USD index is trading sideways for some time now, ideally unfolding an Elliott wave triangle correction in wave B that is part of a three-wave corrective decline. A triangle is a continuation pattern, which has five legs in a sideways range, so breakout is expected to occur lower after A-B-C-D-E sub-waves; ideally into the same direction as previous wave A. 

At the moment we see price making an intra-day rally, ideally final leg E) of a triangle in B, so be aware of a sharp reversal lower, from around the Fib. ratio of 61.8 (100.0/100.3 zone).

USD Index, 4h

Well, if USD Index is headed lower after that pattern unfolds, then cable can see more upside from current supports. In fact, on a daily chart we see price in a possible higher degree recovery that should be made by three waves. Ideally, this recovery has a missing third leg up, which may resume away from current 50.0 and 61.8% Fibonacci levels, so wave B can be coming to an end.

GBPUSD, daily

An Elliott Wave Triangle Formation

A Triangle is a common 5-wave pattern labelled A-B-C-D-E that moves counter-trend and is corrective in nature. Triangles move within two channel lines drawn from waves A to C, and from waves B to D. A Triangle is either contracting or expanding depending on whether the channel lines are converging or expanding. Triangles are overlapping five wave affairs that subdivide 3-3-3-3-3.

Triangles can occur in wave 4, wave B, wave X position or in some very rare cases also in wave Y of a combination.

An example of a symmetrical triangle in a downtrend:

Trade well.