The Dismal Manor Gardens have a new accessory, a WeatherFlow Tempest weather station. This post introduces the device and the company. Our little device includes a rain fall sensor and a lightning sensor that supplements the live sensors (greyhounds). We get a pretty good idea of the amount of rain that has fallen and the amount of nearby lightning.
WeatherFlow collects, refines, and analyzes meteorological data, produces refined data from it, and produces near-cast forecasts using national forecast guidance with the local data.
WeatherFlow offers several applications of its refined observations and model results. Interestingly, the example applications do not require a local sensor as they use near-cast offshore conditions and activity specific models to make judgements about the suitability of the forecast conditions for the several sailing sports and fishing.
References
- https://weatherflow.com/about-us-old/
- https://tempestwx.com/station/58318/
- https://www.santacruzsentinel.com/2020/02/05/weather-app-provides-forecast-real-time-updates/
WeatherFlow’s Mission
WeatherFlow’s mission is to “mitigate and control the cost of weather on business and daily life.”
WeatherFlow goes about its mission as follows.
- It collects weather data from the general public (our individual Tempest weather stations).
- It collects weather data from weather service grade sensors (sensors placed at paying client sites).
- It processes the collected data to make best-estimate data
- It prepares near-casts (projects the data forward) using models
- It offers access to data and models to subscribers
- It develops near-casting tools that support customer use cases.
Interestingly, WeatherFlow is entirely an application based service. Traditional weather services offer local forecasts for outdoor event safety, school closings, snow removal planning, etc. WeatherFlow makes no mention of these traditional private forecast services. They are delving into new applications like venue-specific sailing conditions, field level agricultural irrigation and spraying management, etc. The agricultural applications make use of on-site data. The marine applications make use of shore-line and near off shore results.
Our Little Weather Station
Our Tempest weather station differs from professional stations in a couple of important ways.
The weather station collects and logs the data internally. Periodically, it transmits the data by WiFi to a microcomputer connected to the house WiFi network. The little microcomputer forwards the data to WeatherFlow via our WiFi access point and land line.
Wind Sensor
First, its wind sensor is mounted about 2 meters above ground level rather than at the standard 10 meters. The wind sensor is shadowed by large trees and the house on 3 sides. So wind speed measurements are well below those reported at the airport about one mile away.
Seating level winds are indeed light. We do have some ground level gusts. Tree branches are moving so 10 mph is consistent with visual observation.
Second, the wind sensor is an acoustic Doppler sensor that measures Doppler shift of emitted sound over two paths orthogonal to the each other. Doppler shift is proportional to the wind speed. Each of the sensors provides a scalar wind speed in the direction of the path from source to sensor. The two values are combined using trigonometry to give a wind speed vector magnitude and direction.
These sensors have long been used on wind turbine towers. There use in a home weather station is unique to WeatherFlow Tempest. The ultrasonic sensors can measure winds too low to be measured by moving blade sensors.
Sensor siting may affect measurements other than wind speed. The sycamore tree to its west affects late afternoon sun and cloud cover estimates.
Rain Sensor
Rain fall measurements use a haptic sensor that counts rain drop impacts on the sensor’s bonnet. The model converting the strength and number of these to rainfall rates and amounts is approximate but accurate enough to be useful.
The rain sensor does not accumulate liquid so it will have trouble measuring drizzle and may saturate below heavy rainfall rates. Six inches per hour is an accepted upper bound rain fall rate.
In siting the weather station, we took care to ensure that it was not under a tree.
Thermodynamic Properties Sensors
Tempest’s temperature sensor, relative humidity sensor, and pressure sensor are microelectronic devices mounted in a radiation shielded enclosure that protects them from the influence of sunlight. The results from these sensors correlate well with National Weather Service data from the Norfolk Airport about 1 mile from our weather station.
These sensors agree with observations much better than the temperature and relative humidity results from Eve Weather do. The Eve outdoor sensor is not a weather data grade device.
Additional Sensors
The Tempest weather station includes a solar illumination sensor, a solar energy flux sensor, a UV sensor, and a lightning sensor. These give the illumination level, incident solar energy per square meter, and the UV sun burn index.
The lightning sensor observes the broadband radio noise resulting from a lightning stroke. The sensor does not differentiate between cloud to cloud and cloud to ground lightning. The sensor is effective out to about 25 nautical miles and estimates the range to the event. The sensor data can be monitored for an approaching storm.
The NWS lightning safety rules should be observed – if you can hear the thunder you are at risk of being struck and should take shelter in a sturdy building or enclosed vehicle immediately.
What Do We Get Out of the Deal
WeatherFlow’s Tempest app lets us see the hourly near-casts for our location in real time. You can see our current conditions and forecast at the link in [2].
WeatherFlow offers several personal subscription applications of individual use that serve as examples of its professional offerings. These applications offer 3 service levels, “Plus”, “Pro”, and “Gold” available in monthly and 12 month periods of performance.
Local Near-casts for the Manor
Dismal Manor receives hourly resolution forecasts for our location, our little patch of dirt at (37N, 76W) (yep, that rounded coordinate is feet wet).
As the station runs, it sends in actual observations to WeatherFlow. WeatherFlow uses these to tune the model to bring its forecast for our location and the observation into better agreement. The longer the station is on site, the better these forecasts become. These are best estimate model results.
The model can tell you the likelihood of a condition developing but the results are always probabilistic. The observed weather will be consistent with the model prediction but different in the specifics.
Weather Flow Demonstration Applications
Weather Flow offers several example applications on a subscription basis to the general public. These applications require a subscription offered in monthly and yearly periods of performance and 3 service levels. Monthly rates range from $4 to $15 discounted for 12 month subscribers.
You need not have a WeatherFlow Tempest sensor to use the applications. Only the WindAlert app benefits from a local sensor. The nautical applications work with coastal and near off shore conditions where sensors are not generally present. The AggWeather application uses a portable sensor set up in the field to be irrigated or sprayed.
- Wind Alert provides subscribers with high temporal and spatial resolution warning of high wind conditions at your location.
- FishWeather offers subscribers weather conditions and fishing conditions at popular off-shore fishing locations.
- SailFlow offers subscribers sailing conditions in inland and off shore waters.
- IWindSurf offers subscribers wind surfing conditions at popular locations.
- IKiteSurf offers subscribers kite surfing conditions at popular locations.
- AggWeather collects weather conditions at pesticide application time. It can predict pesticide drift and can be used to stop spraying when drift limiting conditions are reached at the site. The app can also be used for irrigation planning. A portable sensor collects data in the field. The Application subscription does not mention a subscription but one or more purchased sensors are required.
I expect the kite sports applications will prove popular as kiting time is borrowed from other activities and, for many surfers, significant travel from home to venue is required. For many, a surfing trip is an all day evolution.
Dismal Manor Dispatches 
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