Staying Hot & Mainly Dry

By Jay Grymes & Steve Caparotta

WAFB Storm Team QuickCast:

- hot and mostly-dry again for Tuesday
- higher rain chances later in the week
- “Invest 91L” on the verge of becoming the season’s first ‘named’ storm?

It was a summer-season hot and mainly-dry weekend for most WAFB communities and today stayed the course. What’s more, our forecast calls for more of the same for Tuesday and probably Wednesday too.

We closed-out a ‘wet’ June with a final three days of mainly-dry weather across the viewing area. Metro Airport finishes the month with 11.36” of rain, tied with 1962 as the sixth “wettest” June in more than 120 years and the “wettest” June since 2001 (when Allison dumped from 15” to 30” of rain over southeast Louisiana over a 10-day stretch.) 

Mid/upper-level ridging (high pressure) has provided a fairly solid ‘lid’ on the atmosphere, with sinking air suppressing vertical development. We expect that to be the case for at least one more day -- possibly two days -- before the ridge gives way to an advancing upper-air trough and begins to weaken. As it typical for this time of year, even with the upper-air ‘lid,’ spotty showers can’t be ruled out over the next two days. However, those that do get a shower will be the lucky ones: the rest of us will deal with a pair of very hot afternoons, with highs reaching the mid 90°s for parts of the viewing area. Factor in the Gulf humidity and we can expect Heat Index readings in the triple digits for both Tuesday and Wednesday.

Headed into the latter half of the work week -- and into and through the July 4th holiday weekend -- we expect a return to typical summer weather for the region. That means morning lows in the low to mid 70°s, afternoon highs in the low 90°s, and daily rain chances in the 30% to 40% range. The way it looks for now, Friday evening fireworks should go off without a weather-related hitch: any thundershowers that do develop on Friday should be over-and-done before the sky-shows begin (around 9 pm). And for the rest of the holiday weekend? Just more of the same.

In the tropics, eyes are on the area of low pressure off the Florida Atlantic coast and just to the north of the Bahamas labeled Invest 91L. There is clear evidence of a low-level circulation and this afternoon’s visit by a Air Force Reserve Hurricane Hunter found peak winds of 35-40 mph in the vicinity of the center. However, the National Hurricane Center (NHC) failed to upgrade 91L to a tropical cyclone (a depression or tropical storm) because of a lack of widespread thunderstorm activity around the center. Given that 91L as most of the ingredients in place, the NHC is giving 91L an 80% chance of cyclone development in the next two to five days. The good news for us is that the forecast consensus keeps this system out of the Gulf. However, interests along the U.S. Atlantic seaboard should keep close tabs on developments throughout the week.

Sunday (6/29) Tropical Update

Here is your tropical update for South Louisiana for June 29th, 2014.

5 DAY OUTLOOK:

All has been quiet this hurricane season...at least for the Atlantic Basin.  But it appears we might be seeing our first tropical system of the season.  An area of low pressure has moved off the coast of Georgia / Florida this weekend.  This broad area of low pressure is not a tropical depression at this time (5:00 PM CDT).  But appears to be getting more and more organized every day.

The National Hurricane Center has classified this disturbance as Invest 91L.  91L is expected to stay in the Western Atlantic slowly drifting South/Southwest.  The NHC is giving this system a 60% chance of becoming a tropical depression in the next 48 hours and an 80% chance over the next 5 days.  Now the good news for South Louisiana is that whatever (if anything) develops is not expected to impact Louisiana or the Gulf of Mexico for that matter.

Model plots continue to indicate a slow drift to the SW before a gradual turn to the North and then Northeast through this week.  This is because the primary steering current will be a trough that will be moving from west to east.  It will block this system from making any westward progress by the middle of the week.  But as it carries it North, the system may clip coastal sections of the Carolinas.

As for intensity...I expect this system to be very slow in getting organized.  Dry air is in the general area and there remains some wind shear in the upper levels.  This should keep this system fairly weak over the next few days.  This is illustrated by our Tropical PrecisionCast.

Tropical PrecisionCast is a high resolution short range model.  It shows a weak area of low pressure sitting off the coast of Florida Tuesday morning.

Image Credit NCAR and can be found at: http://www.ral.ucar.edu/guidance/realtime/plots/northatlantic/2014/al912014/

About half of the early cycle weather models indicate slow strengthening of this system.  We also don't have complete agreement on tropical storm status being reached.  The GFTI (subset of GFS model) keeps it below Tropical Storm strength.  The GFS or American model which has been the most aggressive tropical formation model so far this system has been very quiet as it pertains to this system showing little if any development.

The European model has been the primary long range global model showing development of this system.  The ECMWF has a possible tropical storm skirting the East Coast July 4th into the holiday weekend.

So here's what you need to know:
1) This system will have NO direct impact and is not headed towards South Louisiana
2) Travel along the East Coast could prove difficult for 4th of July
3) First named storm of the season would be Arthur

10 DAY OUTLOOK: ***(DISCLAIMER: 10 day outlook is a long range forecast and can change rapidly and should NOT be accepted as "gospel" truth but only a small possibility and something to keep an eye on over next several days.)***
The long range models indicate a quiet outlook minus this system previously discussed.  In other words no new systems are expected/indicated.

More Rain for Wednesday & Thursday

By Jay Grymes & Steve Caparotta

WAFB Storm Team QuickCast:

- good rain chances for Wednesday & Thursday
- a little “quieter” for Friday & the weekend

A cluster of healthy storms that formed over Acadiana around the lunch hour held together and tracked east-northeast, reaching portions of the WAFB viewing area by the mid-afternoon. Several of the core storms were highly “electrified” and we did see Severe Thunderstorm Warnings posted for a few areas (St. Landry, Avoyelles, Pointe Coupee, West Feliciana, northern Tangipahoa parishes and southern Pike Co.).

And if you happened to get caught beneath one of the stronger afternoon cells you certainly had to deal with a serious downpour or two as well as some vivid lightning. There were even a few reports of wind damage around the area, including 2 minor injuries to infants in Kentwood when a tree fell on a house and some of the falling ceiling material caused some scratches.

Most WAFB neighborhoods can expect a dry but muggy start to Wednesday with mostly cloudy skies and patches of mainly-light early morning fog. Sunrise temps should be in the low to mid 70°s for most WAFB communities. But rains will be more widespread for Wednesday … and Thursday.

The high-pressure ridging that has limited afternoon storm development over the last several days will take a short vacation from our viewing area, allowing for scattered to numerous afternoon and early evening rains for the next two days. We’ll post rain chances at 60% to 70% -- which means that most neighborhoods will get at least a little rain. These won’t be all-day rains, just a broader coverage each day. The better rain chances also mean that most or all of us top-out in the 80°s for the next two afternoons.

As we head into Friday and the weekend, the guidance indicates that the high will sneak back into the weather mix, once again limiting -- but not shutting-off -- the opportunity for afternoon rains. We’ll go with a 30% rain chance for Friday, Saturday and Sunday -- back to something more typical for late June. That also means that the 90°s will return for the weekend as well.

It’s Lightning Awareness Week, and we note that Louisiana ranks among the deadliest states for lightning when weighted by population size. There have been 17 lightning-related fatalities in the Bayou State since 2000 (14+ years), just over one-per-year, on average. All of the victims were males, most were adults (age 21 or older), all were outside at the time of the accident … and in many cases, witnesses say that it was not raining when the deadly strike occurred.

Lightning safety is simple: when you see a flash or hear a rumble, go inside! Inside can also be a car, a bus … anything enclosed (with the windows up if it’s a vehicle).

All is still quiet in the tropics, with the NHC calling for no development through the next five days, at least.

No Big Changes in the Outlook

By Jay Grymes & Steve Caparotta

WAFB Storm Team QuickCast:

- hot, humid, summertime weather pattern through the week
- slightly higher rain chances around mid-week

We started the day with a band of mostly light-to-moderate rainshowers to the north and west of the Capital City as well as a thundershowers along the coast. But for most WAFB commuters, it was a dry morning drive under mostly cloudy skies. In addition, much of the early-morning rains dissipated into the mid-to-late morning hours. At the same time, the lingering clouds kept temperatures from climbing into the 90°s for many communities and the day’s slower warm-up meant fewer showers and storms for the afternoon.

For the trivia buffs, today is the first day since June 15th with a high under 90° at Metro Airport (BTR).

However, a few showers and storms still managed to pop-up during the afternoon and a few of those storms were rather active in terms of lightning. At this time of year, if the air temps get up into the upper 80°s to near 90°, that is usually enough to fire-up at least a few storms even on a mostly-cloudy day. And as is usually the case, we look for most or all of the day’s rains to dissipate around sunset or soon after.

Frankly, there is nothing new ‘weatherwise’ in terms of our outlook through the coming week. Our daily forecast stays fairly steady right through the weekend:
- sunrise temperatures in the low to mid 70°s with some pockets of mainly-light fog possible,
- afternoon highs in the low 90°s for most WAFB communities, with Heat Index readings
peaking in the mid to upper 90°s, and
- isolated to scattered afternoon thundershowers each day (from 20% to 50% coverage).

Rain chances may shift a little from day to day, but we’re not expecting any all-day rains this week. For Wednesday, we may nudge rain chances up to 50% or so, but the bottom line is a forecast that essentially reads, “More of the same.” But then, that’s how summer rolls in our neck of the woods.

All remains quiet in the tropical Atlantic … and there are no complaints in that department!

This is National Lightning Safety Awareness Week. Lightning is one of the most underrated weather threats, accounting for roughly 50 fatalities in the U.S. each year. For the Bayou State, there have been 17 lightning-related fatalities since 2000 and every one of them occurred to someone outdoors. Louisiana is certainly a hot spot for lightning strikes, ranking as the #2 state for hits (behind Florida). In fact, the number of cloud-to-ground strikes might surprise you: the statewide average is 20 strikes per square mile per year, but the annual average is actually a little higher for the southeastern portion of the state, including the WAFB viewing area! 

WAFB Storm Team QuickCast:
- summer “officially” began this morning
- not much change in the forecast for the next couple of days
- better rain chances later in the work week

Did you notice the change in seasons this morning when summer kicked-in at 5:51am?  Nope, me neither … but today is the Summer Solstice.  That means for everyone living north of the latitudinal line known as the Tropic of Cancer (23.5°N), two things happen today: (1) the duration of sunlight is the longest of any day in the year and (2) the mid-day sun reaches its highest point in the sky of any day in the year.

For Baton Rouge, today’s “sunrise-to-sunset period” is roughly 14 hours and 7 minutes.  Starting tomorrow, that length of time will slowly decline, and will continue to do so until the Winter Solstice (on December 21st).  The other bit of trivia is that at about 1:06pm, the sun was almost directly overhead for Baton Rouge (that will be the case tomorrow as well).  Directly overhead would mean a solar altitude of 90° ... today’s solar peak altitude for the Red Stick was roughly 83° (also occurring at about 1:06pm).

As for the metro area weather over the coming days … no notable changes, at least in the short term.  Rain chances will run around 30% for Sunday, but that’s not much of a change from what we’ve seen the last several days.  And after another morning start for the Capital City in the low 70°s, we’ll return to the low 90°s for Sunday afternoon under a sun/cloud mix.  Yes, a few neighborhoods will deal with a thundershower, but the afternoon heat will be the bigger weather story for most WAFB communities, with the peak mid-afternoon Heat index once again returning to the mid-to-upper 90°s.

The forecast looks about the same for Monday too, as well as Tuesday.  But we are going to ‘up’ those percentages a bit as we head into the middle and latter part of the work week. The upper-air ridging that has helped minimize afternoon shower development over the better part of the past week will no longer be a significant factor in our regional weather.  As a result, by taking the ridge’s “lid” off the atmosphere, daytime heating will help lift our moist, unstable air mass; that should lead to more widespread afternoon action and better rain chances.

In the tropics, the National Hurricane Center is watching an area in the western Atlantic roughly 200 miles east of the Georgia/Florida coast.  This area has a very low probability for development over the next few days.  In addition, even if it were to get better organized in the coming days, all indications are that it would move towards the northeast -- away from the U.S. coastline.  Elsewhere, all appears quiet in the Gulf, the Caribbean and the remainder of the tropical Atlantic.

Hot, Iso'd T-Storms...You Know the Drill

By Jay Grymes & Steve Caparotta

WAFB Storm Team QuickCast:

- plan on more of the same summer “sultries” right through Sunday
- summer officially begins on Saturday morning (at 5:51am CDT)
- hit-n-miss afternoon thundershowers for Friday & the weekend

Our high today at Metro Airport of 93° is the highest reading of the year thus far. But we are almost certain to top that in the coming weeks.

We’ll keep this short since the forecast reads the same as it has for most of the week. To summarize, the outlook for Friday and the weekend looks like this:
- morning lows in the low 70°s for most of us with patchy, mainly-light fog near sunrise,
- afternoon highs running in the low 90°s with peak Heat Index readings in the mid to upper 90°s, and
- afternoon rain chances running around 20% to 30% each day.

The upper-level ridge that has kept a modest ‘lid’ on our afternoon t-shower development remains in play, but it continues to slowly weaken. We still think that it will continue to hamper the onset of afternoon rains but may ‘soften-up’ just enough to allow a very slight increase in rain coverage over the weekend. So let’s call it a 20% rain chance for Friday and Saturday and then at about 30% for Sunday -- which means most WAFB neighborhoods remain dry each day.

Here’s a little ‘math’ game if you are into raw statistics. If we assume that chances-of-rain for your yard are 20% for both Friday and Saturday and then 30% for Sunday, what are the chances that you go all three days without any measurable rain? If you’ve never contemplated this one, the purely ‘mathematical’ solution is not as simple as you might first think.

The answer is: [(1 - 0.2) x (1 - 0.2) x (1 - 0.3)] = [(0.8) x (0.8) x (0.7)] = 0.448

. . . roughly a 45% chance (44.8%) that you go through Friday, Saturday and Sunday without getting any rain at all. In other words, even with our relatively low day-to-day rain percentages, there is better than a 50-50 chance you’ll get at least one sprinkle sometime over the next three days. And even with those low percentages, a few of you will see rain on two or more days.

And remember that the “chance of rain” does not translate into a forecast for an “amount of rain.” Just like we’ve seen the past several days, although the majority of WAFB neighborhoods have remained dry each afternoon, a someone has gotten something each afternoon. And one or two of those neighborhoods have experienced significant downpours. The truth is, forecasting exactly where it will rain in the summer is almost impossible ... and how much it will rain at any one place is just as difficult!

Here’s some good news: it remains quiet in the tropics and is expected to stay that way through the next several days, at least.

 

WAFB Storm Team QuickCast:

- no significant changes to the forecast through the next five days, at least

- hot & humid afternoons continue into the weekend

- staying with 20% to 30% rain chances each day

 

Not much to talk about really: “What you see is what you get.” Looks like we are locked into a daily pattern of humid Gulf air, daytime heat, and afternoon ‘hit-or-miss’ thundershowers. The forecast numbers for the rest of the week are just about ‘normal’ for June and there’s nothing in the short-term forecast that appears ready to change it up.

 

 

So here it is -- and it’s not really any different from yesterday: morning lows in the low 70°s for most of us (mid to upper 70°s closer to the coast), afternoon highs running around 90° to 92° (upper 80°s along the coast), and afternoon rain chances running around 20% to 30% -- each day. Factor in the heat and humidity and you can expect Heat Index readings at or above 90° for several hours with peak afternoon Heat Index numbers in the mid to upper 90°s. And don’t forget, the Heat Index is the ‘feels like’ temperature in the shade -- direct sunshine can add another 10° or more to the ‘apparent’ temperature.

 

(By the way, if you are thinking that this you read virtually the same thing yesterday, you’re right!)

 

The near-steady inflow of Gulf air will keep dew points near or above 70° through the week. That comes with a daily early-morning forecast for patchy, mainly-light ground fog. Fair to partly-cloudy skies during the first half of the day will become partly-cloudy to a sun/cloud mix by the mid-afternoon for most WAFB neighborhoods as daytime heating works the moist and unstable Gulf air to generate an abundance of cumulus clouds. Some of those clouds will grow into rainmakers.

 

 

The upper-level ridge that I showed you on Monday afternoon an evening persists over the southeastern U.S. and the current guidance keeps it there through Friday, at least. That upper-air dome will continue to limit the onset of widespread afternoon rains through the remainder of the work week but will not fully stop the development of a few healthy thundershowers each day. The moist-and-unstable Gulf air is getting a lifting boost from the daytime heating, and a few of those vertically-developing clouds will pop-through the ‘capping’ effect of the upper-level ridge.

 

Result: a 20% to 30% coverage of mainly-afternoon rains with a few lightning strikes mixed- in for a few WAFB communities. And just like the past couple of days, whatever rains do develop wind down near sunset each day.

 

 

All looks good (quiet) in the tropics for the time being. A couple of tropical waves are evident on satellite imagery, but there is far too much shear on-going over the basin for any waves to show an organizing trend for now. That’s not uncommon this early in the Hurricane Season. The bigger question is, “Will an El Niño develop later this summer and help to maintain a hostile, shearing environment?”