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NWS Cold Hazard Warning Changes

Started by wxfree, October 07, 2024, 04:17:53 PM

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wxfree

The National Weather Service is making changes to their cold hazard warnings.  The Wind Chill Watch and Wind Chill Warning are being changed.  The rewording is meant to emphasize that cold, although more dangerous with wind, can also be dangerous without wind.

Winter hazards are different based on location.  Here in the DFW area, anything more than a dusting of snow warrants a Winter Weather Advisory.  Years ago, a Winter Weather Advisory was used when there were multiple hazards (more than one precipitation type), while a single hazard would have resulted in a Snow Advisory or Freezing Rain Advisory.  Places that get snow frequently don't get advisories for every event.  The criteria for a Winter Storm Warning (or the earlier Heavy Snow Warning) are different, also.  Around here, I think either four or six inches is a "heavy snow" warranting a warning.

For cold, we get a frost or freeze advisory for the first frost or freeze of the season, which marks the end of the growing season.  Sometimes another will be issued early in the year when a frost or freeze is expected after a warm spell that caused plants to start growing and be at risk from cold weather.  Our local office issues a Hard Freeze Warning when temperatures below 10 are expected.  This is based on the risk of damage to things such as pipes.  Other nearby offices issue a warning for temperatures below 28, or several hours below freezing.  This is more oriented toward agricultural damage.

Cold weather is relative, as are the criteria for advisories and warnings, which are set locally.  The name changes don't necessarily affect what will warrant an advisory or warning.

The Wind Chill Watch and Warning will be combined with the Extreme Cold Watch and Warning.  The criteria for extreme cold will be based on either temperature or wind chill.

The Hard Freeze Watch and Warning will be changed to Freeze Watch and Warning, with enhanced wording to distinguish between a "freeze" and a "hard freeze".  Frost and Freeze Advisories are not changed.  I don't remember getting any freeze warnings from the local office, since we get advisories.  I'm guessing that the warning rather than advisory may be used in places where freezes are unusual.

The Wind Chill Advisory, for less severe cold, will be changed to the Cold Weather Advisory.  It doesn't say whether a temperature criterion will be added to constitute "cold weather."  They may be changing the name just to get rid of "wind chill" from the advisory and warning products.  Cold weather without wind chill may not get a notification until it reaches "extreme cold levels."  This determination may be local and not the same everywhere.

As a note, the difference between a frost and a freeze is the depth of the freeze.  The official temperature is measured 2 meters above the ground.  32 degrees there is a freeze.  A higher temperature there while ice forms near the ground, obviously at a freezing temperature, is a frost.  Frost happens mainly because of radiational cooling.  The sunlight warms the ground, but does very little to warm the air.  The air is mostly heated by the ground.  Likewise, the air itself doesn't cool much, but is cooled by the ground or other other solid surface.  Since cold air sinks, it isn't uncommon for the air at the ground to be more than a little colder than the air six feet up.  Wind can prevent a frost by mixing the air cooled by the ground with the less cold air a few feet up.
I'd like to buy a vowel, Alex.  What is E?


CtrlAltDel

Interesting. My issue with the terms, and who knows if it's shared by anyone else, is that I get watch and warning confused, in no small part because they start with the same letter. If they went with watch and alert, or something else like that, I think it would help.
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thenetwork

I miss the old "Travelers Advisory" used in the winter months.  It was an easy, polite way to tell the amateur drivers to STAY THE HELL OFF THE ROAD!!!

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wxfree

We've now seen how these products are used.  In my area, within the Fort Worth office county warning area, previously, a freeze advisory was issued for a killing freeze (first freeze of the season or late freeze in spring) and a hard freeze warning was issued for low temperatures below 10.  Nearby southern offices used a more agricultural definition of hard freeze, such as several hours below freezing or low temperature below 28.  My area is cold enough that this happens multiple times every winter, so it's too common to warn about.  We haven't gotten cold enough for a freeze warning, the replacement for a hard freeze warning, to see how it's used.  I believe the standard should be the same as the hard freeze warning.  That cold is fairly rare, and warrants a warning.

We now have a cold weather advisory, for wind chills as low as 5 degrees.  Previously, a wind chill advisory was issued for wind chills below zero.  I think wind chill warnings were used for wind chills below -10 or -15.  I don't remember because that almost never happens.  I seem to remember a wind chill warning once.  Maybe the threshold was too low, but now it's too high.  The current cold weather advisory isn't just for the mornings, but is for multiple days, even though we have highs above freezing and wind chills into the 20s.  I'm not suggesting that it isn't cold, but it isn't advisory-level cold.  This is just a normal cold snap level of cold.

This reminds me of the period when they used the lower standard for heat advisories, issuing them whenever the heat index was expected to of at least 105 or a temperature of at least 103.  You might as well just issue it for 62 straight days and call it a July and August advisory.  Heat is the most deadly weather, but overuse of advisories doesn't really protect anyone, it just takes away from the significance of an advisory.  Historically, they used the same temperature threshold, but issued an advisory for at least two consecutive days with a heat index over 105 and a low "near 80" and officially defined as 78 or higher, because the effect of heat is cumulative.  That was good.  I think what they're using now two consecutive days but without the low temperature element.  Lows in the upper 70s and 80s are no longer unusual, so that element wouldn't make much difference.

I know I'm being pedantic, but that is what we do here.  I haven't seen how my local office will use extreme cold warnings.  The Lake Charles office currently has a cold weather advisory for wind chills of 10 to 15 tonight and an extreme cold watch for wind chills of 2 to 6 tomorrow.  Those levels seem right for them.  That's pretty damn cold for Gulf Coast swamp.

I propose that my area office should keep the freeze warning standard where the hard freeze warning standard was, for actual lows below 10.  They should put the cold weather advisory level at temperature or wind chill below 15, and extreme cold warning at temperature or wind chill below zero.  And they shouldn't stay in effect if the highs go above freezing and the wind chills go into the 20s.  I think they're overadvertising the cold.  It's cold today, but not advisory cold all day.

By the way, since I checked the Lake Charles weather, I see that they're expecting a low of 12 on Wednesday.  Here, in a colder area, we're expecting lows about twice as high.  They're also expecting heavy snow with 4 to 6 inches.  That much snow would be quite a storm for us.  For them, it's historic.  The second highest on record for Lake Charles is 5 inches, after an absurdly high total of 22 inches in 1895.  We have a similar record high in the DFW region, but we also have more of a history with 6 to 12 inch totals, so that record isn't as much of an outlier.
I'd like to buy a vowel, Alex.  What is E?



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