Subj : Wx Terms (H)(2)
To : All
From : Daryl Stout
Date : Wed Aug 09 2017 12:05 am
Heavy Snow
This generally means...
Snowfall accumulating to 4" or more in depth in 12 hours or less; or
Snowfall accumulating to 6" or more in depth in 24 hours or less
In forecasts, snowfall amounts are expressed as a range of values,
e.g., "8 to 12 inches." However, in heavy snow situations where there is
considerable uncertainty concerning the range of values, more appropriate
phrases are used, such as "...up to 12 inches..." or alternatively
"...8 inches or more...".
Heavy Snow Warning
Issued by the National Weather Service when snowfall of 6 inches (15 cm)
or more in 12 hours or 8 inches (20 cm) or more in 24 hours is imminent
or occurring. These criteria are specific for the Midwest and may vary
regionally.
Heavy Surf Advisory
An advisory issued by the National Weather Service for fast moving deep
water waves which can result in big breaking waves in shallow water
(the surf zone).
Hectopascal
A unit of pressure equal to a millibar (1 hPa = 1 mb). Abbreviated hPa.
Height
In meteorology, usually a reference to Geopotential Height; roughly the
height above sea level of a pressure level. For example, if a station
reports that the 500 mb height at its location is 5600 m, it means that
the level of the atmosphere over that station at which the atmospheric
pressure is 500 mb is 5600 meters above sea level. This is an estimated
height based on temperature and pressure data.
Helicity
A property of a moving fluid which represents the potential for helical
flow (i.e. flow which follows the pattern of a corkscrew) to evolve.
Helicity is proportional to the strength of the flow, the amount of
vertical wind shear, and the amount of turning in the flow (i.e.
vorticity). Atmospheric helicity is computed from the vertical wind
profile in the lower part of the atmosphere (usually from the surface
up to 3 km), and is measured relative to storm motion. Higher values of
helicity (generally, around 150 m2/s2 or more) favor the development of
mid-level rotation (i.e. mesocyclones). Extreme values can exceed 600
m2/s2.
Hertz
(abbrev. Hz)- An international unit of frequency equal to one cycle per
second, and named after a German physicist.
HI
High- In meteorology, a region of high pressure; also known as anticyclone.
HIC
Hydrologist In Charge
High
(abbrev. HI)- In meteorology, a region of high pressure; also known as
anticyclone.
High Clouds
These clouds have bases between 16,500 and 45,000 feet in the mid
latitudes. At this level they are composed of primarily of ice crystals.
Some clouds at this level are cirrus, cirrocumulus, and cirrostratus.
High Energy Event
In solar-terrestrial terms, flares (class two or more) with outstanding
Centimetric Bursts and SID. High Energy Protons are reported at the
Earth in case of most of these events occurring on the western part of
solar disk. (Class X flares).
High Frequency (HF)
The portion of the radio frequency spectrum between between 3 and 30 MHz.
High Latitudes
With specific reference to zones of geomagnetic activity, "high
latitudes" refers to 50� to 80� geomagnetic.
High Risk (of severe thunderstorms)
Severe weather is expected to affect more than 10 percent of the area.
A high risk is rare, and implies an unusually dangerous situation and
usually the possibility of a major severe weather outbreak, including
strong to violent tornadoes, among other forms of severe weather.
High Seas Forecast
(HSF) - Marine forecasts for the major oceans of the world. In this
context, major gulfs or seas (e.g., the Gulf of Mexico or the Bering Sea)
are included within these forecast areas. Areas of responsibility for
the U.S. are determined by international agreements under the auspices
of the World Meteorological Organization (WMO).
High Surf
Large waves breaking on or near the shore resulting from swells spawned
by a distant storm.
High Surf Advisory
A High Surf Advisory is issued when breaking wave action poses a threat
to life and property within the surf zone. High surf criteria vary by
region. High Surf Advisories are issued using the Coastal and Lakeshore
Hazard Message (CFW) product.
High Surf Warning
A High Surf Warning is issued when breaking wave action results in an
especially heightened threat to life and property within the surf zone.
High surf criteria vary by region. High Surf Warnings are issued using
the Coastal and Lakeshore Hazard Message (CFW) product.
High Wind
Sustained wind speeds of 40 mph or greater lasting for 1 hour or longer,
or winds of 58 mph or greater for any duration.
High Wind Advisory
This product is issued by the National Weather Service when high wind
speeds may pose a hazard. The criteria for this advisory varies from
state to state. In Michigan, the criteria is sustained non-convective
(not related to thunderstorms) winds greater than or equal to 30 mph
lasting for one hour or longer, or winds greater than or equal to 45
mph for any duration.
High Wind Warning
This product is issued by the National Weather Service when high wind
speeds may pose a hazard or is life threatening. The criteria for this
warning varies from state to state. In Michigan, the criteria is
sustained non-convective (not related to thunderstorms) winds greater
than or equal to 40 mph lasting for one hour or longer, or winds
greater than or equal to 58 mph for any duration.
High Wind Watch
This product is issued by the National Weather Service when there is
the potential of high wind speeds developing that may pose a hazard or
is life threatening. The criteria for this watch varies from state to
state. In Michigan, the criteria is the potential for sustained
non-convective (not related to thunderstorms) winds greater than or
equal to 40 mph and/or gusts greater than or equal to 58 mph.
High-Speed Stream
In solar-terrestrial terms, a feature of the solar wind having velocities
that are about double average solar wind values.
Hinge Crack
In hydrologic terms, a crack caused by significant changes in water level.
HLS
Hurricane Local Statement
HMD
(Hemispheric Map Discussion)- This discussion is issued once a day around
1 PM EST (2 PM EDT) and is primarily intended to provide insight into the
hemispheric circulation patterns over the next 5 days. This includes a
discussion of the 5-day mean circulation pattern. Comparisons,
differences, and continuity among the numerical models are highlighted,
and preferred solutions are proposed with an explanation of why a
solution is preferred. This includes any reasons why the preferred
solution differs from any model. In cases where certain models are not
universally available, an attempt will be made to describe that model's
solution to an extent that a reader can understand it's important aspects.
HND
Hundred
Hoar Frost
A deposit of interlocking crystals formed by direct sublimation on
objects, usually those of small diameter freely exposed to the air, such
as tree branches, plants, wires, poles, etc. The deposition of hoar frost
is similar to the process by which dew is formed, except that the
temperature of the frosted object must be below freezing. It forms when
air with a dew point below freezing is brought to saturation by cooling.
Hodograph
A polar coordinate graph which shows the vertical wind profile of the
lowest 7000 meters of the atmosphere. These plots are used to determine
the advection patterns aloft, whether a thunderstorm will rotate, and
the type of thunderstorms that you will likely see that day.
Homologous Flares
In solar-terrestrial terms, solar flares that occur repetitively in the
same active region, with essentially the same position and with a common
pattern of development.
Hook Echo
A radar reflectivity pattern characterized by a hook-shaped extension of
a thunderstorm echo, usually in the right-rear part of the storm
(relative to its direction of motion). A hook often is associated with
a mesocyclone, and indicates favorable conditions for tornado development.
Horizon
The distant line along with the earth and sky appear to meet.
Obstructions are not considered as part of the horizon.
Hourly Precipitation Data (HPD)
It contains data on nearly 3,000 hourly precipitation stations
(National Weather Service, Federal Aviation Administration, and
cooperative observer stations) in inches to tenths or inches to
hundredths at local standard time. HPD includes maximum precipitation
for nine (9) time periods from 15 minutes to 24 hours, for selected
stations.
---
� Synchronet � The Thunderbolt BBS - wx1der.dyndns.org
