Irma, what makes it turn north??

[Watchfoxheadexplodes]

Been west north west and now due west just what pulls it north?

I have yet to hear anyone note a possibility of it staying on the northern Cuban coast splitting the keys and moving west into the gulf.

[Roland99]

1. Per NHC

The initial motion is now 285/10. Irma is moving along the
southwestern side of the subtropical ridge, which is about to
weaken due to a mid- to upper-level trough moving into the
southeastern United States. The track guidance is in good
agreement that Irma should continue west-northwestward for the next
12-24 h, followed by a turn toward the north-northwest that would
take the center parallel to the west coast of the Florida
peninsula. Later in the forecast period, the cyclone should turn
northwestward and eventually stall as it interacts with the
aforementioned trough.

[BigmanPigman]

2. I said yesterday that I think it could move further west into the Gulf and go north

toward the panhandle. It seems to continue to do this but I don't know what the highs and lows are doing in that area Hurricanes are so unpredictable and no one should ever blame the forecasters for unnecessary evacuations.

[Loki Liesmith]

3. Pressure differentials

[nmgaucho]

4. Explanation given by a meterologist

"A dip in the Jet, will pick it up like someone floating on an inner tube in the Guadalupe is in a cutoff eddy then gets caught back in the current and starts moving again. Irma is riding the Easterly trades, which is a summer occurrence, westward. Once they get far enough west, the Jet and continental steering currents over or just off the land mass take over and generally blow west to east.

When and where a storm turns north depends on a lot of things, but essentially how those things arrange themselves and line up to push storms.

Sad thing is that a week ago, a trough of low pressure was hanging out on the SE coast. If Irma came by then, she'd have turned up and back out to the Atlantic. But the Atlantic subtropical high pushed it back (westward), the trough retreated, and the Jet dipped south and west to where its strongest winds are now (SW of Florida, up through the state). The Jet is flowing along the western edge of that high, where the current is now."

[Watchfoxheadexplodes]

5. Thanks all

Made me wonder when I heard a weather channel person say...

"Remember weather is not precise "

[Igel]

7. Weather is a hard problem.

There are a lot of things that affect it, and a lot of things that affect those. Even if we had all the math right to be able to be really precise and accurate, we'd probably lack (a) inputs, the data necessary for doing the math and (b) computational power to run the scenarios.

All three have improved in the last century, by a large amount.

[beachbum bob]

6. call weather forecast models and the EGRI model has been pretty damn consistent

for past 4 days on Irma tracking to the west side/west half of Florida. Computers and data can and will give accurate forecasts, especially the European model

[Igel]

8. When we had actual weather maps it was easier to follow.

They'd show high pressure areas and pressure areas, they'd show ridges and troughs. It was easier to follow and we didn't have accurate but useless things like "steering currents" as the only thing to hang understanding on.

So much so that one person was able to say that the "steering currents" (which in the case of Harvey was mostly just a high pressure system, but high pressure in one place + low pressure in another will give you "current&quot were breaking down because of "global warming." Instead of, "Oh, the high pressure system is weakening because, well, that's what all high pressure systems have eventually done."

[RainCaster]

9. Because Bengahzi!! nt

[SharonClark]

10. It's all over the weather sites and tv weather