Severe Thunderstorm and Tropical Storm Bertha Impacts

Numerous severe thunderstorms are expected across a broad region from the Ohio Valley to the Mid-Atlantic and Northeast States today into tonight. Swaths of damaging wind gusts are expected and some tornadoes are possible. Bertha is expected to bring tropical storm conditions to portions of the Gulf Coast from the Florida Panhandle westward to southeastern Louisiana later today and Wednesday. Read More >

X-Band

A frequency band of microwave radiation in which radars operate.

X-Ray Background

In solar-terrestrial terms, a daily average background X-ray flux in the 1 to 8 angstrom range. It is a midday minimum designed to reduce the effects of flares.

X-Ray Burst

In solar-terrestrial terms, a temporary enhancement of the X-ray emission of the sun. The time-intensity profile of soft X-ray bursts is similar to that of the H-alpha profile of an associated flare.

X-Ray Flare Class

In solar-terrestrial terms, rank of a flare based on its X-ray energy output. Flares are classified by the order of magnitude of the peak burst intensity (I) measured at the earth in the 1 to 8 angstrom band as follows:

Class	Intensity (in Watts/m²)
B	I < 10^-6
C	10^-6 <= I < 10^-5
M	10^-5 <= I < 10^-4
X	I >= 10^-4

X-Rays

Very energetic electromagnetic radiation with wavelengths intermediate between 0.01 and 10 nanometers (0.1-100 Angstroms) or between gamma rays and ultraviolet radiation. Essentially all X-Rays from space are absorbed in the Earth's upper atmosphere.

XBT

Expendable Bathythermograph

XCITED

Excited

XCPT

Expecting

XPC

Expect

XSEC

Cross Section

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