And a useful reference on the climate (plus the natural, cultural and
Local environment) of Hawaii is the Atlas of Hawaii, 3ED from
the University of Hawaii at Hilo Department of Geography (1998),
University of Hawaii Press (ISBN 0-8248-2125-4/paperback or
ISBN 0-8248-1745-1/cloth cover).
2. What do the weather symbols used on your station plots and hourly weather
maps represent?
The station circle represents the cloud cover; open
circle means clear; and a completely covered circle means
100% cloud cover (or fog). The line extending outward from the station
circle is called a wind barb and represents the wind flow;
where the wind is blowing from the direction of the barb (north
is towards the top of the map and east is towards the viewer's right).
The line(s) extending from the end of the barb are called feathers
and represent the windspeed. There are three types of feathers;
a normal length represents a wind of 10 knots; a half-length
one represents 5 knots and a triangular shaped one is 50
knots: So a 25 knot wind would have two full and one half-length
feathers. The various symbols to the left of the circle represent
the weather phenomenon. There are different symbols for rain, drizzle,
fog, thunderstorms and other weather.
Here is a gif plotted legend which
depicts the symbols and explains the numeric values that are plotted
about the station circle. This WXP
map legend shows the various symbols plotted by our imaging
software, which are called GEMPAK (aka N-AWIPS) and WXP.
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11. Reading Times on Maps
Weather maps often cover large regions, and may span multiple time zones.
Similarly, people access this WWW server from many locations around the
world. To standardize map times, most follow the convention of using
Greenwich Mean Time (GMT) or Coordinated Universal time (UTC) to denote the
time for which the map is valid. Additionally, time is always reported
using a 24 hour clock frequently referred to as military time, or Zulu
time, which is often denoted using the letter "Z". Midnight Greenwich
time would be denoted as 0000Z and noon would be 1200Z, while times after
noon are added to 1200, so 6:00 PM is 1800Z (note that the colon is not used).
Weather maps generated from observed data are valid at the time of the observations.
Forecast maps are valid at some time from the observations from
which the forecast is generated. The initial time of the forecast
is often referred to as either the 0 (zero) hour forecast or the
analysis. The zero hour forecast is used to initialize forecast
models. Since the basis for all forecasts depends on how well the
initial field represents the actual state of the atmosphere, careful
consideration must be given access the representativeness of this
field.
On the weather charts and satellite images in our web pages, if the time
reference is not specified, then it is based on Universal time.
When forecast maps have time stamps in the form shown below:
970131/0000V024 --or-- 970228/1200V072
The first map is a forecast for 1997 January 31 at 0000UTC and is a 24hour
forecast product; and the second one is for 1997 February 28 at 1200UTC
and is a 72hour forecast product.
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12. What Time is it?
exec cmd="cgi-bin/date.csh GMT"
exec cmd="/cgi-bin/date.csh HST"
Hawaii is in the Hawaiian Standard Time (HST) zone which is 10 hours behind
Greenwich time. GMT = HST + 10 hours. Hawaii does not change to
daylight savings time. UTC is the abbreviation for Coordinated Universal
Time and it is the same as GMT. In recent years, UTC is being used more
frequently as the reference time at the prime meridian at 0 degrees East,
which is the longitude of Greenwich, England.
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13. How do you get your data and what software do you use to create
the weather maps, satellite images and the text files of weather
forecasts and bulletins?
And why are text files in upper case characters?
We participate in the National Science Foundation program called
Unidata.
The Unidata Program Center (UPC) is located in Boulder, Colorado. The UPC
oversees the transmission of data from the
National Weather Service and
National Environmental Satellite, Data, and Information Service
to our university (and many others throughout North America) using the
computer system called
the Internet Data Distribution
(IDD).
Unidata is a program of the National Science
Foundation to support the study of meteorology.
The University of Hawaii Department of Meteorology maintains
a current weather database from our offices in Honolulu
located in the Hawaii Institute for Geophysics building on the
Manoa Campus of the university.
Weather maps for the WWW
are regularly updated to allow interested users to actively participate in
studying the many aspects of weather phenomenon.
Data are continually received by our computer systems. Selected data
are then automatically sent to programs that use them to generate
1) maps of the hourly weather observations, 2) maps of the forecasted wind,
temperature and pressure patterns for various periods up to 10 days,
3) satellite images, 4) text files with forecasts of
SEVERE WEATHER/surf conditions/local weather and 5) coded airport weather
observations (international weather code). All data files are erased
or overwritten when a newer web product is produced; although the
original data are saved nightly in their raw (undecoded formats) for
use by students and professors in their research work.
The computer software programs we use are GEMPAK, MCIDAS and WXP.
The
GEMPAK programs are our primary display software. This
software was developed by NASA and is now maintained by NOAA/National
Center for Environmental Prediction (NCEP) and Unidata.
The MCIDAS software formats the satellite products and comes from the
University of Wisconsin-Space Science and Engineering Center
(SSEC).
WXP (version 4) display software was provided by Purdue University through
Unidata: WXP has been transferred to the
Unisys Corp.
which is the new location for Dan Vietor, developer of
WXP
(versions 4, 5 and previous).
It and GEMPAK are used to create the weather maps and satellite images.
About upper case text files:
Text files are presented as they are transmitted by the forecasting office.
These will be in upper case characters as these data flow through international
communications circuits which in some locations involve teletype equipment
which generally can only handle upper case letters.
The forecast office within the United States (USA), is the National Weather
Service (NWS) and although current USA communications are with computer
circuits, the NWS conforms to the international agreements and prepare
their bulletins with upper case characters.
Many members of the Unidata
community actively share ideas and scripts used in campus weather
displays around the country, as well as help provide support to
their fellow meteorologists. Please acknowledge their hard work
by visiting those Webs.
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Below is a Color Bar Temperature key for GMS/GOES-10 Satellite IR images:
Satellites also detect water vapor in the atmosphere.
Below is a Water Vapor key for GOES-12 or GOES-10 Satellite WV images:
Below is a Water Vapor key for GMS/GOES-10 Satellite WV images:
