Tuesday, August 28, 2012

Massive Hurricane Issac strengthens as he closes in on landfall

It is still important not to focus on the wind speed as much as the pressure and the size of the system. Hurricane Issac's central pressure is 970 mb, a strong Category 2.  Storm surge near and east of the landfall will very likely be well above what one would expect off a Cat 1. Take a look at the massive sphere of influence that Issac has in the below water vapor image.  Take notice of the tremendous inflow from the deep tropics and the buildup of heat and moisture at the SE US Coast which is far away from the storm center.

Anytime a storm has this influence, it means business!
Image Source:  Univ of Wisconsin SSEC
Issac still has about 12 hours over water.  I would not be surprised to see Category 2 wind speed at landfall and a Category 3 pressure.  We really need to hope and pray for a landfall point less unfavorable to New Orleans.  No one is interested in seeing the city fill with water again.

Monday, August 27, 2012

If the NHC will not promote Issac to Hurricane, I will!

Even though the NHC calls Issac a 70 mph Tropical Storm. I confer upon the storm the title of Hurricane. Issac's 981 mb central pressure is at the low end of Cat 1 (almost Cat 2) and the Eye is becoming apparent. Therefore based on the 
Saffir-Simpson Scale (The detailed description) Issac easily fits into Cat 1.

Last year's devastating storm Hurricane Irene was a "Category 1" that contained a central pressure of 942 (Category 4!). People stayed in the impact area who would have fled. There was a miraculous preservation of life despite the flooding + amazing local wind damage for a "Category 1" storm.

So, when you examine the stats of the hurricane factor in the Central Pressure when determining likely impacts. Even though the highest measured wind speed may be low it does not mean that the ability to produce small scale wind events of much greater damage potential does not exist. The worse problem near the coast was the record storm surge at Oriental, NC, easily equal to a Cat 4 hurricane.  Another argument against Irene being only a Cat 1 was her wide area of damaging influence.  60-80 mph winds spread up the I-95 corridor, far from center.


Sunday, August 26, 2012

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.

Sunday, August 5, 2012

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.

Saturday, August 4, 2012

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

Friday, August 3, 2012

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.

Thursday, August 2, 2012

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.