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Michael Carr 05-13-2001 08:00 PM

Monitoring Weather
 
<HTML><!-- eWebEditPro 1.8.0.2 --><DIV><DIV>In the Northern hemisphere, without the benefit of&nbsp;instruments, how can we be relatively certain that the winds we are currently in are the result of a high-pressure system and not the leading edge of a low-pressure system?&nbsp;</DIV><DIV>&nbsp;</DIV></DIV><DIV><STRONG>Michael Carr responds:</STRONG></DIV><DIV>Great question! It's interesting that you should ask because&nbsp;this is&nbsp;something that&nbsp;always comes up&nbsp;in mariner weather courses, in fact it's a&nbsp;topic that I covered recently in a seminar on&nbsp;Using Ocean Currents and Weather to Win.</DIV><DIV>&nbsp;</DIV><DIV>Here is how you tell the difference between winds associated with low pressure or high pressure:</DIV><DIV>&nbsp;</DIV><DIV>1. Monitor surface pressure readings. Normal sea level pressure is 1013 mb. If pressure is lower than 1013 and falling, a low is approaching; if it's above 1013 and rising then a high is approaching.</DIV><DIV>2. Cloud cover. Clouds thicken and lower with an approaching low, while they dissipate and provide clear skies with high pressure.</DIV><DIV>3. Relate the present weather you're seeing to the&nbsp;weather pattern. If you have been under the influence of&nbsp; good weather, i.e. high pressure, for the past several days and winds have been SW (we are talking about any venue on the US East Coast), then a shift of winds to NE, accompanied by increasing cirrus clouds, a lowering barometer and increasing winds, is no doubt a developing area of low pressure. The reverse is true of a high-pressure system approaching.&nbsp;If the conditions are clearing and you experience a dissipation of clouds and a shift in the wind to a northerly direction, that shows the arrival of high pressure from the west.</DIV><DIV>&nbsp;</DIV><DIV>The very best way to keep tuned in and maintain good situational awareness of the weather is to look at the Marine Prediction Center surface and 500-mb charts each day. These are available via weatherfax and the Internet.&nbsp;</DIV><DIV>&nbsp;</DIV><DIV>Without some instruments you will always have a difficult, if not impossible time sorting our the differences between&nbsp;local weather (sea breezes, etc.) and larger (synoptic scale) weather events. At a minimum you need a reliable and&nbsp;calibrated barometer, and at the high end you need satellite imagery, and easy access to charts via weatherfax or satcom systems. I hope this helps. </DIV></HTML>


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