GOES-15 Visible Channel (0.62 µm) imagery (click to play animation)

GOES-15 visible imagery from after sunrise on 7 August 2014 shows the approach of Pacific Hurricane Iselle towards the ‘Big Island’ of Hawai’i. Orographically-forced clouds are apparent on the northern shores of the entire Island chain, and significant rains are possible as the storm passes — Flash Flood Watches are up for the entire state until 6 AM (HST) Saturday.

There are products available to assess how much rain could potentially fall. For example, the Orographic Rain Index (ORI) uses Total Precipitable Water, 850-mb winds from the Global Forecasting System (GFS) Model and high-resolution topography to determine how much rain might occur if winds are orthogonal (or nearly so) to topography. A real-time display of the product is here.

GOES-15 Water Vapor Channel (6.5 µm) imagery at 1200 UTC 7 August (click to enlarge)

The moisture environment surrounding Iselle appears to be less hostile today. The water vapor imagery from 1200 UTC, 6 August, showed significant dry air between the storm and Hawaii. That dry air is not so pronounced today (above). Both images cover the same domain and use the same enhancement. Hurricane Julio is apparent in the eastern part of the image from 7 August, above; that storm is forecast to remain north of the island chain.

GOES-15 Infrared Channel (10.7 µm) imagery (click to play animation)

GOES-15 Infrared Channel (10.7 µm) imagery from 7 August shows periodic deep convection forming in the northern half of Iselle’s circulation, north of an eye-like structure in the infrared. The plot of overshooting tops around Iselle (here) shows that overshoots are being detected again after a relatively quiescent period yesterday and the day before.

Morphed Microwave Imagery of Iselle (click to enlarge)

Microwave data can be used to measure the intensity of precipitation in/around a tropical cyclone, and the MIMIC-TC pages show animations for active storms. The animation above shows Iselle’s slow weakening — as measured by the intensity of the precipitation in the eyewall.

View only this post Read Less

Suomi NPP True Color Imagery of Iselle 2245 UTC 5 August (click to enlarge)

Hurricanes Iselle and Julio in the central and eastern Pacific Ocean, respectively, are forecast to affect the Hawaiian Islands in the coming days. The True-Color image of Iselle, above, derived from data from Suomi NPP downloaded at NOAA’s X/L Antenna in Hawaii from 2245 UTC on 5 August shows asymmetries in the storm that testify to the presence of dry air ahead of the storm that is wrapping into the circulation from the southwest. (Compare the storm’s presentation at 2245 UTC 5 August, above, to the more circular one 24 hours earlier, at 2300 UTC on 4 August (from this post), when dry air was not impinging on Iselle’s side). The toggle below, between the 11.35 µm imagery, at 1113 UTC and the Day Night Band at the same time shows the ragged appearance of the storm. Coldest cloud tops were -63 C.

Suomi NPP 11.35 µm Infrared and Day Night Band Visible Imagery at 1113 UTC 6 August (click to animate)

GOES-15 water vapor imagery, below, shows the region of dry air in between Iselle and the Hawaiian Islands. Such warm values (the yellow in the enhancement) in the water vapor channel mean the top of the moist layer is low in the troposphere. Of course, water vapor imagery does not quantify the amount of moisture in the atmosphere, it only identifies where the top of the moist layer is. Total Precipitable Water (TPW) can be estimated, with accuracy, using microwave imagery, and the MIMIC TPW for the 72 hours ending at 1100 UTC on 6 August (from this site), below, shows very dry air in advance of the Iselle. Further Information and advisories on Iselle can be found at the website of the Central Pacific Hurricane Center in Honolulu (Link).

GOES-15 6.5 µm Water Vapor Imagery, 1200 UTC 6 August 2014 (click to enlarge)

Morphed Integrated Microwave Imagery at CIMSS – Total Precipitable Water (MIMIC-TPW) for 72 hours ending 1100 UTC 6 August 2014 (click to enlarge)

Hurricane Julio is also obvious in the TPW animation above, following close on the heels of Iselle. Julio will not have as much dry air to deal with, compared to Iselle, as it moves west-northwestward. However, Julio will move farther north than Iselle, and the cooler water under Julio’s projected track (and somewhat stronger shear) should limit its strength as it moves north of the Hawaiian Islands. (Click here the forecast track for Julio valid 6 August 2014; Click here for the forecast track for Iselle).

GOES-15 0.62 µm Visible Imagery, 00 UTC 6 August 2014, of Julio (click to enlarge)

Visible imagery from GOES-15, above, at 00 UTC on 6 August, shows that Julio (at that time still a tropical storm) is circular in appearance and lacking an identifiable eye. A burst of convection is apparent over the center, however. The infrared imagery from 00 UTC and 12 UTC, below, shows little change in Julio. It nevertheless strengthened to become the fifth hurricane of the eastern Pacific season.

GOES-15 10.7 µm infrared Imagery, 00 and 12 UTC 6 August 2014, of Julio (click to animate)

The toggle above of the 10.7 µm imagery shows an obvious overshooting top at 1200 UTC. Overshooting tops have been correlated with storm intensification. The plot below shows where overshooting tops were identified at 1330 UTC on 6 August (taken from this site). Plots showing the number of overshooting tops as a function of time are available for Iselle and Julio.

Infrared 10.7 µm Imagery and auto-detected Overshooting Tops, 1330 UTC 6 August 2014 (click to enlarge)

View only this post Read Less

Terra MODIS True Color Imagery (click to play animation)

As happened in 2011, an algae bloom is ongoing over Lake Erie. The current bloom has contaminated at least one water intake for Toledo, Ohio’s municipal water supply with microcystin, a cyanobacter that when ingested can damage the liver and nauseate people. (There is also significant danger to pets). A series of true-color images (from 4 July, 1 August and 4 August) taken from the MODIS Today website, above, (combining visible channels at 0.6465 µm [red], 0.5537 µm [green] and 0.4656 µm [blue]) shows changes in the water color over the past month. (Image Source: MODIS Today) Some changes are apparent over western Lake Erie that are associated with the toxic bloom.

The algal growth is more readily apparent in the false-color imagery below. This red/green/blue image is constructed with 2.1143 µm imagery as ‘red’, 0.8567 µm imagery as ‘green’ and 0.6465 µm imagery as ‘blue’. The animation including scenes from 4 July, 1 August and 4 August shows dramatic growth between 1 and 4 August. Near-infrared channels — such as 0.8567 µm — are sensitive to energy reflected by algae.

Terra MODIS True Color Imagery (click to play animation)

A series of True-Color images for six days this Spring/Summer is here. The increase in algae in the western part of Lake Erie is apparent, but it seems that the outbreak this year is less wide-spread than the outbreak in October of 2011. A series of False-Color images is here.

[Update, 5 August 2014: Toledo’s water supply has been deemed safe to drink]

View only this post Read Less

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

GOES-15 0.63 µm visible channel images (above; click to play animation; also available as an MP4 movie) revealed the presence of mesovortices within the eye of Category 4 Hurricane Iselle on 04 August 2014. Mesovortices are sometimes seen in the eye and eyewall of tropical cyclones that are going through a period of intensification.

Before sunrise, a 10:30 UTC comparison of GOES-15 10.7 µm IR and TRMM TMI 85 GHz microwave images from the CIMSS Tropical Cyclones site (below) showed that Iselle was beginning to exhibit the appearance of an annular hurricane; note that the ring of high-intensity rainfall within the eyewall was much larger on the microwave image than the “cloud-free” eye that was seen on the IR image.

GOES-15 10.7 µm IR and TMI 85 GHz microwave images

========================= Update, 5 August 2014 ==========================

Hourly imagery from 1300 UTC on 4 August to 1300 UTC 5 August shows Iselle maintaining a generally westward track. Cloud-top temperatures have warmed over the 24 hours shown, however, and the eyewall is becoming less distinct. Iselle’s path has been over SSTs that are progressively cooler. Further weakening is expected today.

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

Suomi NPP overflew Iselle late in the afternoon of the 4th, and a true color image of the storm is shown below (Image Source: NOAA Hawaii X/L Antenna). A mesovortex can be identified in the eye in this high-resolution image.

Suomi NPP True Color Imagery of Iselle, 2300 UTC 4 August 2014 (click to enlarge)

View only this post Read Less