Wednesday Derecho Could Hit Areas Affected By June 2012 Derecho

I have a very real concern that many of the same areas affected by the late June 2012 derecho may be affected by another potential derecho coming up this Wednesday. It should be noted that derechos cannot be accurately predicted, and this may end up just being a regular cluster of thunderstorms.

The Storm Prediction Center has issued a slight risk of severe weather from far western Illinois to central Pennsylvania, expanding from south central Michigan to the bottom 2/3rds of Ohio and Indiana, as the image shows above. This slight risk area is not angled in a position I would expect to see with a derecho potential, but then again, we are still 2 days out from the potential event. The Storm Prediction Center indicates there is room for an upgrade (possibly to a moderate risk of severe weather) for Wednesday, as their discussion shows: ...THE MIDWEST...
   AS THE POTENT SHORT-WAVE TROUGH CROSSES THE MIDWEST...EXPECT SHOWERS
   AND THUNDERSTORMS TO INCREASE THROUGH THE AFTERNOON...WITHIN AN
   AIRMASS ACQUIRING MODERATE INSTABILITY IN CONJUNCTION WITH DAYTIME
   HEATING.  THE GFS AND NAM DIFFER WITH SURFACE FRONTAL EVOLUTION/LOW
   POSITION ACROSS THIS AREA...SO DETAILS REMAIN DIFFICULT TO
   DETERMINE...BUT IN GENERAL A RELATIVELY BROAD ZONE OF AT LEAST
   ISOLATED HAIL/WIND POTENTIAL IS EVIDENT GIVEN MODERATE WLY WINDS
   WITHIN THE LOWER TO MIDDLE TROPOSPHERE ACROSS THIS REGION.  ONCE
   DETAILS BECOME A BIT MORE CLEAR...MORE SUBSTANTIAL WIND THREAT MAY
   BECOME EVIDENT ACROSS PARTS OF THIS AREA...WHICH WOULD WARRANT
   INCREASED PROBABILITIES IN LATER FORECASTS.

A certain WRF model has a thunderstorm complex entering Illinois by 8:00 AM central time. Other forecast parameters gained from the NAM model depict a very moist surface environment, with precipitable water values closing in on 2.00'' in northern Illinois and surface dewpoints beyond 70 degrees. This high moisture content, combined with instability surpassing the 3000 j/kg mark, sets up conditions deemed as appropriate for potential derecho formation by multiple publications from various sources around the National Weather Service. The shape this complex takes on as it moves into Illinois kind of gives away the idea that it will be at least a bow echo; maybe not a full-fledged derecho, but it will at least be some sort of bowing segment that will add to the damaging wind threat. Cities like Chicago IL, Gary IN and South Bend MI could all be affected by this bow segment.

By 2:00 PM Eastern time, this bow segment has progressed into Ohio, practically running over the same areas that were hit by the devastating June 29, 2012 derecho event. This WRF model projects the bowing segment to remain rather small as it moves into Ohio and beyond, although there is still a lot of time for the track and size of this potential derecho to change. Columbus OH, Caldwell OH, Kenton OH and Dayton OH could all be affected by this potential derecho.

Quick note of comparison to those concerned about this being a repeat of June 29- this bow segment event looks to be weaker than the June 2012 derecho, and should cover less ground. The area it tracks over may be very similar, but as far as any potential damage goes, it will likely be exponentially less than what was seen on June 29.

Andrew

'Ring of Fire' Pattern Ramps Up Severe Weather Threat

The upcoming weather pattern will signal the start of summer with the Ring of Fire pattern evolving over the Plains, leading to increased chances of severe weather over parts of the nation.

Over the next 10 or more days, we should see development of high pressure over the Plains, leading to that high pressure system settling in over the region and permitting the development of the Ring of Fire. In the Ring of Fire pattern, high pressure fills much of the Plains and sits there for a prolonged period. In response, multiple mesoscale convective systems (MCS's) will form on the edge of this high pressure system (usually the north and east sides of the ridge). It is these MCS's that put the 'fire' in the Ring of Fire. Short range models already have over three MCS's hitting Iowa and Illinois in the next 84 hours, which could lead to over 2 inches of rain in some spots.

The Ring of Fire pattern is considered one of the better patterns for severe weather. It's not a convective system every few days- we're talking instances of possibly more than once MCS each day. No guarantees on if that will happen this time around, but the potential is certainly there.

Andrew

Tropics Heat Back Up in Late June, Early July

After the first named storm of the 2013 Atlantic Hurricane season was also the first system to make landfall on the US Mainland this season, questions arise as to if the rest of the season will involve more landfalls and tropical cyclone formations. While my Official Outlook can address those questions, the one we're here to answer is when the next shot at tropical cyclone formation is.

The long range GFS model has been supportive of another tropical cyclone forming in the Gulf of Mexico, proceeding to make landfall in either Texas or Mexico. This would supposedly happen in the final days of June. While the GFS has been trending with this idea, I see a much better potential coming on in the first weeks of July, as what could be a strong Madden-Julian wave makes its way eastward towards the Atlantic. Already in the Gulf of Mexico we can see some light shades of green, meaning below normal velocity potential values and thus a better chance for tropical convection to fire up in the area. If the MJO wave is able to sustain itself and shift into the Atlantic, I would not be surprised to see a solid hurricane (or multiple tropical systems) form as a result.

With a pattern still conducive to development sticking around to the end of June on the US Mainland, it is possible that the chances of tropical cyclone formation may be enhanced.

Andrew

Tropical Storm Andrea - Bulletin #2

Satellite imagery for Tropical Storm Andrea shows that the system has indeed strengthened overnight, with her western flank now starting to build back in the immediate vicinity around the eye. Aircraft reconnaissance last night showed very strong winds in the southeast quadrant of this tropical storm, where winds maxed out at or just above 60 knots. That little eye-like feature we see would be another sign of strengthening if the system wasn't right up against Florida.

My potential landfall zone now extends further north, from Apalchicola to roughly New Port Richey, FL. My expected point for landfall is nearly due west of Gainesville, but that could change in coming hours. Landfall is expected in the afternoon, with tropical storm force winds already starting to scrape west-central Florida. With a tornado watch in effect, it can be expected that an all-day tornado threat will continue to evolve today. We have already seen a few reports of tornadoes, but nothing in an outbreak context is expected.

Andrew

Tropical Storm Andrea - Bulletin #1

As we hinted at on May 28th, satellite imagery and aircraft reconnaissance  confirms the formation of Tropical Storm Andrea at this hour, allowing the Atlantic tropical season to get off to a fast start. Satellite imagery depicts a strong eastern flank of Andrea but a very quiet western side to this tropical storm. Considering the conditions in the Gulf of Mexico aren't totally primed for tropical formation, the rather unusual build of this cyclone isn't that extraordinary. Satellite imagery also indicates clouds from Andrea have already overspread Florida, and it is in Florida where I expect the primary landfall to occur.

Atmospheric steering winds for this afternoon over the Atlantic basin are shown to be trying to push Andrea due north into Alabama, and the official National Hurricane Center track predicts the tropical storm to move slightly north in coming hours. However, going into the next few days, it is anticipated that these steering winds will begin to gain a more eastward component, allowing Andrea to maintain less of a northward track and more of an eastward track, combining to make for a northeast movement.

Landfall is expected to occur Thursday afternoon.

I believe the potential landfall zone will extend from the immediate vicinity of Cross City to Sarasota, Florida. This zone is where the models are converging for a landfall. The yellow star indicates where I believe the cyclone will make landfall. This landfall spot would be right around Hudson and New Port Richey. It is expected almost everyone in this potential landfall zone could experience tropical storm force winds and potentially flooding rains. Preparation plans are advised to be activated as the first named system of 2013 becomes the first landfalling system of 2013.

Andrew