Local Radar

Local Radar Loop-click

UTC Time (see below)

MST= UTC-7
PST= UTC-8

Reflectivity Colors
(see below)

What do the colors mean in the reflectivity products?

The colors are the different echo intensities (reflectivity) measured in dBZ (decibels of Z) during each elevation scan. "Reflectivity" is the amount of transmitted power returned to the radar receiver. Reflectivity (designated by the letter Z) covers a wide range of signals (from very weak to very strong). So, a more convenient number for calculations and comparison, a decibel (or logarithmic) scale (dBZ), is used.

The dBZ values increase as the strength of the signal returned to the radar increases. Each reflectivity image you see includes one of two color scales. One scale (far left) represents dBZ values when the radar is in clear air mode (dBZ values from -28 to +28). The other scale (near left) represents dBZ values when the radar is in precipitation mode (dBZ values from 5 to 75). Notice the color on each scale remains the same in both operational modes, only the values change. The value of the dBZ depends upon the mode the radar is in at the time the image was created.

The scale of dBZ values is also related to the intensity of rainfall. Typically, light rain is occurring when the dBZ value reaches 20. The higher the dBZ, the stronger the rainrate. Depending on the type of weather occurring and the area of the U.S., forecasters use a set of rainrates which are associated to the dBZ values.

These values are estimates of the rainfall per hour, updated each volume scan, with rainfall accumulated over time. Hail is a good reflector of energy and will return very high dBZ values. Since hail can cause the rainfall estimates to be higher than what is actually occurring, steps are taken to prevent these high dBZ values from being converted to rainfall.

dBZ	Rainrate (in/hr)
65	16+
60	8.00
55	4.00
52	2.50
47	1.25
41	0.50
36	0.25
30	0.10
20	Trace

What is UTC Time?

Weather observations around the world (including radar observations) are always taken with respect to a standard time. By convention, the world's weather communities use a twenty four hour clock, similar to "military" time based on the 0° longitude meridian, also known as the Greenwich meridian.

Prior to 1972, this time was called Greenwich Mean Time (GMT) but is now referred to as Coordinated Universal Time or Universal Time Coordinated (UTC). It is a coordinated time scale, maintained by the Bureau International des Poids et Mesures (BIPM). It is also known a "Z time" or "Zulu Time".

To obtain your local time here in the United States, you need to subtract a certain number of hours from UTC depending on how many time zones you are away from Greenwich (England). The table (right) shows the standard difference from UTC time to local time.

The switch to daylight savings time does not affect UTC. It refers to time on the zero or Greenwich meridian, which is not adjusted to reflect either changes either to or from Daylight Saving Time.

However, you need to know what happens during daylight savings time in the United States. In short, the local time is advanced one hour during daylight savings time. As an example, the Eastern Time zone difference from UTC is a -4 hours during daylight savings time rather than -5 hours as it is during standard time.

AST - Atlantic, AK - Alaska time, HI - Hawaii time, *The previous day, %The next day
	Standard Time								Daylight Savings
UTC	Guam	HI	AK	PST	MST	CST	EST	AST	PDT	MDT	CDT	EDT
Diff	+10	-10	-9	-8	-7	-6	-5	-4	-7	-6	-5	-4
00	10a	2p*	3p*	4p*	5p*	6p*	7p*	8p*	5p*	6p*	7p*	8p*
01	11a	3p*	4p*	5p*	6p*	7P*	8p*	9p*	6p*	7p*	8p*	9p*
02	12N	4p*	5p*	6p*	7p*	8p*	9p*	10p*	7p*	8p*	9p*	10p*
03	1p	5p*	6p*	7p*	8p*	9p*	10p*	11p*	8p*	9p*	10*	11p*
04	2p	6p*	7p*	8p*	9p*	10p*	11p*	12M	9p*	10p*	11p*	12M
05	3p	7p*	8p*	9p*	10p*	11p*	12M	1a	10p*	11p*	12M	1a
06	4p	8p*	9p*	10p*	11p*	12M	1a	2a	11p*	12M	1a	2a
07	5p	9p*	10p*	11p*	12M	1a	2a	3a	12M	1a	2a	3a
08	6p	10p*	11p*	12M	1a	2a	3a	4a	1a	2a	3a	4a
09	7p	11p*	12M	1a	2a	3a	4a	5a	2a	3a	4a	5a
10	8p	12M	1a	2a	3a	4a	5a	6a	3a	4a	5a	6a
11	9p	1a	2a	3a	4a	5a	6a	7a	4a	5a	6a	7a
12	10p	2a	3a	4a	5a	6a	7a	8a	5a	6a	7a	8a
13	11p	3a	4a	5a	6a	7a	8a	9a	6a	7a	8a	9a
14	12M%	4a	5a	6a	7a	8a	9a	10a	7a	8a	9a	10
15	1a%	5a	6a	7a	8a	9a	10a	11a	8a	9a	10a	11a
16	2a%	6a	7a	8a	9a	10a	11a	12N	9a	10a	11a	12N
17	3a%	7a	8a	9a	10a	11a	12N	1p	10a	11a	12N	1p
18	4a%	8a	9a	10a	11a	12N	1p	2p	11a	12N	1p	2p
19	5a%	9a	10a	11a	12N	1p	2p	3p	12N	1p	2p	3p
20	6a%	10a	11a	12N	1p	2p	3p	4p	1p	2p	3p	4p
21	7a%	11a	12N	1p	2p	3p	4p	5p	2p	3p	4p	5p
22	8a%	12N	1p	2p	3p	4p	5p	6p	3p	4p	5p	6p
23	9a%	1p	2p	3p	4p	5p	6p	7p	4p	5p	6p	7p