TS Issac appears to be making the LA Coast his target

Those following me on Facebook know the questions and consternation about the destiny of TS Issac.  At first my thought was that the -SOI from Aug 7 - 15 would have successfully introduced a progressive weather pattern thus turned the storm toward the east coast of FL and the SE Coast.  It appears that 2 years  of blocked weather patterns are not easily swept away.

The biggest winner so far in determining the TS Issac track has been WxRisk.com.  David Tolleris correctly chose the Central Gulf as the target zone.  Now that Issac is past the disruption of dry air and Hispaniola + Cuba we will now see the various tools used to determine the track of the system become more accurate.

In the Water Vapor image below I highlighted the frontal system stretching across the middle of the country and the current direction of the moisture plume preceding Issac.  Eventually Issac's circulation will be influenced by the front and be turned right.  The question is whether that influence and the weakness between the Bermuda High and the Inland heat ridge draws the storm sooner or later.

Source: Univ of Wisconsin SSEC

There are good reasons to be fearful for the whole region. Not only is New Orleans likely to be affected to some extent, there are a great deal of Refinery assets at risk,   Gasoline prices are already exorbitant.  Outages in the limited US Refinery capacity would seriously impact the price of gasoline and other oil based products.

Ernesto not worthy of a name

What I would now call an alleged Tropical Storm, Ernesto, was looking good yesterday.  The steering flow strengthened late yesterday which both increased his speed and resulted in the center losing its alignement with convection.  Further damage to the storm took place when he ran headlong into dry air.  Now it takes imagination to see more than a strong tropical wave.

Ernesto's central pressure has been a bit unconventional for a tropical storm.  His lowest pressure has been near 1006 MB, not all that impressive.  His winds and cyclonic spin were baroclinically enhanced by high pressure located N and another W of the system.  Now that those relationships are weakening, Ernesto has to power himself via tropical means (oceanic heat) if he wants to succeed going forward.

Here is a Water Vapor image showing Ernesto (South) and an open Tropical Wave affecting FL.  So, why would Ernesto not simply be a bigger version of the FL Tropical Wave?

Source: Univ of Wisconsin SSEC

Being weaker or non-existent "Ernesto" will track most west and will eventually impact southern Mexico and Belize.  If anything substantial finds its way into the Bay of Campeche then it may be possible for a storm to be worthy of a name.

Ernesto slows and strengthens, Nice Day here in NC

Ernesto is surprising me a bit. He slowed to 18 mph (which helps the storm structure stay together) and instead of running headlong into dry air and shear has a nice environment to develop. The other system over the Bahamas yesterday is now moved just east of FL and is running out of space but still has inflow and outflow... so that one may bother FL with heavy rains + strong T-Storms ...BUT... not an organized banded storm.

Here in NC we are benefiting from the simplest of weather principles: High Pressure flows into Low. Therefore a NW flow and drier air is making for a great summer day.  Time to mow the yard so that next weeks rain and t-storms can grow it back again :>(

Source: Univ of Wisconsin SSEC

Tropical System over Bahamas, Explosive Potential

Take notice of the vigorous tropical wave over the Bahamas.  It has a jet stream feeding it and a source of baroclinic energy (NE upper level winds) west of it.  This is something that can birth a tropical storm or a hurricane very quickly because of the hybrid (tropical + veering winds) situation.  take a look at this water vapor image from the Univ of Wisconsin SSEC.

Source: Univ of Wisconsin SSEC

In addition to the potential tropical threat another in an endless series of disturbances will pass through from the NW triggering more Thunderstorms including the damaging heavy and severe variety during the weekend.  So, keep one eye on the sky when doing activities this weekend.

Changes afoot but Summer heat to linger a little longer

If I could take my size 12 foot and kick the weather pattern, it would be done.  The fact is that the Pacific is not just in cold mode, its really cold!  Since weather patterns generally move west to east in our hemisphere it means that drier air than normal ends up in ridges of high pressure overland that outperform and clog up the weather pattern.

There is a proverbial foot kicking the weather machine. Even though cooler air from Canada is not going to reach us this week the march toward a weak El Nino or at least a whole lot less La Nina is clawing its way forward.

The big tipoff that getting cooler will wait until mid-month is the westward tracking of tropical storms in the West Pacific.  This is an indicator of high pressure dominating their eastern seaboard.  Therefore the ups and downs of the jet stream lead to a ridge that heats our region.

Here is the track of Tropical Depression #12 in the West Pacific and its forecast indicates that cooler air is not coming until at least late next week - mid-month.

Source: Joint Typhoon Warning Center

It is a disappointment not to get cooler air by the 4th.  I should have known that the "Super Glue" (TM) that has stuck this weather pattern would not be so easily dislodged.  Do not lose hope! Out in the equatorial Pacific the little island of Tahiti has gotten some rainy days (lower pressure) and Darwin, AU basked in bright sun.  This reversal of fortunes is felt in our region around the 15-16th (like last year).

So, delayed but not denied. Fall, like last year is still coming early.  Our only consolation this summer was the fact that a "sort of " trough was over the region much of the season promoting thunderstorm activity but failing to get temperatures to the normal realm.  Winter has some questions but generally appears colder than average and a sharp departure from the alleged Winter of 2011-12.

Summer 2012's familiar pattern soon coming to an end

This summer is not going entirely as I expected.  June was supposed to be the back and forth month with the wildest weather and the only blast of heat.  July and August was projected to be more reasonable as the last vestiges of the 2 year La Nina had faded away in a transition toward an eventual weak El Nino.  As we know the summer has not gone entirely as planned.

Some good news is that the dog days of Summer will end earlier than last year's Aug 16 date.  Until then a familiar pattern centered further west than 2011 has dominated.  An active and fast Pacific jet stream that is common in a La Nina/Low AAM situation has not yet broken down.  Furthermore, global AAM tanked just in time for the historic heat wave here in the East.  Take a look at the below Water Vapor image from the University of Wisconsin SSEC.

The fast Pacific Jet buckles in the NW US bringing a trough and cool conditions there.
Heat gets concentrated on the SE side of the Jet Stream in a process similar to a heat pump.

In 2011 the jet buckled further inland leading to the epicenter of the heat being over NC.  This year it is further west, locking in the heat over the Central US.  Our region suffered a relatively brief intrusion of outrageous heat at the end of June - early July and has stayed in the "Ring of Fire" periphery since that time.  Therefore since the historic highs most days have been in the mid-upper 90's with plenty of opportunities for rain from the disturbances being transported in by the torrid Central US High Pressure.

Changes are afoot as the La Nina-ish Low AAM condition is receiving a big jolt from Mountain Torque.  My oversimplified explanation is that the buildup of air particularly at the Andes has led to an ever so slight decrease in the earth's rotation in exchange for a jolt of momentum into the atmosphere at the equator.  It will take until the first week of August for the changes to work its way through the global weather machine to NC and VA so just a little more patience is required.

Image Source: NOAA Earth Science Research Laboratory
Note: The negative torque in late June/early July was not
THE cause of the heat wave, but b/c of the season be suspected as
a contributor toward the crash in AAM.

I suspect that some of the long range forecasting problems of recent years has some basis in the best data occurring since the 1960's and especially the 70's.   The period of 1980-2000 was relatively mild compared to the cold Pacific (-PDO) warm Atlantic (+AMO) of this decade.  Our current ocean pattern was more reminiscent of the 1930's and 1950's which still hold most all-time heat records and lots of extreme weather. Therefore we are missing the data that might have led to better accuracy in  forecasting the extremes of recent years.

One good thing is that even stubborn conditions like the extended La Nina must give way to her brother El Nino if only to temporarily satisfy imbalances in the economics that drive the atmosphere.  This and several other influences point the way to a cold winter with a very cold one as a possibility.  Until the Pacific warms and the Atlantic cools the overall propensity toward La Nina and extreme weather can be expected.  

Heavy Thunderstorms may be taking aim at Raleigh-Durham Overnight.

My last check of Radar before heading to bed is a cause for concern.  A fast moving line of heavy to severe thunderstorms is crossing the mountains and seems to be taking aim at the Triangle.  So far the organized system is maintaining its shape and intensity and could be a problem several hours from now if it continues to encounter a favorable environment.

A cause for concern is the vast area of temps in the Low 80's North and West of RDU that would raise the likelihood that the system will hold together through the night.   Oddly enough, areas south and east of the Triangle feature a broad swath of upper 60's to low 70's .  Here in Garner we seem to be in a buffer zone between the warm and cool areas as it is a nice 75 degrees outside.

--
Dean Grubbs
The Dean Report
http://deanreport.blogspot.com