Tropical Storm Ana approaches the Big Island of Hawai’i

October 15th, 2014
Suomi NPP 11.45 µm Infrared Imagery 13-15 October 2014 (click to enlarge)

Suomi NPP 11.45 µm Infrared Imagery 13-15 October 2014 (click to enlarge)

Suomi NPP VIIRS 11.45 µm Infrared imagery, above, shows the slow strengthening of Ana as it approaches the Big Island of Hawai’i from the east-southeast. For further information on this storm, consult the Central Pacific Hurricane Center website. Ana possesses a noticeable central dense overcast, with overshooting tops that are very cold; brightness temperatures are as cold as -95º C! A similar loop as above, but of the Day Night band is here.

GOES-15 Infrared Imagery (10.7 µm), below, shows the storm making steady progress across the central Pacific. Very cold overshooting tops are also observed with GOES; values as cold at -91.5º C occur (in the animation at 0830 UTC). The very cold cloud tops indicate two different things: The tropopause is high and cold in the Tropical Pacific; there is a lot of latent heat being released in the developing storm.

GOES-15 10.7 µm Infrared Imagery 15 October 2014 (click to animate)

GOES-15 10.7 µm Infrared Imagery 15 October 2014 (click to animate)

The rocking animation below shows that Ana appears to have emerged from the interaction between westward propagating and eastward propagating waves in the Intertropical Convergence Zone. (A similar animation using water vapor is here).

GOES-15 10.7 µm Infrared Imagery 10-15 October 2014 (click to animate)

GOES-15 10.7 µm Infrared Imagery 10-15 October 2014 (click to animate)

The approach of Ana suggests that Rapid Scan Operations might be needed for Hawaii later this week. The most recent RSO Testing, on 15 October, showed that GOES-15 RSO data can be viewed in AWIPS. (Link, scroll to the bottom).

Added, 16 October 2014.

Strong convection near the center of Ana has become less organized early on 16 October, and the maximum estimated sustained winds of the storm have dropped. The animation of sequential Suomi NPP 11.45 µm IR imagery, below, does show deep convection reappearing at 1222 UTC.

Suomi NPP VIIRS 11.45 µm Infrared Imagery at 1047 and 1222 UTC 16 October 2014 (click to enlarge)

Suomi NPP VIIRS 11.45 µm Infrared Imagery at 1047 and 1222 UTC 16 October 2014 (click to enlarge)

October snowfall on the Big Island of Hawai’i

October 14th, 2014
GOES-15 6.5 µm water vapor channel images (click to play animation)

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

McIDAS images of GOES-15 (GOES-West) 6.5 µm water vapor channel data (above; click image to play animation) showed an upper-level low that moved from east to west over the Hawaiian Islands during the 13 October – 14 October 2014 period. This low forced the development of widespread showers and thunderstorms, especially over the Big Island of Hawai’i — and even produced some snowfall in the highest elevations around the summits of Mauna Kea and Mauna Loa. Some excerpts from Area Forecast Discussions issued by the National Weather Service at Honolulu on 13 October:

FXHW60 PHFO 131350
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
400 AM HST MON OCT 13 2014
[…]
FORECAST MODELS HAVE BEEN CONSISTENTLY CALLING FOR 500 MB TEMPERATURES BETWEEN -12 AND -13C WITHIN THE CORE OF THE COMPACT UPPER LOW. THIS IS EXCEPTIONALLY COLD FOR OCTOBER
[…]
FORECAST MODELS SHOW THAT THIS FEATURE WILL HOLD AS IT MOVES OVER THE BIG ISLAND LATER TODAY INTO TONIGHT…LIKELY PRODUCING ACCUMULATING SNOW OVER THE SUMMITS ABOVE 12000 FT. AS A RESULT…A WINTER WEATHER ADVISORY HAS BEEN ISSUED.
[…]

=====

FXHW60 PHFO 140152
AFDHFO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HONOLULU HI
330 PM HST MON OCT 13 2014
[…]
THE SUMMITS OF THE BIG ISLAND HAVE BEGUN TO REPORT SNOWFALL ACCUMULATION…AND THIS WILL CONTINUE WITH A COUPLE OF INCHES POSSIBLE OVERNIGHT.
[…]

While examining a nighttime (11:21 UTC or 1:21 am local time) comparison of AWIPS II images of Suomi NPP VIIRS 0.7 µm Day/Night Band (DNB) and 11.45 µm IR channel data covering Tropical Storm Ana (below), the main feature of interest was the inner core of cloud-top IR brightness temperatures as cold as -86º C (yellow color enhancement) associated with Ana — however, equally interesting was the appearance of a pair of bright white features in the middle of the Big Island on the DNB image (which highlighted the areas of snow cover that remained at the higher elevations).

Suomi NPP VIIRS 0.7 µm Day/Night Band and 11.45 µm IR channel images

Suomi NPP VIIRS 0.7 µm Day/Night Band and 11.45 µm IR channel images

A closer view comparing the VIIRS DNB and IR images centered over the Big Island (below) seemed to suggest that the 2 patches of bright snow cover (well-illuminated by a nearly Full Moon) were located along the western slopes of Mauna Kea and Mauna Loa. A similar comparison of the DNB image and high-resolution topography can be seen here.

Suomi NPP VIIRS 0.7 µm Day/Night Band and 11.45 µm IR channel images

Suomi NPP VIIRS 0.7 µm Day/Night Band and 11.45 µm IR channel images

An animation of GOES-15 0.63 µm visible channel images during the following daylight hours of 14 October (below; click image to play animation) revealed the gradual melting of the 2 patches of high-elevation snow cover as temperatures rose from around freezing into the 50s F near the summits (Cooperative observations).

GOES-15 0.63 µm visible channel images (click to play animation)

GOES-15 0.63 µm visible channel images (click to play animation)

Suomi NPP and GOES Views of Hurricane Gonzalo

October 14th, 2014
Suomi NPP 11.45 µm Infrared Imagery and Day Night Band Imagery, 0617 UTC 14 October 2014 (click to enlarge)

Suomi NPP 11.45 µm Infrared Imagery and Day Night Band Imagery, 0617 UTC 14 October 2014 (click to enlarge)

The VIIRS instrument on Suomi NPP yielded compelling nighttime imagery of Hurricane Gonzalo in the western Atlantic. The toggle above of the Day Night Band and the 11.45 µm Infrared imagery shows a circular central dense overcast over the storm (imagery courtesy of William Straka, CIMSS). No eye structure is immediately apparent, although very cold cloud tops are present at the storm center. A larger-scale view of the Day Night Band and 11.45 µm imagery, below, shows a storm in a low to moderate wind shear environment with a well-defined outflow channel to the northeast. Note the pronounced “transverse banding” signature along the southern periphery of the hurricane – such transverse banding is often seen in areas of high-altitude of turbulence. Gonzalo was forecast to strengthen (see the National Hurricane Center website for more details).

Suomi NPP 11.45 µm Infrared Imagery and Day Night Band Imagery, 0617 UTC 14 October 2014 (click to enlarge)

Suomi NPP 11.45 µm Infrared Imagery and Day Night Band Imagery, 0617 UTC 14 October 2014 (click to enlarge)

During the subsequent daytime hours on 14 October, Hurricane Gonzalo did indeed continue to intensify, becoming a Category 3 storm by the late afternoon (ADT plot). The GOES-13 satellite had been placed into Rapid Scan Operations (RSO) mode, providing images as frequently as every 5-7 minutes; 0.63 µm visible channel images (below; click image to play animation; also available as an MP4 movie file) showed periodic convective bursts around the eye of Gonzalo as the tropical cyclone moved northwestward.

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

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

Severe Weather Outbreak Across the Deep South

October 14th, 2014
Suomi NPP 11.35 µm Infrared  Imagery, 1933 UTC 13 October 2014, with Lightning strike data overlain  (click to enlarge)

Suomi NPP 11.35 µm Infrared Imagery, 1933 UTC 13 October 2014, with Lightning strike data overlain (click to enlarge)

An intense extratropical cyclone over the central United States spawned a Quasi-Linear Convective System that moved through the Deep South on 12-13 October 2014; the QLCS was responsible for a spate of severe weather including wind damage, hail and tornadoes (Storm reports from 12 October, 13 October). The image above, from 1933 UTC on 13 October, shows Suomi NPP 11.35 µm imagery over Mississippi. Widespread cold cloud tops are apparent, with embedded overshooting tops. Indeed, the top in southern Hinds County may have been associated with severe Hail. Visible imagery from Suomi NPP (link) also show overshooting tops. The amount of solar reflectance at mid-day, however, makes it difficult to identify all features. The 1.61 µm imagery, below, is darker because ice crystals at cloud top will absorb some energy at that wavelength, yet most features are still recognizable.

Suomi NPP 1.61 µm Near-Infrared  Imagery, 1933 UTC 13 October 2014 (click to enlarge)

Suomi NPP 1.61 µm Near-Infrared Imagery, 1933 UTC 13 October 2014 (click to enlarge)

The GOES-13 Water Vapor Animation, below, is a textbook example of cyclogenesis. Strong sinking in and around the comma head is indicated by the warm water vapor brightness temperatures observed there. This system is also characterized by a very sharp upstream trough and developing warm conveyor belt that turns anticyclonic as it moves over the upper Great Lakes.

GOES-13 Water Vapor 6.7 µm Infrared  Imagery, 1200-2100 UTC 13 October (click to animate)

GOES-13 Water Vapor 6.7 µm Infrared Imagery, 1200-2100 UTC 13 October (click to animate)

GOES-13 10.7 infrared imagery animation, below (also available here as an mp4 file or here as a YouTube video), shows evidence of many overshooting tops in the strong thunderstorms that developed across the deep south. (Indeed, automatic detection of overshooting tops(and cumulative totals from this website) — show some on the 12th, but many more on the 13th) as the extratropical cyclone became organized.

GOES-13 10.7 µm Infrared Imagery, 1600 UTC 13 October - 0700 UTC 14 October 2014 (click to animate)

GOES-13 10.7 µm Infrared Imagery, 1600 UTC 13 October – 0700 UTC 14 October 2014 (click to animate)

The strong system enjoyed a vigorous moisture feed from the Gulf of Mexico, as shown in the MIMIC Total Precipitable Water animation below. Moisture surged northward especially after 1200 UTC on 13 October, and the 24-hour precipitation totals ending at 1200 UTC on 14 October (from this site) showed heavy rain over much of Tennessee and Alabama (and adjacent states).

MIMIC Total Precipitable Water for 72 hours 1200 UTC 14 October 2014 (click to enlarge)

MIMIC Total Precipitable Water for 72 hours 1200 UTC 14 October 2014 (click to enlarge)

GOES Sounder data also shows a quick moistening on 13 October as high Precipitable Water air over the Gulf of Mexico surges northward. Moisture from Pacific Hurricane Simon is unlikely to be a contributing factor to this storm.

GOES Sounder DPI estimates of Total Precipitable Water from through 6 October through October 14 2014 (click to enlarge)

MIMIC Total Precipitable Water for 72 hours 1200 UTC 14 October 2014 (click to enlarge)

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MTSAT-2 and GOES-15 Water Vapor (6.5 µm)Infrared imagery, times as indicated (click to enlarge)

MTSAT-2 and GOES-15 Water Vapor (6.5 µm)Infrared imagery, times as indicated (click to enlarge)

An interesting question arises: Where did some of the energy and moisture for this (somewhat early in the season) storm originate? Water Vapor imagery from MTSAT-2 and GOES-15 show clearly that the Super-Typhoon Phanfone, that was near Japan on 4-5 October, contributed some of the energy to the impulse that moved across the Pacific Ocean and then over the Ridge on the West Coast of North America before diving southeast and forcing cyclogenesis. In the animation above, Phanfone approaches Japan, and is picked up by a mid-latitude jet that crosses the Pacific (tracked by red arrow), induces strong cyclogenesis in the Gulf of Alaska on 8 October and then continues up and over the ridge on the west coast of North America.