## Monday, August 31, 2015

### Sides of a Tropical Cyclone, Part 2 Meteograms.

In Part 1 of this topic, we looked at a way to study the wind and pressure on both sides of a tropical cyclone (TC) using any grib viewing program. There are many such programs available and the method outlined does not require any special features. Any of them could be used.  In this note we look at another way to study this that takes advantage of a special meteogram feature of the navigation and weather program Expedition.

In the presence of an approaching TC, we can judge where we are relative to its path by watching the wind speed, wind direction, and pressure from the perspective of being on one side of the storm's path or the other. In the Northern Hemisphere (NH) the right-hand side when facing in the direction of the storm's motion is called the dangerous side, whereas the left-hand is generally more manageable, at least if some distance away from the center, and it is called the navigable side. Part 1 included background on this and references.

The names are in large part based on the fact that the approaching winds on the dangerous side tend to push you into its path, whereas on the navigable side the approaching winds push you away from its path. The sea state on the dangerous side is also notably steeper and more chaotic.

A meteogram is just a plot of the wind, pressure, temperature, etc as a function of time. Time can be plotted forward (a forecast) or backward, a history.  The latter plots are a nice way to see, for example, that wind direction undergoes a prominent veer at the passing of any front.  Using a meteogram as a forecast we can show graphically the behavior expected on each side of a TC, as shown in Figure 1.

 Hurricane Guillermo on Aug  3-5, 2105. The same example was used in Part 1. The background and meteograms are from Expedition, version 10.0.12.
Here we see in a much more direct manner what we discussed in Part 1. The blue stripe in each case marks the conditions we would observe from a stationary position over the day the system approached.  The two side points are about 70 nmi to each side, with all 3 being about 200 nmi off—which before any further discussion we have to say are all three very close to this system.  Such intense systems to not emerge suddenly, or if so, extremely rarely.  In this case we would have had at least 3 days earlier to know where this storm was going to be at this time. Thus how we ended up in one of these positions is an entirely different issue!  In short, we would have to say that we are primarily thinking about rare situations in which we did not have contact with the outside world and thus did not have the official forecasts.  But then, even with that assumption, we have to assume further that we did not have a \$200 SW radio on board that would have told us the storm location and motion at least once every hour. Such a radio runs on batteries and is not dependent on the ships power.

Looking at conditions during the blue bar, we see first one important factor.  In all three locations we did not see much interesting at all for the first 6 hr, and that is because the closed isobars of the system had not yet reached us.

Once the closed system reaches us we see the expected behavior. On the right the wind builds and starts to veer. On the left we see the wind backing, but it actually falls off a bit, and in any event this far off the axis it never does build much.  This illustrates the value of getting as far as possible from the center of the storm as it passes.

In all three cases we see the pressure going down as the Low center approaches. There is more discussion in Part 1. The main goal here was to shown this new way of studying this behavior.  As it turns out, we have three very large systems in the Pacific right now, so I will try to grab some data and make a video of the use of these metorgrams.

There are other ways to generate meteograms using online resources, once you know the Lat-Lon and time you want. Most of these must be near live times, however. One example is https://ready.arl.noaa.gov/ready2-bin/main.pl  but I recall others that are easier to use.  I will add them here as i find them.

## Wednesday, August 26, 2015

### Commercial Echart Ad is Food for Thought

It is not clear that they have thought through the marketing logic here, which only adds to the challenges we face moving into the realm of modern navigation.

[Recall MacDonalds long term request that we "Put litter in its proper place," which has to mean throw your trash on the ground... else it would not be litter.]

 From an August 26 email ad.

If they do indeed make 2,000 corrections per day, what is it they are correcting?

The true charts themselves are not changing anywhere near that rate, even on a global basis. So this simply means they are mostly correcting their own errors in their own proprietary electronic charts. [*]

Thus we learn several things. Good—these charts are getting better every day. Bad—they indeed do have a lot of errors in them. (See related note.)

So the recommendation we make remains the same. When using electronic charting we are still better off with raster charts (RNC) when available. These are direct copies of the latest official charts, which these days are updated every week at no charge. Then if we want the convenience of some commercial vector chart such as this one in a packaged set of electronics of software program, we can then check it with the latest RNC or ENC.

See www.starpath.com/getcharts.

[*] To be fair, maybe they are not just correcting actual errors but adding new information, to an otherwise correct chart. That would have to  be checked, and evaluated. If the addition is something that is already on the official charts, then is that an "error"? If it is adding something that is not crucial, then that is what it is.

The reason vector charts (official or commercial) will eventually be our main resource is they offer so many layers of information, and are indeed easy to update, even remotely. Some of the information in deep layers is not crucial often, but could be in special circumstances.

So the 2,000 updates a day shows they are working on this.  My comment here has more to do with the choice of marketing idea. My first impression was with that many updates, they must have a lot to fix.

Sort of like advertising ones level of experience in navigation by citing all the hurricanes they have sailed through.  I would tend to listen more to the person who has sailed all their lives and never been in a hurricane.

## Monday, August 17, 2015

### Mariner’s Weather Checklist Before Departure

It is fundamental to safe efficient weather work at sea that these items be checked off and tested before departure. Having it all onboard without prior testing does not count!

(1) Barometer. This is key instrument to any ocean or coastal passage. Check it over a large pressure range using free service at www.starpath.com/barometers,  or just interpolate the isobars to get the correct pressure for your location at the synoptic times from unified map at http://www.opc.ncep.noaa.gov. For electronic barometers, you likely have an excellent one in your phone. Use our free marine barometer app, and read the help file that comes with it—a short course on barometer usage. We have extensive notes on barometers.

(2) Wind instruments.  To measure apparent wind speed and apparent wind direction, and they should be calibrated.

(A nice backup to both of these is the small handheld Kestrel 5500. The barometers on these that we have tested have been excellent. It is easy to check the windspeed driving along in a car holding it out of the window. Using one of these to check your onboard instruments, remember that wind at the masthead can be notably different from wind on the deck.  Might have to take it up the mast.)

(3) Calibrated knotmeter and magnetic Compass, and calibrated heading sensor.

(4) True wind from Apparent solution. We need some procedure to convert apparent wind to true wind that is well tested and practiced. This can be done within the wind instruments themselves or some other electronics box they plug into, or it can be done by inputing the data to a computer and computing it there,. Or it can be done by hand with a calculator, which is best done with one that is programmed to do this. There are numerous smart phone and computer apps for this.

(5) Laptop computer. There are certainly ways to do safe weather work without one, but  a computer makes everything related to weather very much easier, more versatile, and better. I would consider it a required item since so many of our best resources are obtained via the computer. In fact since computers are so inexpensive these days, it is not even unreasonable to set up one with all your nav and wx software and connections and then just clone it to another one which you take as a back up.  For PC users, Acer has several very good low cost laptops. Mac users know what is available.

(6) Communications.  This would mean either a sat phone or an HF radio with Pactor modem.  The sat phone is definitely easier, but day to day usage is more expensive.  HF radio work could be near free once set up, but the investment would be notably more than a sat phone to set up from scratch.  It would be nice to have both, that is if the boat is already set up for HF radio then add a sat phone for convenience and dependability.  If not set up already, it would be harder to justify the expense compared to sat phone only.

There are these days all sorts of other communications options, from satellite broadband to systems that connect everything on the boat wirelessly.  However, the basics are in item (6) and they should be there regardless of the other luxuries.  In a sense, the more you have the more that can go wrong, so you want to be able to pick up the sat phone and make a call, or plug it into your computer and send an email.

(7) Software for email. We need software to send and receive emails with attachments… with no restrictions on what we say or include, which rules out the basic ham radio programs. There are numerous options. Airmail from Saildocs is one. Ocens, Xgate, or UUPlus are a couple other options. Each has unique services or features; the prices vary somewhat, but not a lot.

With (6) and (7) in place you can send and receive emails and email attachments by satellite phone.  All of these offer the option in setup to switch between communicating by sat phone or communicating by Internet.  Underway you will use the sat phone, but once in a harbor with Internet, you switch to that.

On the other hand, for getting set up and tested before departure you would also primarily use the Internet connection, but it is crucial that you just spend the air time and do several transfers by sat phone long before departure date. You want to be 100% certain that this system is working, i.e. send and receive emails with attachments. Turn it on and off, computer on and off, reboot, close all, start again, switch back and forth between sending by sat phone and by Internet, try multiple types of files (discussed below), etc. The main point is to be sure this is all working well before leaving and that you have used it for a couple of weeks at least getting your weather information, as outlined below.

(8) Software for GRIB viewer. Many, if not most, echart programs include the option to overlay GRIB formatted weather data right on the echart you are navigating with, but these are sometimes limited, so supplementing that with an app that can display and analyze weather data is crucial.

I assume you will have some echart program in a laptop for navigation that is tracking your GPS position. Almost any one of these will show grib files for weather analysis. ( If this has not been planned, i.e. you have a console unit from your navigation electronics doing this tracking, then you may want to consider adding the laptop or tablet navigation option. You can do very much more with your own echart or weather app in a laptop than possible with any of the packaged units which are then restricted to just the chart formats they provide as well as limited navigation tools.)

In any event, it pays to have a stand alone grib viewer in your laptop if you do not have one in your echart program. There are numerous options. For the PC there is Viewfax from Saildocs, qtVlm, Expedition, and many others. For the Mac there are fewer choices, but LuckGrib for Mac or iOS remains at the top of the line for both data delivery, display, and analysis.

(9) Source for grib data. Establish and practice with some source of grib weather files. Saildocs is an excellent source. Many of their download options are included in a convenient Viewfax utility called “Get Data”, but they have much other data that are not listed there that must be obtained by email request to saildocs.  LuckGrib has the state of the art data selection, including ASCAT measured satellite winds and OSCAR currents, which others no longer include. See our Weather Course for details.

And again, it is crucial to download some of the files and learn to use these forecasts before departure.

(10) Text forecasts. Don’t forget the text forecasts. Practice receiving by email the crucial text forecasts, as outlined in another note in the references below.

(11) Seawater temperature. When sailing in the Gulf Stream or any other strong current system, or when sailing in the tropics in general, it is extremely valuable if not crucial to have a through-hull seawater temperature measurement, or some other permanent way to continuously read and display seawater temperature.  For ocean currents the water temperature marks the boundaries of various features, and for the tropics the water temperature is a measure of TS development, i.e. hurricane formation usually require seawater > 80º F.

References:

## Thursday, August 13, 2015

### High Seas Forecasts and Tropical Cyclone Alerts by Email Request

In several articles we point out that standard analysis and forecast maps of tropical systems do not have nearly enough information on them to make weather routing decisions.  We need more information. One approach is to download a GRIB formatted numerical prediction. The GFS is the most popular; the NDFD would be superior if that were available to your waters.

With or without these GRIB files, it remains valuable to also obtain the text forecasts from the NWS, in part because the GFS—or any one single model—can sometimes be quite a bit off on the tropical system intensity.

We have three basic text reports that might be of interest: high seas forecasts, high seas discussions, and tropical cyclone alerts. The basic ones we need to supplement the maps are the forecasts, and these are easy to get.

In principle we can get all of the text reports we need from the NWS FTPmail service, but this requires a very specific format and list of file names. An alternative is the excellent services of Saildocs, which have proven very dependable and versatile; it is relied upon by thousands of mariners worldwide, so we will limit the source to this one.

The eastern half of the Pacific Ocean is in the IMO GMDSS forecast zone called Metarea XII; the western half of the Atlantic Ocean is in Metarea IV.

To get text report and forecast for Metarea XII (North Pacific)

send an email to query@saildocs.com with the body of the text blank except for
send met.12  You can put anything in the subject line, which can serve for finding the mail for a repeated request. Be sure there is no signature or other text or graphics in the body.

This is all there is to it.  Try it here.

You can also subscribe to this request to have it sent to you automatically every day.  Send a blank email to info@saildocs.com for details.

For other metareas, use these Saildocs abbreviations

 Code Metarea description Met.1a North Part of North Atlantic Ocean (High Seas) Met.1b Northeast Part of North Atlantic Ocean (Offshore) Met.2 East Part of North Atlantic Ocean Met.3e East Mediterranean Sea Met.3w West Mediterranean Sea Met.4 West Part of North Atlantic Ocean Met.5 North Part of South Atlantic Ocean Met.6n South Atlantic Ocean North of 60S Met.6s South Atlantic Ocean South of 60S Met.7 Southeast Atlantic Ocean + extreme SW Indian Ocean Met.8n North Indian Ocean Met.8s Southwest of Indian ocean Met.9 Red Sea, Gulf of Aden, Arabian Sea, Persian Gulf Met.10ne Northeast of Australia (Pacific ocean) Met.10n North of Australia Met.10w Southeast of Indian ocean Met.10se Southeast of Australia (Pacific ocean) Met.11ior West part of the North Pacific Ocean (from China) Met.11por West part of the North Pacific Ocean (from Japan) Met.11sW West part of Pacific Ocean, 0-12S 90E-142E approx Met.12 East part of the North Pacific Ocean Met.13 Northwest of Pacific Nord and part of Arctic waters Met.arctic From SW corner 67N, 44E to NE corner 80N, 165W Met.14s South Pacific south of 25S Met 14trop South Pacific north of 25S Met.15 Southeast Pacific Met.16 Southeast Pacific between 18S and 3S)

We can also see these reports online two ways. Directly from the IMO see
http://www.jcomm.info/index.php?option=com_content&view=article&id=105&Itemid=37

and we have similar reports from the NWS from this folder:

http://weather.noaa.gov/pub/data/forecasts/marine/high_seas

The files matching metarea XII and IV are  north_pacific.txt  and  north_atlantic.txt

If you are sailing across one of these oceans, you would want to set up a schedule with Saildocs to send you the text report at least once a day, automatically.  This will supplement your maps and GRIB file weather analysis.

You can of course get this information from the HF radio. The USCG broadcasts voice versions of the above forecasts 4 times a day. See http://www.nws.noaa.gov/om/marine/hfvoice.htm

* * *
Any of these services that might potentially be used underway
should  be thoroughly tested before departure.

* * *

### Sides of a Tropical Storm

In principle if we have all of our weather resources working properly, then we can see where we are relative to an approaching tropical storm or hurricane, and from its forecasted motion we could determine which way to best proceed.

Unfortunately, life is never quite so simple in the real world. First, what are these “resources” referred to here?  We have more details elsewhere, but they would include the weather maps (surface analysis and forecasts), and they would include the GRIB files of numerical weather predictions such as those from the GFS.

We shall see in the videos below, however, that the maps themselves are often not detailed enough if we happen to indeed be inline with, or close to, a TC. The GRIB model predictions on the other hand, give us very detailed forecasts for wind and pressure, but we must be aware that these unvetted model predictions could be wrong!  This is actually more likely with a TC than with more climatically normal forecasts, and indeed more likely to be wrong during the first day or so of formation.

Thus it turns out that perhaps the most crucial official weather information we have underway in a case like this are the email text or radio broadcasts that give the official NWS numerical information on the location, motion, and extent of the systems. These are available at least 4 times a day, and often hourly on the storm warning broadcasts segments of the WWV and WWVH HF radio.  We can pick these up with a standard, battery-operated SW receiver.  The voice broadcasts are usually a voice synthesized rendering of the text reports. Here is a note on how to get these text forecasts by email.

From these text reports we learn the Lat-Lon of the system at a specific time, and we learn the speed of the system in kts, and the true direction it is moving—this might be stated as “northeast or 050,” in which case the numbers are the more specific value; this phrase is not a range of directions or an uncertainty statement.

Instruments
For the best work here we need an accurate barometer and calibrated wind instruments. Many places elsewhere we discuss barometers and how to check that they are reading properly. This is fundamental to ocean voyaging.

Wind instruments are frankly harder to calibrate properly, but the more accurate they are at this point, the better off we are. The crucial point here is we need to know true wind speed (TWS) and true wind direction (TWD). We get this from the apparent wind speed (AWS) and apparent wind angle (AWA) along with our COG and SOG from the GPS. Some instruments will make this conversion for us, which is a great convenience once it is tested to be working properly. Otherwise, we can use a calculator to convert the AWS and AWA to TWS and TWA, then we can combine the TWA with COG to get the TWD.

Without any wind instruments, you can look into the waves to estimate the true wind direction. The TWA will always be aft of the AWA. That is if you have instruments telling your the AWA is near the beam; the TWA will be more on the quarter, etc. Then add this to the true heading of your vessel at the time, being the compass heading corrected for variation.

The barometer is dropping and the wind is building. Which side of the storm am I on?

Simple enough question, but it needs all kinds of clarification. First of all a reminder that we are talking primarily about “tropical” systems, either within the tropics, or those that have moved out of the tropics…. and we are discussing another rarer type of system which is a “tropical storm” that formed well outside the tropics.  An example of the latter is TS Claudette from July 2015 that formed off the coast of NC and moved NE.

The key characteristic we are calling “tropical” means a small and well defined system with closed isobars. A typical extra-tropical storm in the North Atlantic or North Pacific does not qualify.  Which side of these is rarely a question we face—the other side could be more than a thousand miles away. A tropical storm is typically a few hundred miles across, or less. These are the ones whose sides we care about in this discussion. We can also have the barometer dropping and wind building with an approaching frontal system, but this discussion would not apply to that situation at all.

When sailing in the tropics, however, we are not often confused by what is going on. We are used to glorious trade wind sailing, with the wind and barometer pretty stable. In fact, the barometer is actually more stable than the winds. We can see the trades vary from 10 to 20 kts with not much change in the barometer.  Throughout the tropics summertime pressures will be 1011 to 1014, depending on month and location, and more to the point, the standard deviation (SD)  in this pressure will be only 2 or 3 mb. In the absence of a tropical system, a pressure drop of 2 SD occurs only 2 or 3% of the time. Thus if you see the mean pressure drop 4 or 5 mb then you have a very good warning that a system could be approaching, even if the wind has not started to build. Note we have to say mean or average pressure because within the tropics there is a semi-diurnal variation of the pressure with an average amplitude of 1.7 mb.  Worldwide pressure statistics and how to interpret them is covered in the Mariner's Pressure Atlas.

Now a video review of the key issues of wind shifts as a closed system of isobars approaches and passes.

Sides of a Tropical Storm,  Part 1.  Background and References (10 min)

For full screen, double click and wait a few seconds for focus.

Step by Step Procedures
(1) On a chart or universal plotting sheet, plot the latest known location of the storm.  Also then, look into your logbook to see where you were located at that time, and plot that position on the chart as well.

(2) Using the forecasted course and speed of the storm and your known position now, plot your present position as well as the DR position of the storm at the present time.

(3) Now plot the forecasted track of the storm and its forecasted locations.  We are getting this information from the text reports if we have them (see below).

(4) If we have this data, then we have a picture of what is taking place and where we are relative to the storm. More specifically, you see how far away the storm is and how close it will pass if you do not move.

(5) Now the crucial check to see if the forecasts are correct by recording our barometer and wind speed and direction at least every hour.  With a good barometer, you might learn something on an hourly basis. (Examples in the videos below.)

(6) You might also at this point do a reality check with the Buys Ballot law (refer back to Video 1). Namely, with your back to the true wind direction, i.e. true wind blowing against your back, put left arm out and rotate it forward by 25º. Now check the compass to see which way you are pointing and record that, then convert that compass direction to a true direction.  Then you can go back to your plot and draw a line from the boat to the storm and see if that direction is the same as you just measured with Buys-Ballot.  If yes then you can try this again once the wind direction changes enough to detect it.  If still pointing to the storm, then you are indeed inside the closed isobars of the storm.

If the Buys Ballot direction does not match your plot, and you checked both, then chances are you are not quite into the closed isobars.  This could also be indicated by a pressure that is not dropping or dropping very slowly.

Now we have a couple specific examples.

Sides of a Tropical Storm,  Part 2.  Hurricane Guillermo 2015 (17 min)

For full screen, double click and wait a few seconds for focus.

Sides of a Tropical Storm,  Part 3.  TS Claudette 2015, Value of a Good Barometer (15 min)

For full screen, double click and wait a few seconds for focus.

Now that you see the pressure dropping and wind maybe building, and you have from Buys Ballot a good check on the direction to the storm, you are prepared to consider a course of action.  They key issue is almost always getting as much separation from the storm center as possible at the time it passes you… or with confident knowledge, the possible choice of getting across the front of it before it gets to you. This is especially true with these TC that have strong winds. These strong winds are usually located fairly close around the system… that is, we see that 80 or more nmi gain is usually a huge safety factor.

The video examples we have show this, but we can use the data from a typical TC to see this for other cases.  You can also go to http://www.nhc.noaa.gov/archive/2015/  and choose any of hundreds of storms to check this.

Here are a couple examples.  For tropical storms or for TS stage of a hurricane, the safety radii are smaller, so it is easier to get out of the way of them.

__________________________

NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI   EP092015
0900 UTC MON AUG 03 2015

HURRICANE CENTER LOCATED NEAR 16.2N 145.4W AT 03/0900Z
POSITION ACCURATE WITHIN  20 NM

PRESENT MOVEMENT TOWARD THE WEST-NORTHWEST OR 300 DEGREES AT   9 KT

ESTIMATED MINIMUM CENTRAL PRESSURE  990 MB
MAX SUSTAINED WINDS  65 KT WITH GUSTS TO  80 KT.
64 KT....... 30NE  25SE  20SW  20NW.
50 KT....... 70NE  40SE  25SW  35NW.
34 KT.......115NE 100SE  50SW  70NW.
12 FT SEAS..300NE 200SE 270SW 310NW.

(skipping a few reports)

FORECAST VALID 04/0600Z 17.5N 148.1W
MAX WIND  55 KT...GUSTS  65 KT.
50 KT... 50NE  30SE  15SW  30NW.
34 KT... 90NE  80SE  40SW  60NW.
__________________________

TROPICAL STORM CLAUDETTE FORECAST/ADVISORY NUMBER   6
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL032015
2100 UTC TUE JUL 14 2015

TROPICAL STORM CENTER LOCATED NEAR 42.5N  59.8W AT 14/2100Z
POSITION ACCURATE WITHIN  30 NM

PRESENT MOVEMENT TOWARD THE NORTHEAST OR  50 DEGREES AT  18 KT

ESTIMATED MINIMUM CENTRAL PRESSURE 1005 MB
MAX SUSTAINED WINDS  40 KT WITH GUSTS TO  50 KT.
34 KT....... 60NE  70SE  60SW   0NW.
12 FT SEAS.. 60NE 120SE  60SW   0NW.

__________________________

Once you see where you are and how the storm is moving, you can then figure the best plan of action.  Here is a video showing a couple choices. It uses the program Expedition, which does automatic routing, but that powerful feature is not required for a good judgement. Also since the sea state will likely be much larger than usual, chances are any polar diagram you have might be an overestimate of performance.

Sides of a Tropical Storm,  Part 4.  Maneuvering from a Known Side (15 min)

For full screen, double click and wait a few seconds for focus.

Before making a major decision such as trying to cross in front of a system you are nearly in line with, it is best to run for a while in the chosen direction to know true SMG and CMG possible. In some cases, like the example shown, it will be pretty clear if you can or cannot make it across to the navigable side.

That choice, however, is crucially tied to the proper identification of where you are relative to the storm path… and projected storm path.  Recall if you do not have any data at all from the NWS, we must rely to some extent on the known average trend of a storm turning poleward at some point.  The statistics of storm speeds and directions as a function of age is discussed in the text book, and hundreds of actual examples are online at the NHC to test these averages.

## Sunday, August 2, 2015

### New GRIB Viewer for Macs

For years we lamented to our Mac friends and students that there were so few good marine applications for the Macintosh that they were better off biting the bullet and buying a PC for their marine navigation and weather applications. This litany followed us right into these modern times when we ourselves started running our own PC programs on virtual machines in a Mac.

But sure enough, when the demand grew high enough, these apps have started to appear. In the weather department, our neighbors at Ocens were the first to bring high-quality weather products to the Mac with a series of valuable applications.

And the bar keeps rising, in this case with a new GRIB weather data viewer for the Mac called LuckGrib. As it turns out, this is also a product of the Pacific Northwest, though its developer Craig McPheeters happens to be underway sailing in the South Pacific at the time his product will first appear in the App Store sometime in August.

In keeping with Mac standards, LuckGrib has an elegant design and convenient interface, with several unique features added to the standard functionality we expect from a high-quality weather tool. Besides its versatile display options, it also offers a way to download the data from an Internet connection. Built in data sources include: GFS, WW3, and CMC Ensemble.

Though we tend to reply mostly on wind and pressure for routing, and the 500-mb data for evaluation, and sometimes the precipitation, this new LuckGrib app offers very much more. In a deep Advanced Option you can request any of the 320 weather parameters predicted by the GFS system, including temperatures, humidity, cloud cover, convective properties, and many more at essentially any altitude level in the atmosphere. You would have to be a professional forecaster to make use of much of this info, but it can be found here if desired.

Other outstanding features include:

• Fast operation and smooth performance on all options using even relatively large files.

• Convenient data selection and request interface. It is always, however,  the navigator’s job to select only the data needed, only over the region needed.

• Versatile track pad pinch zoom and pan. A slider bar can also adjust the zoom level, and standard mouse click and drag also works to crisply adjust the map view.

• Many options for personal preferences in color schemes and actual data display configurations available for each of the data types.

• A dynamic feedback option that shows the values at the cursor not just of wind arrows, but also wind speed contours, pressure, or any parameter or combination of parameters. A very informative way to look at the distribution of data.

• A min and max point display within the wind contour option offers nice way to see strongest parts of a storm.

• Option for selecting GFS resolution of 1º, 0.5º, or 0.25º.

• Time to next update for each model. A very nice feature that prevents users from extraneous data downloads underway.

• A draw route leg option, with ticks at specified user-selected intervals. This can be used as an electronic range and bearing line to read the maps, or as a route leg to check wind along a path at a fixed time—or it has the very useful application of setting a day or two route leg, and then sliding the time marker to continuously watch the winds all along that path.

• Time control allows for interpolation of wind fields at times intermediate to the forecast times, which is valuable for comparing with satellite wind data, or making wind predictions at specific times.

• Low price—which has to be considered a practical outstanding feature. It is predicted to be \$20, which would make this a must have app for all sailors using Macs for weather work. There is one other high-quality GRIB viewer for the Mac called Grib Explorer for Mac from Ocens, which has many outstanding features of its own. In the ideal world we would have both of these fine tools, but at \$199 for the Grib Explorer it requires a larger budget plus an external source for downloading the data.

We have used the beta version of LuckGrib extensively for several months. The LuckGrib viewer is elegant, fast, and functional. Regardless of other weather tools you might have, this tool will add new functionality that will improve your weather work.  If you have not used GRIB forecasts at all, LuckGrib is an excellent way to get started—but we must remind all GRIB users that unvetted numerical weather prediction data (such as GFS GRIB files) should always be compared with the actual professional forecasts prepared by the NWS and their counterparts around the world.

Tech support and related information can be found at http://luckgribapp.blogspot.com.

We will add illustrations later and a video on standard and special operations.