Hurricane Joaquin moved slowly through the eastern Bahamas on 1 and 2 October 2015. ASCAT data from 1356 UTC, above, shows rain-flagged values near 90 knots not far from the storm center (Joaquin is a potent Category 4 Hurricane; its strongest winds are confined to within about 50 miles of the center).

Joaquin is embedded within a very moisture-rich environment, and that tropical moisture will move inland over the Carolinas and surrounding states over the weekend and produce heavy rains. The animation of MIMIC Total Precipitable Water, above, shows a corridor of very high total precipitable water just offshore of the Carolinas at the end of the animation, ready to shift inland.

Water Vapor Imagery, below, shows a strong trough over the northern Gulf of Mexico. This trough is serving to move Joaquin out of the Bahamas, and it will also serve as a potent precipitation producer on the East Coast. Percent-of-Normal plots from NESDIS’s Blended Precipitable Water product shows a large region of nearly 200% of normal over South Carolina, and greater than 200% of normal over North Carolina and regions north and east. Flood Watches have been issued from northeast Georgia to southern New Jersey.

For the latest information on Joaquin, consult the National Hurricane Center. Additional information is available at the CIMSS Tropical Cyclones site, and in a previous Blog Post.

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The YouTube video embedded above shows all GOES-13 (GOES-East) Full Disk Water Vapor (6.5 µm) images for all of September 2015. The 10.7 µm Infrared window channel animation is shown below. Animations for GOES-15 (GOES-West) are at the bottom.

GOES-13 animations show more tropical activity over the Atlantic, as expected from climatology, during September compared to August.

The GOES-15 animations show many tropical cyclones in both the eastern and central Pacific Ocean. Indeed, 2015 ranks as the most active year for the central Pacific for Tropical Cyclones (Hurricane Oho, now south of Hawaii, is the 12th named storm of the year).

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Joaquin reached Category 1 hurricane intensity on the morning of 30 September 2015 (NHC advisories). An eye structure was becoming apparent on a 1259 UTC Microwave (85 GHz) image from the SSMIS instrument on the DMSP-18 satellite (above).

The GOES-13 (GOES-East) satellite was placed into Rapid Scan Operations (RSO) mode, providing images as frequently as every 5-7 minutes. Visible (0.63 µm) images (below; also available as an MP4 movie file) showed a number of convective bursts during the day, with a few overshooting tops.

GOES-13 Infrared (10.7 µm) images (below; also available as an MP4 movie file) showed that cloud-top IR brightness temperatures associated with these convective bursts were in the -80º to -90º C range (violet colors). An organized eye structure was beginning to appear on the IR images at the end of the day.

===== 01 October Update =====

The ASCAT Scatterometer on board METOP-A sampled the eastern half of Joaquin shortly after 0230 UTC on 1 October, as shown below. Hurricane-force winds were observed 20-30 miles away from the storm center; tropical storm-force winds extended about twice as far out.

Joaquin intensified into a Category 4 hurricane late in the day on 01 October (ADT intensity plot) as the storm slowly moved of the warm sea surface temperature and high ocean heat content waters in the vicinity of the Bahamas. Joaquin became the first Category 4 hurricane to move though the Bahamas in October since 1866 (Capitol Weather Gang blog).  A fairly persistent but rather ragged-appearing eye was seen on GOES-13 Infrared (10.7 µm) images (below; also available as an MP4 movie file). Once again, the well-defined eye structure was more evident on DMSP SSMIS microwave imagery.

GOES-13 Visible (0.63 µm) images (below; also available as an MP4 movie file) showed a continuation of the development of convective bursts with overshooting tops in the eyewall region of the hurricane.

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Tropical Storm Joaquin over the Tropical Atlantic is forecast to move northward off the East Coast of the United States during the week of 28 September to 3 October. The toggle above shows Suomi NPP VIIRS 11.45 µm Infrared imagery and Day/Night Band 0.70 µm visible imagery (illuminated by a near-Full moon) at 0642 UTC or 1:42 am local time on 29 September. The presence of northerly deep-layer wind shear (image below from the CIMSS Tropical Cyclones site; animation of GOES-13 IR images) causes the strongest convection to be displaced to the south of the surface circulation, and a small cloud swirl (the low-level circulation center of Joaquin: magnified image) is apparent in the night-time visible imagery near 26.7º N, 70.3º W, northwest of the strongest convection.

Analyses of Total Precipitable Water, below, from Morphed Microwave Data, show the storm forming in an environment rich in moisture. Note also the generous moisture amounts in the northeastern Gulf of Mexico. Joaquin is forecast to move northward off the East Coast of the United States. As it moves, the storm will draw with it abundant moisture.

A week-long animation of GOES-13 Water Vapor imagery, above, shows Joaquin developing over the tropical Atlantic in a region that was initially a large upper-level low pressure system.

The animation above shows GOES-13 10.7 µm Infrared imagery centered on the latitude/longitude point for each of the 6-hour-interval advisories issued by the National Hurricane Center during Joaquin’s first two days (click here for an animation without a map). The slow increase in organization, symmetry and high cold cloud tops is apparent. Note also that outflow to the north is occurring at the end of the animation, suggestive of a relaxation in northerly wind shear.

For the latest information on Joaquin, consult the National Hurricane Center and the CIMSS Tropical Cyclones site.

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