Tuesday, June 30, 2009

Global Tropical Outlook

Western Atlantic Ocean
A strong tropical wave flared up over the weekend, but interaction with the Yucatan Peninsula quickly ended its chance for development. Otherwise, the Atlantic basin is extremely quiet as a MJO pulse is exiting to the east and resulting in sinking air across the tropical waters. A TUTT is parked over Hispaniola and is contributing to strong upper level westerly winds across much of the basin. Any tropical waves moving in this environment will be significantly sheared by the strong winds. Another interesting development is occurring in the Caribbean Sea where stronger than normal low level winds are being observed. The Colombian heat low is primarily responsible for this anomalously strong low level easterly flow, and this will also rip apart any waves moving through the Caribbean. The only location where any development could occur would be off the Southeast U.S. coast or the Gulf of Mexico where a washed out frontal boundary remains. Showers and thunderstorms are occurring in the waters adjacent to Florida, but development in these areas also appears unlikely.

Eastern Pacific
The Eastern Pacific is much more active than the Atlantic as a mass of thunderstorms exists off the Central American coast between 87 and 100 degrees West longitude. Closer inspection of the convection shows a cyclonic swirl south of El Salvador, and it's very possible this could be some remnant energy of Invest 93. In any case, the environment appears favorable for some development of this system in the next couple of days with wind shear remaining light, SSTs in the lower 80s, and a moist ambient environment. A larger mass of thunderstorms is centered near 10 deg N and 96 deg W, but this area does not appear to have any type of circulation at this time. However, wind shear remains on the strong side so short-term development of this system does not appear likely.

Northwest Pacific
Very strong sinking motion is occurring in this basin since it is located east of a MJO pulse in the Indian Ocean. Therefore, short-term development looks very unlikely despite favorable shear and water temperatures in the main development region.

Indian Ocean
The most convection in any ocean basin currently resides in the Indian Ocean as a MJO pulse is moving through. This is much welcomed relief to India as they have experienced very hot, dry conditions for the last several weeks. Despite the active look on satellite, extremely strong wind shear covers most of the basin, and any tropical development appears unlikely in the short-term. However, this may be a blessing in disguise as India will receive rain without the damaging wind and flooding effects of a tropical cyclone.

Dry Heat

It was quite refreshing if you were able to get outside just before sunrise this morning, but temperatures are quickly warming into the 70s. The quick warm up will continue through the morning with temperatures near 90 by noon. High pressure at the surface will supply us with northerly winds, which will keep dew points in the 50s and 60s today. This will ensure that the heat index won't be a problem, but it will be a dry heat this afternoon as highs top out near 94.

The weather may be a little more tricky to forecast tonight as our upper air pattern is dominated by northwesterly flow associated with a big upper low over the Great Lakes. A subtle shortwave will eject out of this upper low tonight and will likely move just to our north. It's possible that a few showers could develop early tomorrow morning across Tennessee and Arkansas in advance of this energy. If a complex does develop, the upper air flow would move it very close to our area. On the other hand, it would be encountering a slightly less stable environment in East Central Mississippi so it's very likely that it would be weakening or even dissipate before it impacts the area. However, a few clouds will be generated by the upper level wave, and this may only allow temperatures to drop to 67 tomorrow morning. Looking ahead, the 4th of July weekend looks cooler, but the price to pay will likely be better rain chances. I still don't think many folks will gripe about that.

Monday, June 29, 2009

Slightly Cooler, Less Humid

A weak cold front that sparked a few scattered showers and thunderstorms yesterday has pushed into South Mississippi. It doesn't seem that the weather has changed as temperatures remain muggy this morning despite the frontal passage. However, much drier air will filter into the area via northwesterly winds throughout the day, and dew points could even drop into the upper 50s later this afternoon. Additionally, an upper air trough located to our northeast has caused temperatures above the surface to drop almost 8 degrees compared to low level temperatures for much of the last week. This should allow temperatures to top out near 90 this afternoon. Skies should be clear this evening with dry air and light winds, and this combination should allow for temperatures to drop to 63 tomorrow morning. That's about as crisp as it gets for summertime! The upper air trough to our northeast will deepen later this week and could yield a few surprises in the rain and temperature columns. Regardless, don't get used to the slightly cooler temperatures and low humidities because a classic summer heat wave may take shape after the middle of July.

Friday, June 26, 2009

Hot, Slightly More Humid

It's another pleasant start to the day with temperatures in the upper 60s, but temperatures this afternoon will be anything but pleasant. The persistent upper level ridge will slide slowly eastward today and will allow temperatures to soar well into the 90s again this afternoon. Low level temperatures also warm a few degrees compared to the last couple of days so we should top out around 98 today. A cold front will be approaching the region from the north and this will allow winds to turn more southerly later today. As a result, dew points will begin rise and this will make it feel a little more uncomfortable than the last couple of days. The heat index still shouldn't be a major factor for most of the day, but you'll probably notice it feels more sticky by this evening. The front will inch its way closer to the area this evening, and it appears likely that a few clouds may arrive early Saturday morning. This cloud cover and increasing moisture will only allow for lows tomorrow morning to drop to 72. Latest computer model guidance is actually indicating the possibility of highs in the upper 80s for Monday and Tuesday. That would be a welcomed relief!

Thursday, June 25, 2009

Hot but Less Humid

Temperatures are starting out in the upper 60s to near 70 this morning which a nice change of pace from the mid 70s of the last few days. These temperatures can be attributed to the weak frontal boundary that pushed through yesterday and dropped dew points in the 60s. Dew points will remain the 60s again today with northeast winds so the heat index should not be a problem this afternoon. However, the upper level ridge will expand eastward slightly today and that means temperatures will be a degree or two warmer than yesterday. In fact, the high will top out near 95 this afternoon. Skies should be clear overnight with temperatures dropping to 70 tomorrow morning.

Wednesday, June 24, 2009

Slightly Cooler, Still Hot

Yesterday's rain and storms provided some much needed relief from the heat and the dry spell. We won't get that lucky today, but a weak backdoor cold front will sneak through the area this afternoon. This weak front will allow temperatures to drop off a few degrees, but it will still remain on the hot side with an afternoon high of 94. Dew points will drop into the 60s this afternoon so the heat index should not be a problem. A few clouds may arrive overnight and may prevent temperatures dropping into the 60s. We should bottom out near 70 tomorrow morning. My forecast for a slightly cooler and wetter pattern from a couple of weeks ago will be off by a few days. However, late this weekend and early next week it appears that a true cold front will pass through the area and give us some better rain chances and cooler temperatures.

Tuesday, June 23, 2009

CPC Long Range Forecast

I find the recently updated monthly and seasonal forecasts from the CPC to be intriguing for the Deep South. The graphic below shows that the CPC expects temperatures to be above normal across most of Mississippi and the eastern half of the country from December 2009-March 2001. The accompanying discussion is very good and well worth a read, but there are a couple of factors that I did not see included in the discussion.

The first is the potential impact of the Pacific Decadal Oscillation. Clearly, the PDO has been in a cold phase for the last couple of years, coinciding with the persistent La Nina conditions. However, since the first of May, SST anomalies have become positive across much of the North and Northeast Pacific Ocean; a cold pocket remains off the Alaskan Peninsula. It's interesting to note that the upswing in the SST anomalies across the North Pacific has coincided with the developing El Nino in the equatorial Eastern Pacific. If this pattern of positive SST anomalies continues or strengthens, the PDO may likely transition back to the warm phase. How soon this occurs remains to be seen, but a warm PDO would make it very difficult to have above normal temperatures across the Deep South and the eastern third of the United States.

Although the developing El Nino was the basis for their forecast, El Nino conditions typically cause cooler and wetter than normal conditions across the South. The key to this will be the placement of the subtropical jet stream. It tends to fluctuate between the Deep South and Florida during El Nino years, and a more suppressed STJ would keep above normal precipitation to our south. Regardless of the STJ placement, a warm PDO would make it difficult to have above normal temperatures for a four month period.

The second factor that was not considered, not surprisingly, is the Global Wind Oscillation (GWO). Given that we are headed for a weak to moderate El Nino, westerly winds will increase atmospheric angular momentum and should lead to the GWO persisting between phases 5-7 for much of the winter. If this indeed occurs, GWO composites for these phases correspond to cooler than normal temperatures across the South and Eastern U.S. As a caveat, more than wind direction (frictional torque) is factored into the GWO, but El Nino conditions generally cause the global circulation to vary from phases 4-7. The intent of this post isn't to disagree with the CPC's forecast, but I think the two factors mentioned above should be followed closely as we head into the fall. It should be interesting!

Severe Thunderstorm Warning

The NWS in Jackson has issued a severe thunderstorm warning for Oktibbeha County until 6 p.m. This storm is producing gusty winds along the leading edge, some small hail, lightning, and torrential rains. The storm should pass through Starkville within the next 15 minutes and should exit the county by 6:15 p.m.

Heat Wave Continues

Granted, this isn't one of those typical summer heat waves, but it's impressive in its own right for so early in the season. The pesky upper ridge that was centered over us for the last several days has actually shifted westward and has placed us on the eastern periphery. This is important because it places us very near the primary road for convective complexes to our north to follow. The only problem is that it doesn't appear that any complexes will form to the north. However, computer models are finally indicating the possibility of a few clouds this afternoon and evening and a very slim chance for a shower. Before cloud cover can increase and showers can develop, highs will top out around 98 this afternoon. As previously mentioned, there may be a few clouds around this evening, but it will remain mild overnight with a low near 73.

Monday, June 22, 2009

Hot, Hot, Hot

A potent upper level ridge will remain parked over the region today and will allow the persistent heat to continue. In fact, a heat advisory has been extended through 7 p.m. on Tuesday. We got a little lucky yesterday that some high clouds moved through and limited the maximum heating potential. However, it doesn't look like we'll be fortunate enough to get the same high clouds this afternoon. Therefore, I think highs this afternoon will top out around 98, but the heat index will make it feel like it's over 105 this afternoon. Skies will remain clear overnight with a morning low dropping to 73.

Sunday, June 21, 2009

Heat Advisory

The weather for the first day of summer will be fitting as the National Weather Service in Jackson has issued a heat advisory for Oktibbeha County through Monday evening at 7 p.m. Highs should top out around 98 today, but the temperature tonight will likely stay above 75. Additionally, heat indices will exceed 105 this afternoon, and these combinations can create considerable stress on the human body. Make sure you drink plenty of water and stay indoors as much as possible.

Friday, June 19, 2009

Summer Heat

Temperatures are going to warm rather quickly this morning with sunny skies overhead. We'll hit 90 degrees by 11 a.m. and will rise into the mid 90's this afternoon. We should top out around 95, but it will feel much hotter than that as heat index values will exceed 100 again. Needless to say, take it easy if you're going to be outside for any extended period and drink plenty of water. Skies will remain clear this evening and overnight, but it should remain muggy again with a morning low of 74.

Thursday, June 18, 2009

Hot and Humid

These are the days I don't envy being a broadcast meteorologist trying to use new phrases to make hot and humid sound different. Skies are clear this morning and should remain mostly sunny throughout the day with an upper level ridge parked over the area. Low level temperatures continue to remain similar to the last few days so persistence seems to be the way to go with the forecast. I think the high will top out around 94 this afternoon, but the temperature will feel like it's over 100 for most of the afternoon. Skies will remain clear this evening, but it will continue to be muggy with a morning low of 73.

Wednesday, June 17, 2009


It's another warm start to the day as temperatures are in the low to mid 70's across the area. A persistent and dominant upper level ridge will squash the development of clouds and showers again today. This means we'll see a full supply of sunshine, and with low level temperatures warming, today will be the hottest day of the year so far. I think the past couple of days haven't achieved on the high because of the wet soil, but that is quickly beginning to dry up and may not be able to keep temperatures in check. The high today will top out near 96, but heat index values will exceed 100 at times making it feel steamy. Skies will be clear this evening and overnight with temperatures dropping to 73 tomorrow morning. I continue to feel strongly that relief from the heat is coming next week with a chance for rain and slightly cooler temperatures.

Tuesday, June 16, 2009


The title of the post pretty much sums up today's weather with those three letters. An upper level ridge will dominate our weather again today by inhibiting thunderstorm development and allowing the temperature to soar well into the 90's. Skies will be almost completely sunny and the temperature should be able to top out around 95 this afternoon. Dew points in the 70's will make the temperature feel like it's over 100 at times again this afternoon so take it easy and drink plenty of water if you'll be outside. We won't get much relief overnight as temperatures will continue to stay rather warm. The low tomorrow morning will only drop to 73.

Monday, June 15, 2009

Evening Light Show

A large complex of severe storms that produced widespread wind damage across Tennessee weakened considerably while moving through Northeast Mississippi this evening. The dying storms produced a healthy outflow boundary with wind gusts up to 40 mph measured at Hilbun Hall. Very little lightning accompanied the storms, but the little amount there was happened to be shrouded by low stratus clouds. However, I was lucky enough to snap a couple of shots when the storms were over Chickasaw and Clay Counties. With the help of Photoshop and Michael Carter, I was able to remove the noise in the images.

Heat Cranks Up

After a wet and stormy weekend at times, the atmospheric heater is about to kick into high gear. An expanding upper level ridge centered to our west will push the main storm track back to the north and east which will not allow for any thunderstorm relief today. We may see a few higher clouds at times today, but there won't be enough of them to block out the sun. I'm not biting off on the very warm MOS guidance as low level temperatures don't support highs that warm, but I will forecast an afternoon high of 94. With dew points in the lower 70's today, the temperature will feel even warmer than that so make sure you take it easy and drink plenty of water if you'll be outside today. Skies should be clear this evening, but temperatures will only bottom out near 72 tomorrow morning.

Sunday, June 14, 2009

Severe Thunderstorm Watch

The SPC has issued a Severe Thunderstorm Watch that includes Oktibbeha County until 3 p.m. A line of strong to severe storms currently extends from McNairy County, TN to Grenada County, MS and is moving to the east southeast. On this motion, we may get clipped by the very southernmost part of the line after 10:30 this morning. This line will likely intensify before it reaches the area since it will be encountering a more unstable air mass, but I'm not expecting anything like what we dealt with on Friday. The strongest storms will stay just to our north, but if the southernmost storms do clip the county, they could produce some gusty winds as they move through.

Friday, June 12, 2009

Quiet Night?

The squall line rapidly moved through and cleared the area earlier this evening. It has since weakened considerably over Central Alabama. The damage could have been a lot worse, but it appears that minor tree damage, some power outages, and minor street flooding are the worst reports thus far. The highest wind gust measured at Hilbun Hall was 49 mph, but an estimated report of an 86 mph wind gust came from north of Ackerman as the storms rolled through. I highly doubt the winds were that strong, but I'm sure there were gusts easily over 60 mph within the line. There are lingering showers to our north across Northeast Mississippi, but these should not affect us for the remainder of the evening. I'll be keeping a close eye on new convection that is trying to develop across Eastern Oklahoma. If this manages to form into another convective complex, we may see some more rain just before sunrise tomorrow. On the other hand, if this convection does not develop into a complex, we should remain quiet overnight with temperatures remaining in the upper 60's.

PDS Severe Thunderstorm Watch Issued

A Potentially Dangerous Situation Severe Thunderstorm Watch has been issued for Oktibbeha County until 7 p.m. This watch is rarely issued by the SPC, but the current situation certainly warrants its issuance. An intense derecho is currently plowing through Eastern Arkansas and has been associated with extensive and widespread wind damage across Arkansas and Oklahoma. A wind speed of 100 mph was reported in Northwest Arkansas early this afternoon and other reports suggest that hurricane force winds are very likely with this complex of storms.

It does appear that Oktibbeha County will be clipped by the southern end of this bow echo after 7 p.m. The current thermodynamic environment does not suggest this derecho will lose strength anytime soon; in fact, the thermodynamic environment actually supports strengthening! However, this derecho is running away from stronger vertical wind profiles as it progresses further east. This indicates that the thermodynamic and dynamic environments across Mississippi are not as favorable for sustained maintenance as the environment across Arkansas. I expect a little but not a tremendous amount of weakening of the derecho as it plows across Mississippi in the next few hours. These extreme wind events typically take a few hours to wind down, especially given that a mature cold pool is present.

What can we realistically expect in Starkville and surrounding areas?
*The derecho will approach the area just after 7 p.m.
*A severe thunderstorm warning is almost guaranteed
*Wind gusts could exceed 65 mph
*Expect streets to be littered with small sticks and some larger branches; some trees may even be knocked down
*There could be many power outages across the county

Rain This Morning, Warm Later, & Storms Overnight

A weakening line of thundershowers is moving through the county as I type and should exit by 9:00 a.m. This may not be the only time it rains this morning, and in fact, showers continue to move in our direction from Western Mississippi. It's also possible that isolated thundershowers may pop up this afternoon. However, the upper level energy responsible for the current rain may create enough warming aloft as it passes to the east and this may squash the threat of rain later today. The majority of the morning will feature more clouds than sun, but we should see more sun later this morning and for the afternoon. Highs will once again be on the warm side with most areas topping out in the upper 80s; I'll forecast a high of 89 this afternoon. I think the best chance to get wet will be overnight as another convective complex forms to our northwest and drifts into the area after 4 a.m. The storms may be on the strong side overnight given the strengthening upper level winds and lingering instability. Granted, I don't expect a severe weather outbreak or anything, but one or two storms could be severe with damaging winds being the primary threat. The low tomorrow morning will be 71.

**11:00 a.m. update to forecast: A well-organized squall line over Northeast Oklahoma will move to the southeast throughout the course of the day. It appears that this complex will arrive in our area by this evening and could bring a chance of severe weather to the area between 7-9 p.m. Damaging winds will be the primary threat with these storms.

Thursday, June 11, 2009

Scattered Thundershowers, Still Steamy

It's a very summerlike start to the morning as temperatures are running in the mid 70s. A weakening line of showers is actually passing to our north this morning and its associated cloud cover may block the sun for a short time this morning. It appears that we'll see off and on clouds for most of the morning, but the sun will be mixed with afternoon cumulus later. With the flattening upper air flow and a southward sagging cold front front approaching Northern Arkansas and Tennessee, we'll stand to see a better chance for afternoon thundershowers than anytime in the last 6 days. It won't be a washout by any means, but any shower that does pop up could provide some temporary relief from the heat later this afternoon. Speaking of the heat, it will be another hot day with an afternoon high around 91 again. By this evening, clouds will continue to linger around and another convective complex appears likely to develop across Western Arkansas. The upper air flow would steer this complex toward our area overnight, but I feel like it will be weakening as it approaches and it should arrive after sunrise tomorrow. It will remain very muggy overnight with a low of 72 in the morning.

Wednesday, June 10, 2009

Several Clouds, Still Hot

Cloud cover from storms to our north has made for an unpleasantly muggy morning as temperatures are in the lower 70s. The upper level ridge that kept clouds at bay yesterday has flattened out thanks to upper level energy ejecting out of a Western U.S. trough, which should allow for more clouds today than the last several days. However, the primary storm track will remain just to our north over the next 24 hours so we'll continue to be hot and dry today. One factor that will make today feel more uncomfortable is the fact that dew points will remain in the 70s today. Combine that moisture with a high temperature around 91 and it will feel quite steamy this afternoon. A complex of thunderstorms will erupt this evening across Texas and will send a stream of clouds in our direction overnight. This will only allow the temperature to drop to 72 tomorrow morning. If you're not used to the heat just yet, you might want to make quick adjustments because next week appears even warmer. After next week, we should switch to a slightly cooler and wetter pattern.

Tuesday, June 9, 2009

Some Clouds, Continued Warm

An upper level ridge will remain in tact once again today, but low level temperatures should be a bit warmer. This will result in a hot day with highs into the 90s at every location. The only fly in the ointment is the presence of some cloud cover to our southwest, but it appears to be breaking up as it encounters the ridge axis. Still, we'll probably get a few clouds at times this afternoon and that leads me to stay on the cooler side of model guidance and forecast a high of 91. Increasing dew points and some lingering clouds tonight should keep temperatures rather muggy. I'll forecast a low of 69 tomorrow morning.

Monday, June 8, 2009

Mostly Sunny, Warm

It's a slightly warmer start to the morning than the last few days thanks to passing high clouds. Our weather will be dominated by an upper level ridge and a surface low pressure to our southeast. These features will combine to create a warmer and slightly more humid air mass today. The high this afternoon will top out near 89. Skies should be mostly clear tonight with lows around 66. Our next good chance of rain won't come until the end of the week.

Thursday, June 4, 2009

Scattered Storms, Slightly Cooler

Today will be the wettest day of the week by far as a cold front and upper air disturbance will aid in the development of showers and thunderstorms by late this morning. I sure hope we can get some decent rain today because we likely won't have another good chance for at least a week. The good news is that extensive cloud cover and rain will give everyone some relief from the heat as they keep highs much below normal this afternoon. In fact, I think we'll top out around 78 later today. The passage of the cold front this evening will take all of the showers and thunderstorms off to the east. In its wake will be a cooler and drier air mass even though clouds will hang tough for much of the night. I'll pessimistically forecast skies to remain cloudy through sunrise tomorrow so the low temperature should be near 60. If skies are clear for a couple of hours, lows will likely be in the upper 50s.

Tuesday, June 2, 2009

A Few PM Clouds, Hot

Winds have begun the turn to a more southerly direction and that's certainly evident this morning as temperatures are starting out near 66. An area of high pressure is located across South Carolina and this will gradually slide eastward today, which will continue to increase the moisture content across the area. A subtle upper level disturbance is moving through Arkansas this morning and this has contributed to a pocket of cooler temperatures aloft which has supported the development of a few showers and thunderstorms to our northwest and northeast. This disturbance will pass to our north by this afternoon and temperatures aloft will begin to warm. What this means is that we should stay dry and the best chance for showers and thunderstorms today will be to our north where the coolest temperatures aloft are found. Skies will be partly cloudy this afternoon as the high will top out near 92. It will feel hotter today than the last few days since dew points will be higher so make sure you drink plenty of water if you'll be outside doing any strenuous activities. Clouds may increase a bit as we go throughout the overnight hours, and the low tomorrow morning will be near 68.

Monday, June 1, 2009

Hurricane Season Begins

It's June 1 and it's that time of the year again. Yes, today marks the beginning of hurricane season in the Atlantic Ocean and will run until November 30. It's already been active prior to the official start with a tropical depression and strong unnamed system both affecting the Gulf Coast. However, official hurricane forecasts from Colorado State University and NOAA both expect a near average year for tropical cyclone activity in the Atlantic basin. Colorado State is forecasting 12 named storms, 6 hurricanes, and 2 major hurricanes. NOAA, on the other hand, is forecasting 9-14 named storms, 4-7 hurricanes, and 1-3 major hurricanes. The average season consists of 9.6 named storms, 5.9 hurricanes, and 2.3 major hurricanes.

Both forecasts suggest that there may be slightly higher than normal activity for named storms, but hurricane and major hurricane activity should be near normal. A developing but weak El Nino episode (check back soon for a future discussion on this) is cited as the main reason for an average year. Since El Nino has not truly developed yet, it's possible that the early part of the season could be more active than normal. This seems to be a common theme during years where ENSO-neutral conditions are present at the beginning of the season.

In fact, it appears that the middle to end of June could see an upswing in tropical cyclone activity as a Madden-Julian Oscillation pulse moves into the Caribbean. In the middle and later parts of the season, El Nino should be developed to the point that stronger than normal westerly upper level winds will be located across the Atlantic basin. This will enhance vertical wind shear, which will act to rip apart most easterly tropical waves. The tropical systems most likely to cause headaches for the U.S. in the middle to later part of the season are home brew storms that initiate from stalled frontal boundaries or upper level disturbances. Like my buddy Greg Nordstrom always says, it only takes one storm to make an unforgettable season. Most everyone will remember the 1992 hurricane season for Hurricane Andrew, but do you remember how many named storms there were that season? Only six. That's not to say that another Andrew will occur this year, but the point is that only one storm can make a season.

Mostly Sunny, Hot

It's felt rather pleasant in recent mornings, but the thermometer in the afternoon has slowly been creeping upward. An upper level short wave ridge is responsible for the warm temperatures and for limiting the development of afternoon showers and thunderstorms. This means that this afternoon will be hot and dry with a passing cloud from time to time. The high this afternoon will top out near 94! The good news is that dew points will remain low enough that the heat index shouldn't be a major problem. However, it would still be a good idea to drink plenty of water if you'll be outside for any long period of time. By tonight, winds will finally veer to the southeast and dew points will slowly climb throughout the overnight hours. A few stray high clouds are possible early tomorrow morning due to anvil blow off from convection in Texas. The low tomorrow morning will be near 68.