CIMSS Satellite Blog

MIMIC Total Precipitable Water, 1500 UTC 19 January — 1400 UTC 22 January [click to enlarge]

A storm forecast to produce near-record snowfalls over the Nation’s Capitol has started to move up the east coast of the United States. Snow that will fall requires two things: abundant moisture, and cold temperatures. The MIMIC Total Precipitable Water Product, shown above for the 72 hours ending at 1400 UTC on 22 January (Source) shows the circulation of the developing storm drawing moist air northward. Similarly, the toggle below shows the NESDIS Operational Blended Total Precipitable Water Product (Source, a product that ‘blends’ Total Precipitable Water observations from GPS and GOES-Sounder*). Significant moistening is apparent over the southeastern part of the United States.

NESDIS Blended Total Precipitable Water, 1400 UTC on 21 and 22 January 2016 [click to enlarge]

Cold air is also present. MODIS Land Surface Temperature imagery from 0731 UTC on 22 January shows temperatures (in clear regions) colder than -5º C southward into Virginia. Dewpoints in this region are colder than -10º C. High Pressure over the East Coast is promoting cold air damming along the Appalachians as well.

MODIS-based Land Surface Temperature, 0722 UTC and the 0900 UTC HPC Surface Analysis, 22 January 2016 [click to enlarge]

Suomi-NPP carries on board two instruments that provide vertical profiles of moisture and temperature in the atmosphere, the CrIS and the ATMS. NUCAPS Soundings combine information from those two soundings. NUCAPS Soundings sites from the early morning Suomi NPP Pass on 22 January are shown superimposed on the MODIS Land Surface Image below; five sounding sites (highlighted in red) were selected: northwest of Boston, over western Connecticut, New York City, Washington DC and central Virginia. These soundings all have common attributes: They are dry (although the vertical profiles from DC and Virginia show the most moisture: ~0.3″ of total precipitable water), they are too warm near the surface (detection of low-level inversions from satellite data is difficult) and they show lapse rates at mid-levels that suggest vigorous ascent may be possible. The 0600, 1200 and 1800 UTC Soundings from KIAD (below) also show dry air (at least initially: total precipitable water doubled from 0.24″ at 1200 UTC to 0.49″ at 1800 UTC) and steep mid-level lapse rates.

MODIS-based Land Surface Temperature, 0722 UTC and 0700 UTC NUCAPS Sounding Sites (in green) and the 0900 UTC HPC Surface Analysis, 22 January 2016 [click to enlarge]

Rawinsonde from KIAD (Dulles International Airport) at 0600, 1200 and 1800 UTC on 22 January 2016 [click to enlarge]

[Check back later; More to come!!]

*As the GOES-13 Sounder is now off-line due to an anomaly (Link), the principle driver of this product is now GPS data.

from CIMSS Satellite Blog http://ift.tt/1NpYzQi