Over the weekend Tropical Storm (TS) Franklin formed off of the coast of Honduras, a prime location for viewing with GOES-16.  NHC forecasters have found the higher spatial and temporal visible imagery very useful for analyzing genesis in the past.  However, TS Franklin formed overnight, a time when visible satellite imagery is not available.

NHC 3-day Forecast Track,Initial Wind Field and Watch/Warning Graphic for Tropical Storm Franklin on 06 August 2017, 11 PM EDT – the first advisory after being classified a Tropical Storm. (http://www.nhc.noaa.gov/archive/2017/FRANKLIN.shtml?)

Fortunately, there are several new capabilities available from GOES-16 for nighttime viewing – including the Nighttime Microphysics (Advanced) RGB product (originally created by EUMETSAT).  The Nighttime Microphysics RGB product uses infrared channels to provide information about the fundamental properties of clouds including drop size and phase (water, mixed phase, ice) at nighttime. It can help distinguish between ice phase clouds at high elevations and water phase clouds at lower elevations, providing a pseudo three-dimensional view of the atmosphere. NHC forecasters found this product particularly useful in determining whether or not TS Franklin had a closed surface circulation, a necessary condition for formation.  

From the 5am Tropical Cyclone Discussion, it’s clear that the GOES-16 Nighttime Microphysics imagery provided forecasters with information that other data sources could not:

In the ASCAT image below, there are no westerly winds along the south side of the pre-Franklin disturbance (which was situated just off the coast of Honduras at this time), which would suggest the surface circulation was not yet closed.

ASCAT-A pass mentioned in the above TCD.  Source:  https://manati.star.nesdis.noaa.gov/datasets/ASCATData.php/ASCATData.php

However, in the GOES-16 Nighttime Microphysics imagery, the motion of small, low-level clouds along the south side of the pre-Franklin disturbance could be seen to have a westerly component of motion, indicating that the circulation may in fact be closed after all.

Full-disk GOES-16 Nighttime Microphysics RGB imagery over the pre-Franklin disturbance from 0-6 UTC on 8/7/17.  **THIS DATA IS PRELIMINARY AND NOT OPERATIONAL**

These low-level cloud motions were much easier to see in the 5-minute resolution imagery, which was available because the pre-Franklin disturbance was within the CONUS domain at this time.

CONUS GOES-16 Nighttime Microphysics RGB imagery over the pre-Franklin disturbance from 0-6 UTC on 8/7/17.  **THIS DATA IS PRELIMINARY AND NOT OPERATIONAL**

-Andrea Schumacher, CIRA/CSU and Michael Folmer, CICS/UMD

“The GOES-16 data posted on this page are preliminary, non-operational data and are undergoing testing. Users bear all responsibility for inspecting the data prior to use and for the manner in which the data are utilized.”

The official start of the Atlantic hurricane season is still about 2 months away, but an area of low pressure that formed east of the Bahamas has caught the eye of forecasters at the National Hurricane Center (NHC).  Earlier this week, NHC forecasters began monitoring invest AL90 for signs of potential subtropical or tropical cyclone development.  This system became a dangerous marine cyclone but did not develop the characteristics needed to be classified a subtropical or tropical cyclone.   Even so, AL90 did give NHC forecasters an early opportunity to explore GOES-16 data and imagery for a potential tropical system.

NHC Marine Graphicast issued Sat 25 Mar 2017 22:38 UTC. Click here to open in a separate window.

During the monitoring of AL90, NHC forecasters noted a couple of ways that GOES-16 imagery improved upon current GOES-13 imagery.  The higher spatial and temporal resolution of GOES-16’s 0.64-µm visible channel helped forecasters discern clouds at different vertical levels and diagnose individual cloud motions.  For example, in the loop below low-level cloud motions on the west side of AL90 are easier to see in the GOES-16 visible imagery (right) compared to the GOES-13 visible imagery (left).  You may be wondering why hurricane forecasters need to see individual clouds when they are trying for forecast a larger-scale weather phenomenon.  Tracking the motion of low-level clouds provides information about the low-level winds.  This information is especially important during the formation stage when forecasters are looking for indications of a closed low-level circulation.

GOES-13 visible (left, courtesy of D. Lindsey) and GOES-16 0.64-µm visible (right, from N-AWIPS) imagery of AL90 on 28 March 2017 from 1530-1815 UTC. *Preliminary, Non-Operational Data* NOTE: Black pixels in the GOES-16 visible imagery are a result of data being erroneously flagged as “no data” and set to zero when reflectance is >=1.0. This is a known error that occurs when imagery is viewed in N-AWIPS that scientists expect to have resolved soon.  Click here to open in a new window.

Forecasters also noted that GOES-16 water vapor imagery provided an advantage over GOES-13 during AL90.  The GOES-16 7.3-µm water vapor band (right) highlighted mid-level moisture wrapping around the west side of the system. This moisture was not as easy to see with the current GOES-13 water vapor band (centered at 6.5 µm, left) since its weighting function peaks much higher up in the atmosphere (see Weighting function profiles graphic below).

GOES-13 water vapor (left, courtesy of D. Lindsey) and GOES-16 7.3-µm water vapor (right, from N-AWIPS) imagery of AL90 on 28 March 2017 from 1530-1815 UTC. *Preliminary, Non-Operational Data* Click here to open in a new window.

Weighting functions for GOES-13 water vapor channel (dashed) and GOES-16 water vapor channels (solid) for a standard atmosphere. The weighting function for the current GOES water vapor channel peaks at approximately 350mb while the 7.3-µm water vapor channel on GOES-16 peaks lower, around 600-700mb.   Courtesy of the GOES-R Foundational Training Course.  Click here to open in a new window.

And to think, this is just a glimpse of the advantages we will have with GOES-16 in orbit once hurricane season rolls around.  Thanks for reading!

-Andrea Schumacher (CSU/CIRA)

with contributions from Jack Beven (NHC), Mark DeMaria (NHC), Michael Brennan (NHC), and Michael Folmer (CICS)

*The GOES-16 data posted on this page are preliminary, non-operational data and are undergoing testing. Users bear all responsibility for inspecting the data prior to use and for the manner in which the data are utilized.