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Ken's Weather Links

Think predicting the weather is easy? Below are just some of the stages that SeacoastNH.com meteorologist Ken Mitchell goes through to arrive at the most accurate forecast for the seacoast area.

 

 

Current weather maps are linked below although there may be days when they are not available. For detailed reasoning of Ken's forecasts click here. For safety information check out the Tornado Safety Rules, Lightning Safety Rules and the Severe Thunderstorm Rules. Go here for an important list of Winter Saftey Rules (print these out and keep them handy).

MB = millibar, a pressure measurement unit. Air pressure falls off with height, so the lower the number, the higher you are. Also, the height above the ground of any given MB value (say 500) changes..sometimes it's higher up (high pressure aloft) and sometime lower down (low pressure aloft). So the lines on a 500MB map represent the HEIGHTS (in meters) of this pressure reading above the ground..not the pressure reading itself (after all, the entire map is at 500 MB).

500MB map500MB Map: Around 20,000 feet. Here is where I check for upper level low and high pressure areas that "drive" what happens at the surface. This map also shows where the highest concentration of spin potential (vorticity) is in the air..and these concentrations enhance storm and/or precipitation development as they move along in the wind flow. Winds at most levels tend to flow along the lines of constant height shown on the maps. Click here for current 500MB map or if unavailable try here.

700MB map700MB: Lower down, around 10,000 feet. Here we look for low pressure troughs (areas where the height values are lowest) and ridges (highest). This map also shows the highest/lowest vertical velocity (where the air is rising/sinking most) areas..as you know, when air rises it cools and can condense, so an important map for figuring out precipitation areas. As air sinks, it warms and dries. Click here for current 700MB map or if unavailable try here.

850MB map850MB: Lower yet, around 5000 feet...very important for seeing lows and highs unaffected by surface features like mountains. Also useful for finding cold and warm front locations unaffected by surface features, which tend to bend and distort these fronts at the surface. Also, the temperatures at this level are critical for rain/snow decisions. Great tool for deciding on temperature patterns for the next few days. Click here for current 850MB map or if unavailable try here.

mrf mapMRf model: "This map projects the surface weather out for 9 days, depicting the evening map for each day. This is good for medium range planning, but goes so far out solutions can change from day to day. I'll often temper my forecasts based on this product with caution until it produces similar results for several days running. Click here for the map. Click here for the 5000 foot (850 MB) version.

RH mapRELATIVE HUMIDITY/LIFTED INDEX (RH/LI) MAP: The average RH of the atmosphere is shown here..helps us decide if it will be cloudy or clear, and by how much. The Lifted Index is a number that also tells us about vertical velocities of the air..and again, rising air is suspect for precip and clouds. The lower the LI number, the more likely clouds and precipitation is. Click here for current RH/LI map or if unavailable try here.

surface mapSURFACE: Of course, everything that has been happening in the above maps shows up here for us. This map tells us where the high and low pressure areas are, the fronts, and how much precip may fall in a 12 hour period. Surface winds are also derived from this map. Also very important on this map are thickness lines (this map shows 500MB to 1000MB height difference: in colder air, the air is more condensed, so the difference in height between the 500 MB "surface" and the 1000MB "surface" shrinks and gives smaller values..when air warms, it expands, the difference between the heights expands and gives larger values). We use those lines to tell what kind of air is moving in (colder, warmer), and also helps us decide on rain/snow. Click here for current surface map or if unavailable try here.

radar mapRADAR: One of many radar shots we use, this tells us in nearly real time where the precipitation echoes are, and how intense they are. When looped, radar shots give a motion effect that helps us decide when echoes will get here or leave. Some loops also show whether rain, ice or snow is falling..a great help in deciding what to forecast. Click here for current USA radar map or Boston radar loop.

satellite mapSATELLITE: Nothing like seeing the clouds. When looped, this shows us movement of the clouds (where and how fast they are going). The night shots are infrared, so they are taking pictures of cloud temperatures, not the clouds themselves. Because of this (and if often happens) clouds that have the same temperature as the ground surface disappear..you don't see them..surprise! Click here for current satellite map.

skew mapSKEW-T: A weird name for a chart that shows the result of the measurement of the atmosphere by a weather balloon. As the balloon rises it takes wind, temperature and dewpoint readings. These balloons are sent up twice a day at points around the country and world, and these readings are what are fed into our computer models to produce the maps you see. But the Skew-T also gives us a good picture of what is happening in the air..exactly where the clouds are, exactly where the winds shift, etc. Also very important for determining instability for thunderstorms, freezing rain potential..almost eveything. Our nearest launch points are Albany NY and Chatham MA..too bad there isn't a Portsmouth NH launch! Click here for current Skew-T map.

3hr mapTHREE-HOUR PRESSURE CHANGE: I use this map to tell me where the surface pressures are changing the most over the past three hours. This is critical for deciding if storms are moving/forming where the models predictes they would. Also good for spotting things the models missed. Click here for current pressure map.

 

 


dewpoint mapSURFACE DEWPOINTS: This national map of current dewpoints tells me in a second where the moist air is, how moist it is, and using wind flow forecasts from other maps, if it will be getting moister or drier here. Very useful for comfort-level forecasting in the summer, too. Click here for current dewpoint map.

 

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