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Before I get to the impact of COVID 19 on forecasting, I wanted to show this image I took Friday evening of what's known as an orphan anvil north of my place in Portland, Maine. You can clearly see the anvil top of what was once a thunderstorm. However, the updraft that caused it was shut down and so was the warm moist air that was driving the storm. The base is gone but the anvil aloft still retains its shape. Choked off from its life support, the anvil is in a decaying state and will soon dissipate as its pulse fades away and the storm perishes. A beautiful but harsh reality of what it takes to sustain a thunderstorm.

The COVID virus has impacted just about everything you can imagine and that includes the weather. The World Meteorological Organization (WMO) is concerned about the increasing impact of the COVID-19 pandemic on the quantity and quality of weather observations and forecasts, as well as atmospheric and climate monitoring. Below is an article from the World Meteorological Society on how the virus is impacting weather data and potentially the quality of forecast models.


The World Meteorological Organization (WMO), is concerned about the increasing impact of the COVID-19 pandemic on the quantity and quality of weather observations and forecasts, as well as atmospheric and climate monitoring. Meteorological measurements taken from aircraft have plummeted by an average 75-80% compared to normal, but with very large regional variations; in the southern hemisphere, the loss is closer to 90%. Surface-based weather observations are in decline, especially in Africa and parts of Central and South America where many stations are manual rather than automatic

WMO’s Global Observing System serves as the backbone for all weather and climate services and products provided by the 193 WMO Member states and territories to their citizens. It provides observations on the state of the atmosphere and ocean surface from land-, marine- and space-based instruments. The data is used for the preparation of weather analyses, forecasts, advisories and warnings.

According to WMO Secretary-General Petteri Taalas, "National Meteorological and Hydrological Services continue to perform their essential 24/7 functions but are facing increasingly severe challenges as a result of the Coronavirus pandemic, especially in developing countries”

“The impacts of climate change and weather-related disasters continue and as we approach the Atlantic hurricane season, the COVID-19 pandemic poses an additional challenge, and may exacerbate multi-hazard risks at a single country level. Therefore it is essential that governments pay attention to their national early warning and weather observing capacities,” said Taalas.

Large parts of the observing system, for instance its satellite components and many ground-based observing networks, are either partly or fully automated. They are therefore expected to continue functioning without significant degradation for several weeks, in some cases even longer. But if the pandemic is prolonged, then missing repair, maintenance and supply work, and missing redeployments become of increasing concern.

Overall, the decrease in the number of commercial flights has resulted in a reduction of around 75-80 percent in observations of meteorological measurements from aircraft platforms. The loss is closer to 90% in some of the most vulnerable areas where other surface-based observations are scarce, i.e. in the tropics and in the Southern Hemisphere.

Some countries are launching extra radiosondes to partly mitigate the loss of aircraft data. This is taking place especially in Europe under coordination by the European Meteorological Services Network (EUMETNET). Radiosondes are flown on weather balloons and transmit measurements critical meteorological variables back to the ground during their flight from the surface up to altitudes of 20 to 30 kilometers.

In most developed countries, surface-based weather observations are now almost fully automated.

However, in many developing countries, the transition to automated observations is still in progress, and the meteorological community still relies on observations taken manually by weather observers and transmitted into the international networks for use in global weather and climate models.

“These human links in the observation and data delivery chain are highly vulnerable to current lockdowns and mandatory teleworking policies, and we have seen a substantial reduction in the current availability of surface pressure observations compared to the pre-COVID-19 baseline (January 2020), especially over Africa and parts of Central and South America,” said Lars Peter Riishojgaard, Director, Earth System Branch in WMO’s Infrastructure Department.

“The coronavirus pandemic clearly demonstrates the importance of having resilience in the observing system,” said Riishojgaard.

“The overall impact of the missing observations probably will not be fully assessed and understood until well after the virus outbreak is over. However, at this point, none of the global Numerical Weather Prediction (NWP) centres have reported catastrophic losses in skill due to the lack of observations,” he said.

“Aircraft observations are a good illustration of this. They are universally considered to be among the most important contributors to NWP skill. However, the current crisis reminds us that aircraft observations are data of opportunity that may come and go due to circumstances that are beyond any control of the WMO community. Having complementary systems and maintaining the possibility to mitigate such losses will be important also once the COVID-19 crisis belongs to history, hopefully in the not too distant future,” states Riishojgaard.

WMO is also monitoring the exchange of observations from the marine observing systems, which provide critical information from the 2/3 of the earth’s surface that are covered by the oceans.

The ocean observing systems also rely on a high degree of automation, and most parts are expected to continue to be working well for a period of up to several months. However, drifters and floats will need to be redeployed, moorings will need to be serviced and ship observing systems will need to be maintained, calibrated and resupplied. Over time a gradual decline in observation numbers may therefore be expected, and this will continue until the necessary supply and maintenance activities can resume. At this point, the most significant impact is on the Voluntary Observing Ships (VOS) program, where a reduction in data availability of about 20% compared to normal levels is seen.

In addition, there are over 10 000 manned and automatic surface weather stations, 1 000 upper-air stations, 7 000 ships, 100 moored and 1 000 drifting buoys, hundreds of weather radars and 3 000 specially equipped commercial aircraft measure key parameters of the atmosphere, land and ocean surface every day.


On that note, we switch gears to shower and thunderstorm chances Saturday. They will exist but it appears the greatest intensity and coverage will be in the morning and perhaps again later in the afternoon. While a few strong storms are possible the biggest concern will be heavy rains in spots due to weak steering currents and abundant moisture. No doubt there will be some dry hours for outdoor activities but passing clouds should keep highs in the upper 70s to low 80s. It will be muggy with dew points in the upper 60s.

Father's Day still looks to be decent. After scattered shower and thunderstorm chances early Saturday night forcing pushes east just in time for Sunday. Under partly sunny skies highs should hit the low 80s with slightly lower humidity levels. The first full day of summer looks to be a good one. Make your Father's Day plans outside! Roll weather....TS

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