Colorado Wildfires Rage; No End in Sight

The fires in Colorado continue to ravage the state, with the Black Forest fire doubling in size yesterday and becoming the most destructive in state history.

Satellite imagery above shows smoke from these fires billowing across Colorado and even into the western Plains as meteorological summer is only 13 days old. Poor winter conditions, combined with an ongoing drought through the Plains and Western states have led to the enhancement of annual wildfires.

Considering the atmospheric pattern currently in place appears to have enhanced wildfires (especially the Black Forest fire), it is unlikely we are going to see a break from these fires. The pattern coming up in the next 16 days involves little to no precipitation (under 1.00'' of rain) for areas currently experiencing these wildfires. With temperatures likely to stay high, and winds unlikely to cease in the next few days, it is highly likely that these ongoing wildfires will be enhanced.

Model projections from the HYSPLIT model suggest smoke from these wildfires will track north across Wyoming, Montana and North Dakota before shifting well into Canada. From there, any smoke still prevalent in the air mass will either circle around in Canada and shift east or dissipate in the western portion of that nation.

Regardless of where the smoke goes, it is the unfortunate probability that the next several days will see an enhancement of ongoing wildfires in the state of Colorado.

Andrew

Late June/Early July Holds Tropical Threat

Latest indications are that the next tropical threat could arise in late June into early July, and that this threat could be more formidable than when Andrea formed.

The long range forecast over the seven day period from June 20 to June 27 depicted above shows upper level divergence anomalies. Areas of green depict below normal anomalies and thus increased chances for enhanced tropical convection, while above normal anomalies signal a less favorable environment for tropical convection. The GFS Ensembles project these divergence anomalies to drop into the below-normal range and increase the risk of tropical cyclone formation. This would supposedly be associated with a Madden-Julian Oscillation (MJO) wave making its way to phases that are favorable for tropical cyclone formation. However, a comparison to other models suggests that the GFS Ensembles may be a bit too fast with the movement of this MJO wave into favorable phases, and that is why early July remains on the table for timing.

The GFS Ensembles, between June 23 and June 28, then predict a large swath of the Gulf of Mexico to be under the influence of rather substantial low mean sea level pressure (MSLP) anomalies. This would seem to indicate the willingness of the GFS Ensembles to attempt and formulate an environment favorable for tropical cyclone formation. Towards the end of this particular GFS Ensemble run, the SLP anomalies are even lower than what is shown above, leading me to believe there is a growing consensus that late June into early July is a reasonable timeframe for the Atlantic basin's second shot at tropical cyclone formation. Support by the aforementioned MJO wave would make this second shot the more formidable of the two.

Andrew

Derecho Likely Tomorrow; Moderate Risk Issued

The likelihood for a derecho is on the rise tomorrow, as new model data and an upgrade from the Storm Prediction Center launch Wednesday into a significant weather event status.

The Storm Prediction Center has issued a moderate risk of severe weather for much of Illinois, nearly all of Indiana and the western half of Ohio in anticipation of a potentially significant weather event tomorrow. Latest reasoning from the SPC cites abundant and high instability in the highlighted areas, as well as high moisture content in the lower levels of the atmosphere as supportive for a significant damaging wind event. Expectation is for isolated supercells to grow into a bowing line segment, with the potential for a derecho to evolve.

Model probabilities for derecho formation tomorrow afternoon into the evening hours are pretty high, with upwards of a 70 percent chance of derecho formation across nearly all of the moderate risk area. My personal expectation is for the moderate risk to be modified slightly further east to account for increasing derecho parameters late Wednesday into early Thursday, however if the moderate risk were to remain unchanged I would understand the reasoning.

Evolution of this significant weather event should commence with multiple cells in northern and western Illinois before coagulation of these cells brings about a line segment of storm cells. With time, this segment should easily bow out and develop the danger for some serious damaging winds. Derecho formation is most likely to commence in east-central Illinois, throughout Indiana and into western Ohio. High resolution models initiate convection in the early afternoon hours, roughly around 4 PM Central time. Upscale development into a sustained bowing segment should ramp up going into the evening hours of 6 or 7 PM central.

 Oddly enough, this bow segment is expected to follow an almost identical path as the June 2012 derecho that left thousands upon thousands with damaged property across a wide swath of this country.  While the environment is not conducive for an incredibly damaging derecho like the one observed last year, it is very possible we could see a weaker derecho move through Indiana and Ohio after commencing in Illinois. Damage is possible.

Andrew

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