Bore over Kansas

June 3rd, 2015 |
GOES-13 Imager 0.63 µm visible channel images (click to play animation)

GOES-13 Imager 0.63 µm visible channel images (click to play animation)

Visible imagery after sunrise on 3 June 2015 over Kansas, above, shows the parallel lines of low clouds that characterize a bore feature. As the bore penetrated southward, winds initially shifted before becoming more variable. Bore propagation requires the presence of an inversion, and 1200 UTC Soundings from both Dodge City and from Topeka contain inversions. Because inversions are present, it is unusual for convection to form in the presence of a bore.

The initial southward push the became the bore may have emerged from strong convection over central Nebraska early in the morning of 3 June. Suomi NPP VIIRS imagery captured that convection; the Day Night Band (under near-Full Moon conditions) and 11.45 µm infrared imagery, below, show the strong convection at 0848 UTC on 3 June 2015).

Suomi NPP VIIRS 0.70 µm visible Day Night Band and 11.45 µm infrared imagery at 0848 UTC on 3 June 2015 (click to enlarge)

Suomi NPP VIIRS 0.70 µm visible Day Night Band and 11.45 µm infrared imagery at 0848 UTC on 3 June 2015 (click to play animation)

GOES-14 was performing SRSO-R observations over Kansas on 3 June. One-minute imagery of the bore evolution is available here in animated gif format (74 M in size) and here in mp4 format (2.8M in size). The YouTube video is embedded below.



Andres and Blanca in the eastern Pacific

June 2nd, 2015 |
GOES-15 Imager 0.64 µm visible channel images (click to play animation)

GOES-15 Imager 0.64 µm visible channel images (click to play animation)

Hurricane Andres (above) in the eastern tropical Pacific was on 2 June 2015 joined by Tropical Storm Blanca (below). Blanca was forecast to become a Hurricane later on 2 June as Andres weakens. The circulation of Andres, above, is well-established, with good anti-cyclonic outflow and curved inflow bands. Shear values are low. (Graphics come from this site). However, Andres has moved over relatively cool Sea Surface Temperatures that spell weakening.

GOES-15 Imager 0.64 µm visible channel images (click to play animation)

GOES-15 Imager 0.64 µm visible channel images (click to play animation)

Blanca, in contrast, has a circulation that is not so well-defined. However, the storm is over very warm water, and also in a region of relatively low shear. Strengthening is forecast.

The animation of Andres at top shows a ragged appearance as dry air intrudes upon the circulation from the south and west. This dry air is apparent in the MIMIC Total Precipitable Water animation below. The circulation of Blanca appears at the end of the animation, embedded within a rich source of tropical moisture.

3-day animation of MIMIC Total Precipitable Water over the eastern Pacific (click to enlarge)

3-day animation of MIMIC Total Precipitable Water over the eastern Pacific (click to enlarge)

Sea-surface temperatures off the Pacific Coast of Mexico have been warmer than normal for much of this year (Map, data from here). Warmer-than-normal sea-surface temperatures argue for stronger hurricanes, and Andres was a Category 4 storm on 1 June with a well-developed eye. Andres is one of only 5 May storms in the eastern Pacific since 1970 to achieve Major Hurricane status (Link).

Aqua overflew Andres shortly before 1800 UTC on 1 June, and the water vapor imagery of the storm at that time is here. The True-Color imagery is shown below.

Aqua True-Color Imagery, 1748 UTC on 1 June 2015 (click to enlarge)

Aqua True-Color Imagery, 1748 UTC on 1 June 2015 (click to enlarge)

A storm-centered animation over Andres’ lifecycle is shown below. The storm starts in the moisture-rich ITCZ and ends as an isolated region of moisture surrounded by dryness.

GOES-15 Water Vapor Infrared Imagery (6.5µm) centered on Andres' center (click to animate)

GOES-15 Water Vapor Infrared Imagery (6.5µm) centered on Andres’ center (click to enlarge)

For further information on these storms, consult the National Hurricane Center website.

Water Vapor Animations for May 2014 and May 2015

June 1st, 2015 |
GOES-15 Imager 6.5 µm water vapor infrared channel images (click to play animation)

GOES-15 Imager 6.5 µm water vapor infrared channel images from May 2015 (click to play animation)

Historically heavy rains fell over the southern Plains in May of 2015, with numerous stations setting record monthly rainfall marks. For example, Oklahoma City reported 19.48″ of rain in May 2015; the previous record wet month was 14.66″, set in June 1989 (14.52″ of rain fell in May 2013). The three-hourly water vapor imagery, above (Click here for mp4 file; the animated gif above exceeds 90 M), from GOES-13 shows repeated thunderstorm development over western OK and western Texas that subsequently moved east. Persistent southwesterly flow is also apparent. In comparison, three-hourly water vapor imagery from GOES-13 for May 2014, below (Click here for mp4 file), shows less frequent convection and more northwesterly flow. Widespread convection is much less frequent over the Plains in May 2014 (a month that saw 4.44″ of rain fall in Oklahoma City).

GOES-15 Imager 6.5 µm water vapor infrared channel images (click to play animation)

GOES-15 Imager 6.5 µm water vapor infrared channel images from May 2014 (click to play animation)

The mean 6.5 channel GOES-13 Brightness Temperature for May 2015 was more than 2 degrees cooler than in May 2014 (237.2 K in 2015 vs. 239.6 K in 2014). It should not be surprising that the top of the moist layer in 2015 was higher (cooler) than in 2014.