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Old 17-06-2006, 12:10   #1
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Weather Knowledge?

There are so many sources for weather maps, forecasts, grib files, etc. available it would sure be nice to know who to believe when they diverge.

How to know if you are going to have to motor or reef that afternoon or the next day by reading the weather maps and current conditions.

On our recent cruise from Massachusetts to Maine we either had no wind or to much. A small craft advisory ended up in near gale conditions. The wind increased from 8 - 10 to 30 - 35 very quickly. We were reacting rather than anticipating which left me feeling that I should have recognised what was happening sooner, reefed sooner, etc.

Long story short, I want to gain some weather knowledge from a course in addition to and possibly before the school of hard knocks convenes again.

Anyone used Starpath? Any other courses out there that are recommended?

Thanks,

John
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Old 28-02-2008, 20:02   #2
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Did you ever get a response as we are looking into Starpath courses but wondered if anyone has had any experience with them? Please advise. thanks
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Old 29-02-2008, 02:39   #3
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See the earlier discussion “Reading Weather Charts” at:
Reading Weather Charts

Reading a Weather Map Station Plot

Clockwise from upper left (11 O'Clock)

Temperature:
In the upper left, the temperature is plotted in Fahrenheit. In this example, the temperature is 77̊F.

Cloud-type:
Along the center, the cloud types are indicated. These cloud types use the same cloud codes as found in the cloud chart section.
The top symbol is the high-level cloud type followed by the mid-level cloud type.
The lowest symbol represents low-level cloud over a number which tells the height of the base of that cloud (in hundreds of feet)
In this example, the high level cloud is Cirrus, the mid-level cloud is Altocumulus and the low-level clouds is a cumulonimbus with a base height of 2000 feet.

Sea-level air pressure:
At the upper right is the atmospheric pressure reduced to mean sea level in millibars (mb) to the nearest tenth with the leading 9 or 10 omitted. In this case the pressure would be 999.8 mb. If the pressure was plotted as 024 it would be 1002.4 mb. When trying to determine whether to add a 9 or 10 use the number that will give you a value closest to 1000 mb.

Visibility:
On the second row, the far left number is the visibility in miles. In this example, the visibility is 5 miles.

Present weather condition:
Next to the visibility is the present weather symbol. There 95 symbols which represent the weather that is either presently occurring or has ended within the previous hour. In this example, a light rain shower was occurring at the time of the observation.

Skycover plot:
The circle symbol in the center represents the amount of total cloud cover reported in eighths. This cloud cover includes all low, middle, and high level clouds. In this example, 7/8th of the sky was covered with clouds.

Air pressure tendency and change:
This number and symbol tell how much the pressure has changed (in tenths of millibars) in the past three hours and the trend in the change of the pressure during that same period. In this example, the pressure was steady then fell (lowered) becoming 0.3 millibars LOWER than it was three hours ago.

Wind speed and direction:
These lines indicate wind direction and speed rounded to the nearest 5 knots.
The longest line, extending from the sky cover plot, points in the direction that the wind is blowing FROM. Thus, in this case, the wind is blowing FROM the southwest.
The shorter lines, called barbs, indicate the wind speed in knots (kt). The speed of the wind is determined by the barbs. Each long barb represents 10 kt with short barbs representing 5 kt. In this example, the station plot contains two long barbs so the wind speed is 20 kt, or about 24 mph.

Dewpoint temperature:
The 71 at the lower left is the dewpoint temperature. The dewpoint temperature is the temperature the air would have to cool to become saturated, or in other words reach a relative humidity of 100%.

Past weather:
The lower right area is reserved for the past weather, which is the most significant weather that has occurred within the past six hours excluding the most recent hour.
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Old 29-02-2008, 08:16   #4
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I haven't had experience with the classes you mentioned, but if you have time and enjoy reading. I've read some good books relating to weather including

Mariner's Weather by John Crawford
Weather Wizards Cloud Book by Louis Rubin
Sailor's Weather Guide by by Jeff Markell.

I would have posted the links but I wasn't sure if that was against the rules. In any event, some parts of them can be dry but it can give you an appreciation for weather and topics specifically relating to weather and sailing. Perhaps they can tide you over until you find a course.
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Old 29-02-2008, 08:32   #5
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Mariners weather from Daschew is good. Very in depth and a good explanation of 500 mb and surface pressure systems.
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Old 29-02-2008, 08:37   #6
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USCG Approved Officer in Charge of a Navigational Watch Courses
METEOROLOGY (Operational Level)
http://www.uscg.mil/stcw/training/oicnw-course.pdf
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Old 29-02-2008, 09:00   #7
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I added a link on that other thread GordMay mentioned with the NOAA weather fax/GRIB user's manual, which is decent...

Here's a decent guide put out by NOAA for reading weather fax/GRIB files.
Ocean Prediction Center Text & Charts Radiofacsimile User's Guide:
Ocean Prediction Center User's Guide
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Old 29-02-2008, 09:26   #8
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We did take a number of the Starpath courses including the weather course. However, I can not recommend them as the material comes as Xeroxed pages with many faded spots, dated information, and many mistakes.

We have found more weather sources since then.

I do recommend Chris Parker's book

Coastal and Offshore Weather, the Essential Handbook


Very well written with the description of how weather works easier for me to understand than any other source I've come across.
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