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[Propagation] Es & Thunderstorms

To: "a Propagation Reflector" <>
Subject: [Propagation] Es & Thunderstorms
From: "Thomas Giella KN4LF" <>
Date: Mon, 25 Apr 2005 19:00:54 -0400
List-post: <>
Volker et all,
 On my website KN4LF LF/MF/HF Radio Propagation Theory Notes at I have published the following:

18.) Sporadic-E (Es) Absorption, Blocking & Refraction-

Just as the E-layer is the main refraction medium for medium frequency
(300-3000 kc) signal propagation within approximately 5000 km/3100 mi, so is
Sporadic-E (Es). Sporadic-E clouds occur at approximately 100 km/60 miles in
altitude and generally move from west to east but at times east to west.
Like stratospheric level warming and troposphere level temperature and
moisture discontinuities, Sporadic-E  can depending on the circumstances
absorb, block and refract medium, high and very high frequency RF signals in
an unpredictable manner.

The main source for high latitude Sporadic E is radio aurora activity.

The main sources for mid latitude Sporadic-E  include wind shear, internal
buoyancy/gravity waves (IBGW's), and traveling ionosphere disturbances
(TID's), most of which are produced by severe thunderstorm cell complexes.
The tie in between Sporadic-E and a severe thunderstorm is the sprite and

The main sources for low latitude Sporadic-E  include wind shear, internal
buoyancy/gravity waves (IBGW's), and traveling ionosphere disturbances, most
of which are produced by severe thunderstorm cell complexes tied to tropical

The forecasting of Sporadic-E has long been considered to be impossible.
However it is possible to identify certain troposphere level meteorological
conditions that can lead to the formation of Sporadic-E. One is as mentioned
above the severe thunderstorm cell complex.

Sporadic-E have been observed to occur within approximately 150 km/90 mi to
the left of a severe thunderstorm cell complex in the northern hemisphere,
with the opposite being observed in the southern hemisphere. To complicate
matters is the fact that Sporadic-E clouds not only have been observed to
move from west to east but at times also east to west. So one has to look
for Sporadic-E on either side of a severe thunderstorm cell complex.

Not all thunderstorm cell complexes reach severe levels and not all severe
thunderstorm cell complexes produce Sporadic-E. This is where knowledge in
tropospheric physics and weather forecasting is necessary. Coincidentally I
have a B.S. in Meteorology and an M.S. in Space Plasma Physics and am
qualified to identify which severe thunderstorm complexes are most likely to
produce Sporadic-E.

Some but not all key elements in identifying which severe thunderstorm cell
complexes have the potential to produce Sporadic-E via wind shear, internal
buoyancy/gravity waves, traveling ionosphere disturbances, sprites and elves

1.) Negative tilted mid level long wave troughs.

2.) Approximate 150 knot/170 mph jet stream jet maxes that produce
divergence and therefore create a sucking vacuum effect above thunderstorm
cells, that assist thunderstorm cells in reaching and penetrating the
tropopause into the stratosphere.

3.) 500 mb temperatures of -20 deg. C or colder, which produce numerous
positive and negative lightning bolts and inter-related sprites and elves.

4.) Approximate 150-175 knot/172-200 mph updrafts within thunderstorm cells
that create overshooting tops that penetrate the tropopause into the
stratosphere (See definition #20 on Stratospheric Warming), launching
upwardly propagating internal buoyancy/gravity waves, traveling ionosphere
disturbances and wind shear.

73 & GUD DX,
Thomas F. Giella, KN4LF
Retired Space & Atmospheric Weather Forecaster
Plant City, FL, USA
Grid Square EL87WX
Lat & Long 27 58 33.6397 N 82 09 52.4052 W

Contesting Propagation eReflector:
HC-DX Propagation Channel:
KN4LF Daily Solar Space Weather & Geomagnetic Data Archive:
KN4LF Daily LF/MF/HF Radio Propagation Outlook:
KN4LF HF/MF Radio Propagation Theory Notes:
KN4LF Amateur & SWL Radio History:

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