So, let's take a minute to talk about romance. Romance novels are almost always universally terrible. Twilight, the most recent romance phenomina, is an objectively bad novel. Not because of sparkly vampires or other absurdities contained within, but because adverbs sprout like weeds, the writing is wooden at best and the author spends too much time telling us about things. We're told a lot about how pretty Edward is, but we're not to my knowledge, ever shown his grooming habits. This is because most romance is written with much the same mindset as porn is created with. Get to the climax quickly, and then heap on more and more until you've filled your allotted word or time limit and then check out quickly as possible with the profits in hand. There's the same mindless desire and instant fulfillment. There's also the same general level of production values. There's a reason these things are called porn for women.
I'm afraid you don't have much future as a romance writer Voidchicken. You would be torn to shreds for spending far too much time developing the character people are supposed to project onto before getting to the 'good stuff.' I mean, the third and final story? Get serious.
For anyone who doesn't have the required appetite for the Smoopy-doo and Sweetums saccharine romance angle, romance is usually a distraction and generally not well written. How many times have you been to a movie and there's a love interest angle that has very little development but they ride off happily ever after anyways because romance is what appeals to females ages 11 and up? Too many, I imagine.
That said, there is such thing a thing as good romance. Usually it is the result of clear character development and phrased in terms that are outside the usual romance tropes. There's a scene in the movie 'In a lonesome place' that describes good romance writing perfectly. The main character, played by Humphry Bogart, is making breakfast for his distressed girlfriend. ' A good love scene should be about something else besides love. For instance, this one. Me fixing grapefruit. You sitting over there, dopey, half-asleep. Anyone looking at us could tell we're in love.'
(Of course, the scene is actually about him trying to convince himself they're still in love while she's beginning to grow afraid of him. Which is the ultimate example of what he's trying to illustrate. Don't make the subtext the main text.)
This is where Stormy Nights 3 comes in to the picture. This is to a large degree a romance story, but it doesn't read like one. The first overt hint of it we get is Spyglass giving her a flower, but he does so while buying flowers for his mothers grave. While this might be mildly off putting in real life, depending on context, in the story itself it makes a perfect excuse to covertly introduce the romance angle. The weakest part of this scene is the blush. An overt line about a smile would've probably sufficed.
The story is full of writing like this, so I don't think I need to call out any more examples, for the most part, the romance is both believable and covert enough at first as to not to get annoying. It develops naturally, and doesn't feel forced. This is good writing.
One scene I do want to point out though:
Stormy looked at her sandy legs and dirty robe. “You call this covered? This is nothing! I grew up in the desert! I got sand in so many places as a filly I had to make up words for the parts of my body they got in. And this! This sand is cool and wet. The desert was HOT. I had to lug water around everywhere to keep myself from getting heatstroke or something.”
Compare this to:"I don't like sand. It's coarse and rough and irritating and it gets everywhere. Not like here. Here everything is soft and smooth."
One of these things is not like the other.
Now, onto quibbles.
Here is the one thing I didn't like about this story. Romance as redemption. It's a common theme that crops up in literature, and it's clear you try to sidestep it by making Celestia the ultimate source of redemption, (never mind that the character never is in severe need of it beyond her own delusions). That said, I can't help but feeling there's an undercurrent of this running through the story. I'm not sure what you could do to remove it, but it's a pet peeve of mine.
This passage in particular felt rather awkward to me:
With the high sun pounding on the water, the evaporation potential became overwhelming. There was the possibility of some very severe weather in that ocean. And no pegasi around to exploit it. Such wasted potential.
For one, it's a little too dry. You say evaporation potential and I begin to feel like I'm reading a science textbook There's also the repeated 'potential.' Repetition is good for emphasis, but here it just feels awkward, like you couldn't find proper wording. I understand you were trying to express a complex idea and falling on more concise language to do so, but that's no good for the sense of longing or regret you're trying to evoke here. Some more actiony verbs would have given it a lot more flow at the very least. Here's how I might write something like this in my typical purple style:
The sun's heat bore down heavy on the bay, and the water evaporated, seeping into the air. Stormy could feel the moisture in the air all around her, sharp and ready and full of potential, like a static charge. Even a single pegasus could create massive, grand storms of endless water with this bountiful wealth. None ever would.
Another thing, there's a clear subtext going on with the Sherlock Holmes reference, but I didn't really get it? Care to explain? I'm tired and cranky.
Overall this was a good conclusion to the series. Things come full circle with Strawberry. The characters are well developed although I felt like Stormy could have used a little toning down on the emoness meter in this one. More pancakes, less sobbing.
What can I say? It was well written and it made me smile.