Precipitation forecasts

Posted on
Sun Jun 28, 2015 8:47 am
gglockner offline
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Precipitation forecasts

I'd like to understand how I can get both the forecast precipitation probability and volume. The reason is that I'd like to determine which days I can skip watering the lawn. So if the probability of rain is 90% but the volume is only 0.05 inches, I still want to water the lawn, but if the probability is 60% for a volume of 0.3 inches, I want to skip watering that day.

In the Weather device for the WUnderground plugin, I see Forecast Precipitation - Today; based on the source code, this looks like volume. Is that correct, and how do I find the probability value? Any help would be greatly appreciated.

Posted on
Sun Jun 28, 2015 6:04 pm
DaveL17 offline
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Re: Precipitation forecasts

In the Weather device for the WUnderground plugin, I see Forecast Precipitation - Today; based on the source code, this looks like volume. Is that correct, and how do I find the probability value? Any help would be greatly appreciated.

As far as I know, the WUnderground api doesn't expose forecast precip volume. All precip forecast data within the plugin is POP -- probability of precipitation. That's what I'm reporting in the plugin.

Dave

I came here to drink milk and kick ass....and I've just finished my milk.

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Posted on
Sun Jun 28, 2015 6:49 pm
FlyingDiver offline
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Re: Precipitation forecasts

DaveL17 wrote:
In the Weather device for the WUnderground plugin, I see Forecast Precipitation - Today; based on the source code, this looks like volume. Is that correct, and how do I find the probability value? Any help would be greatly appreciated.

As far as I know, the WUnderground api doesn't expose forecast precip volume. All precip forecast data within the plugin is POP -- probability of precipitation. That's what I'm reporting in the plugin.

Dave



You sure? What are the qpf_XXXX fields? Here's the JSON for part of a 10 day query. I think qpf stands for "Quantity Precipitation Forecasted" or similar.

Code: Select all
"date":{
   "epoch":"1436223600",
   "pretty":"7:00 PM EDT on July 06, 2015",
   "day":6,
   "month":7,
   "year":2015,
   "yday":186,
   "hour":19,
   "min":"00",
   "sec":0,
   "isdst":"1",
   "monthname":"July",
   "monthname_short":"Jul",
   "weekday_short":"Mon",
   "weekday":"Monday",
   "ampm":"PM",
   "tz_short":"EDT",
   "tz_long":"America/New_York"
},
      "period":9,
      "high": {
      "fahrenheit":"94",
      "celsius":"34"
      },
      "low": {
      "fahrenheit":"74",
      "celsius":"23"
      },
      "conditions":"Chance of a Thunderstorm",
      "icon":"chancetstorms",
      "icon_url":"http://icons.wxug.com/i/c/k/chancetstorms.gif",
      "skyicon":"",
      "pop":50,
   "qpf_allday": {
      "in": 0.10,
      "mm": 3
      },
      "qpf_day": {
      "in": 0.07,
      "mm": 2
      },
      "qpf_night": {
      "in": 0.02,
      "mm": 1
      },
      "snow_allday": {
      "in": 0.0,
      "cm": 0.0
      },
      "snow_day": {
      "in": 0.0,
      "cm": 0.0
      },
      "snow_night": {
      "in": 0.0,
      "cm": 0.0
      },
      "maxwind": {
      "mph": 10,
      "kph": 16,
      "dir": "E",
      "degrees": 94
      },
      "avewind": {
      "mph": 9,
      "kph": 14,
      "dir": "E",
      "degrees": 94
      },
      "avehumidity": 73,
      "maxhumidity": 94,
      "minhumidity": 51
   

joe (aka FlyingDiver)
my plugins: http://forums.indigodomo.com/viewforum.php?f=177

Posted on
Sun Jun 28, 2015 7:23 pm
DaveL17 offline
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Re: Precipitation forecasts

You sure? What are the qpf_XXXX fields?

Huh! Need to do some more research, but it looks like you're right. Based on some initial searching, QPF looks like it might be Quantitative Precipitation Forecast. Thanks for the head's up on this. I'll add it to the future update list (I'm not exposing this data within the plugin right now.)

Dave

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Posted on
Sun Jun 28, 2015 8:22 pm
RogueProeliator offline
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Re: Precipitation forecasts

Thanks for the head's up on this. I'll add it to the future update list (I'm not exposing this data within the plugin right now.)

+1 :-)

Posted on
Sun Sep 13, 2015 8:11 am
Richard offline
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Joined: Feb 05, 2015

Re: Precipitation forecasts

Wow Dave!
I just update the plugin an there's a lot of neat stuff been added, I have been away playing with web cams and return to find out I am so far behind with my weather pages. Because home automation is to have your home automated so less time is spent Ha ha, is there any plans or possible of having quantitative precipitation forecast added to the hourly forecast before I start revamp my weather pages again?


QPF looks like it might be Quantitative Precipitation Forecast.

Posted on
Sun Sep 13, 2015 3:38 pm
DaveL17 offline
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Re: Precipitation forecasts

Richard wrote:
[SNIP]...is there any plans or possible of having quantitative precipitation forecast added to the hourly forecast before I start revamp my weather pages again?

You had better leave some room on those pages! :D

I've been knee-deep in a big update of the OWServer plugin which I'm about to roll out. Then I plan to turn my attention back to the WUnderground Plugin.

Stay tuned!
Dave

I came here to drink milk and kick ass....and I've just finished my milk.

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Posted on
Tue Sep 22, 2015 8:50 pm
DaveL17 offline
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Re: Precipitation forecasts

Richard wrote:
...is there any plans or possible of having quantitative precipitation forecast added to the hourly forecast before I start revamp my weather pages again?

Crack open that control page editor. QPF and snow have been added to hourly forecast devices. :D

Dave

I came here to drink milk and kick ass....and I've just finished my milk.

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Posted on
Thu Sep 24, 2015 5:51 pm
Richard offline
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Re: Precipitation forecasts

Dave Look great thanks it's going to be another late night :D

Posted on
Thu Sep 24, 2015 6:07 pm
Richard offline
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Re: Precipitation forecasts

Dave one question. Does the WUnderground api expose forecast precip volume in the hourly forecast e.g. mm vs %.
I seen in there website there is data for both but not sure in api.

Posted on
Thu Sep 24, 2015 7:49 pm
DaveL17 offline
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Re: Precipitation forecasts

Hi Richard - good catch. My implementation of QPF and snow isn't quite right. I need to go back and make some adjustments. You can still link to the device states as the names shouldn't change. When I roll out the hot fix, your choices for both hourly and ten day forecasts will be based on device configuration:

QPF and snow - english (standard, mixed)
QPF and snow - metric (metric, mixed SI)

Thanks for the heads up.
Dave

Edit: (corrects categorizations)

I came here to drink milk and kick ass....and I've just finished my milk.

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Posted on
Thu Sep 24, 2015 8:41 pm
DaveL17 offline
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Re: Precipitation forecasts

I just uploaded v0.9.23 which has a:
- Hotfix to correct implementation of QPF and Snow forecasts.

I will post a link in the plugin update thread directly.

Sorry for the hassles.
Dave

I came here to drink milk and kick ass....and I've just finished my milk.

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Posted on
Fri Sep 25, 2015 2:26 pm
Richard offline
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Joined: Feb 05, 2015

Re: Precipitation forecasts

Dave I want to make sure I am thinking how the precipitation forecast works. QPF is the value of how much liquid precip. I will receive either in standard or metric values not percentage base on my setting. I think something is screw up I believe it's pulling percentage value and for example I have a QPF of 51 and it also say snow value of 51 in the hourly forecast and no way it's snow this early in the season if so I 'am moving.
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Posted on
Fri Sep 25, 2015 2:42 pm
DaveL17 offline
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Re: Precipitation forecasts

Hi Richard - I looked at the code (quickly) and it looks right to me, which leads me to believe that there is something amiss with the WUnderground JSON return for your location. I don't see where I might've put the amount in both the QPF and Snow states. But I will double check this PM.

My understanding of the API is thus:

QPF: amount of precip in IN or MM
Snow: amount of snow in IN or CM
POP: percentage chance of precip.

A note on percentages. You can have a 50% chance of precipitation for a daily forecast and have a 75% chance of precipitation for an hourly forecast. In other words, there's a 50% chance of rain today, with a 75% chance that -- if it rains -- it will fall during a certain hour. At least that's what I'm led to believe. :D

Dave

I came here to drink milk and kick ass....and I've just finished my milk.

[My Plugins] - [My Forums]

Posted on
Fri Sep 25, 2015 3:46 pm
Richard offline
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Re: Precipitation forecasts

Dave also if this helps after I done the latest update 20 minutes later the log say "Daily call limit ( 500 ) reached. Taking the rest of the day off. , So I disable the WU plugins till I hear from you again no panic whenever.

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