Working Cold Fronts from Turks & Caicos to Miami

[teluit]

How do you decide when to leave port for a 48 hour sail from TCI to Georgetown based on the cold fronts that happen all winter?

For instance, is the cold front moving through the area (this week) look normal for wind and sea rotation?
WED E 6kt Sea 8'/9s NE
THU S 6kt Sea 6'/10s NE
FRI SW 13kt Sea 4'/9s ENE
SAT S 8kt Sea 3'/11s NE
SUN NW 7kt Sea 4'/12s N
MON N 5kt Sea 4'/10s NNE
TUE NE 12kt Sea 4'/9s NE
WED NE 13kt Sea 5'/9s NE

All the seas have a north component, can we expect seas to be more E or will they usually be NE in the winter?

[skipmac]

Usually easterly trades in the T&C have a bit of northerly component in the winter. More later in the winter and usually blow harder later in the winter.

When a cold front comes down from our friends up north, IF it makes it as far as the T&C then the winds will shift and clock around the compass to south, west and north, returning to E - NE when the front passes.

Some fronts don't make it that far south and you never see them. Some fronts get that far and stall over you for days and days and you end up with strong north winds until the tropical patterns eventually return. Also some fronts are weaker than others and may just show a reduction the strength of the easterly winds and never shift to the north.

So, I guess I would say there is no "normal" cold front. Just like snowflakes every one is different but you do see some general patterns. However, planning a trip don't depend on the general patterns, try to analyze the specific front you will have to deal with.

Skip

[fareweather]

We've tried figuring out the frontal behaviour and most of the time we seem to be wrong. Our best strategy has been to be ready to go when the wind is blowing in the right direction. Sometime the front will only give you a 12 to 24 hour window so you have to jump on it when it presents itself.

[skipmac]

One pattern I have seen a few times is to watch for a sudden drop in the regular easterly trades. For example, if the trades have been blowing steadily from the ENE at 10-12 and all of a sudden you get a dead calm it's probably because a fairly strong front is almost on you. So don't let an unexpected calm lull you into thinking you have a window.

Been there, done that, got my butt kicked, found a hole and dropped an anchor to wait a little longer.

[Hud3]

On your waves question...

You'll usually see swells coming down from the N or NE, because that's where the big Low's have been churning up the Atlantic. It takes them a few days to get down to the islands. Then you'll have your local wind-waves, which will usually be crossing the N or NE swell, depending on the wind direction and strength. Sometimes you even see three distinct wave trains.

[nautical62]

Barometer bob has this to say about the large front shown:

" COLD FRONT IS EXPECTED TO MOVE FROM THE SE USA TODAY AND REACH THE EAST COAST OF S FLORIDA BY TONIGHT, IT WILL PASS OVER ABACO SOMETIME THURSDAY EVENING AND CONTINUE FURTHER INTO THE CENTRAL BAHAMAS ON FRIDAY , INTO THE SOUTHERN BAHAMAS SATURDAY AND OVER THE TURKS AND CAICOS SUNDAY."

Hopefully all that high pressure following will see a return to the normal trades for you.

The prediction you sent and this don't seem to line up quite right to me, but that's probably due to issues involved in guessing exactly when the front will come through and how strongly.

[teluit]

So, heading West, most of the time, good conditions will be found just after the fronts pass due to (usually) the trades recovering.

So, assuming our East winds are blowing...

What sea state do you wait for at TCI, anything under 6'/8s to 8'/10s? Or do the waves and swell bunch up more in this area than the GFS weather reports?

[skipmac]

Originally Posted by teluit

So, heading West, most of the time, good conditions will be found just after the fronts pass due to (usually) the trades recovering.

So, assuming our East winds are blowing...

What sea state do you wait for at TCI, anything under 6'/8s to 8'/10s? Or do the waves and swell bunch up more in this area than the GFS weather reports?

First question I would emphasize more on "the trades recovering" part than "just after the fronts pass) since the passing part is variable. Some pass through quickly, some pass slowly and the "recovery" takes longer.

As Hud pointed out, the seas locally can be influenced by lows far to the north but in my 2-3 trips through the T&C I didn't notice the seas building in the T&C any worse than the rest of the north Caribbean.

Being a wimpy sort of sailor I would probably wait for a 4-6' sea to leave. Wait for local conditions to look good for your comfort level, check forecasts to make sure another front is not due for the time you need to reach your next stop and head out.

[Joli]

If you look at the grib files you can tell where the lows are and how deep they are. Depending on where you want to go pick how you want to use them. Just make sure you are not sailing with converging surface lows and 500mb lows or plan on getting pasted.

Surface data:



Here is the 500 mb data: What you want to watch out for is the upper level trough over running the surface low.