| Development Division report, on the evaluation of the 6-Hour cycle pre-implementation test for the NMC FINAL cycle - :12649 | National Weather Service (NWS)
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Development Division report, on the evaluation of the 6-Hour cycle pre-implementation test for the NMC FINAL cycle
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Development Division report, on the evaluation of the 6-Hour cycle pre-implementation test for the NMC FINAL cycle
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  • Description:
    "For many years the normal cycle-time for analysis/forecast systems at NMC has been 12 hours, i.e., analyses performed at 00 and 12 GMT. These analysis times agree with some of the synoptic times of upper-air (radiosonde and pilot balloon) and surface observations made throughout most of the world. Besides these observations, numerous aircraft reports are also available but are basically asynoptic. In the early 70's, NMC began to receive more asynoptic meteorological information (cloud patterns, estimates of winds from picture pairs and cloud-top blow offs, moisture estimates, tropospheric and stratospheric vertical temperature soundings) from polar-orbiting and geo-stationary satellites. In the mid 70's we have seen data from TWERLE, constant pressure balloons, drifting buoys, and others, coming into the scene for consideration in analysis schemes...and the beat goes on! As more and more asynoptic data becomes available, we believe it becomes important to reduce the time-window for asynoptic observations used in analysis procedures. Currently, NMC allows for the use of asynoptic data which may be as much as 6 hours off-time in operational analyses. Some attempt is made in the LFM analysis to correct the asynopticity of VTPR (McMillin, et al, 1973) soundings with the use of a time-tendency correction (Desmarais, 1972); however, this procedure is not used in the Flattery global analysis scheme (Flattery, 1971) which provides the operational and final analyses"--Introduction.

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