STATUS: IOP

We will be conducting an IOP on Thursday, 24 March.  We anticipate fairly strong forcing associated with a mid-level wave, strong shear (850 flow approaching 50 kt), and CAPE in the range of 300-600 J/kg.  The expected structure will be a QLCS or a QLCS with embedded supercell structures.

Observations will possibly commence in the pre-dawn hours of Thursday, and terminate on Thursday afternoon.  CAPE and shear are expected to grow strongly during a 6-h period prior to passage of the convective line.

Details of the observing plan will depend on the expected time of passage of the convective line, and we await two more days of computer guidance to formulate that plan.  The plan will be discussed more at the Tuesday and Wednesday briefings, and in an evening planning session on Wednesday.

PI’s are reminded to keep the instrument status spreadsheet updated!

STATUS: IOP Watch

Most numerical guidance still points to a frontal passage on Thur 24 March through northern AL, with some disagreement about the time of day.  Shear and CAPE should be increasing through Wednesday night and early morning Thur ahead of this event.  Convection is nearly certain owing to strong lift.

At this time, low-level moisture looks like it will be sufficient for perhaps ~300 J/kg CAPE, and this is close to the climatological threshold for QLCS tornadoes in AL.

A final IOP go/no-go decision will be made at the 1 PM briefing tomorrow (Mon 21st).  For those thinking about travel plans, we will want to be observing by the early morning hours of Thur 24 March.  We will have to conjure a plan starting at the Wednesday briefing, and perhaps also later via SASSI chat/GeoWhiteboard.

STATUS: IOP Watch

We continue to watch the evolution of the system that will move through northern AL late next week.  Passage of the conditions most supportive of tornadic storms should occur between Thur (24th) noon and Fri (25th) noon.  There are still big questions about the return of humid air from the Gulf of Mexico, and the degree of instability that will develop associated with the moisture return.  Otherwise, it is more likely that strong shear will develop, sufficient for tornadic storms.  A final IOP decision will be made no later than the Monday (21st) daily briefing.

STATUS: IOP Watch

We continue to watch the wave and cold front that will affect the northern AL region around Thur/Fri of next week (24-25 March).  If current guidance is correct, shear will be sufficient, but CAPE will be marginal.  The latter is because moisture is not returning strongly off of the Gulf of Mexico after the passage of a cold front tomorrow.

If the models trend toward better moisture return, this IOP becomes more likely.  The IOP decision likely will be made on Sunday or Monday (20 or 21 March).

STATUS: IOP Watch

We are now beginning to watch the system that is expected to move through the southern US around Thur/Fri next week (25-26 Mar).  We will try to make a decision regarding an IOP on this system on Sunday (20th), or Monday (21st).

STATUS: Down

The next system that we are watching will pass through on ~ Thur 24 March.  If this forecast persists, we will consider starting our IOP watch tomorrow 17 Mar, with an IOP decision around Sunday 20 March.

IOP in progress.

A compact mid-level wave continues to approach from the west.  It is expected to cause an increase in CAPE and shear after ~midnight local time.  Thunderstorms are possible in this environment between about 3 AM and sunrise.  Serial soundings have commenced from the Belle Mina supersite, and at the time of this posting (4:20 PM LT) all other teams are moving toward their observing sites.

No decision has been made concerning extending the IOP through the Tuesday cold front event.

STATUS:  IOP commences midday Sunday

This IOP focuses on the passage of a compact mid-tropospheric wave on Sunday night.  It now appears that shear will begin increasing around midday tomorrow (Sunday 13 March).  This will be followed by an increase in CAPE, albeit to rather mediocre values.  With wave passage between midnight and sunrise Sunday night/Monday morning, there could be convection.  We will commence observations midday Sunday with serial sounding launches from the Belle Mina supersite, with extensive radar, surface, and sounding observations beginning later in the day, and lasting through the night.

The IOP may be extended through much of the day Monday if the current hints of lingering CAPE and shear with a chance of convection persist.

We are still monitoring the evolution of a cold front event on Tuesday when a combination of shear and CAPE supportive of supercells will exist, but it is possible that low-level vertical motion may be insufficient to initiate convection.  There will be additional discussion at the Sunday briefing to design the deployment, as well as to consider observations that bridge that gap between the Sunday night and late Tuesday systems.

STATUS: IOP Sunday 13 March

We continue the IOP declared yesterday.  The Sunday evening/night event still appears marginal, but the overall idea of a compact mid-level wave passage,  an attendant brief increase in flow and shear through the depth, and an increase in CAPE to perhaps 300 J/kg, is enough to motivate us to observe the passage of this system.  We will begin observing the “ramp-up” in CAPE and shear around midday Sunday, with operations likely through part/much of the night.

The next system is a cold front that should pas through northern AL on ~Tuesday.  Significant CAPE, deep shear, and storm-relative helicity (SRH) should accompany the passage of this front.  On Sat and Sunday, we will evaluate the need to extend the current IOP through Tuesday.

STATUS: IOP commencing Sunday morning, 13 March.

The IOP for Saturday has been scrubbed.  Instead, the IOP will commence Sunday morning.  It is anticipated that a compact upper system will pass the study area after sunset on Sunday, with a slight threat of tornadoes.  CAPE may be insufficient, but shear should be adequate.

On Sunday, we will make a decision on whether to have another IOP on Tue/Wed, which will mean that some traveling researchers will likely stay in Huntsville for the duration of these two events.  The mid-week system is a cold front, likely with sufficient CAPE and shear for a tornado threat.  However, at this time the degree of forcing to initiate storms is uncertain.