Things are looking better each day now for the furnace dome High shrinking and actually losing grip on the TX Coast region very soon as even NOAA's, NBM output @ https://mag.ncep.noaa.gov, which is typically very conservative with its rainfall projection, is staying more consistent now for some kind of rainfall, daily on its 6-hr periods, the following week of the 21st.
Most likely from deeper atmospheric moisture influxes (PWs 2 in. or greater which I'm seeing more persistently now on latest GFS runs coming ashore over TX coast), in a deeper E/SE flow aloft with those TUTT lows coming closer.
The latest Euro run tonight is actually showing one TUTT moving northwest and coming really close to South TX just off to my south, basically tracking right along the Rio Grande on the 22nd. And the mid/upper-level High center moving significantly further north/east of TX than it's ever done anytime this summer.
I haven't studied up too much yet on the MJO itself, but I am aware of the phases (1-8) and its impact on convective and precip patterns around TX. Though at least down here in the southern region, it doesn't seem to be a large driver of the often tropical (heavy-duty type) summer rains, until later September when the cold fronts get close. Unless.., most of the support aloft for convective development is Non-tropical like upper-level jet stream influence from the north/west.
Also, now that El Niño has finally returned and as long as it doesn't strengthen too fast, I am looking forward to a fairly convectively active upcoming Fall pattern as shortwave troughs/impulses in the subtropical or southern stream jet do tend to track farther south in TX more often during EN phases (as opposed to LA ones), with a generally more northwesterly upper-level flow instead of southwesterly as that tends to cause more of the stronger impulses to eject farther north into the Plains and leaves more of TX, capped for deep convection and drier especially down here which just sucks.
Hence, a 'lowering dew point front' only
Which, even that on its own would actually be 100% welcome down here in STX at this point. Though because of the lower DP, it can actually allow overnight lows to end up lower without any cool air advection at all behind the front.
Heat Index is not an issue at all when you have much lower dew points around 50 F (which is well below normal and very uncommon this time of year around TX coast). Even if actual air temp is 100 F, it can still feel "cooler" in a way because there's essentially no surface air moisture at all, at those DP values to produce a 'discomfort reaction' on the skin.
Though I find those projected 40 DPs right around Houston like that of the this evening's GFS run to be a little too generous (unless the front does actually move off the upper TX coast there). That global model has its own little "excitement" ups and downs with each run. So I prefer the more stable Euro model/ensembles before being convinced, but does show DP dropping into the 50s around there for a short period.