How would thunderstorms southeast through southwest of the observation location be encoded for transmission in an observation?

The correct choice, "TS SE-SW," is an accurate encoding of the location of thunderstorms relative to the observation point. In meteorological observations, direction is usually indicated starting from where the observed phenomenon is originating.

In this case, "SE-SW" clearly denotes that the thunderstorms are located to the southeast and extend to the southwest of the observer's position. This format follows the standard meteorological practice of indicating the directional range of the conditions being reported, allowing other users of the information to understand exactly where the thunderstorms are in relation to their location.

It’s important to note that meteorological notation requires clarity in direction. The other options either provide incorrect or reversed directional indicators that do not appropriately describe the location of the thunderstorms concerning the observer. For instance, "SW-SE" incorrectly implies that the storms are oriented from southwest to southeast, which does not reflect the intended observation.