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Looking at radar patterns for winter weather around the great lakes makes a couple of observations pretty evident. Much, if not most of the winter weather involves cloud decks of 10,000 feet or less. This especially true for “lake effect” snow storms which are directly a result of the moisture contribution of the relatively warm lake water. The first image below shows streamers (darker blue) developing on the lee shore of Lake Erie as the moisture laden air cools coming onshore, and sets up a dump of light snow in Niagara and east of Buffalo.

The red arrow shows the air mass direction, which just happens to be right down Lake Erie. The western end of Lake Ontario shows the development of new streamers from the short fetch of open water at the western end of the lake. (The areas of high intensity just southeast of KBUF are “windfarm anomalies” – the large spinning blades of windfarms are creating havoc with doppler radar. There is serious concern for interpretation of severe weather due to these anomalies.)

Lake effect snows tend to cease if the winter is cold enough to freeze Lake Erie and the western end of Lake Ontario. Subsequent snow after that comes from larger continental low pressure systems moving across the region. It is easy to see however, that until the lakes freeze, lake effect snow can impact any part of the shorelines depending on wind direction.

The second image shows the Echo Tops pattern for the same period. The grey areas indicate tops of 5-10,000 feet or less. This is the radar interpretation of the vertical density pattern of moisture over the region. Its apparent straight out that these lake effect squalls are thin and have little vertical development.

From a radar interpretation perspective this lack of vertical development is important. Since the radar beam sweeps upward at fixed angles relative to the horizon, it is easily seen that because of the shallow altitude of the cloud deck, the beam will overshoot the deck in a fairly short distance. This creates the idea that the event is very local to the radar site, when it fact it may encompass a very much larger region. The national maps at the top of the EWR pages will confirm how broad the weather pattern is, and illustrate why its important to understand the visual limit of the radar in low decks. The chart below will show the relationship between beam height and distance from the radar site.


Finally! After a month of messing around with Bell and and my ISP, DSL service has been restored. While I have some catching up to do on some development issues, EWR should now be continuously operational. Those who requested to be added to the alert system will be added shortly.

Update 2010-01-15: EWR is expected to be fully operational again by this time next week.

Ephemerata Weather Radar is offline due to an external DSL connection failure. This has been reported to the ISP, but it is not known when service will be restored. It is expected this may be several days as the problem is thought to be line failure. We have had significant issues this summer (and in the past) with old Bell lines getting wet and failing when they do. The alert system will be offline as well. We apologise for any inconvenience. Email service remains intact through our Blackberry network.
Update 2009/12/15: Network issues continue. Looks like EWR will be effectively offline until after Christmas. Alternate internet networks are being considered, including a separate internet connection for EWR. Scans can be updated on a periodic basis through an open wifi link, but not on a regular basis.
The small maps that lead the page remain online, as do the “National” series on the Mosaic page. The target scan General Analyses are updated the same time the main scans are, but really are intended to be used with continuous scanning. Annoying.


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  • GH-GTA Scan Zone Severe Weather Alert #ONStorm October 2, 2016
    SEVERE WEATHER ALERT — 01:35 PM EDT Oct 02 2016 This is an automated alert of potentially severe weather for the Golden Horseshoe/ Greater Toronto/Niagara Peninsula/South-Central Ontario Monitored Area, from Ephemerata Weather Radar. See attached scan image. The alert triggered at 01:35 PM EDT on Oct 02 2016, from radar data analyzed from NWS radar site KBUF […]

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