Happy Father's Day Weekend and happy Summer!  We just had a record wet Spring and now the pattern is changing again.  With the remnants of Tropical Storm Bill long gone the old summer ridge has a chance to take hold and more than likely will dominate our weather for the next few months. The summer ridge refers to an upper level high pressure system that usually forms in the summertime and wobbles around back and fourth across Oklahoma during the summer months. 

Here's a look at what the upper level Summer ridge looks like on a weather map.  This is the forecast for next week from one of our medium range forecast models.  The circle over Oklahoma is the center of the high pressure system Monday afternoon.

Sometimes the summer heat dome is right over Oklahoma and other times it shifts west or even east but bottom line our sensible weather is more or less controlled by this summer heat dome as it wobbles around like a weeble all summer long.  And just like a weeble it wobbles but never really falls down until late September when the jet stream dives south again and we call that Fall.  

So expect hot weather to take hold and persist for a while.  Rain chances won't be completely zero with the best rain chances occurring when the center of the heat dome wobbles or shifts west (northwest flow) or shifts east (tropical flow).  In those cases our rain chances will go up but otherwise as long as the high pressure ridge is nearby our weather won't change all that much.

The one thing different about this Summer is what happened this past Spring.  All that rain has broken the drought and placed significant moisture back into the soil.  What does this mean for our Summer?  Two things, #1 the moisture in the ground will be evaporating into the air and since the evaporating process is a cooling process actual air temps might not be that hot this summer.  #2 with all that moisture being evaporated back into the atmosphere the humidity and heat index temps could be out of control!  It's a trade off.

But what is the heat index?  The heat index is NOT a real temperature.  It's an apparent temperature or a feels like temp.  Example:  if the air temp is 100 and the heat index is 212 water will not boil!  The heat index is an estimation of what it feels like with the actual air temp and the humidity combined but not a real temp.

Here's the heat index chart. If the temp remains constant and the humidity goes up the feels like temp will go up accordingly.

Notice, if you look at this chart above, if the actual air temp is 98 degrees and the humidity is around 50% the feels like temp or heat index is a whopping 113 degrees!  So the humidity does matter.  We deal with this every Summer in Oklahoma but this Summer with so much moisture evaporating back into the air the heat index might be a bigger factor compared to the actual temp. Hence the saying, "it's not the heat, it's the humidity" absolutely applies this year!

Did you ever wonder how we calculate the heat index.  Check this out, this is the heat index equation.  So you say you want to be a meteorologist do ya?

1. HI = -42.379 + 2.04901523T + 10.14333127R - 0.22475541TR - 6.83783x10-3T2 - 5.481717x10-2R2 + 1.22874x10-3T2R + 8.5282x10-4TR2 - 1.99x10-6T2R2
   
   where T = ambient dry bulb temperature (°F)
   R = relative humidity (integer percentage) 

I made this calculation every night during the Summer right before showtime for 27 years!  Just kidding.  Thankfully, we have computers!

But what the heck does all of this really mean to you and me?

As I stated earlier evaporation is a cooling process.  There's an equation for that too but I'll skip that this go around.  

If you're outside playing in Summer heat your body is going to perspire, sweat.  You body sweats as a natural cooling mechanism.  As the moisture or sweat on your skin evaporates into the surrounding air it cools your skin off.  So sweating is how your body cools off.  Makes sense, right.

Here's the important part...If the air surrounding your body is humid then it takes longer for your sweat to evaporate into that air and your body can't cool down.  If the air is dry then your sweat evaporates fast and you cool off.  This is why you feel hotter when it's humid outside!  Your body has a harder time cooling off.

So the heat index is an attempt to measure what it might feel like when it's hot on humid days when your body can't cool off.  On dry days there is no heat index but as the humidity goes up so does the inability of your body to cool down so the heat index rises.

There ya go.  You now know more than the average tv weathercaster.

Have a great weekend and try not to make dad sweat too much on Sunday.

Here's the latest...New data tonight has the center of Tropical Depression Bill moving on a path slower and slightly more west than earlier predictions.  Main threats flash flooding rains across central and eastern Oklahoma Wednesday through Thursday.  A few isolated small brief tornadoes not out of the question.

The remnants of Tropical Storm Bill heading on a northward track early this Wednesday morning that will bring flash flooding rains to central and eastern Oklahoma Wednesday through Thursday before slowly moving northeast into Arkansas and Missouri Friday.

This has the potential to be a serious and life threatening flooding situation depending on the exact track and speed of the tropical system.

The heaviest rainfall and thus the most dangerous flooding will occur along and to the east of the exact track of the center of the tropical system.

Here's the latest track from the National Hurricane Center.

This track is not set in stone and in fact some new data Tuesday night is showing a slightly more westward and slower track.

The graphic posted above is the latest information available as I write this from the NWS OKC. Check the NWS for all the very latest updates during Wednesday.

Below I've posted some of the new data coming in late Tuesday night.  I'm tracking the upper level reflection of the weakening tropical cyclone as it moves north and then northeast across southeastern and eastern Oklahoma Wednesday and Thursday.  You can see the system is predicted to track near or just east of a Ardmore to OKC to Tulsa line.

Here's Wednesday evening moving slowly north across the red River.

Here's Thursday morning just southeast of OKC.

Here's it is moving just southeast of Tulsa Thursday evening.

Here's a real interesting low level wind forecast showing the circulation of the remnants of Bill just southeast of OKC Thursday morning.  Tropical systems weaken rapidly in terms of wind as they move over land so the wind speeds are generally going to be 20-30 mph and gusty around the center as it moves up into central / eastern Oklahoma.  Nothing to write home about but it's very interesting to see the remnants of Bill maintain it's structure this far inland!  Sometimes we get small brief tornadoes within the northeastern quadrant of these weakening land falling tropical systems and it's not out of the question this go around.  Although, the main threat is going to be flash flooding rains along and east of the track I can't totally rule out a brief small tornado or two.

Here's the rainfall totals through Thursday predicted from one our high resolution forecast models. I'm expecting 3-6 inches of rain possible along and east of a Duncan to OKC to Stillwater to Bartlesville line with higher amounts likely!  This all depends on the exact track of the center of the tropical system and any wobble east or west will impact where the heaviest rain occurs.  There will be a huge contrast / cutoff on the northwest edge of the rain shield.  It's going to be very tricky to forecast exactly where the northwestern edge of the rain will set up but expect a major difference in rainfall totals over a very short distance on the northwestern edge of the storm.  The northwest edge will be setting up near a Duncan to OKC to Stillwater to Bartlesville line so in other words the heavy rain is not a done deal in these cities.  However, areas further east and southeast of OKC and Tulsa are in the bullseye or the sweet spot.  Portions of southeastern and eastern Oklahoma could receive rainfall amounts in excess of 6 inches!  Obviously, this is a very serious flooding threat and everyone should be watching the weather extremely closely Wednesday through Thursday!  Looks like western Oklahoma is missing out for sure.

As predicted upper high pressure ridge taking over rest of this week and through the weekend. What does this mean?  No rain with mostly clear skies, temps slowly warming 80s to mid 90s and plenty of humidity.  I guess the southern plains storm season is ending about two weeks early this year.  We'll have more thunderstorms next week as ridge breaks down and we go back to northwest flow but as far as organized high end severe / tornado threat we're probably done. Don't know where you live but at my place far NW OKC I didn't have any severe weather this season only lots of rain.

The pic I posted above shows the upper level weather pattern Friday afternoon and you can clearly see the upper ridge of high pressure building over Oklahoma.  It's not a heat wave high but almost zero rain chances through this up coming weekend with warm muggy weather.  Thanks to all the rain / wet soil air temps slow to rise but still we'll climb into the 90s in the west and northwest, near 90 in OKC and Tulsa and did I say the word humidity!!!

This next pic above is valid for Saturday afternoon indicating the high firmly in place across Oklahoma.  It's blocking the trough to the west and keeping any tropical disturbances at bay for now.  The weekend will be very warm and muggy with little if any chance for significant rainfall.

With the high pressure ridge over Oklahoma and Texas the rainfall forecast through next Monday shows a "ring of fire" pattern.  No rain over Oklahoma and Texas with showers and thunderstorms around the outer edges of the high resulting in the "ring of fire" presentation.  Well, almost a complete ring except to the south along the gulf coast it's somewhat open.

However, the pattern changes again early next week.  The high pressure ridge breaks down and we go back into west northwest flow aloft.  This will shove a front south into Oklahoma Monday night / Tuesday of next week with an increasing chance for showers and t'storms.  Also, that tropical disturbance in the Pacific could get pulled north into the rockies around the west side of the ridge and then shift east around the north side of the ridge over the southern plains possibly enhancing rainfall potential next week.  But it's unlikely that what's ever left over from the tropical system as it comes up through the rockies and then east into the plains has any organization left over.  Honestly, I doubt the tropical system will have any big influence on our weather.  Time will tell.

Only two of these kids are mine but the boys of summer are gathering.  I'll be spending the next few months playing basketball / baseball with the children of the hood with probably less and less weather updates.  Ride like the wind to be free again....

Front coming in overnight through Saturday morning with scattered brief showers and thunderstorms.  Rain chances will be ending from northwest to southeast as the front passes your location.  Front approaching northern Oklahoma right now as I write this and reaches OKC & Tulsa before sunrise and then pushes into southeastern Oklahoma by Saturday afternoon.

Here's a radar grab of the thin broken line of showers and t'storms developing along cold front as it comes southward out of Kansas into northern Oklahoma.

Behind the front you can expect very nice weather for the weekend with dry conditions!  The dry weather will last all of next week and possibly beyond as an upper ridge of high pressure builds in. Temps will gradually rise through the 80s and we will make a run at 90 by the end of next week. Although all this wet ground / saturated soil will help keep temps in check the humidity will be out of control.

And just like that Friday into early Saturday morning is the last chance for significant widespread rainfall in what could be a week or two.  Looking at all the weather maps the last few days it's becoming clear, with high confidence, that a dry period is on the way starting Saturday afternoon. OKC and Tulsa should go at least a week and maybe more without rain.  Let's take a look at the situation.

The pattern actually starts changing Friday (pictured above) as the southwest flow aloft shifts to a west northwest flow as a ridge of high pressure aloft builds out west.  There's a small disturbance embedded in the west northwest flow that tracks east southeast across Oklahoma and this pushes a cold front across Oklahoma Friday night into Saturday morning.  There's a decent chance for thunderstorms along the front as it moves southeast across Oklahoma Friday into Saturday morning. 

Checkout the map posted above showing the upper flow by Saturday afternoon.  You can see the small upper disturbance is moving east of Oklahoma and the upper ridge is moving in.  Say goodbye to the rain for a while if this forecast holds true.

Here's the Sunday forecast.  The upper disturbance is over Arkansas and moving slowly southeast.  It will more than likely stall out along the gulf coast and get cut off from the main flow as the upper ridge builds into Oklahoma.

Yep, just as I suspected.  Here's a look at the Monday upper level weather pattern.  The small upper disturbance is cutting off from the flow over the gulf coast states and the upper ridge over Mexico and New Mexico is building into Oklahoma. The rain chances might not be zero in this pattern but this is a MAJOR change in the over all pattern and a much drier one!  I'm not saying this is the summer death ridge, way too early for that, just recognizing a pattern change that should end the deluge and bring dry weather to Oklahoma for at least a week, maybe more. Eventually, that upper trough out west moves east and breaks down the ridge and it rains again. So the storm season isn't over yet but a drier, calmer week or more on the way.

Here's one of our hi res computer models showing the cold front entering northwestern Oklahoma Friday afternoon.  Note the thunderstorms forming on the front!

The front reaches OKC / Tulsa area around midnight Friday night / wee hours Saturday morning and the computer shows showers and thunderstorms with it.

By 7am Saturday morning the front is moving across southeastern Oklahoma with showers and thunderstorms.  After the front moves across your location the rain is done for a while.

Now, will this prediction actually happen?  I don't know for sure, that's why we play the game...

More showers and thunderstorms in the forecast today, tonight, Friday into Saturday morning.  I think the pattern will start to dry out some Saturday afternoon and Sunday.  Until then the threat for flash flooding and some severe weather will continue!

Here's the severe weather risk for today from the National Weather Service in OKC.  Main threats heavy rain, large hail and damaging winds.  The tornado threat is low but not zero. 

The showers and thunderstorms from last night and early this morning stabilized the atmosphere limiting the atmospheric instability and therefore limiting the severe weather risk somewhat this afternoon.  So the big question is, will the atmosphere recover enough for more severe weather and flash flooding tonight.  Hard to say but already the next wave of thunderstorms is developing in the Texas Panhandle and moving east northeast toward southwestern Oklahoma.  There's a decent chance that most of this next round of thunderstorms near Lubbock will track to our south across North Texas but still too early to call exactly how this will play out tonight.

Here's my latest weather video blog on what to expect...

Here's the new updated Slight Risk for tonight and through the early morning hours.  Heavy to severe thunderstorms in the western high plains slowly moving east toward Oklahoma.  There's a chance the t'storms weaken after sunset as they move into the main body of Oklahoma but there's also a chance they form into one or more clusters and continue strong to severe all night.  Main threats large hail and damaging winds early on but then transitioning into a flash flood threat as we go through the wee hours Thursday morning.

Here's a weather update for northeastern Oklahoma and the Tulsa area.  This is NOT a Live update.  

Scattered strong to severe thunderstorms are possible today in Oklahoma.  There's a slight risk for severe weather with the main threats large hail, damaging winds, locally heavy rainfall and dangerous lightning. The tornado threat is relatively low but not zero.  Any thunderstorms that can get established and create their own enhanced shear environment can produce isolated tornadoes.

Here's the brand new Day 1 forecast for severe weather from the Severe Storms Prediction Center.  This is valid for Tuesday afternoon / evening.   But this forecast is unclear and this risk outline will probably change 6 times between now and 3pm.

This is NOT a live weather report.  The threat for severe weather and flash flooding is shifting east into eastern Oklahoma and Arkansas for the rest of this afternoon / evening.  

Watch the weather this afternoon / evening.  Severe thunderstorms possible with large hail, damaging winds, tornadoes and flash flooding especially south and southeast of OKC!

Latest weather update with new Tornado Watch!

Another round of showers and thunderstorms with potential heavy rainfall and severe weather today!

Brand new Flash Flood Watch issued for today.  Small compact upper level disturbance located over the Texas Panhandle around Noon today is forecast to track from Texas into central and eastern Oklahoma. Grounds obviously totally saturated so any thunderstorms have the potential to produce flooding rains!

Also, the potential for severe weather.  There's a Moderate Risk for severe weather across far southeastern OK and North Texas today.  The Slight Risk comes up into the OKC Metro area with a Marginal Risk for northwestern Oklahoma.  Main threat large hail, damaging winds.  However, there is a tornado threat especially in the Moderate Risk zone but tornadoes can't be ruled out into central Oklahoma as well.

Please watch the weather very closely this afternoon / evening.  Quite frankly this could be a dangerous weather situation setting up with dangerous flash flooding and a tornado threat.  Not exactly sure how this is going to play out this afternoon so watch the sky today!  If you are out playing on this Memorial Day make sure you have a way to stay up to date on the latest weather warnings.  It's crucial that you take action if severe weather is heading your way!

The center of the severe storm / tornado risk area is down in North Texas where a few significant tornadoes are possible along with a high threat for damaging winds.  But again pay close attention to weather warnings because tornadoes and severe weather also possible this far north in Oklahoma today!