Q:

Finding the position of a succession of blanks in large data set - EXCEL

I'm going through a large amount meteorological data through excel in order to do some climatic modelling on a building. As a lot of data out there, there are some missing chunks. 
So my first concern was to figure out the largest succession of blanks in my data I have done this by using =MAX(FREQUENCY(IF(T5:T101893="",ROW(T5:T101893)),IF(T5:T101893<>"",ROW(T5:T101893)))).
So this returns the maximum succession of blanks in a given column. In my case the maximum succession of blank cells was 28.
What I would like to figure out is where in the 101,893 lines is that succession of 28 blanks.
I've tried scouring the internet without much success. I've also tried using the match and index functions by trying to match an array of 28 blanks (which obviously didn't work) or an array of 28 1s (I made an extra column next to my data with =if(T5="",1,0)), so it could match my array to the one in that column and return its position. It returned an incorrect position.

A:

In the following simplified example below, the helper column tracks the 'run' of blanks using:
=IF(AND(ISBLANK(A1),ISBLANK(A2)),B1+1,1)

Which you copy down to the last row of data. You can then use this formula to get the row of the max of the 'longest' run:
=MATCH(MAX(B2:B25),B2:B25)+1

In that formula, I've use +1 (at the end) because there is 1 row with headers. In your sheet it needs to be +x where x is the number of headers and blank rows etc at the top of your sheet. 
Screenshot:

