NASA Meteoman

[asteven221]

Has anyone got one of these? If so I would really appreciate it if someone could advise me on one of the displays and what it's telling me.

There is main display showing the actual readings over the past hours/days and that's the display that's shown on every Meteoman image you see on the internet. It's the barograph image, but it's not that display I am confused about as it's function seems obvious. It's the one that shows the rising/falling on the right vertical axis and time on the horizontal axis. A line graph. Even the NASA manual doesn't explain it, nor does the manual even refer to it. I can't find even one image of the display in a google search, so I apologies for my crude explanation of what the display shows. People that have a Meteoman will hopefully know what on earth I am on about!

It seems to me that the "confusing" line graph is just a more granular version of the bargraph display, but in truth I am really not sure what it's telling me. I believe it's showing the tendency, but is the ups and dons of the line literally the pressure going up or down over time, or should I just be interested in the leading edge on the right and where it is on the axis? Or is it saying what the tendency was over the past x hours at every plotted point i.e. pick a point plotted say 2 hours ago and look to the vertical (Y) axis and that would have been the tendency at that point in time, two hours ago?

As you can tell I am totally confused on this!! Perhaps someone can enlighten me as an email to NASA Marine didn't get me anywhere.

Thanks a lot.

 

[Roberto]

It might be the barometric tendency, the pressure variation over the previous 3 hours (?)

As you have the continuous graph/values, it's quite simple to check if it is so.

 

[Roberto]

is it like the top image ? It seems to be the one-hour tendency

 

[asteven221]

Hi Roberto

Yup the top image is the graph I am talking about. Thanks for taking the time to reply.

Using you image - At the current point in time the pressure tendency was rising at 0.5mb per hour. 11 hours ago the tendency was rising at just over 3mb/hour. Nearly 16 hours ago the tendency at that point was falling at nearly 3mb/hour. Is that correct? So what can I tell from the plot what's the likely weather scenario at any given time?

Would I be correct to suggest that using your image, I should look back at the plots between 16 to 12 hours ago and expect to be going trough a period of much improving weather, but going forward it will get worse again?

Once again, thanks for replying.

 

[Graham_Wright]

Has anyone got one of these? If so I would really appreciate it if someone could advise me on one of the displays and what it's telling me.

There is main display showing the actual readings over the past hours/days and that's the display that's shown on every Meteoman image you see on the internet. It's the barograph image, but it's not that display I am confused about as it's function seems obvious. It's the one that shows the rising/falling on the right vertical axis and time on the horizontal axis. A line graph. Even the NASA manual doesn't explain it, nor does the manual even refer to it. I can't find even one image of the display in a google search, so I apologies for my crude explanation of what the display shows. People that have a Meteoman will hopefully know what on earth I am on about!

It seems to me that the "confusing" line graph is just a more granular version of the bargraph display, but in truth I am really not sure what it's telling me. I believe it's showing the tendency, but is the ups and dons of the line literally the pressure going up or down over time, or should I just be interested in the leading edge on the right and where it is on the axis? Or is it saying what the tendency was over the past x hours at every plotted point i.e. pick a point plotted say 2 hours ago and look to the vertical (Y) axis and that would have been the tendency at that point in time, two hours ago?

As you can tell I am totally confused on this!! Perhaps someone can enlighten me as an email to NASA Marine didn't get me anywhere.

Thanks a lot.

The button access to the page should be labelled trend>

 

[Trundlebug]

What it's telling you is how windy it's likely to be getting.

Refer to your RYA theory lessons, I can't remember the exact detail but basically:-
If the pressure rise or fall is less than 1mBar per hour, light winds
The greater the rate (trend) of pressure rise or fall in mbar per hour, the stronger the winds.
They estimate a number in miles per hour wind for every millibar rise or fall of pressure per hour.

That's why it's useful

Hope that clarifies?

 

[Roberto]

Sorry I had not seen the message (I'm half covered in antifouling)

Barometric tendency is more usually measured over three hours, pressure variations over time of course depend on the relative motion of the observer and the pressure system, as well as what happens inside the weather feature (deepening, filling, etc), so no hard and fast rules.

Along our latitudes, as for pressure falls, 3hPa over 3hrs may mean about 4-5Bft winds, 6hPa over 3 hours more like 6Bft; 8hPa or more /3hours something more serious like 8Bft. For the sake of interest, meteorological "bombs" in extratropical latitudes are defined as pressure features showing falls of at least 1hPa per hour over 24 hours, ending up in very very serious weather.

One similar thing that IMHO would be really significant for people sailing in tropical latitudes, would be showing the 24hr difference. Along those latitudes (but also elsewhere), pressure shows a well defined daily cycle (look for "barometric tide" for more details), calculating 24h differences would highlight any underlying pressure trend, which might remain hidden if one looks at hourly data only. One can clearly see changes when trade winds abate and disappear, or for example in the Mediterranean when some new system is coming through.

 

[Graham_Wright]

One similar thing that IMHO would be really significant for people sailing in tropical latitudes, would be showing the 24hr difference.

24 hr is the time scale.

 

[Roberto]

24 hr is the time scale.

Sorry I may not have been clear. 24 hour is usually the time frame shown on the display (or shorter or longer), most barographs show pressure, or 1hour or 3hour differences say for 24 hours. The Meteoman above says "One hours averaged rate in mb/hour", and show data for the past 24 hours.

What I am talking about is some kind of display (24hour if one wishes so) where the units being plotted are "pressure differences between the last available pressure data minus the pressure data of 24 hours earlier".
This type of differences removes the cyclical component in the time series (in this case the 24h cycle), hence it shows a lot better if there is a trend in pressure which is hidden by the cyclical component.

Example, no underlying trend in pressure, only the 24h cycle. If one computes the difference between the last pressure and the one 24 hours earlier, in case of a perfect cycle the difference will always be nil; in practice there will be probably small differences around zero.
If the pressure movement has an underlying trend, what one measures is the sum of the cycle and the trend, and it may be very difficult to detect the trend. 24h time differences will remove the cycle, and if there is a trend it will be shown a lot more clearly: the display would show a somewhat rising or dropping line, without all the confusing ups and downs related to the 24h cycle.

regards