VISIT: Meteorological Interpretation Blog

Some Advected Layered Precipitable Water (ALPW) Comparisons Between Florence, Harvey (2017), Maria (2017) and Matthew (2016) with Respect to Rainfall and Severe Weather

This blog entry is by Sheldon Kusselson and in the format of a PDF document:

Florence 2018 Comparisons With Harvey and Matthew and More_Sep21,2018update

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Hurricane Florence

The hurricane season in the Atlantic has been quite inactive throughout the majority of the summer, until this past week. Currently there are three active hurricanes located in the eastern, central and western Atlantic Ocean, named Hurricane Helene, Isaac, and Florence, respectively; all with varying magnitude, intensity, and storm tracks. However, with all the present activity, we will focus our sights on Hurricane Florence, since Florence can have major impacts (i.e. flooding, high winds, storm surge and potential power outages) along the southeastern United States. According to the latest forecast models and National Hurricane Center (NHC), Hurricane Florence appears to make landfall along the Carolinas, Thursday morning, 13 September 2018, although the storm track is subject to change, since it is only Monday, 10 September 2018. Refer to the NHC product below. Note that Florence is anticipated to become a Major Hurricane (i.e. hurricane greater than 110 mph) as it makes landfall later in the week.

The Suomi-National Polar-orbiting Partnership (S-NPP) satellite observed Hurricane Florence early this morning at 0505Z, 10 September 2018, using the Near-Constant Contrast (NCC) product. For unaware readers, NCC is a derived product of the Day/Night Band (DNB) that utilizes a sun/moon reflectance model that illuminates atmospheric features, and senses emitted and reflected light sources during the nighttime (i.e. a ‘nighttime visible’ product). Note the NCC imagery is taken during the new moon phase of the lunar cycle, where atmospheric features are still seen in the imagery due to an atmospheric phenomenon called ‘atmospheric nightglow’.

NCC captured the large areal extent of Hurricane Florence, along with the eyewall, circulating clouds and rain bands. Lightning was also observed on the southern side of the hurricane, denoted by the horizontal white streaks. Streaks are produced due to the time discontinuity between the satellite overpass (i.e. on the order of seconds) and the duration of the lightning strike (i.e. on the order of milliseconds).

Below, is a CIRA ALPW surface-850mb animation of the hurricane activity in the Atlantic Ocean between 18Z, 9 September 2018 to 15Z, 10 September 2018. The ALPW product highlights the precipitable water (i.e. a quantifiable measure of how much water vapor is in an atmospheric column) within four layers of the atmosphere (i.e. surface-850mb, 850-700mb, 700-500mb, and 500-300mb). Notice the high precipitable water values with each hurricane (i.e. indicating the horizontal moisture distribution and indicate areas that are favorable for heavy precipitation) as the hurricanes move westward through time.

For the latest updates on Hurricane Florence, click the following link.

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Hurricane Lane

Hurricane Lane is making headlines this week, as the storm approaches the Hawaiian islands. As of the latest National Hurricane Center (NHC) update (8 am HST, 23 August 2018), Lane is moving quite slow, with a northwest movement at ~ 7 miles per hour. Within the last day or two, Lane has weakened, but is still a Category 4 hurricane that can bring heavy precipitation, high winds, storm surge and coastal flooding. Some parts of the Hawaiian islands have experienced heavy precipitation already, and more is expected, throughout the next few days. As seen in the NHC image below, the forecasted track shows the ‘probable path’ of Hurricane Lane, but does not indicate the magnitude of the storm. The forecasted track is subject to change.

The Suomi-National Polar-orbiting Partnership (S-NPP) satellite observed Hurricane Lane via Near-Constant Contrast (NCC) product, earlier this morning at 1228Z, 23 August 2018. The NCC is a derived product of the Day/Night Band (DNB) sensor, that illuminates atmospheric features and senses emitted and reflected light sources (i.e. cloud cover and cloud convective tops from Lane) during the nighttime. In the NCC image, notice the large areal extent of Hurricane Lane, as the northern/northeastern periphery of the storm has reached the southern shores of the Hawaiian islands, bringing heavy precipitation rates.

In complement to the NCC, the CIRA -Advected Layered Precipitable Water (ALPW) product (shown below), derived from microwave retrievals, shows high precipitable water values of Hurricane Lane, as the storm moves northwestward. The ALPW product is partitioned into 4 layers, to identify where most of the moisture lies within the atmosphere, and indicates the horizontal moisture distribution. In the animation below, ALPW highlights ‘surface-850mb layer’ precipitable water values, where high values are concentrated within and near Hurricane Lane (orange, dark orange colors), indicating areas that could experience heavy precipitation. Precipitating regions are indicated as ‘missing data’, represented by black colors in the imagery, since microwave retrievals are made in cloudy regions but not precipitating regions. Animation is from 18Z, 22 August 2018 to 15Z, 23 August 2018.

For the latest updates on Hurricane Lane, click on the following NHC link.

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Hurricane Hector

Hurricane Hector has been a ‘Major Hurricane’ in the Central Pacific for the past week. At one point, the hurricane was nearly categorized as a Category 5 hurricane, however weakened, and is currently a Category 3 hurricane (i.e. ~120 mph winds as of 8AM Hawaiian Standard Time (HST), 9 August 2018). The storm is moving west at ~16 mph, and was ~350 miles southwest of Hawaii.

Polar-orbiting satellites observed Hector, earlier this morning, via the Near-Constant Contrast (NCC) and the Advected Layered Precipitable Water (ALPW) satellite products. The NCC, a derived product of the Day/Night Band (DNB) sensor, utilizes a sun/moon reflectance model to illuminate atmospheric features, and sense emitted (i.e. city lights) and reflected (i.e. clouds) lights during the nighttime.  NCC image is at 750-m spatial resolution and is taken at 1152Z  (0152 local time), 9 August 2018, during the new moon phase of the lunar cycle. Imagery shows Hector’s large areal extent, eye wall, and cloud cover, along with nearby emitted city lights from the Hawaiian islands.

In complement to NCC, the ALPW product, derived from polar-orbiting satellites,  highlights precipitable water values within 4 atmospheric layers, different from the Blended Total Precipitable Water (TPW) product. The ALPW animation below, shows one of the layers (surface to 850mb), where high TPW values are observed within Hector. High TPW values indicate large amounts of moisture within the surface-850mb layer that are then transported westward with respect to time (i.e. see animation). It is important to note, missing data values are observed in the imagery (i.e. black pixels), representing regions of precipitation. Animation is from 18Z, 8 August 2018 to 15Z, 9 August 2018, showing Hector’s westward movement as the hurricane skirts along the southern edge of the Hawaiian islands. So far, the islands have received some rainfall and high surf along its southern shores. ALPW product is at 16-km spatial resolution.

For more updates on Hurricane Hector, click on the following link.

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Dust off the coast of Africa!

Earlier this morning, a large areal extent of dust advected off the coast of Africa. The new National Oceanic and Atmospheric Administration  – 20 (NOAA-20) satellite, launched into orbit back in November 2017, captured the dust via Day/Night Band (DNB) product at 0323Z, 1 August 2018. DNB illuminates atmospheric features, senses emitted and reflected light sources (i.e. dust and clouds in this case), during the nighttime. Notice in the DNB image below, the opaque, milky white features that resemble dust along the African coast and west of Africa. Corresponding cloud cover over the ocean and over land are also seen.

Although the DNB image above is only a static image, in animation of the dust can be seen later in the day, via geostationary data (higher temporal resolution). Clicking on the video below shows dust advecting west, towards the U.S., between 13-16Z, 1 August 2018. Products seen within animation are the GeoColor and Dust products, identifying dust in milky brown and pink colors, respectively.

Satellite observations of dust and forecasting dust can assist in assessing convective initiation, hurricane development/dissipation processes, along with determining visibility levels. As dust advects westward the next few days, Weather Forecast Offices (WFO’s) will determine how dust levels will impact their County Warning Areas (CWA’s), especially along the southeastern U.S. and Puerto Rico (U.S. territory).

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