Reliance on GRIB Files

[Paul L]

if you have good local knowledge too

Just the thing you don't have as a cruiser. Most cruisers are making new passages to new locations.

[belizesailor]

Originally Posted by Paul L

Just the thing you don't have as a cruiser. Most cruisers are making new passages to new locations.

Often true, but some of us move more slowly than others or at least spend extended time within given regions. Me, Ive been mostly cruising the W Carib since 2005...wouldnt want to miss anything! [emoji16]

[belizesailor]

Case in point of over reliance of GRIBs: Friend of mine is in San Andreas, Colombia working their way back to Belize. They glanced at GRIBs of prevailing winds only and decided today was a good day to jump...oops...if thay had looked synoptic charts they would have seen the tropical wave bearing down on them (shown at 80W in attached chart).

The result:

"
Tried to leave first light today. Coast guard caught us up after 2 hours and told us to return. Then we got a 40 knot squall overhead and wave after wave of them. Made anchoring interesting but all went well. Now beer and football. Looking at the net yesterday it just said 15-20 of sustained and isolated thunderstorms. Nothing of *40 knotters.*

What’s your thoughts?
"

[estarzinger]

current gfs . . . . if you care to look, the wave is clearly there . . . .

[jackdale]

Originally Posted by estarzinger

current gfs . . . . if you care to look, the wave is clearly there . . . .

Attachment 172979

What parameters did you use when downloading the grib? Wind? Pressure? Precipitation?

[estarzinger]

Originally Posted by jackdale

What parameters did you use when downloading the grib? Wind? Pressure? Precipitation?

Precipitation is usually the easiest factor to see tropical features.

Pressure deltas are usually (too) low (except in hurricanes)

there are other factors which will also identify tropical features, but not displayed by some grib viewers

[wingssail]

The addition of WeFax or anything they could get on Iridium Go would probably not have made a huge difference in the outcome of the Kelaerin case. They were well into a long passage, in fact close to the end of it, and the weather caught them with nowhere to escape. Any WeFax, Grib, or ocean forecasts they got before they left would have been long obsolete, and once out there they pretty much had to take what they got.

In this case it is likely that a deep cyclonic storm approached the Pacific coast from the southwest of them, moving northeast to the east of them, and they got hit by the northerly winds on the west side of it. GRIBs will give the big picture and tell this story as well as a Wefax chart or SSB voice weather broadcasts.

See the attached jpg of today's July 7, 2018 situation. This is from a 14kb Grib file, displayed on OpenCPN. It covers a 1000 nm x 1000 nm area. The colors represent Waves. The storm which hit Kelaerin would have shown on grib files with at least 24 hours advance notice, but so what? What would they do except be prepared for bad weather, which they were not (chaos of loose items in the cabin).

On ocean crossings we have NOTHING on deck except a small dodger. No Life raft, no dingy, no jerry cans. NOTHING (except a small can of dingy gas). Everything else is secured below. The life raft is in it's own small lazerette. Every thing is well secured. No books can fly, no laundry bags, no food bags or boxes, no equipment can get loose. But we still figure a big wave could do a lot of damage.

When we set out on an ocean crossing we get all available forecasts before we leave and pick up grib files and WeFax as we go (via SSB). We try to be prepared for anything including being rolled. But in the case or a huge wave, there is little you can do.

Going out on the ocean, particularly a North Pacific crossing is playing for keeps. You go and you takes your chances. They are lucky they were close enough to be rescued.