Sunday, July 10, 2016

Tropical Cyclone Advisories by Email Request

If you sail in hurricane zones or their broader waters, you might eventually see something like this:


The unforgivable red arrows on this map mark two entirely different things. The horizontal ones show the directions  of motion of the Lows; the down bound ones are associating the text notice with the systems they refer to.

The NWS tells us to see the Advisory, because they know that no map they make, nor any map that anyone makes, will tell us what we need to navigate in the vicinity of the path of these storms. (We do have a cyclone danger area map available by rfax, but it does not layout the winds).  We also know that the grib formatted GFS forecasts for these systems are not dependable, especially in the early days of formation... and we have to interpret "not dependable" as including "very wrong." 

So it is crucial that we know how to get these Advisories underway.... and we can, once again, be very grateful for the wonderful services of saildocs.com, as they will send them to us promptly with an easy request—though we should keep in mind that saildocs is just tapping into the NWS's long established FTPmail program, which is the primary source.

Send an email to query@saildocs.com and in the body of the text have these 6 lines

send met.12
send epac.disc

send epac.disc4
send epac.tech_advis4

send cpac.disc4
send cpac.tech_advis4

Then in a few  minutes you will get 6 emails back, all small text only.

The first is an overview with some TC data covering all of Metarea 12.  The second is the forecasters discussion of what they forecasted.

The data for Metarea 12 is given in 3 separate parts in the text file.
The "4" in the next requests identify the 4th Pacific storm of the season, which is Celia.  Blas is #3, and the next is Darby,  #5.  Change this number in the request to the number of the storm you are following.

The last two requests (Central Pacific) are only needed if you and the storm are west of 140W.

It is worth sending that email now to see what you get. You can cut and paste the above request lines, then remove any signatures that come up.

Here is what you get in the tech_advis report looks like for Celia, storm #4 of the 2016 Eastern Pacific season.  Note that each Advisory has a number so it is easy to keep track of what you have. They are issued every 6h.

____________________________________

WTPZ24 KNHC 100232
TCMEP4

TROPICAL STORM CELIA FORECAST/ADVISORY NUMBER  14
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP042016
0300 UTC SUN JUL 10 2016

THERE ARE NO COASTAL WATCHES OR WARNINGS IN EFFECT.

TROPICAL STORM CENTER LOCATED NEAR 14.5N 118.9W AT 10/0300Z
POSITION ACCURATE WITHIN  20 NM

PRESENT MOVEMENT TOWARD THE WEST OR 275 DEGREES AT  10 KT

ESTIMATED MINIMUM CENTRAL PRESSURE  994 MB
MAX SUSTAINED WINDS  55 KT WITH GUSTS TO  65 KT.
50 KT....... 30NE   0SE   0SW  30NW.
34 KT....... 80NE  60SE  60SW  80NW.
12 FT SEAS..140NE  60SE  60SW 110NW.
WINDS AND SEAS VARY GREATLY IN EACH QUADRANT.  RADII IN NAUTICAL
MILES ARE THE LARGEST RADII EXPECTED ANYWHERE IN THAT QUADRANT.

REPEAT...CENTER LOCATED NEAR 14.5N 118.9W AT 10/0300Z
AT 10/0000Z CENTER WAS LOCATED NEAR 14.4N 118.3W

FORECAST VALID 10/1200Z 14.5N 120.6W
MAX WIND  65 KT...GUSTS  80 KT.
64 KT... 20NE   0SE   0SW  20NW.
50 KT... 40NE  30SE  30SW  40NW.
34 KT...100NE  70SE  70SW 100NW.

FORECAST VALID 11/0000Z 14.6N 123.0W
MAX WIND  75 KT...GUSTS  90 KT.
64 KT... 30NE  20SE  20SW  30NW.
50 KT... 50NE  40SE  40SW  50NW.
34 KT...110NE  80SE  80SW 110NW.

FORECAST VALID 11/1200Z 14.6N 125.3W
MAX WIND  85 KT...GUSTS 105 KT.
64 KT... 35NE  25SE  25SW  35NW.
50 KT... 60NE  50SE  50SW  50NW.
34 KT...120NE 100SE  90SW 120NW.

FORECAST VALID 12/0000Z 15.0N 127.3W
MAX WIND  90 KT...GUSTS 110 KT.
50 KT... 60NE  50SE  50SW  60NW.
34 KT...130NE 100SE  90SW 120NW.

FORECAST VALID 13/0000Z 16.7N 130.7W
MAX WIND  85 KT...GUSTS 105 KT.
50 KT... 60NE  50SE  50SW  60NW.
34 KT...130NE 100SE  90SW 120NW.

EXTENDED OUTLOOK. NOTE...ERRORS FOR TRACK HAVE AVERAGED NEAR 125 NM
ON DAY 4 AND 150 NM ON DAY 5...AND FOR INTENSITY NEAR 15 KT EACH DAY

OUTLOOK VALID 14/0000Z 19.0N 134.5W
MAX WIND  75 KT...GUSTS  90 KT.

OUTLOOK VALID 15/0000Z 21.0N 138.5W
MAX WIND  60 KT...GUSTS  75 KT.

REQUEST FOR 3 HOURLY SHIP REPORTS WITHIN 300 MILES OF 14.5N 118.9W

NEXT ADVISORY AT 10/0900Z

$$
FORECASTER BERG
____________________________________

Our job is to

(1) Plot these positions on the chart and also sketch in the quadrants marking the 34 kt wind zones for the next 2 days or so. 

(2) Plot the extended 34-kt radii using the Mariners 1-2-3 Rule that expands the radii by 100 nmi for each 24h of forecast. If the radius is 20 mile now, it should be extended to 120 nmi for tomorrow at this time, and 220 miles for the next day. 

(3) Then try to maneuver to avoid this extended regions (Mariners 34-kt rule).

Note that the 34kt-wind Rule was designed for ships, so they obviously apply to small craft as well. It is not marking unmanageable conditions—experienced sailors can sail in 34 kt winds—but it is just a way to mark that region wherein the storm can change quickly either in direction or intensity. Staying out of that extended region (Mariners 1-2-3 Rule) is the recommended policy of both the NWS and the US Navy.  We have seen tragic loss of life at sea in recent times because that rule was violated.

______

Here is a video example of applying these Advisories in the echart program Expedition.


______

Deep back up  for all of this are the HF time tic broadcasts that include storm warnings every hour. These can be received by a simple shortwave receiver.

...AND, of course, the NHC has a Twitter feed for the E. Pacific @NHC_Pacific, but i do not know yet how we might use that.  It should be a useful way for fast info.





3 comments:

  1. This post is very relevant as we plan our passage from Bora Bora to Aitutake, Cook Islands. We use saildocs daily. It is valuable service. One question, however. Text forecasts often refer to forecast areas, e.g. Nadi forecast refer to Part 1, Part 2, etc. NWS refers to Metareas and Parts. Are there base maps that show the geographical regions covered by the Metareas and Parts? Are these coordinated by the WMO, or established idiosyncratically by each national forecast office? Having a base map (not the forecast map) to refer to would make interpreting the text forecasts much easier. I have been searching the web sites, but searches for maps always bring up the current forecasts.

    Many thanks,

    Randy Webster
    s/v Velic
    lying Huahine, French Polynesia

    ReplyDelete
  2. The areas are defined here http://www.wmo.int/pages/prog/www/ois/Operational_Information/VolumeD/GMDSS/LimitsOfMetareas.html and each has a sub page with more info. Also valuable for your region is the work of Bob McDavitt at https://metbob.wordpress.com/author/metbob/

    ReplyDelete
  3. Just found a new link to the advisories. Start with http://weather.gov/marine, then choose marine cell phone pages and get to: http://cell.weather.gov/marine/marine.htm then hurricane / central pacific/ and take largest numbers as most recent storms.

    ReplyDelete