Pressure Gradients and Winds

First let me explain the "mad crazy" winds on Long Island.  When storms strengthen off the coast of Long Island...the pressure in the center of the storm drops.  Usually there is high pressure following the storm from the west.  So...when the storm passes Long Island...you are between the low pressure to your northeast and high pressure to your west.  This is the tight pressure gradient you were referring to and the reason why the winds blow so hard.  Take a look at an article I wrote on "why the wind blows" in the madmariner weather archives.

 Now...how does this translate when looking at a barometer.  First I want to clarify that there is no hard and fast rule of how many millibars must decrease for a storm to arrive.  Every storm is different and every weather scenario is unique.  What you probably saw on your barometer if you were looking at regularly is this...as the storm strengthened to your south...you would see your barometer decrease.  Then...as the storm reached its closest point to you...you would see the lowest pressure on your barometer before it began to increase again.  Without looking at satellite...radar...or anything other than your barometer and the wind direction...you can determine when a storm has passed by you.  This is invaluable if you were in the middle of the ocean and had nothing but your barometer as a weather guide.  In more primitive times...sailors would steer their ship right into the path of storms.  Now...back to the barometer on Long Island.  As the pressure began to rise...high pressure would be filtering into the area and you would see general improvement in the weather shortly thereafter.  The barometer can be effectively used for short-term forecasts (generally less than 24 hours in advance).  This is the reason why on some barometers...there will be "fair"weather on the higher pressure readings..and stormy weather on the lower pressure readings.