Topband: 3B9C Propagation

[Thomas Giella KN4LF]

Terry K4RX Said:
.....I heard W9, W1, W2, W3, W5, and northern-W4 giving fine reports, but nothing
was heard at this qth.  If it was spotlight propagation, then the beam never
shined on North Florida.....

Thomas KN4LF Says:
3B9C was propagating into North America via the E layer valley/F layer duct mechanism. The duct was ruptured "in a manner of speaking" allowing the 3B9C RF signal to drop into New England and the Mid Atlantic States in a spotlike appearance. 

If you look at the weather map last evening there was a strong extra-tropical surface-250 mb low off the coast of New England. This winter storm system produced an upward propagating Internal Buoyancy/Gravity Wave that ruptured the E layer valley/F layer duct open on the North America end of the path. In the S.E. states including Florida high pressure is dominant with no mechanism in place to our east to produce upwardly propagating Internal Buoyancy/Gravity Waves that would rupture the duct mechanism on a bearing into Florida.

You can see this winter storm system on this weather map at http://weather.cod.edu/forecast/ETA/etaUS_500_avort_0.gif . Also if you look in the vicinity of Baja California there is a fledgling new 500 mb shortwave/vorticity maximum. This next disturbance will rapidly track across the southern latitudes of the U.S. the next several days and emerge into the Atlantic in the vicinity of the Carolina's. This will produce an opportunity for the S.E. U.S. including Florida to be able to work the 3B9C with more consistency, as the E layer valley/F layer duct mechanism is ruptured on a bearing into Florida.

You can find more information on Internal Buoyancy/Gravity Waves on my "HF/MF Propagation Theory Notes" website at http://www.kn4lf.com/kn4lf8.htm .

73 & GUD DX,
Thomas F. Giella, KN4LF
Retired Space & Atmospheric Weather Forecaster
Plant City, FL, USA
Grid Square EL87WX

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