Jet stream

So, this morning  i was watching the  the news and   the weather  came on .  While giving the forecast the  weather man  said  that  we  will  be  having unusually warm temperatures due to the changes in the  jet stream. This made  me  wonder  what causes  changes in the jet stream so   I have  some  information I  found  on  what  causes these changes.
Jet streams are caused by a combination of a planet's rotation on its axis and atmospheric heating (by solar radiation and, on some planets other than Earth, internal heat). The Coriolis effect describes how a planet's surface and atmosphere rotate fastest relative to each other at the planet's equatorwhile virtually not rotating at all at the poles. Jet streams form near boundaries of adjacent air masses with significant differences in temperature, such as the polar region and the warmer air towards the equator.^[2]

In general, winds are strongest under the tropopause (except during tornadoes, hurricanes or other anomalous situations). If two air masses of different temperatures or densities meet, the resulting pressure difference caused by the density difference (which causes wind) is highest within the transition zone. The wind does not flow directly from the hot to the cold area, but is deflected by the Coriolis effect and flows along the boundary of the two air masses.^[22]

All these facts are consequences of the thermal wind relation. The balance of forces on an atmospheric parcel in the vertical direction is primarily between the pressure gradient and the force of gravity, a balance referred to as hydrostatic. In the horizontal, the dominant balance outside of the tropics is between the Coriolis effect and the pressure gradient, a balance referred to as geostrophic. Given both hydrostatic and geostrophic balance, one can derive the thermal wind relation: the vertical derivative of the horizontal wind is proportional to the horizontal temperature gradient. The sense of the relation is such that temperatures decreasing polewards implies that winds develop a larger eastward component as one moves upwards. Therefore, the strong eastward moving jet streams are in part a simple consequence of the fact that the equator is warmer than the north and south poles.^[22]

The thermal wind relation does not immediately provide an explanation for why the winds are organized in tight jets, rather than distributed more broadly over the hemisphere. There are two factors that contribute to this sharpness of the jets. The first factor is the tendency for developing cyclonic disturbances in midlatitudes to form fronts — sharp localized gradients in temperature. The polar front jet stream can be thought of as the result of thisfrontogenesis process in midlatitudes, as the storms concentrate the north-south temperature contrast into relatively narrow regions.^[15]