NWP - Understanding Alaska weather can be a challenge

Using the 500mb Chart at sea

Posted on February 26, 2013 by Fred Pickhardt (http://oceanweatherservices.com/blog1/)

One quick and easy method to estimate where the heavy weather will be found is to look at the 500mb chart.  On NOAA 500 MB charts issued by the Ocean Prediction Center (OPC), the 5640 m height contour is printed in bold.   This is an excellent marker for the southern limit of force 7-8 “westerlies” during the winter season and force 6-7 “westerlies”  during the season in the northern hemisphere.  In general, the worst weather will be found poleward of this line.

NOAA OPC 500MB Analysis 12Z 26 Feb 2013 - Note 564 line in bold

On the 500 mb chart today (above), you can see the 5640 m line (564 on the chart) extending from west to east near 30N latitude over the western North Pacific then extends northeastward across the central North Pacific to near 40-42N latitudes over the eastern North Pacific.  If you look at the wind and wave analysis (below) the position of the 564 line in is marked in yellow.  As you can see, most of the heavy weather lies to the north.

NOAA OPC North Pacific Significant Wave Analysis 00Z 26 Feb 2013 Note 564 line position is marked in yellow

For more insight see “Mariner’s Guide to the 500 Millibar Chart”

For the professional mariner consider buying Ma-Li Chen and Lee S. Chesneau’s book :Heavy Weather Avoidance and Route Design

NOAA National Weather Service

Alaska Marine Weather: http://pafc.arh.noaa.gov/marfcst.php

and low bandwidth links: http://pafc.arh.noaa.gov/pf.php?dir=marine

and radiofax charts links: http://weather.noaa.gov/fax/alaska.shtml

SUGGESTION - learn to use NWS ftpmail to receive latest informations underway over Internet/satellite e-mail.
http://www.nws.noaa.gov/om/marine/internet.htm#pda