Please access the related link below for life-saving advice from the US NOAA regarding Tornado-survival tips. -They say NOT to open windows and doors...
If two tornadoes came together they would merge to form a single, larger tornado. Such instances are rare, but they have happened. In most tornado mergers a large tornado absorbs a small one.
A a radar is better: it can detect a tornado at a distance. A barometer would be of no use unless the tornado came dangerously close.
While it would be possible for a tornado to cause major damage to a significant portion of Washington D.C. (in 2002 a large F4 tornado came within 30 miles), no tornado would be large enough to affect the entire city.
Leave the mobile home for a sturdy building or an underground shelter.
Any part of a home can be impacted by a tornado, depending on how strong it is. A weak tornado will probably not damage more than the exterior. The basement is the least likely part to be affected, but an EF5 tornado could easily remove a house from its foundation and expose the basement to the winds.
If two tornadoes come together they merge into one tornado.
twister
You should not be in a mobile home if there is a tornado coming. Mobile homes are very susceptible to tornado damage and should be abandoned for sturdier shelter during a tornado warning.
Never
It came out of the west.
That can vary widely. First of all, it depends on how severely damaged the house is. Damage can range from a few peeled shingles (with a cost of hundreds of dollars) to the complete destruction of the home, in which case the cost would depend on the value of a new home, which is variable.
a tornado warning would be issued if it is in your county and a tornado watch if it is out of your county.