Overview of sea breeze fronts in Florida

Forecaster comments from EWP blog...

We’re currently monitoring the rapidly inland moving see breeze front over NE Florida with enhanced TCU present along the convergence zone, whereas the west coast see breeze has trouble to move inland within dominant easterly wind regime. Both convergence zones enter an area over N-C Florida where slightly lower dewpoints (lower to mid 60s) are present. With ongoing diabatic heating, cap continues to weaken or has already vanished with isolated initiation possible over N-C Florida in the following hours but ongoing large-scale weak subsidence seems to delay initiation a bit. HRRR quite aggressive with initiation mainly along the western sea breeze front with RUC also showing sporadic storms over N-C Florida. Overall set-up is not impressive and favors only the development of a few thunderstorms. Moderate CAPE and weak shear environment may result in a few strong and slow moving storms.

Neither CI nor Cld top cooling products showing robust signs for initiation … mainly over C Florida. Both products however show more vivid activity offshore over the Atlantic, where mid-levels remain a bit cooler.

1800Z VIS and station data.

1745Z; UAH-CI (upper left) and CIMSS Cld Top Cooling (upper right).

Southeast US still providing areas of CI

The pesky upper low over the Southeast US continues to move offshore. With strong surface heating and "cool" mid-level temperatures with this low, airmass thunderstorms continue to develop over the Southeast US. UAHCI has been indicating many areas with Strength of Signals over 60 from the Southeast up into the Mid-Atlantic States. Many of these storms will not become severe due to the surrounding synoptic environment, yet will produce heavy rainfall and frequent lightning with the stronger storms. This example of UAHCI tracks a slow developing storm in Washington County, GA. These two images are from 1632 UTC and 1645 UTC with Strength of Signals (SOS) of 52 and 57 respectively, suggesting only slow growth at the time.

At 1702 UTC, the SOS ramped up to 73, suggesting more rapid growth and increasing confidence that this cell will actually CI.

At 1715 UTC, the SOS increases further to 83. The UAHCI algorithm stopped tracking the object after this time period as it was deemed mature within the cloud mask, which is evident within the visible imagery at 1725 UTC.

Outlook 24 May 2012: Week 3, Day 4

From the EWP blog...

Operating today during the first mod risk of the experiment, however, that is not where we are operating today… at least not to start.

In order to try and get lightning data into the experiment this week, we’ve initialized in the Sterling, VA and Melbourne, FL domains.

For the FL domain, we’re hopeful that storms will get going as the sea breeze front sets up across the state.  Already, the UAH-CI product is flagging cumulus for development (consistently 50-60%) along the line from Sanderson to -Orlando to just northwest of Okeechobee.

UAH-CI & Visible Satelllite for central FL @ 1830 UTC on 24 May 2012.

For the DC domain, the CI alg is also flagging development generally a bit lower on the probability though. A region of SBCAPE of >1500-2000 J/kg extends from eastern NC to over much of the LWX CWA, so it appears possible that we could at least see some convective development across some of the DC LMA though likely only marginally severe.

Our observers and some PIs are keeping an eye over central WI and the associated moderate risk region for development of surface based storms (as to now all development across Minnesota appears to be elevated).  Currently instability is limited across much of the region, but we do expect additional destabilization with daytime heating and enhanced lift as the cold front moves in.

EWP daily debrief 5/24

Yesterday we had a good day in operations for the CI products especially.  Below is some feedback we gathered from the forecasters during our daily debrief...

UAH SATCAST (CI) / UW Cloud-top Cooling (CTC)
- "They were very helpful... it was environment you knew the cloud would cool quickly, but you didn't know which clouds would go up... I think it's benefit is really in that marginal environment... discriminating between that severe/non-severe borderline is where we really need help."
- "Really all the satellite based products would be useful for us in terms of aviation forecasting... if we could get an hour lead time on CI, it would be really helpful to us... especially in a place like NY where just one thunderstorm will mess up everything with regards to air traffic... just to see the CI and the CTC, you can update your TAF and contact the proper folks and give them a more confident message than if you're just using radar... with just radar we can't give them the lead time they need."
- "When we were deciding when to switch, it seemed like the CI was showing a widespread 30-50% for that whole area, but it didn't really happen." ... Developer explained that sometimes many cumulus clouds close together can become clustered together (especially at night when the visible channel isn't utilized), which will give you relatively lower probabilities over a broader area.
- "That region of Cu was a strongly forced/capped area... that broad view of the CI product gave you an idea that there is some upward motion and told you to pay attention."
- "I really loved the CI products yesterday... seeing the CI and CTC zippering down the line, we actually warning on one CTC signal when we saw that everything else ahead of it was going."

Overall / Training
- "With what you show the forecasters, simpler is better."

Nighttime UAHCI Success

As daylight begins to wane along the East Coast, the UAHCI algorithm transitions to a nighttime cloud mask that no longer depends on visible imagery. With the lack of visible imagery, the algorithm appears much more blocky in nature due to the decrease in spatial resolution (1 km visible to 4 km infrared). However, we are able to still track cloud objects that are not stratiform in nature. In this case over Clay County in Southeast South Dakota into Dixon County in Northeast Nebraska, the UAHCI Strength of Signal reached 92 on cells behind the main line of storms. Although not severe, the cell did develop with reflectivity values over 40 dBZ. It is important to note that the UAHCI product is not meant for the predictability of severe storms, but any type convection.

CI product over E-Nebraska

Forecaster comments from EWP blog...

The cold front over NC-Kansas and SE Nebraska was monitored for further development. As expected, storms began to build SW-wards towards the KS boarder and CI products were effective in highlighting the area with highest probabilities for potential development along that boundary.

The event occurred over Clay and York counties (Nebraska). A series of images will be added to show the evolution

UAHCI product upper left, CIMSS Cld top cooling upper right, lightning data lower left and surface reflectivity at -10 C isothermal level at 2232 Z

UAHCI product upper left, CIMSS Cld top cooling upper right, lightning data lower left and surface reflectivity at -10 C isothermal level at 2245 Z

UAHCI product upper left, CIMMS Cld top cooling upper right, lightning data lower left and surface reflectivity at -10 C isothermal level at 2302 Z

Roughly 30 min before surface reflectivity at -10C isothermal level revealed first signs of development, the CI product highlighted both counties with 50-60 % probabilities. The cloud top cooling product showed values of -15 to -25K/15 min at 2315Z (not shown) and the first significant reflectivity signal (56 dbZ ) became visible at 2330 Z. At 00Z onwards a 63 dBz cell evolved out of that NE of York.

OAX: Cloud-Top-Cooling (UW-CTC) Success!

Forecaster comments from EWP blog...

Issued a severe thunderstorm warning strictly off of explosive CTC at 2315 UTC (previous post), with very little showing up on radar at the time.  As would be expected, through the following 15-20 minutes, the storm exploded, with MRMS MESH spiking up to 1″ by 2334 UTC, and a quarter size hail report by 2336 UTC.  This gave us 21 minutes of lead time from the initial warning issuance off of CTC.  Would have likely issued the warning based on traditional base products by 2325 UTC, 10 minutes after the CTC-based issuance.

UAH-CI/UW-CTC Tag Team Leads to Successful Experimental Warning

*** This is a joint post from Chris Jewett and Lee Cronce ***

A forecaster covering the OAX CWA was able to place an experimental severe thunderstorm warning based on the trends recognized in the UAH-CI and UW-CTC products.  This great example shows how the UAH-CI and UW-CTC products can work collectively to create strong forecaster confidence in a severe weather situation.

The initial recognition of severe potential took place at 2302 UTC when the UAH-CI product showed a strength of signal of 80 out of 100 (see Fig. 1).

Fig. 1

The next scan at 2315 UTC had the UW-CTC product exhibiting a strong cooling rate of ~-25K/15 min.  This information combined with what the forecasters have learned/noticed about our product in other situations prompted the forecaster to issue the warning with high confidence that the growing convective element would eventually become severe.  See Fig. 2 for the UW-CTC cooling rate along with the warning polygon created.

Fig. 2

Comparison synthetic-real IR over E-Nebraska

Forecaster comments from EWP blog...

The area over E-Nebraska was monitored for initiation. The synthetic images did a pretty good job in timing of thunderstorm development. The real development occurred only slightly to the north to what the synthetic ones proposed. The model forecast however overestimated the development along the cold front over C/S Kansas, where warm mid-levels prevented DMC of developing until now (although showers finally try to form at 23Z onwards).

Another CTC success case in the OAX CWA

Forecasters shifted their domain of interest to the OAX CWA for the potential of severe convection in the area.  Convection initiated around 2145 UTC with the UW CTC product exhibiting strong cooling for the cu popping up in the area.  The cooling rate was ~-20K/15 min (see Fig. 1).

Fig. 1

About an hour later at 2244 UTC, the cell that the CTC product flagged with the strong cooling rate produced a MESH value of 1.89" (see Fig. 2).   Again, good lead time over the potential of severe hail.

Fig. 2