"But seeing they could not See; hearing they could not Hear"
“The views expressed herein are those of the author and do not necessarily represent those of the National Weather Service or affiliate/related organizations. Please consult .gov sites for official information”

"From its chamber comes the whirlwind, and cold from the scattering winds." - Job 37:9.

"The wind blows to the south and turns to the north; round and round it goes, ever returning on its course".

Thursday, April 28, 2011

Slight Chance of Strong to Marginally Severe Storms Today - With Caveats

This is the official thunderstorm outlook issued by the Storm Prediction Center (SPC) this morning.
Severe Storms are Possible Roughly north of I-4. Additional images are included further down in this post with a slight variation to this outlook of the authors own  only

WEB PAGE UPDATES: If you haven't visited the web page recently, you will now find the current, running  conditions for Cocoa Beach just south of SR 520 reflected on the page. This information is not available via mail distribution. The page has been reformatted to hold larger images and the Post History (archives) is now only available view a pull down menu so that the day's post (only) will load faster. 

RECAP: If you are not already aware, an EPIC TORNADO OUTBREAK has occurred over the past 24 hours in the Deep South from Mississippi, Alabama, North Georgia, parts of North Carolina, Tennessee, South Carolina and Virginia just to name a few. The fatality count when I woke was 174 and is now over 217. The huge piles of twisted debris (including vehicles) is still being dug through, so it seems probable that more fatalities will be accounted for before the day is through.  The shear number of tornadoes and the path length of a few of them, one (or many) of which were generated from one single storm that tracked over 300 miles from Mississippi to nearly Virginia, is astoundingly record breaking or nearly so.  Yesterday is going down in weather history to match that of the infamous Tri-State Tornado of March 18, 1925 and the Super Outbreak of April 1974.  Interestingly, another infamous outbreak occurred in Kansas on nearly the same date  (April 26, 1991).  In fact, one of the tornadoes yesterday, the worst so far known of which hit a part of Tuscaloosa, Alabama closely resembled the Andover Tornado from certain angles with the appropriate lighting.

 This day is already going down in Meteorological History as an Epic Event of unmatched or nearly so proportions due to the number and intensity of tornadoes. In fact, there was more tornadoes reports or nearly so that of hail.  Aerial and ground assessments are being made today to determine the strength, width, and length of tornado paths. I have not seen any indications of EF5 intensity yet, but certainly EF3/EF4 strength tornadoes will be determined (on a scale of 0-5).  I am not going to go into the finer details, images, and video links that are widely available on the Internet concerning this event in assumption that anyone who desires to hunt this information out can easily do so at will with minimal effort via a Google or YouTube Search. There is a LOT of video out there that is quite astounding and shocking, but this is one is a astounding for starters. Once you reach this link, you will see others as well. This tornado resembles the Andover, KS Tornado of April 26, 1991:

RECAP LOCALLY: A few storms finally materialized after dark yesterday which impacted mainly Okeechobee and Osceola Counties. The storms made it as far east as the Brevard County line. Lightning was beautifully visible from the beaches of Brevard and surrounding areas as the activity peaked, but as it reached Brevard it ran into a stout, strong sea breeze 'wall' and collapsed.

TODAY: The Storm Prediction Center has issued a severe thunderstorm watch box this morning for most of the area in the outlined Slight Risk area shown above. 

Refer to for details.

Otherwise, they have  'generously' placed the entire peninsula in a chance of thunderstorms today; however, most of this area will not receive rain today. Therefore, I introduce the self annotated images  below:

The first image shows the current location of an approaching cold front with my own slight risk area overlayed on the current (high) dewpoints. Note  that really the only difference in my self assessed slight risk for severe  is that it is a bit further south than that of the official outlook.

To the right is the SPC outlook for General Thunderstorms which shows all of the state in a chance of thunder after 4pm with a higher chance of coverage within the bounds of the blue line. I have added two items here. First, the extension south of a chance of severe level thunderstorms (green line)  and second, the chance of strong thunderstorms within the orange/brown area.

Note that these areas do NOT mean that everyone within either of these regions will even receive rain today. Storms will be isolated, with a greater coverage or chance (more appropriately) of coverage within the two areas. No guarantees. Odds are there will be less coverage rather than more than current thinking. 

TODAY: Cold front will move only slowly South and East today through sunset. The strongest activity will be located closer to the front where the more favorable wind fields exist to support severe level type storms combined with colder air aloft  for  stronger surface thunderstorm winds and possibly hail, although it  does not seem severe sized category hail is possible south of a St. Augustine to Cedar Key line.

FURTHER SOUTH: First off, be aware that the activity over most of North Central Florida to South Florida will be in no way related to the Epic Event that occurred yesterday over parts of the Deep South into the Mid-Atlantic and Mississippi River Valley Basin area. Today will be more like a summer day over Central and South Central Florida that would favor stronger storms due to 1) a dry mid layer, and 2) somewhat cold air aloft, but not impressively so.
This activity will be most enhanced near Lake Okeechobee Boundaries and/or both west and east coast sea breeze convergence boundaries just inland from either coast or a combination thereof.

Yesterday, the sea breeze boundary started up not only earlier than thought  by several hours, but was also stronger. Even as I type the same trend seems to be getting underway. Winds at Melbourne are SSW though still,  whereas at the beach in Cocoa Beach the winds are SE-SSE so perhaps the sea breeze is holding off just a bit more today.

The first image above is an overlay with dew point temperatures. We see very high dew point air at the surface embedded within the prevailing SSW Flow off of the Gulf. However, not shown is a pronounced tongue of warm, dry air in the mid levels.  

Therefore, the atmosphere south of the Slight risk area (especially on the east side) will remain capped and non-conducive for even a shower well into the early afternoon.  A weak surface, thermal type low pressure circulation could develop over the interior through early afternoon which might enhance the east coast sea breeze south of Daytona Beach, but I do not think that low level moisture will be completely scoured. 

What happened yesterday to prevent daytime storms, as I see it, was that the winds at the lower levels over came the winds in the mid-levels and essentially 'cut-off' any otherwise potential convection. This very will could be the case once again today; however, given that nearly every single model is breaking out precipitation this morning I will not differ far from this solution. However, I think it will be only isolated in nature rather than the great coverage that is shown by model guidance. Assuming it can manifest at all.

The capping environment is forecast to break down from west to east beginning around 1-2pm..with activity spreading west and south from North and Northwest Florida...and possibly up from the SW near Lake Okeechobee after 2:30pm. 

Showers/storms appear will enter Central Florida proper (such as Orlando/Daytona/Lake County between the hours of 3pm- 6pm with the strongest storms just west of how far inland the East Coast Sea-breeze penetrates. Expecting it to penetrate inland more the further south one goes, thus the slanted nature of my "Possible Strong" area.

It is possible that no thunder will be revealed east of I-95 south of Titusville/Mims area...but this is not set in stone.

**For Official short term graphic casts and hazardous weather potentials please consult the NWS web page/blog at. This page is normally updated by them as conditions warrant for either the good or bad. (Central Florida Interests).

OTHERWISE: Activity will dwindle after dark, although some nocturnal activity once again cannot be fully discounted anywhere over South Central Florida toward the east side.

OVERNIGHT: The cold front itself will move south into Central Florida with the best chance of rain showers just ahead to just behind the boundary along the east side of the state from Daytona Beach to Ft Pierce. The front will be located approximately near South Brevard shortly after day break.

FRIDAY: The front will progress in a much weakened state with virtually no upper level support remaining as it continues south toward Southern Palm Beach county by peak heating hours. South Florida can expect another day of diurnally driven thunder and showers until it progresses to the Keys or Florida Straits after dark.

WEEKEND: Onshore winds of 10-18 mph over the weekend. Much drier to start the weekend with only a gradual moistening of the atmosphere through Monday morning...with a bigger rebound into Tuesday afternoon. Another front will approach the state on Tuesday into Wednesday, but just exactly where it will get hung up to the north, if it does, is TBD. It might not reach the state at all. 

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