It is a non-monsoonal precipitation pattern driven by the westerlies. Thereafter, the cyclone accelerated further and curved northeastward due to the mid-latitude westerlies. Europe lies mainly in the temperate climate zones, being subjected to prevailing westerlies. Wind shear from westerlies increases substantially through November, generally preventing cyclone formation. Major SSWs occur when the winter polar stratospheric westerlies reverse to easterlies. The depression then turned eastward in response to becoming entangled in the mid-latitude westerlies. The prevailing westerlies in these zones blow strongest in winter. This eliminates maritime moderation from westerlies that are prevalent in moderating summer temperatures. The cyclone then accelerated due to the influence of the mid-latitude westerlies. In the mid-latitude westerlies, upper level troughs and ridges often alternate in a high-amplitude pattern. This route is the fastest, as it follows the prevailing westerlies. In early July, a shortwave trough embedded in the westerlies crossed the United States. This excludes areas south of 40S where it is dominated by westerlies. Downward motion of the easterlies is usually more irregular than that of the westerlies. The jet streams are systems of upper-air westerlies.