YES VIRGINIA … and Midwest & Deep South & Middle Atlantic… EXTREME HEAT IS COMING TO END then for some a LOT of rain
2000 EDT 5 JULY STARDATE 201207.05
Back at the end of JUNE I made a post about the potential for the severe drought in the Midwest and Deep South …which has now spread to much of the country… coming to an end sometime after the July 4 holiday. Or at least being significantly diminished. The bases of that forecast was to a large degree made on the projected movement of the current MJO. On JUNE 23 the MJO was on Phase 1 … moving through Phase 2. In late JUNE and early JULY ….Phase 2 favors a hot and dry pattern for the Midwest. But I thought the MJO would reach Phase 3 after JULY 5 — in the month of JULY Phase 3 favors above normal rainfall across most of the Midwest and the Northeast.
That weekend of JUNE 22-23-24 with the MJO in phase 1 there were some areas of moderate rain in the Midwest . However the MJO in Phase 2 stalled at the end of the month and into early July which meant a prolonged interval of more hot and dry conditions over the Pains …the Midwest …and the East Coast. As all of us have seen over the last several days that is indeed exactly what the weather pattern has reflected– worsening drought and more extreme heat with many many locations seeing day after day of 95-105° max temperatures. This image shows the current MJO phase over the last 40 days out we can clearly see it move through Phase 1 and 2 . Notice that all around JUNE 23 the MJO did a ” stall” or little loop which slow down its progression through phase 2 and into phase 3. Thus my forecast for a wetter and somewhat cooler pattern was going to be delayed.
However the new MJO forecast Models do show that the current MJO is going to make it into phase 3 pretty shortly…. and as I have stated that is significant because Phase 3 in the month of July strongly correlates to a wet pattern over the Midwest and the East Coast. Here we have the MJO forecasts from the ECWMF the Ukmet and the euro ensembles. That being said many of these models then EITHER A) weaken the MJO impulse and drop it into the “circle of death” ( which represents the weakening of the MJO impulse to the point where it no longer impacts the weather patters) or B) RETOGRADE the MJO back into Phase 2.
However the MJO doesn’t seem to want to cooperate with the forecast models. Over the past several days the various models used to forecast the MJO have been consistently showing this retrogression yet the MJO keeps moving forward and closer and closer to phase 3.
But decides the MJO …there is more and more evidence showing that the delayed El Nino event is finally beginning to Kick in. This image shows the current SOI values (SOI is a index used to assess atmospheric and ocean water temperatures that bring about either a El Nino La Nina or Neutral conditions). Whenever the 30 day average of the SOI drops below the value of -8.0 El Nino conditions always develop. The current value is -12.9 so as you can see we are past the threshold by a significant amount.
Interestingly .. if you look at the SOI chart you will see that during March and April it seemed that the SOI was dropping steadily and that by the time we reached the early Summer the El Nino would be under way. Indeed many seasonal forecast were premised on that idea. However in MAY 2012 the SOI had a “spike” which drove the SPI values briefly back into positive territory. This delay the onset of El Nino conditions and allow the current pattern from the Winter and Spring to continue into the early Summer…. which aggravated the developing drought conditions and that in turn enhance the very warm pattern of the Winter and Spring into an very hot one for the first half of the summer of 2012.
In addition ocean where temperatures in the ENSO regions are rapidly warming which is another strong sign that the El Nino is beginning to kick in.
If we focus a little closer to home… We can see the current atmosphere a pattern over North America. This image represents the European model from Thursday afternoon and we can clearly see the enormous heat dome covering the Plains and the Midwest.
However important changes are going to take place starting this weekend which will drive the heat dome back to the West coast. If you have any friends or relatives on the West Coast they have had a pretty cool Spring and early Summer but that is about to change. The development of a large upper low over Eastern Canada will begin to cause the pattern to change this weekend. This Upper Low will establish a deep trough in the jet stream over the Great Lakes/ Midwest and the Northeast which will force the Heat Dome back into the West coast and the Rockies . This development of a major trough to form in the jet stream over the Great Lakes and eastern Canada will drive a pretty strong surface cold front from North to South JULY 7-8-9 reaching into the Gulf coast states and the southeast by JULY 9.
As the cold front drive south it piles up the hot temperatures so that the day before the cold front arrives …many areas over the the lower Middle Atlantic states could be the hottest temps we seen in many years. It is possible that the all time high does temperature on record in Richmond could fall ! The NAM Model on Thursday afternoon is forecasting a Max temperature on Saturday of 107°temperatures and as you can see many areas see temps of 105+ over VA and NC.
By July 9 the cold front is going to stall along the Gulf coast and over the Southeast states and it will become a focusing mechanism for developing a lot of rain … NEXT WEEK July 8-15 … for areas that really need it – MS AL TN GA SC NC southern VA and far southern WVA. Some of the rain will probably get into northern VA as well as central and eastern MD DE and southern NJ at times.. but the vast majority of the widespread significant or heavy rains will fall over the Deep south …into southern Virginia .
This first image shows the 12z GFS from JULY 5… in the 6-10 day with a map on the LEFT being the operational Run — note the 6.46″ bulls eye over northwest SC and southwest NC in the high terrain. The map on the right is the GFS ensemble mean rainfall forecast.
This next image shows the rainfall forecast from the 12z GFS Thursday afternoon run for the 11-15 day time frame . Once more the map on the left side is the operational GFS run and the map on the right side is the GFS ensemble run. As you can see both models/ map show additional significant rain over the Tennessee Valley and the Middle Atlantic states but also we see good rains getting into portions of the drought areas in the Midwest.
Finally here is the 18Z GFS ENSEMBLE model runs… for the 6-10 day on the left and the 11-15 day on the right. The 18z GFS is even wetter across the deep south into North Carolina central and Eastern Virginia Eastern Maryland into Southern New Jersey with a large area of 2-4″ rains. Again in the 11-15 day the front is still bringing good rains to the Middle Atlan tic and the Midwest areas.
SUMMARY even though the next two days are going to be very tough for everybody and the Midwest …the Deep South and the East Coast …the Heat Wave IS going to come to an end. The pattern shift starts this weekend. Next week over all of the Middle Atlantic — but a specially over the lower Middle Atlantic ( VA MD DE) and all Southeast states (NC SC GA) and Gulf coast states ( LA MS AL southern TN) will feature above normal rainfall and cooler temperatures because of the overcast skies and the numerous large areas of showers and thunderstorms . Many areas will see as much as 5 inches a rain over a five day but some of the locations over higher terrain— such as Northern GA far eastern TN western NC southwest VA could see up to 8 inches. The Midwest will see temps in the 80s as will the Northern Middle Atlantic and New England states.