Archive for July, 2008

End of July
July 31, 2008

July wraps up a degree above average in Fort Smith and a degree below in Fayetteville.  Rainfall-wise Fayetteville picked up 4.29”, which is about an inch above average.  For Smith had a dry month, only receiving 1.13”, which is about 2” below average.

 

 By the way, if we hit 100 today in Fort Smith it will be 4th consecutive triple digit day and the 6th of the season.

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Mesocyclone!
July 31, 2008

This is a rotating mesocyclone, the “king” of all thunderstorms.  As opposed to summertime “pop-up” thunderstorms which last about 45 minutes to an hour, going through a complete life-cycle, mesocyclones can last for hours and travel many miles over land.  The main factor that differentiates a mesocyclone from ordinary thunderstorms is the wind field that produces the storm; wind greatly increases in speed and also in direction with height.  This allows the precipitation (hail, graupel, snow, rain) to fall away from the inflow and not “choke” the storm; subsequently, the storm can sustain itself for quite some time.  Not all mesocyclones produce tornadoes, though most tornadoes are associated with a parent mesocyclone.

 

We second the comment!

JETSTREAM! PLEASE DON’T GO!
July 31, 2008

The jetstream is leaving us this weekend and it doesn’t look like it will be returning anytime soon. The jetstream is the river of flowing air anywhere from 20,000 to 30,000 feet above the surface of the Earth. It acts as a divider between the warm and cold air. Over the weekend the jetstream will be well to the North of our viewing region and that is not good news this time of year. This movement will allow a strong ridge of high pressure to dominate our weather. With high pressure we get sinking air and when air sinks it warms. So with this high setting up over us this weekend we will get lots warm sinking air and with the abundant sunshine we are really going to cook. Wait…there is more…I know, I know; how can there be more? I haven’t even mentioned the fact that the humidity will be very high also. That means the heat index values will be very high. Heat index temperatures will range from 109° to ­111° for both Saturday and Sunday. Please use caution for all your outdoor plans…stay hydrated, wear sunscreen, stay in the shade as much as possible and avoid strenuous activities. If the straining activities can’t be avoided then try to take as many breaks as possible. Not the ideal way to start August!

JETSTREAM FORECAST

WEEKEND FORECAST

Wednesday Evening Update..
July 30, 2008

Showers and storms continue to develop across the area in association with an upper level disturbance.  Sunshine and hot temperatures this afternoon have helped to develop showers and storms; fortunately, storms this evening will remain below severe limits.

Isolated strong storms with pea size hail and gusty winds to 40 mph will be possible; stay indoors until the storms have passed.

4:00 P.M. Weather Update
July 30, 2008

 

Showers and storms have started to develop across eastern Oklahoma and western Arkansas as a disturbance moves in from the west.  The hot surface temperatures have helped to destabilized the atmosphere creating isolated showers and storms.

Widespread severe weather is not expected; however, isolated strong storms with small pea size hail and gusty winds to 50 mph are possible.  Stay indoors until the storms have passed.  Abundant sunshine will help to create strong updrafts that may support dime to nickel size hail throughout the late afternoon and early evening.

Death Ridge Arrives….The Heat Cometh
July 30, 2008

Everytime I use the expression “death ridge” it makes me think about Star Wars; unfortunately, there’s no John Williams’ music that plays when the ridge moves overhead. 

The ridge above will actually become strengthened by upper level energy moving across the pacific northwest.  This ridge may yield the hottest temperatures so far this summer; moreover, 100 degree readings may hit northwest Arkansas this time around.  Temperatures at 5,000 ft will be running between 26 and 27 degrees Celsius by Monday; translating to the upper 90s and lower 100’s at the surface.

SPOTTY SHOWERS TODAY…STORM CHANCES TOMORROW
July 30, 2008

We will have a chance for some spotty showers Wednesday morning and Wednesday afternoon. It looks like better storm chances will be with us Thursday. An upper level trough currently out West will slowly move across the area today.

THURSDAY SURFACE MAP

THURSDAY AFTERNOON PRECIPITATION FORECAST

Now the big question is weather or not we will get any severe storms tomorrow and it does look like we could have a few isolated strong thunderstorms. Here is our thinking:

THURSDAY CONVECTIVE AVAILABLE POTENTIAL ENERGY (CAPE)

CAPE is a great indicator of how much energy will be around to help fuel our storm chances. When the CAPE readings are high that means hail, heavy rain and strong winds could be possible. We could have a few isolated strong storms, but we are not expecting a major severe outbreak.

This is a Summer Gift…….
July 30, 2008

 

This is what you pray for in the middle of summer; a trough that creates more cloud cover and chances for showers and storms.  This upper level wave is actually the remnants of Hurricane Dolly; fortunately, her remnants are moving this way, and with a little cold air aloft, we’ll spark off some showers and storms for Wednesday and Thursday.

Temperatures on Wednesday will be very sunshine dependent; however, we’re definitely looking at a cooler afternoon on Thursday as this trough sits over the area.  Look at the latest QPF map for Thursday; we’re now looking to increase chances for scattered showers and storms.  The severe threat will be very low.  Isolated heavy rainfall can’t be ruled out either if you get stuck under the storms.

COMPLETE 180!
July 29, 2008

VISIBLE SATELLITE IMAGE

This morning it looked like our weather story was going to be a spotty shower, increasing clouds and slightly cooler temperatures.  Well mother nature has changed her mind.  The wave of energy out west will not move east and has not moved east all day.  Therefore, the spotty showers, clouds and slightly cooler temperatures will not be with us this afternoon.  Maybe it was a little wishful thinking of slight relief across the area today, but that will have to wait!

A SPOTTY SHOWER TODAY
July 29, 2008

TUESDAY AFTERNOON PRECIPITATION FORECAST

Showers and storms off to the west will try to make it into the area today, but most of the rainy weather should hold off until Wednesday. This system is moving very slowly and therefore our best precipitation chance will be tomorrow. A few spotty showers will be possible today mainly throughout NE Oklahoma and NW Arkansas. Keep that umbrella handy!