…GULF COAST STATES TO SERN ATLANTIC COAST…

AS MENTIONED IN THE SYNOPSIS…SEVERAL MIDLEVEL IMPULSES ARE EVIDENT IN MORNING WATER VAPOR IMAGERY TRANSLATING GENERALLY EWD ALONG LOW-LEVEL BAROCLINIC ZONE. VISIBLE SATELLITE IMAGERY SHOWS MORE EXTENSIVE CLOUD COVER THIS MORNING ACROSS THE TN VALLEY INTO THE CNTRL/SRN APPALACHIANS. HOWEVER…AREAS TO THE S WILL LIKELY EXPERIENCE STRONG DAYTIME HEATING. WHEN COUPLED WITH LOWER/MID 70S DEWPOINTS…ENVIRONMENT WILL BECOME MODERATE TO STRONGLY UNSTABLE BY AFTERNOON. ALSO OF NOTE…12Z OBSERVED SOUNDINGS AND CURRENT VWP DATA SUGGEST A BELT OF 30-35 KT FLOW PRESENT IN THE 3-6 KM AGL LAYER…WHICH WHEN COMBINED WITH THE STRONG INSTABILITY WILL LIKELY FOSTER CORRIDORS OF MORE INTENSE STORMS…PRIMARY IN ADVANCE OF THE MORE PERSISTENT MIDLEVEL IMPULSES. THE PRIMARY HAZARD WITH THESE STORMS WILL BE DAMAGING WIND GUSTS.

The clouds preventing heating have, for the most part, dissipated. All that remains are lower level cumulous pockets and those wont affect how the atmosphere heats. Now that the atmosphere is heating, we will gain some fairly strong CAPE values, but mainly by evening. These storms look like they will show up mainly at or after 7 PM, with 2-3 j/kg CAPE and some pretty nice Helicity values. I haven’t seen helicity like this over Tennessee in a while, so it could be nice. This helicity will also allow for the possibility for tornadoes, with the EHI model showing values ranging from 1-3 over a large area, mainly over western portions of the mid state.

So, in summary…

Thunderstorms will be widespread across the state, mainly this evening but a scattered thunderstorm cannot be ruled out before then. There will be large amounts of instability and shear, allowing for thunderstorms with threats mainly being damaging winds/hail. Tornadoes cannot be ruled out as well.

I am hoping to catch one of the earlier storms, and maybe even tonight’s storms. Check back for updates!

Update: all of Middle Tennessee is under a Flash Flood Watch

DISCUSSION AND 48-HOUR OUTLOOK

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AT 100 PM CDT…1800 UTC…THE CENTER OF TROPICAL STORM ALEX WAS LOCATED NEAR LATITUDE 22.9 NORTH…LONGITUDE 93.6 WEST. ALEX IS NOW MOVING TOWARD THE NORTHWEST NEAR 13 MPH…21 KM/HR. A GRADUAL TURN TOWARD THE WEST-NORTHWEST IS EXPECTED ON WEDNESDAY. ON THE FORECAST TRACK…THE CENTER OF ALEX WILL APPROACH THE COAST OF NORTHEASTERN MEXICO AND SOUTHERN TEXAS ON WEDNESDAY AND MAKE LANDFALL WEDNESDAY NIGHT. MAXIMUM SUSTAINED WINDS ARE NEAR 70 MPH…110 KM/HR…WITH HIGHER GUSTS. STRENGTHENING IS FORECAST DURING THE NEXT 36 HR OR SO BEFORE LANDFALL…AND ALEX IS LIKELY TO BECOME A HURRICANE LATER TODAY. TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 140 MILES…220 KM FROM THE CENTER. NOAA BUOY 42055…LOCATED ABOUT 65 MILES SOUTHWEST OF THE CENTER…RECENTLY REPORTED 1-MINUTE MEAN WINDS OF 38 MPH… 61 KM/HR…AND A WIND GUST OF 45 MPH…72 KM/HR. THE MINIMUM CENTRAL PRESSURE REPORTED BY AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT IS 981 MB…28.97 INCHES.

The storm surge forecast is showing heights ranging anywhere from 3 ft to 6 ft as the hurricane moves in over southern Tx/Mexico. This is not a good thing because of how close to sea level most of the gulf is. If you are at 3 ft or below, I would recommend taking some precaution before this storm moves in. At one point this hurricane was forecast to reach Category 2 strength, but the latest observations indicate that it will remain a Category 1 hurricane until it makes landfall, where it will weaken. Again, the center will make landfall on the Tx/Mex border, but the rest of the storm will impact the majority of the gulf. Take action as needed, but thankfully this wont be too serious. However, please take local National Weather Service advisories seriously. Be safe.

In my own front yard! At 4:49 PM CDT the National Weather Service has issued a severe thunderstorm warning for davidson county. Here is the text…

* AT 445 PM CDT…NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A LINE OF SEVERE THUNDERSTORMS CAPABLE OF PRODUCING DAMAGING WINDS IN EXCESS OF 60 MPH. THESE STORMS WERE LOCATED ALONG A LINE EXTENDING FROM 15 MILES WEST OF ASHLAND CITY TO BURNS…MOVING EAST AT 40 MPH.

So, I decided that since I would be unable to go mobile with the storm, I would make the best of things. I grabbed a tripod, my anemometer, and a zip tie and marched across the street to Julia Green Elementary to set up the anemometer in the best position to measure windspeed. After I got it set up, I grabbed some rocks to anchor the tripod, and then ran back to the house to grab the camera. I had decided that I would stay and observe the updraft side until the core was near hitting and then I would run back home. May I say that that was the most photogenic storm I have seen to date.

The updraft created a weird coronal phenomenon, and you can see it in the gallery below. The other incredible thing, I experience a true and genuine updraft and it scared me pretty bad… warm and almost hot air started rushing towards the thunderstorm, and the clouds above were extremely turbulent. Some clouds began to weakly rotate, while there was some scud also lifting into the base. Just barely, but enough to keep me on edge and repeating, “I have GOT to get out of here…” It was quite the experience, and one of my favorite storms to date.

I was also able to collect some cool data with the anemometer. It recorded windspeed, barometric pressure, dewpoint, humidity, heat index… you name it, it measured it! There were some very cool things it observed… for example, the temperature rose as the thunderstorm drew near, and dropped 25 degrees once the downdraft hit. Max temperature was 101.8, and min was 75 Fahrenheit. The humidity also greatly increased after the downdraft passed over. Minimum Barometric pressure as the updraft passed was 29.89 inHg, with a max of 29.97. Enough of the data, you all just want the photos =) Have at it!

PLEASE leave your comments below!

[View with PicLens]

This outflow boundary that is surging ahead of this line can do one of two things. On one side, it can act as a lifting mechanism, creating more thunderstorms. Or, on the other side, it can cut off and kill these current thunderstorm’s updrafts, causing it all to die. With the current speed and trajectory of the outflow boundary (also known as a gust front), I am guessing it will do the latter. I will keep monitoring things and radar and update as things happen.

The SPC has placed all of Middle Tennessee under a Slight Risk for severe storms today. We have FINALLY picked up some wind shear, so now it looks more favorable for longer living and more severe storms as opposed to the pulse storms we have been having all week. Here is what the SPC says about today…

…TN VLY/SRN APPALACHIANS INTO ERN KY…NC…SRN VA…

MODERATE TO STRONG INSTABILITY WILL DEVELOP WITH DAYTIME HEATING ALONG PORTION OF COLD FRONT CROSSING PARTS OF KY/TN…AND ALONG PREFRONTAL TROUGH OVER VA/NC. MID/UPR LVL FLOW AND ASCENT WILL INCREASE OVER THESE AREAS AS REGION IS GLANCED BY SRN FRINGE OF GRT LKS TROUGH. 35-40 KT WNWLY 700 MB WINDS COULD SUPPORT ORGANIZED STORMS WITH DMGG WIND/HAIL…ESPECIALLY OVER NRN PARTS OF THE REGION. THE SVR THREAT COULD PERSIST INTO MID EVE IN VA/NC.

The SPC even dared to include us in todays tornado risk. At the moment it is a very low risk, but I could honestly care less. Even a small risk gives me hope for something! The models do agree with the possibility of a weak tornado, thanks to the wind shear we have today. However, if a tornado were to develop I would imagine it would be brief. Still, a tornado is a tornado and there is a chance (albeit extremely small) for one today.

So, at the moment a cold front is digging southeast towards us. This will be the mechanism to initiate storms today, and you can see on this radar image that it is already storming our way. My guess is that scattered thunderstorms will arrive in the northern part of the state between 11 AM and 12 PM. However there is a lot of room for error in that guess, so don’t hold me too hard to it. Main risk is large hail and damaging winds, so be looking out for that.

THE NWS STORM PREDICTION CENTER HAS ISSUED A SEVERE THUNDERSTORM WATCH FOR PORTIONS OF

NORTHEASTERN             ARKANSAS

SOUTHERN KENTUCKY

MISSOURI BOOTHEEL

FAR NORTHWESTERN MISSISSIPPI

WESTERN AND MIDDLE TENNESSEE

EFFECTIVE THIS THURSDAY AFTERNOON AND EVENING FROM 215 PM UNTIL 800 PM CDT.

HAIL TO 1.5 INCHES IN DIAMETER…THUNDERSTORM WIND GUSTS TO 70 MPH…AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.

DISCUSSION…THUNDERSTORMS HAVE DEVELOPED ALONG A ZONE OF WEAK CONVERGENCE IN NERN AR/WRN TN AND ARE EXPECTED TO DEVELOP NEWD INTO SRN KY. STRONG INSTABILITY COMBINED WITH STRONGER WINDS ALOFT WILL LIKELY RESULT IN STORMS WITH SEVERE HAIL…LOCALIZED DOWNBURSTS AND HEAVY RAINFALL.

The probabilities for the watch are:

Tornadoes: Very Low (<5%)

EF-2+ Tornadoes: Very Low (<2%)

Severe Wind: Low [10 or more wind events (20%)]

65 kt+ Wind: Low (20%)

Severe Hail: Moderate [10 or more hail events (30%)]

2″+ Hail: Low (20%)

Probability of 6 or more combined severe hail/wind events (60%)

The tornado risk for today is nearly non existent due to lack of helicity (wind shear), and therefore the SPC doesn’t even show a tornado risk over Tennessee. I don’t know what the SPC is looking at, but they are saying that there is enough deep layer shear to sustain these multicell lines, and warrant the risk of hail and damaging winds. I sure hope they are right, because I am itching for a good storm! There are great CAPE values for the day, and I have also noticed that there is very weak capping over Middle Tennessee today. This may be beneficial in preventing the weaker storms from developing. Then again, maybe not… I am still learning a lot about forecasting, so who knows. Enough of my blabbering, here is what the SPC has to say.

…DELMARVA WWD ACROSS THE SRN LOWER OH AND TN VALLEYS…

SEVERAL FEATURES SHOULD AID IN SCATTERED TO NUMEROUS THUNDERSTORMS DEVELOPING ACROSS THE REGION THROUGH THE AFTERNOON HOURS. FIRST FEATURE IS REMNANT MCV…CURRENTLY APPROACHING WRN PA. CURRENT MOTION/EXTRAPOLATION PLACES THIS FEATURE INTO S CENTRAL PA/MD PANHANDLE BY MID AFTERNOON. WEAK CONVECTION HAS ALREADY DEVELOPED AHEAD OF THIS SYSTEM OVER WV…AND SHOULD INTENSIFY AS MOVES INTO VA/MD PANHANDLE/SRN PA THIS AFTERNOON… REFERENCE MESOSCALE DISCUSSION 784.

FURTHER WEST…ANOTHER WEAK SURFACE LOW WAS LOCATED IN FAR NWRN OH…WITH A SURFACE TROUGH EXTENDING WSWWD INTO CENTRAL MO. THIS TROUGH WILL MOVE SLOWLY SWD AND CONVERGENCE WILL BE ENHANCED AHEAD OF IT AS AN UPPER THERMAL TROUGH SHIFTS EWD ACROSS THE TN/OH VALLEYS. DEEP LAYER SHEAR AT 20-30 KT WILL BE SUFFICIENT FOR SUSTAINED MULTICELL STORMS…AND IN CONJUNCTION WITH MODERATE INSTABILITY…SEVERE HAIL AND DAMAGING WINDS WILL BE POSSIBLE DURING THE AFTERNOON/EARLY EVENING HOURS.

Right now there is a mesoscale discussion in effect for western Tn, where a Severe Thunderstorm Watch appears possible. There may be one issued for northern Mid Tn later, but for now I will post the discussion.

AREAS AFFECTED…

NERN AR…BOOT HEEL OF MO…WRN TN…KY CONCERNING…

SEVERE POTENTIAL…WATCH POSSIBLE

VALID 031758Z – 031900Z

A PRE-FRONTAL ZONE OF LOW LEVEL CONFLUENCE CURRENTLY EXTENDS FROM NERN AR…NEWD ALONG THE OH RIVER INTO NRN KY. THIS AXIS WILL LIKELY BECOME THE FOCUS FOR STRONG THUNDERSTORM DEVELOPMENT OVER THE NEXT FEW HOURS AS BOUNDARY LAYER CONTINUES TO WARM/DESTABILIZE. GIVEN THE MARGINAL DEEP LAYER SHEAR IT APPEARS MULTI-CELL UPDRAFTS WILL BE COMMON WITHIN MODERATELY UNSTABLE AIRMASS. LOCALLY STRONG DOWNBURSTS AND HAIL COULD ACCOMPANY THE MORE ORGANIZED STORMS.

So, updates will come later as things progress. I would say it is safe to assume that if you are within the slight risk area, you will see some t-storms today. I just took a look at the SPC Hourly Mesoscale Analysis, and i see more favor in those models. As you can see, thunderstorms are already developing in western Tn. I will be sure to update if we get a severe thunderstorm watch.

The SPC has expanded its slight risk for today into northern and western Middle Tennessee. A squall line is pushing in from Kentucky, with the main threat being large hail and deadly lightning. I am forecasting this from my phone, so I have no idea what the timing is on the squall but I can tell you a weak tornado or two cannot be ruled out. The SPC has us under the 2% tornado risk, so we will see how that goes. Now I will post the SPC graphics.

So, I will see if I can add more info to this post, but that is all for now. This could be a fun one =).

“Sources of uncertainty in this seasonal outlook

1: Predicting El Niño and La Niña (also called ENSO) impacts is an ongoing scientific challenge facing climate scientists today. Such forecasts made during the spring generally have limited skill.

2: Many combinations of named storms and hurricanes can occur for the same general set of climate conditions. For example, one cannot know with certainty whether a given climate signal will be associated with several short-lived storms or fewer longer-lived storms with greater intensity.

3: Model predictions of sea-surface temperatures, vertical wind shear, moisture, and stability have limited skill this far in advance of the peak months (August-October) of the hurricane season.

4: Weather patterns that are unpredictable on seasonal time scales can sometimes develop and last for weeks or months, possibly affecting seasonal hurricane activity.”

The outlook says that there is an 85% chance that this hurricane season will be above normal, 10% chance of a normal season, and a 5% chance of a below normal hurricane season. The outlook also says that if this forecast ends up being true, and hurricanes tend to be on the upper end of the forecast, this 2010 hurricane season could be one of the most active on record. The Climate Prediction Center says the following in their outlook:
“We estimate a 70% probability for each of the following ranges of activity this season:

14-23 Named Storms,
8-14 Hurricanes
3-7 Major Hurricanes
An ACE range of 155%-270% of the median.”

ACE is the Accumulated Cyclone Energy index, and it forecasts the intensity and longevity of hurricanes for a particular season. A quote about ACE, “According to NOAA’s hurricane season classifications, an ACE value above 117% of the 1950-2000 median reflects an above-normal season. An ACE value above 175% of the median reflects an exceptionally active (or hyperactive) season.” In other words, there may be a lot of hurricanes this year. However, this does not predict hurricane landfall, only formation. The Climate Prediction Center does say, however, that historical records show that active seasons have an increase in hurricane landfall.

Yet another quote, “Because of the ongoing oil crisis in the Gulf of Mexico, we are including some historical statistics of tropical cyclone activity for this region (excluding the Bay of Campeche) based on past above normal seasons. These statistics do not represent an explicit forecast for tropical cyclones in the Gulf of Mexico during 2010, as it is impossible to reliably predict such activity so far in advance. Historically, all above normal seasons have produced at least one named storm in the Gulf of Mexico, and 95% of those seasons have at least two named storms in the Gulf. Most of this activity (80%) occurs during August-October. However, 50% of above normal seasons have had at least one named storm in the region during June-July.”

So, this hurricane season may be one bumpy ride! As tropical storms develop over the next few months, I will make forecasts here on the website and try to constantly update as much as I can. Having family live right on the gulf, some of which were badly affected by hurricane Ike, it is definitely something personal. My hope this year is to be able to intercept a hurricane, but I would much rather no hurricanes at all. So, as we come into hurricane season, get your plan together.