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Weather Map
NWS Radar Map for New Jersey
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updated: 924 PM EDT TUE MAY 13 2008
TONIGHT
  CLEAR. LOWS IN THE LOWER 40S. NORTH WINDS 5 TO 10 MPH THIS EVENING...BECOMING LIGHT AND VARIABLE.
WEDNESDAY
  SUNNY. HIGHS IN THE MID 70S. LIGHT AND VARIABLE WINDS... BECOMING SOUTH AROUND 5 MPH IN THE AFTERNOON.
WEDNESDAY NIGHT
  PARTLY CLOUDY IN THE EVENING...THEN BECOMING MOSTLY CLOUDY. LOWS IN THE UPPER 40S. SOUTH WINDS 5 TO 10 MPH.
THURSDAY
  PARTLY SUNNY WITH A 20 PERCENT CHANCE OF A SHOWER. HIGHS IN THE LOWER 70S. WEST WINDS AROUND 5 MPH.
THURSDAY NIGHT
  PARTLY CLOUDY IN THE EVENING...THEN BECOMING MOSTLY CLOUDY. A 20 PERCENT CHANCE OF A SHOWER. LOWS IN THE MID 40S.  NORTH WINDS 5 TO 10 MPH.
FRIDAY
  RAIN LIKELY. HIGHS AROUND 60. CHANCE OF RAIN 60 PERCENT.
FRIDAY NIGHT
  MOSTLY CLOUDY WITH A 50 PERCENT CHANCE OF SHOWERS. LOWS IN THE MID 40S.
SATURDAY
  PARTLY SUNNY WITH A 40 PERCENT CHANCE OF SHOWERS. HIGHS IN THE MID 60S.
SATURDAY NIGHT
  MOSTLY CLOUDY WITH A 30 PERCENT CHANCE OF SHOWERS. LOWS IN THE LOWER 40S.
SUNDAY
  MOSTLY CLOUDY WITH A 30 PERCENT CHANCE OF SHOWERS. HIGHS IN THE LOWER 60S.
SUNDAY NIGHT
  MOSTLY CLOUDY. LOWS IN THE MID 40S.
MONDAY
  PARTLY SUNNY. HIGHS IN THE MID 60S.
MONDAY NIGHT
  MOSTLY CLOUDY. LOWS IN THE MID 40S.
TUESDAY
  MOSTLY CLOUDY. HIGHS IN THE MID 60S.


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Doppler Radar Map for New Jersey

This is the latest Doppler Radar Map for New Jersey from the National Weather Service. This image is generated at the National Weather Service's Mount Holly, New Jersey station by NEXRAD.

NEXRAD (Next Generation Radar) obtains weather information (precipitation and wind) based upon returned energy. The radar emits a burst of energy (green). If the energy strikes an object (rain drop, bug, bird, etc), the energy is scattered in all directions (blue). A small fraction of that scattered energy is directed back toward the radar. This reflected signal is then received by the radar during its listening period. Computers analyze the strength of the returned pulse, time it took to travel to the object and back, and phase shift of the pulse. This process of emitting a signal, listening for any returned signal, then emitting the next signal, takes place very fast, up to around 1300 times each second.

NEXRAD spends the vast amount of time "listening" for returning signals it sent. When the time of all the pulses each hour are totaled (the time the radar is actually transmitting), the radar is "on" for about 7 seconds each hour. The remaining 59 minutes and 53 seconds are spent listening for any returned signals. The ability to detect the "shift in the phase" of the pulse of energy makes NEXRAD a Doppler radar. The phase of the returning signal typically changes based upon the motion of the raindrops (or bugs, dust, etc.).

This Doppler effect was named after the Austrian physicist, Christian Doppler, who discovered it. You have most likely experienced the "Doppler effect" around trains. As a train passes your location, you may have noticed the pitch in the train's whistle changing from high to low. As the train approaches, the sound waves that make up the whistle are compressed making the pitch higher than if the train was stationary. Likewise, as the train moves away from you, the sound waves are stretched, lowering the pitch of the whistle. The faster the train moves, the greater the change in the whistle's pitch as it passes your location. The same effect takes place in the atmosphere as a pulse of energy from NEXRAD strikes an object and is reflected back toward the radar. The radar's computers measure the phase change of the reflected pulse of energy which then convert that change to a velocity of the object, either toward or from the radar. Information on the movement of objects either toward or away from the radar can be used to estimate the speed of the wind. This ability to "see" the wind is what enables the National Weather Service to detect the formation of tornados which, in turn, allows them to issue tornado warnings with more advanced notice.


Astronomy Doppler Radar Map

 

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