Gale Psynergy series

Gale, Typhoon, and Hurricane are a series of Jupiter attack Psynergies featured in the Golden Sun series. It is available exclusively to the Ninja class series. Hence, all of the Adepts in your party, except for Mia and Piers in The Lost Age, and Rief and Amiti in Dark Dawn, can use this series of Psynergy.

Like two other Psynergy series' learned by the Ninja classes (the Thunderclap and Fire Bomb series'), there is another series of Psynergy nearly identical to this one: the Whirlwind Psynergy series. In fact, just like Whirlwind, Gale can be used outside of battle with the exact same effect as its counterpart.

Psynergy spells
Gale: “Attack with the wind's might.”: This costs 3 Psynergy Points, has a base power of 18, and has a range of three targets. A large whirlwind with minor electric charges spins through the enemy party. Gale is also a Psynergy that can be used in the field. It is available at level 1.

Typhoon: “Attack with the wind's might.”: This costs 13 Psynergy Points, has a base power of 76, and has a range of five targets. Two large whirlwinds with minor electric charges spin through the enemy party. It is available at level 18.

Hurricane: “Attack with the wind's might.”: This costs 25 Psynergy Points, has a base power of 150, and has a range of five targets. Four large whirlwinds with minor electric charges spin through the enemy party. It is available at level 44.

Analysis
The Gale Psynergy series costs slightly less PP than the Whirlwind series and it's power is slightly less as a result. The Gale series' overall usefulness in battle is limited because it is not even the strongest Jupiter Psynergy that the Ninja classes have; that honor would go to the Thunderclap Psynergy Series. So this series' usefulness is limited to the levels where an Adept has this power but not the latest Thunderclap spell.

Gale as a Utility Psynergy
Gale is a Psynergy that can be used in the field to blow away green bushes, and can activate the Wind Stones in Air's Rock and Shaman Village. It is pretty much completely identical to the Whirlwind Psynergy except in name and the fact it costs fewer PP. This makes it a very helpful alternative to using Whirlwind (less PP), if one of the characters does happen to be in the Ninja class(es). Even if Gale is used to clear the sand at Shaman Village, the cutscreen proceeds as though Sheba uses Whirlwind.

In Dark Dawn, Gale's mechanics are slightly altered. Like Whirlwind, it can now be aimed in any direction, and will travel for a defined distance once aimed. Gale's helpfulness as a Utility Psynergy is rendered somewhat redundant, as Karis has access to Whirlwind regardless of class. However, it does cost less to use than Whirlwind, and it can be used by other Adepts, so it may be useful in situations where conserving Karis' PP is necessary.