Hawaii to mainland, Tailwinds or Headwinds

[McLuvin]

Simple question. Flying from Hawaii to the mainland, will you have a headwind or tailwind. A particularly stubborn acquaintance swears you'll have headwinds going east because of the trade winds. He flew Cessnas in the islands, and this was the case there. I flew this route in Navy C-40s/737 for ten years, most of which as an over water international instructor and know that prevailing westerlies equal winds from the west 99% of the time, but oh well. What do I know? Lol.

I showed him the winds aloft chart, but he swore it showed East winds. I showed him wind barb explanations from Google, but he said they're wrong. Lol. Anyone have a good reference that I can show him, because I'm out of ideas.

[McLuvin]

NE trades are dominant in HI, but I'm talking about at the upper flight levels going across the pond.

[QA1]

Engineer – not Pilot

Today’s chart shows low level winds as the usual NE trades, but at FL300 the wind is a westerly tailwind.

Flying around the islands at relatively low altitude, your acquaintance would be used to the prevailing NE thru E trade winds.

You could highlight the direction of the Jet stream and the effect of westerly winds aloft producing snow in the Sierra Nevada mountains, which invariably comes in from the west.

Good Luck…

[megan]

Light aircraft ferry pilot Louise Sacchi in "Ocean Pilot" says most of the year the west coast to Hawaii route you can count on mild weather and light winds. In winter when the cold Siberian airmass pushes well below 40° they often had to wait many days for the strong westerlies to abate. The trade winds in the northern hemisphere (Hawaii) will be from the northeast, which is what your mate would be referring to at the bug smasher altitudes. Difference in comparison is you're talking high altitude and your mate low.

Hawaii?s Trade Winds And Kona Winds | Hawaii Life (http://www.hawaiilife.com/articles/2012/01/hawaiis-winds/)

[FlightDetent]

www.windyty.com

at 5000 ft, it is wind from east most of the way...

https://ctrlv.cz/shots/2016/08/11/pIxw.png

[hikoushi]

The winds at flight levels over the Eastern Pacific are predominantly westerly. Summer flight times are closer to even going both ways, but still a good half-hour to an hour different a lot of the time. That is, faster flying from Hawaii to the US Mainland.

In the winter time all bets are off. Can recall one HNL-SFO leg that was 3:58 wheels up to wheels down AT MACH .80. Think about it. The return flight the next morning (SFO-HNL) was almost 6 hours. Have seen a 7:02 flight time from SEA-HNL against a nearly 200 knot jet most of the way.

The tradewinds usually die out at the inversion layer, which is usually around 8000 feet near Hawaii most of the year. A common profile is a 20 - 30 knot northeasterly trade from the surface to 8000, calm from 8000 to 12,000, light westerlies till FL250 or so, gradually building into whatever the jet stream has on offer all the way up to FL4XX.

In a light plane you could in fact have a tailwind both ways a lot of the time if you find that inversion. Fly high going west to east, and fly low going east to west.

But bottom line just pull up FlightAware and look at the region. Click on random aircraft gong each way, and look at the groundspeeds and planned flight times. That should correlate with whatever the wind charts are at the same time and provide all the evidence he needs. If that doesn't work then just go drink a beer and forget the whole thing.

[JammedStab]

Your question reminds me about one time going on a flight in a turboprop from Hawaii to Oakland. Yes we had lots of gas. We would have been in the low twenties at the time with multiple step climbs. About one third of the way through, the captain decided that we could make the ultimate destination of Vancouver non-stop. As a former FO on long range jets, he insisted that we were guaranteed to have tailwinds as there were always tailwinds on that route.

So we got a reroute to Vancouver and guess what? We ended up for part of the flight with a slight headwind. Fortunately, the weather was good and it was late at night and we were able to barely keep our very close, nearby alternate, but it wasn't exactly comfortable for several hours and fortunately, the winds didn't increase much.

[pattern_is_full]

It makes a difference where your mainland destination is.

Due east to Mexico or southeast to most of CAm/SAm, easterly or NE/SE-erly headwinds all the way.

Angling north to the USA mainland and thus changing latitude, you'd start getting a reduced headwind, and eventually a westerly tailwind, starting at about Lat. 30N ("Horse Latitudes").

Not much help to SAN, a few minutes bonus enroute to LAX, perhaps nearly half the flight to SFO or SEA.

But - that is the "big picture" average prevailing winds.

If you get an atmospheric high spinning clockwise south of Alaska as in FlightDetent's map above, you could easily end up in JammedStab's situation - more or less constant headwind components to anywhere on the west coast.

[nomorecatering]

In the winter when the strong westerlies are present, how much do the winds die off above FL450 if at all.

Occasionally I have looked at the FL530 chart and often the winds are oposite to the direction at FL450. Is this common?

[hikoushi]

Never been above FL410 on the route (service ceiling of type) but strongest winds are usually around FL390 and don't really change a whole lot up to 410 on the "average" day. By "average" I mean fall / winter / spring without any weird double-hooks in the jetstream or such, just a basic meandering westerly windfield with a jet core here and there between 80 and 120 knots. G-V guys may be able to give some better answers.

Have flown average 5-8 monthly round-trip crossings on those route for the last few years.

[underfire]

Earthwinds is an interesting link, just choose the flightlevel by pressure.
https://earth.nullschool.net/#current/wind/isobaric/250hPa/orthographic=-156.52,21.40,681

Todays winds over HI at 250hPa, about FL350

http://i66.tinypic.com/fv92s3.jpg