Storm is fairly challenging set to play and players tend to develop love and hate relationships with certain powers. So I would suggest that you not lock yourself into a goal build until you've spent a while leveling up and discovered how you feel about certain powers. How much do you use Thunder Clap? How you feel about Tornado? How often you use Snow Storm? Do you run hurricane all the time, and if so does it make short circuit unusable? How do you feel about the endurance crash on the Thunderous Blast? Do you find yourself running out of endurance, because if so, you might want to take an epic pool with an endurance recover power. etc. Obviously if there are powers that you find you aren't using very often, or are using all the time, slots should be adjusted accordingly.
Some initial thoughts on the build to get you started:
Steamy Mist: I would stick some endurance in Steamy Mist since you will want to run that power all the time, and if you can find additional slots I would put some more resistance in there but this is low priority.
Freezing Rain: Enhancing the -defense in freezing rain is not particularly important. The primary concern should be recharge, and consider the achilles' heel proc. This is a decent start, but I would drop the pure defense debuff for the proc or for more recharge. (I would try to find another slot as well).
Short Cirucit: Since you're not going for defense I would slot 5 obliterations in short circuit rather than sirocco's dervish to get the 5% recharge bonus (include the proc), and if you're going to keep a 6th slot, make it the scirocco proc.
Tornado: The stun in Tornado is only 2 seconds, so slotting for stun is generally a waste. It is better to think of tornado as a damage power than a stun power. Regardless you probably want to maximize damage, and if you find that you use it a lot, you will want to maximize recharge as well. Tornado is auto-hit, so accuracy in Tornado is wasted. 4 expedient reinforcements is a good place to start on that and get's you a 6.25% recharge bonus. (see my guide for a more detailed discussion of various proc that can go in this power if you find you're using it a lot)
O2 Boost: Move the Numina Proc to health. putting in O2 boost won't cause it to fire on enemies, and means that you will need to use o2 Boost every 120 seconds to keep the buff active. That will be a real challenge when you are solo.
Lightning Storm: Again, more recharge, 18% is too low. Chance for heal, is wasted. It will only have a chance to fire on you when you summon LS and do nothing after that. If you want to keep your set bonuses, consider turning your accuracy/damages into accuracy/damage/recharges. Lightning Storm has an inherently high accuracy modifier, and things in Freezing Rain will be easy to hit anyway. Accuracy in LS isn't bad thing, but for the most isn't particularly needed.
Thunderous Blast: I run so many toggles on my Storm Defender that having to retoggle them after an endurance crash is a huge pain, and as a result I steer very clear of teir 9s. Some folks love having a massive attack, so find out where you stand on such a power.
Dark Embrace: The psionic resistance is too small to be worthwhile. Get rid of the slot. Also 7.5% status resistance really isn't worth slotting in my opinion. You are better off using tesla cage, tornado, and hurricane to keep from getting mezzed. There are much better ways to use that slot. the 20% status resistance (Resulting in 16% duration reduction (at least those were the values last I checked), can be marginally more useful, and I might consider keeping that one. Again though, endurance in your toggles will be useful.
Power Boost: Is of limited use for a Storm Defender, and although I love Power Build Up, I'm not sure I would bother with Power Boost.
Draggynn on Virtue: lvl 50 Storm/Psi, 1389 badges
Draggynn's Guide to Storm Summoning(Gale-Tornado, updated 6/25/2011)
Avatar by Wassy full reference here
Draggynn,
Thank you very much for looking at my build. I posted it and then saw you have a great Tornado guide which I am going over right now. Ya, I was unsure about the T9. I thought it may be situational, but you're right about all the toggles. I'll probably drop that for something else. Maybe something like an LotG +Rech mule like CJ? I only have 3 in the build right now.
Personally I love Tornado. The KB isn't bothering me because I can let it blow minions around while I focus on Leuts and Bosses. I run with a small grp of friends and KB isn't really sore spot for any of us.
I'm going to rework the build with your suggestions and see what I come up with. Thank you again for your inputs, I'm still reading your guide as well. 
Nurse Tempest
35 Storm/Elec
If you're moving slots around, you should be able to cannibalize the second end reducer in Snow Storm and move it to Steamy Mist - assuming you don't want to just adjust your sets to include more endurance reduction.
Beyond what Draggynn has already mentioned (and loving a second Accuracy in Gale, because I abuse that power to no end), I don't see any immediate improvements.
Hello 'Fenders,
I am working on something new to me. I would like to make a Storm/ defender, and I picked Electricity as my assault power because it adds to the whole flavor of the character I am trying to make. I'm not a min/max type of player really, so enjoyment of my toon is my number one priority. But at the same time, getting the job done be it solo or on teams is also key.
My background is mostly in Controllers and Doms. Fire/Kin and Illy/Rad are my 50 trollers, and my 50 Dom is a Mind/Psi. So what I have built here may be from a "lock 'em down and whittle away" sort of approach, because that's what I know. I also realize I am not a Blaster or Corr so I didn't build myself to stand toe to toe with those classes.
What I am looking for in the end is a Defender who uses these two power sets both solo and in teams. I'd like to solo EB's, but I'm not worried about AV's. My biggest concern may be that I have under-slotted some powers, but that's what I am hoping the community can help me with. Also, I'd like to stay away from purples and HO's if at all possible.
Thank you all in advance for looking this over.
Hero Plan by Mids' Hero Designer 1.942
http://www.cohplanner.com/
Click this DataLink to open the build!
SS-Ele Build 001: Level 46 Magic Defender
Primary Power Set: Storm Summoning
Secondary Power Set: Electrical Blast
Power Pool: Speed
Power Pool: Flight
Power Pool: Leadership
Ancillary Pool: Soul Mastery
Hero Profile:
Level 1: Gale -- Acc-I:50(A)
Level 1: Charged Bolts -- Thundr-Acc/Dmg:50(A), Thundr-Dmg/EndRdx:50(3), Thundr-Acc/Dmg/Rchg:50(7), Thundr-Acc/Dmg/EndRdx:50(25)
Level 2: Lightning Bolt -- Dev'n-Acc/Dmg:50(A), Dev'n-Dmg/EndRdx:50(3), Dev'n-Acc/Dmg/EndRdx/Rchg:50(5), EnManip-Stun%:20(9)
Level 4: Snow Storm -- EndRdx-I:50(A), EndRdx-I:50(5)
Level 6: Steamy Mist -- LkGmblr-Rchg+:50(A), LkGmblr-Def:50(7), S'fstPrt-ResDam/Def+:30(17), S'fstPrt-ResKB:30(17)
Level 8: Freezing Rain -- LdyGrey-DefDeb:50(A), LdyGrey-DefDeb/Rchg/EndRdx:50(9), LdyGrey-Rchg/EndRdx:50(39), LdyGrey-DefDeb/Rchg:50(39)
Level 10: Short Circuit -- Sciroc-Acc/Dmg:50(A), Sciroc-Dmg/EndRdx:50(11), Sciroc-Dmg/Rchg:50(11), Sciroc-Acc/Rchg:50(13), Sciroc-Acc/Dmg/EndRdx:50(34), Sciroc-Dam%:50(34)
Level 12: Hurricane -- DarkWD-ToHitdeb/Rchg/EndRdx:50(A), DarkWD-Rchg/EndRdx:50(13), DarkWD-ToHitDeb/EndRdx:50(43), DarkWD-ToHitDeb/Rchg:50(45)
Level 14: Hasten -- RechRdx-I:50(A), RechRdx-I:50(15), RechRdx-I:50(15)
Level 16: Hover -- LkGmblr-Rchg+:50(A)
Level 18: Thunder Clap -- Stpfy-Acc/Rchg:50(A), Stpfy-EndRdx/Stun:50(19), Stpfy-Acc/EndRdx:50(19), Stpfy-Stun/Rng:50(23), Stpfy-Acc/Stun/Rchg:50(29)
Level 20: Zapp -- Mantic-Acc/Dmg:50(A), Mantic-Dmg/EndRdx:50(21), Mantic-Acc/ActRdx/Rng:50(21), Mantic-Dmg/ActRdx/Rchg:50(23), Mantic-Dmg/EndRdx/Rchg:50(29)
Level 22: Maneuvers -- LkGmblr-Rchg+:50(A)
Level 24: Aim -- GSFC-Build%:50(A), GSFC-ToHit/Rchg:50(25), GSFC-ToHit/Rchg/EndRdx:50(37), GSFC-Rchg/EndRdx:50(40)
Level 26: Tornado -- Stpfy-Acc/Rchg:50(A), Stpfy-EndRdx/Stun:50(27), Stpfy-Acc/EndRdx:50(27), Stpfy-Stun/Rng:50(31), Stpfy-Acc/Stun/Rchg:50(31)
Level 28: Tesla Cage -- BasGaze-Acc/Hold:30(A), BasGaze-Rchg/Hold:30(40), BasGaze-Acc/EndRdx/Rchg/Hold:30(42), BasGaze-EndRdx/Rchg/Hold:30(42)
Level 30: O2 Boost -- Numna-Heal:50(A), Numna-Heal/Rchg:50(31), Numna-Regen/Rcvry+:50(34), Numna-Heal/EndRdx/Rchg:50(48)
Level 32: Lightning Storm -- Dev'n-Acc/Dmg:50(A), Dev'n-Hold%:50(33), Thundr-Acc/Dmg:50(33), Thundr-Dmg/EndRdx:50(33), Entrpc-Dmg/EndRdx/Rchg:35(36), Entrpc-Heal%:35(36)
Level 35: Voltaic Sentinel -- ExRmnt-Acc/Rchg:30(A), ExRmnt-Acc/Dmg:30(36), ExRmnt-Acc/Dmg/Rchg:30(37), ExRmnt-EndRdx/Dmg/Rchg:30(37), Dmg-I:50(46)
Level 38: Thunderous Blast -- Posi-Acc/Dmg:50(A), EnManip-Stun%:20(39), Det'tn-Acc/Dmg:50(43), Det'tn-Dmg/Rchg:50(43)
Level 41: Soul Drain -- Oblit-Acc/Dmg/Rchg:50(A), Sciroc-Acc/Rchg:50(42), Sciroc-Acc/Dmg:50(48)
Level 44: Dark Embrace -- Aegis-ResDam:50(A), Aegis-Psi/Status:50(45), ImpSkn-Status:30(45), ImpArm-ResPsi:40(46)
Level 47: Power Boost -- RechRdx-I:50(A), RechRdx-I:50(48)
Level 49: Soul Storm -- BasGaze-Acc/Hold:30(A), BasGaze-Rchg/Hold:30(50), BasGaze-EndRdx/Rchg/Hold:30(50), BasGaze-Acc/EndRdx/Rchg/Hold:30(50)
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Level 1: Brawl -- Acc-I:50(A)
Level 1: Sprint -- Clrty-Stlth:50(A)
Level 1: Vigilance
Level 2: Rest -- RechRdx-I:50(A)
Level 2: Swift -- Run-I:50(A)
Level 2: Health -- Mrcl-Rcvry+:40(A)
Level 2: Hurdle -- Jump-I:50(A)
Level 2: Stamina -- P'Shift-End%:50(A), P'Shift-EndMod:50(40)
Level 4: Ninja Run
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Set Bonus Totals: