoom.
3.31 e-6 rad/pixel x 110 = 364.1e-6 rad
(36cm/1000m) (72cm/2000m) (1.09m/3000m) (1.45m/4000m) (1.82m/5000m)

Could it be the weather balloon?
The first weather balloon burst at 12:43 UTC so 4 hours 27 minutes before the sighting.
The second weather balloon was launched at 23:03 UTC so 5 hours 53 minutes after the sighting.
the object observed cannot therefore be a weather balloon

Could it be a birthay balloon?
The shape does not match well with a birthday balloon.
The apparent size is large 364.1e-6 rad but the image is unclear which makes me think the object was far away (compared to other balloon sightings made from the same location) so quite large.
I can't prove it's not a mylar birthday balloon, but I'm skeptical.