Low-pressure area mesocyclones, but more often develop from environments of high instability and low vertical wind shear. In deserts, lack of ground and plant moisture that would normally provide evaporative cooling can lead to intense, rapid solar heating of the lower layers of air. The hot air is less dense than surrounding cooler air. This, combined with the rising of the hot air, results in a low-pressure area called a thermal low. Monsoon circulations are caused by thermal lows which form over large areas of land and their strength is driven by how land heats more quickly than the surrounding nearby ocean.
Blood pressure many causes and may be of sudden onset or of long duration. Long-term hypertension is a risk factor for many diseases, including heart disease, stroke and kidney failure. Long-term hypertension is more common than long-term hypotension, which often goes undetected because of infrequent monitoring and the absence of symptoms. The risk of cardiovascular disease increases progressively above 115/75 mmHg. In practice blood pressure is considered too low only if noticeable symptoms are present. Observational studies demonstrate that people who maintain arterial pressures at the low end of these pressure ranges have much better long-term cardiovascular health. There is an ongoing