The phrase "a significant challenge however" is correct and usable in written English.
It can be used to introduce a contrasting point or to highlight a difficulty that arises in a discussion or argument.
Example: "The project was progressing well; a significant challenge, however, arose when we encountered unexpected technical issues."
Alternatives: "a considerable obstacle nonetheless" or "a major difficulty, on the other hand".
Maintaining this newfound momentum through 2018 presents a significant challenge, however.
A significant challenge, however, has been transferring knowledge about using environmentally sustainable farming techniques to produce higher-value crops to the farmers themselves.
Designing chemical reagents for modern neuroscience remains a significant challenge, however, since the brain is the most complex and least assessible organ in the body.
These supplements face a significant challenge, however: it is very difficult to spell out the distinction between autonomy-conferring reasoning and autonomy-undermining reasoning without implicitly appealing to the very phenomenon one is trying to explain.
Adherence and retention in care for HIV/AIDS patients on ART remained a significant challenge, however, with an average lost to follow-up rate at 12 months of 27% at HIV treatment centers across the country [ 48].
Tuesday brings another significant challenge, however, away to old rivals Fiorentina.
Teens who face such significant challenges, however, demonstrate an enormous amount of resourcefulness.
It encountered significant challenges, however, and this study was designed to explore and document the challenges and constraints in the first 6 months of implementation.
Some of the 20 authors under 40 who were named might have been expected to provide a significant challenge for the Booker; however, the well-known figures selected (among them Adam Foulds, Sarah Hall, Kamila Shamsie, and Zadie Smith) did not produce new novels, and newcomers, such as Taiye Selasi, evidently failed to impress Macfarlane's panel.
The low temperature nitrogen graphite system, being relatively simple, presents, however, a significant challenge in accurate description of the experimental adsorption isotherm at 77 K, which is widely used as a reference system in characterization of porous carbon materials.
However, a significant challenge of this model will be defining and measuring 'outcomes', especially across people with vastly different needs, such as those who require help with housework versus those who need to be given medication.
