Weekend Storm Still Has Many Questions Than Answers!

Some changes to the weekend storm that are worth mentioning.  In my last post I discussed the various model solutions with the GEM (Canadian Model) being the furthest west while the GFS had a coastal storm while the EURO had little phase and the furthest east solution.

Well, AGAIN we have multiple solutions to sort through.




The GFS has now shifted its focus furthest east while the EURO has come back further west along with the GEM.

On the left is the 18z GFS.  This is being treated as the OUTLIER of the model solutions considering it has not lined up with the upper level maps correctly.  The surface low develops way too fast and does not tuck back into the coast (which is the case when you have a 500mb trough becoming negatively tilted.



The Canadian on the left has a very strong low however, keeps the system offshore through Sunday night. The heaviest rains are from I95 east from Baltimore to NYC.  The storm is then forecasted to pivot NW into southern New England as a closed off low intensifies bending the 500mb trough in a negative tilted position.  This is something the GFS has not handled properly











Here's the EURO. (Remember, this kept the low WAY off shore however, has corrected further west). This track mimic's the Canadian as it bends back into central New England. There is even some suggestion of snows over 2000' over the Adirondacks and Berkshires.

It is noteworthy to report the operational models are much further east of their Ensemble members.


Below I have listed the various ENSEMBLE products of the models I have listed above.  The EURO and Canadian both are the furthest west with a coastal storm riding along the jersey shore from Sunday afternoon - Monday Afternoon.  

Severe Weather Threat For The East Coast This Weekend?

Mike Masco
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A forecasting headache is ahead as there appears to be multiple solutions on the table in regards to a storms system that will moving into the eastern third of the nation.  The storm in question is still out over the northern Pacific waters at this time which means the data gathering is limited to a few buoys and simulations.

Short term Forecast.

The Storm over the next 48 hours will come ashore over Alaska and drop down the backside of a ridge west central Canada.  Intensity will play a critical role in how deep the trough gets coming into the Pacific NW.  At the same time a strong Jet Streak will come ashore over OR/WA coastline digging SE on the front side of the Rockies. If the NAM is handling this solution correctly, this would be enough to carve a long wave trough over the center portion of the county.

Agreement: EURO , CMC, GFS




Beyond 72 Hours we come into multiple solutions.  Each solution plays one extreme against the other with rain total potentials between .25 - 2.75" ! THAT my friends is not a compromise ! !

THE CANADIAN (EXTREME SOLUTION)
I call the Canadian 12z model idea the Extreme solution due to the intensity it sees the weekend storm becoming.  I also call it extreme because of the severe weather potential it is showing from GA - NY

The CMC model has a developing low pressure system over the TN valley by Saturday morning with strong WAA (Warm Air Advection) advecting all the way to VT.  The CMC deepens the storm much quicker than all the models creating a full negative tilted jet stream by Saturday evening.  It is at this time dangerous thunderstorms will develop inside the warm sector for GA , NC, SC, VA, MD and beyond going into Sunday.  The Windshear field will expand creating enough spin for potential tornadoes.




THE GFS (COASTAL SOLUTION) 2nd Worst solution

THE GFS follows the CMC's lead with a full phase between the pacific jetstream and southern jetstream.  Warm air will advect northbound however, the region of instability will be confined from eastern VA, NC, SC, FL as the trough will swing further east becoming negative tilted offshore.

This solution favors a coastal front that will setup along I95 enhancing rainfall from Sat night - Monday as the low will track north.  The low strengthens to near 992 before hitting eastern Long Island by Tuesday morning.  This solution spells out significant wind and rain for the east coast while the Ohio Valley and Tenn Valley will undergo negative vorticity advection clearing out by Monday.

The EURO Solution ( NOT A BIG DEAL STORM)

The EURO plays along with the GFS, CMC, and NAM solutions right into Saturday morning.  Positive vorticity advection will be ongoing Saturday afternoon the shortwave deepens over the southern TN valley.  Severe weather will be likely Saturday morning for AL,MS,GA,SC, into Saturday afternoon as the vort max swings east.  The difference comes as the storm tries to lift north.  THERE IS NO PHASE! The north jet pulls north as the low continues its trick ENE.  A phase eventually happens 200 miles east of Cape Cod.




It is hard to come to a correct solution right now from VA - VT however, enough evidence is there to suggest a severe weather situation for Sat-Mon over the SE USA.  Including TN,VA,SC,NC,AL,MS, GA.


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All Eyes on Tomorrow's Tornado Outbreak

BY: Mike Masco

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The big talk today has been over the storm potential for tomorrow and the issuance of the HIGHRISK from the storm prediction center.  

There is NO question that the atmosphere over Kansas, Oklahoma, and Nebraska will be conducive for not only super cell thunderstorms BUT long track F2-F4 type tornadoes.


The image on the right is the latest STP or Significant Tornado Parameter. Anything over 1 suggests tornadoes nearing F2 status while anything over 6 guarantees a loaded atmosphere ready to produce long track tornadoes. 
















The problem tomorrow is the lack of convergence that is expected.  The models have continued to show lack of areal coverage for convection going into tomorrow afternoon (aside from areas north, near the warm front).  


Something I have been monitoring all afternoon is the RPM model runs simulating precipitation intensity going into Saturday.  I tested this model on two supercells in Oklahoma and it nailed the cells down to 10 miles within their development.  There has been little trend towards massive development of convection going into tomorrow (aside from areas near the warm front).  

The possibility of a stronger CAP could be the reason behind this, as the dryline remains nearly stationary tomorrow.  If the CAP holds beyond 0z or 8pm Saturday, there may not be many storms firing ahead of the dry line.  If that is the case the threat for massive( F3+) long track tornadoes may diminish.  If the CAP breaks due to linear forcing after dark we may have more linear storm segments(line segments) that would feature Massive Hail & 60-80MPH wind gusts.


HOWEVER, that is a big IF! IF the CAP breaks early storms will fire immediately due to diurnal heating of the day! 


The 12 Z vs 18 Z GFS and NAM has expanded its convection coverage across Kansas and Nebraska.

Life-threatening Situation Could Develop Tomorrow Over The Plains

The Storm Prediction Center in Norman, OK has issued a rare HIGH RISK region for much of Kansas and Oklahoma going into Saturday afternoon.

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The Setup:

A strong upper level low with associated trough will swing towards the Plains Saturday morning producing a strengthening low level jet from Texas-Nebraska.  As this jet intensifies it will funnel in very moist air raising dew point values to near 70F.

At the same time a stalled dry line will begin its push East, acting as a firing range for storms over central OK,KS,NE.  Deep moisture combined with deep shear will allow for storms to become "Rooted" or established in the boundary layer causing for multiple storms to become "Long Track Tornadoes/Supercells".  

Why The HIGH Risk?

The SPC (Storm Prediction Center) does not always issue HIGH RISK events multiple days out since it's always tough to pinpoint the exact behavior of the atmosphere at a certain forecast time.  However, this situation will be different!  First, the models have remained -eerily consistent with the instability parameters Second, the history of the volatile jetstream/system has produced severe weather in regions that typically DO NOT see severe weather (SanFran & LA).

What does the Storm Prediction Center see? 

Here is a breakdown of some of the many parameters involved in this HIGH risk assessment.

First, Wind Shear.  In order to get the twisting of the atmospheric winds, we need differing winds of strength and direction.  I have drawn in the surface wind along with the upper level winds for you on the 500mb NAM 6z map.  The intersection of upper, lower, and Mid level winds occurs right over central KS and OK.  

- Windshear values will range between 40-60kts in the mid level with upper level winds between 90-120kts.  This is the chance in height and direction needed to give any supercell the forms "a SPIN"! 

Cape values over 2000 j/kg support severe weather/tornadoes .. However, Cape printouts of over 3K j/kg have been showing up which means we have a problem!  CAPE is the rate of the vertical buildup of a storm.   CAPE is directly proportional to the MAX attainable speed of an UPDRAFT of a storm.  HIGH CAPE will build storms quickly.

Yesterday, the forecast was for TORNADOES.  The problem with the forecast for West KS and OK was lack of low level moisture or HIGH DEWPOINTS! This event will be a night and day difference to  to Thursday and TODAY's events over the plains.  A strong dryline will be born between DP values of 70 over east Kansas to 50 over western KS by Saturday night.

The LI or (Lifted Index) is looked at next.  This will be for severe HAIL! The more negative the LI, the more unstable the troposphere is and the more buoyant the acceleration will be for rising parcels of air from the boundary layer.  

Something I like to use is the STP.  STP stands for significant tornado parameter which is a composite of various paremeters put together in an equation.  The equation includes 0-6 km bulk wind difference , 0-1 km storm-relative helicity , surface parcel CAPE , surface parcel CIN , and surface parcel LCL height (sbLCL).

The SREF model prints out percentages or probabilities the atmosphere will produce a certain number. STP numbers of 1 or lower will produce storms (most will even produce a supercell).  However, a value of 2-5 will produce tornadoes and research shows F2 tornadoes are common ESP with STP values closest to 5. Below is a look at the %'s of gaining a STP values of 3 tomorrow.  NEAR 90% !!!!

WHAT COULD GO WRONG??

The one thing that differs with the models is the development of the KEY feature.. THE STORMS!  The NAM vs the GFS show storms firing late with the overall coverage being very low.  This setup should feature numerous supercells developing however, the models do not show it.

THE RPM model has numerous storms firing along the dry line

While the NAM/GFS are dry along the DRYLINE with the heaviest axis of precip north along the warm front

REMEMBER TO FOLLOW MY TWEETS TOMORROW.. SHOULD BE A VERY INTERESTING DAY

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Looking Ahead to Summer...ElNINO Influences Part 1: Temperatures

The last couple of months have been very interesting in respect to what has been happening in the central Pacific.  The region that experiences the warming/cooling of the equatorial Pacific has begun to transfer over to a WARMING phase opposed to the cold (LaNina) event we have dealt with all winter long.  The change has been some what abrupt with a very different look between the FEB SST display to what is happening right now.

Below is a comparison between the two states of the equatorial pacific.  Not only has the surface of the water warmed signficiently... The depth of the water continues to warm dramatically also.

The long range seasonal forecast models have 1 agreement.. We will enter a warm phase by the start of summer yet, the exact strength of this warming and whether this will become an official ELNINO event is yet to be determined.

A look at the 3.4 region via the EURO shows a consensus of .5 by the start of summer however by the middle and end of the summer the spread favors closer to +1.  This warming (3.4) region would guarantee a very deep layer of warm water for the 1.2 region which would sustain WARM CONDITIONS into the fall.

A look at the CFS shows something similar however, the consensus shifts to strengthening winds and a slower warming process through summer.  This would favor a LA NADA event.. 0-0.5 ... The abrupt warming in my opinion cannot be discredited so I will not take the CFS's solution fully.  The trend though is still there of continued warming of the ENSO region into the late spring/ early summer months.

SO WHAT DOES THIS MEAN?

NOAA keeps track of events and averages them out over 50 plus years.  Now remember, this is taking just the ELNINO solution alone without other influences.  

Note the % average favoring BELOW normal temperatures through the period. 

As we move closer to June more variables will be added to the solution to generate a better idea on the summer trend.  Part 1 is provided to show you that a weakening LaNINA state going towards ELNINO conditions seldom equate to a very hot summer, but more of a cooler- seasonable pattern.