Good Afternoon,  I am TSgt LaFramboise, and I will be briefing you today on the application of SYNOPTIC data in the process of METSAT analysis.

We will explore the usefulness of synoptic data in Satellite analysis, the problem areas encountered, and where this data can be found.  Why should I use synoptic data?  How can this possibly help me with my next position fix?  How many times have you stared at an infrared image, looping it back and forth looking for anything that resembles a circulation center, only to may a reasonable guess that you aren’t entirely confident in? How many times have you told yourself, “I wish there was something I could use to get a better idea of where this center is?” Have you ever scratched your head, wondering what the intensity actually is in a poorly organized system? Synoptic data could give you a better idea, when the satellite imagery is not very clear-cut.

This is the early stages of Tropical Cyclone 33S.  Even in animation this center was very hard to pinpoint. 

Even with the position pointed out on this one, you have to scratch your head and wonder if it’s accurate.  As close as this one is to the Philippines, there should be an abundance of synoptic data available.  This was 03W classified as a T1.5.  How helpful would it be to have synoptic data for the time of this fix when conditions haven’t improved as far as organization 6 hours later?

1.  You can verify (or adjust) your position center using available wind directions and speed, and you can use the surface pressures to help zero in on the surface low. 2.  You can also use available wind speeds to get an idea of the minimum intensity of the wind fields.  Of course, the closer the data is to your system center, the more accurate an estimation you will have.  You may also estimate the intensity by how low the surface pressure actually is. 3.  Another use of synoptic data, especially with AWDS, is the ability to overlay plotted data onto the Satellite imagery.  As in any weather information, when you overlay products they make the analysis process easier. When you overlay the synoptic data onto the satellite data, you may pick up on small details that were meaningless before, and you can discount features that can otherwise be misleading.

Many of them have been in use for decades, and continue to prove there value even with all the improvements we’ve made. 1. Land synoptic data can be extremely useful, especially over island stations where data is otherwise sparse. 2. Ship synoptic data, while sometimes less reliable and less accurate then land synoptic data, gives us information in places that are otherwise without any hard data at all.  Over broad ocean areas, ship data is often the only products available to us. 3.  Of course we also have many buoys positioned in areas of sparse data to fill the gaps in data areas. 4.  Over land areas we have the additional information provided by Rawinsonde reports.  We also still get dropsonde data, but not on a regularly scheduled basis. 5.  Satellite derived winds, although less accurate than surface observations continue to improve with new technologies. 6.  Scatterometer data is a fantastic new tool.  When a scat pass is right over your system you get a very accurate position and intensity estimate.

Here is an example of plotted synoptic data.  The black plots are new land or ship data.  Blue plots are older reports the green and yellows are from scatterometer data. (new slide).  As you can see, if this data was condensed around the area your system is at, you would get a pretty good estimate of not only your position but also your intensity.

For those of you unfamiliar with scatterometer data, this is what we normally look at.  Along the top are the wind values associated with each color. The red represents 30-35 knot winds and the brown inside the field of red plots represent 35-40 knots.  This particular pass is from Typhoon Leo during its period of rapid intensification. This data can be found on the internet at the noaa site:

Here’s a close-up of the previous picture.  You can see that the data is pretty dense having a plot for nearly every six miles.  Quite often the winds will be plotted 180 degrees out from the actual wind direction. It seems like the satellite pass rarely goes directly over the system you are interrogating.

Problem areas are substantial.  No data is without limitations and no data is always 100% accurate.  We have to be aware of these limitations, and take them into account when using this data. 1.  Perhaps the biggest problem with synoptic data is the timeliness of it’s availability.  We usually don’t see this data until it is already 3 to 5 hours old.  An then it is not always available when and where we need it.  This is especially  true in ocean areas like the southern Indian ocean. 2.  Data coverage is always subject to the availability to land stations, operational buoys, and ships positioned in the area in concern.Quite often data will not be available when and where you need it. 3.  There is also the problem of erroneous data.  Observations are still subject to human error, and instrument error.  This is especially true with ship data, because the instruments are not stationary fixed instruments.  We also have the problem of codes being converted incorrectly.  We still have site specific information that is not correctly interpreted.  Some areas still report winds in meters per second, some in knots and some in MPH.  Some surface pressures are converted to sea level pressure some in millibars and some in inches of mercury.

Over land areas we see a lot of variation.  The biggest cause of this is the varying terrain.  We have to be aware of the stations we are using.  Two stations can be five miles separated and have 5000 foot differences in elevation.  And both be within five miles of the ocean. Varying pressure are observed again due to the conversions to sea level.  Some stations are not converting there pressure reliably (or correctly). And some convert in inches, some millibars. In underdeveloped countries, instrument calibration is inconsistent at best.  In some cases, calibration is either not done or not possible. In stations above 1700 feet MSL, sea level conversions are less accurate and this must be taken into account.

Ship data is going to be less accurate than land data.  There are many reasons for this, and you should be aware of these reasons.  That is not to say that this data cannot be used or relied upon.  Any data is better than no data. 1.  Wind speeds can be off by as much as .6 knots per Beaufort Scale division.  This can be a very substantial error with winds associated with a tropical storm or typhoon. 2.  Coverage is extremely limited over vast ocean areas.  Of course this is also the reason for it’s value.  As improvement are made in the accuracy of satellite derived winds, this problem becomes less important. 3.  Wind directions reported have an average error of +10 degrees.  Human error comes into effect here as well as the wind direction taken on a moving ship has a world of reasons for being inaccurate.  The very motion of the ship can cause inaccuracies in the observed direction. This is especially true if the wind speeds are fairly light.

On the plus side, we have a large number of buoys and ships giving us information in areas that are otherwise data free.  Buoys can give us accurate information in areas near the center of a tropical system, without endangering lives or assets.  We get an accurate intensity of the Minimum wind speeds and intensities of systems that pass near ships or buoys.  Minimum because the strongest speed associated with the system is not necessarily the speed experienced by our data source.  Depending on how close the system is to our available data, the actual intensity can be dramatically higher. 

Of course we all know that this data is available through the AWN, and through the AFWIN homepage.  Data from these sites are automatically received and processed through AWDS.  We also have internet sites available to us that provide excellent backups for this data. One such site that is used extensively here is the UNCC University of North Carolina-Charlotte site.

Certainly you don’t have to use this data, and these reasons all have validity.  The timeliness of the data is not going to help this fix, but can give you an idea as to the accuracy of past positions, and show if you are on the right track or if you need to adjust your position.  Data too sparse?  Even a single report can give you the information you need.  If you are looking at a system as a 1.5 (25knot system) and you receive a ship report showing 35 knots winds, you may be underestimating the intensity of the system.  It takes too long to process the data.  After 6-8 hours of scratching your head!!  Synoptic data can clear up the picture for you.  Satellite imagery is accurate enough.  We all know that this is not always true.  Quite often we lose the center under infrared only to be surprised by a sheared system when the sun comes up and visible imagery is available.  There are many reasons for not using Synoptic data.  Whether these are reasons or excuses--  The main thing is that the data is available to you and can be used to your advantage. It certainly should not be ignored.

1. Data can help locate hard to find centers. 2.  Observed wind speeds and pressures give us direct feedback as to the accuracy of our intensity 3.  When under infrared imagery, in a cirrus covered center, synoptic data can have tremendous value.