Hurricane Blanca in the eastern Pacific Ocean

June 4th, 2015
Suomi NPP VIIRS Day Night Band 0.70 µm Visible and 11.35 µm infrared imagery over Blanca, 0829 UTC 4 June 2015 (Click to enlarge)

Suomi NPP VIIRS Day Night Band 0.70 µm Visible and 11.35 µm infrared imagery over Blanca, 0829 UTC 4 June 2015 (Click to enlarge)

Suomi NPP overflew Hurricane Blanca early in the morning on 4 June, during a near-full Moon, and the Day Night Band imagery, above, toggled with the 11.35 µm imagery, show the hurricane. (Day/night band imagery of the eye is here, the entire storm is here, and zoomed out is here; click for 11.35 µm imagery of the eye, the entire storm, and zoomed out). Deep convection overnight did not wrap all the way around the storm. Evidence of dry air entrained into the circulation is apparent.

GOES-15 Imager 10.7 µm infrared channel images (click to play animation)

GOES-15 Imager 10.7 µm infrared channel images (click to play animation)

The 3-hourly animation of 10.7 micron imagery, above, from 3-4 June 2015 shows Hurricane Blanca southwest of the Mexican coast, drifting southwestward. Cold cloud tops that were apparent at the start of the loop warm by the end, perhaps because convection is being suppressed by the presence of dry air. MIMIC Total Precipitable Water (below) suggests that dry air is being entrained into Blanca’s circulation from the north. (Update on Andres, also apparent in the MIMIC Total Precipitable Water animation: This overlay of Metop ASCAT winds on top of GOES 10.7 imagery from ~0530 UTC on June 4 shows a swirl that is offset from the convection. Andres is forecast to become post-tropical later on June 4.)

MIMIC Total Precipitable Water animation for the 72 hours ending 1300 UTC on 4 June 2015 (click to enlarge)

MIMIC Total Precipitable Water animation for the 72 hours ending 1300 UTC on 4 June 2015 (click to enlarge)

Visible imagery from GOES-13 from June 3 and June 4, below, show a less distinct/cloudier eye on 4 June compared to 3 June. Multiple overshooting tops persist in the circulation of the system, but the coarse 30-minute temporal resolution of the imagery cannot capture the lifecycle of these quickly evolving events.

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)

Water vapor imagery from GOES-13 from June and June 4, below, also confirm a consistently less organized storm. The dry air penetrating from the north is apparent in the imagery, but it appears not to have entered into the circulation of the storm, at least not at levels detected by the water vapor channel.

GOES-13 Imager 6.5 µm infrared water vapor channel images (click to play animation)

GOES-13 Imager 6.5 µm infrared water vapor channel images (click to play animation)

Morphed Microwave Imagery (MIMIC) from this website shows the evolution of the central eye structure, below. The eyewall that was much closer to the storm center at the start of the animation has been replaced by a weaker, larger eyewall.

Morphed Microwave Imagery, 48 hours ending 1500 UTC 4 June 2015 (click to enlarge)

Morphed Microwave Imagery, 48 hours ending 1500 UTC 4 June 2015 (click to enlarge)

For more information on this storm, please visit the National Hurricane Center website or the SSEC/CIMSS Tropical Weather website.

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.

Antecedent Conditions for a Nor’easter

January 26th, 2015
GOES-13 Sounder Skin Temperature derived product image

GOES-13 Sounder Skin Temperature derived product image

Forecasts have been consistent in the past days for a storm of historic proportions over parts of southern New England. What conditions that are present now argue for the development of a strong winter storm? The image above is the GOES Sounder Land Surface Temperature (or “Skin Temperature”) product; cold air is present over southeastern Canada, with surface temperatures near -30 C, associated with a surface high pressure system. The high pressure will act to reinforce the cold air at the surface, preventing or delaying any changeover to liquid or mixed precipitation (a MODIS Land Surface Temperature product at 1500 UTC on 26 January similarly shows cold air banked over southern Canada).

GOES_SkinT_1400_26January2015

GOES Sounder estimate of Skin Temperature, 1400 UTC 26 January 2015 (Click to enlarge)

Winds over southern New England early on the 26th continued out of the north and northwest, maintaining cold air at the surface. The ASCAT (from METOP-A) imagery above shows brisk northwesterly winds south of southern New England just before 0100 UTC, with southwesterlies east of Georgia and South Carolina just before 0300 UTC. Those southwesterlies are helping moisten the atmosphere, and heavy snows require abundant moisture. MIMIC Total Precipitation (below; click image to play animation) testifies to the moistening that is occurring off the southeast coast as this system develops; the storm appeared to tap moisture from both the Gulf of Mexico and a pre-existing atmospheric river over the Atlantic Ocean.

[Added: The 1540 UTC ASCAT winds show the surface circulation east of Hatteras and the mouth of the Chesapeake Bay! Winds south of New England have shifted to northeasterly. The location of the circulation well off the coast suggests cold air can be maintained over land.]

MIMIC total Precipitable Water (click to play animation)

MIMIC total Precipitable Water (click to play animation)

Given that moisture and cold air are present, what features argue for the development of a strong storm? The GOES-13 water vapor images (below; click image to play animation; also available as an MP4 movie file) with cloud-to-ground lightning strikes superimposed show the potent system developing off the US East Coast and blossoming over the Gulf Stream as a secondary warm conveyor belt forms (a water vapor image with lightning animation from 25-26 January is available here). Strong sinking motion behind the system is indicated by the development of warm water vapor channel brightness temperatures (yellow color enhancement), and strong rising motion ahead of the system helps to generate widespread, strong convection. Convection also occurred over the Deep South late on 25 January in response to solar heating. The system depicted in the Water Vapor imagery is obviously quite vigorous.

GOES-13 6.5 µm water vapor channel images (click to play animation)

GOES-13 6.5 µm water vapor channel images (click to play animation)]

Suomi NPP VIIRS 11.45 µm IR channel and 0.64 µm visible channel images (below) showed that there was a great deal of convective banding within the secondary warm conveyor belt.

Suomi NPP VIIRS 11.45 µm IR channel and 0.64 µm channel images, with lightning, surface fronts and METAR reports

Suomi NPP VIIRS 11.45 µm IR channel and 0.64 µm channel images, with lightning, surface fronts and METAR reports

Total Column Ozone is frequently used as a proxy of tropopause folding; tropopause folds accompany very strong storm development and the vertical circulation associated with the potential vorticity anomaly (maximum) associated with the folding draws stratospheric ozone down into the troposphere. GOES Sounder Total Column Ozone derived product images (below; click to play animation; also available as an MP4 movie file) show that the dynamic tropopause — taken to be the pressure of the PV1.5 surface, red contours — descends below the 400-450 hPa level along the southern gradient of the higher ozone values (green to red color enhancement) as the potential vorticity anomaly pivots eastward along the Gulf Coast states and then northeastward toward the intensifying storm. The presence of clouds prevented ozone retrievals over many areas, but some ozone values over 400 Dobson Units (red color enhancement) could be seen, which is characteristic of stratospheric air.

GOES Sounder Total Column Ozone derived product images (click to play animation)

GOES Sounder Total Column Ozone derived product images (click to play animation)

As the storm approached New England, a MODIS 11.0 µmIR channel image (below) revealed the presence of widespread embedded convective elements within the broad cloud shied, with some cloud-top IR brightness temperatures as cold as -65ºC (darker red color enhancement). These pockets of convection could enhance snowfall rates once they moved inland.

MODIS 11.0 µm IR channel image, with lighting strikes, METAR surface reports, and fixed buoy reports

MODIS 11.0 µm IR channel image, with lighting strikes, METAR surface reports, and fixed buoy reports

An overlay of the RTMA surface winds (below) helped to locate the position of the surface low east of the Delmarva Peninsula. That position agrees well with ASCAT winds from 0158 UTC on 27 January.

MODIS 11.0 µm IR channel image, with RTMA surface winds

MODIS 11.0 µm IR channel image, with RTMA surface winds

A comparison of Suomi NPP VIIRS 0.7 µm Day/Night Band (DNB) and 11.45 µm IR channel images at 06:39 UTC or 1:39 AM Eastern time is shown below. With illumination from the Moon in the Waxing Gibbous phase (at about 60% of Full), the DNB provided a “visible image at night” which showed the expansive offshore “comma cloud” of the storm, along with the locations of bright cloud illumination from dense lightning activity (note the bright lightning signature east of Cape Cod, which corresponded well with a cluster of positive cloud-to-ground lightning strokes). Numerous pockets of convective development were seen well off the coast of North and South Carolina, due to strong cold air advection over the warm waters of the Gulf Stream.

Suomi NPP VIIRS 0.7 µm Day/Night Band and 11.45 µm IR channel images (with cloud-to-ground lightning strikes)

Suomi NPP VIIRS 0.7 µm Day/Night Band and 11.45 µm IR channel images (with cloud-to-ground lightning strikes)

FY-2G sends its first image

January 22nd, 2015
FY-2G Color Composite Image from 0500 UTC 8 January 2015

FY-2G Color Composite Image from 0500 UTC 8 January 2015 (Click to enlarge)

The Chinese Meteorological Satellite FY-2G was launched on 31 December 2014 from Xichang Launch Center in Sichuan Province. It has achieved Geostationary Orbit at 99.5º E and its first full disk Color Composite image, above, from 8 January 2015, has been released.

For more information on FY-2G, click here. FY-2G is the eventual replacement for FY-2E at 105º E.