Friday, August 10, 2012

ECMWF Winter Forecast Looking Good for East Coast

ECMWF Winter Temperature Map
Interpretation by Brett Anderson of Accuweather

ECMWF Winter Precipitation Map
Interpretation by Brett Anderson of Accuweather
The latest ECMWF appears to be showing a scenario typical of El Nino conditions over the upcoming winter, with above normal precipitation over parts of the Gulf Coast and dry conditions over the Northwest.

Brett Anderson of Accuweather writes posts for Canadian weather, but also releases maps of the ECMWF model from time to time. Due to the ECMWF's strict policy of releasing maps, the only legal way to display the seasonal ECMWF forecasts is by 'interpretations' such as his shown above.

The ECMWF is projecting a high latitude blocking pattern setting up, shown by a notable warmer than normal airmass settling in over areas close to Greenland as well as above normal temperatures in Alaska. The Alaskan warmth indicates a ridge in the Gulf of Alaska may be present. This ridge can incite cooler weather to flow into the US, and was not present last year when heat dominated the winter.
Additionally, warmth near Greenland enhances the possibility of a continuation of the negative NAO that has been seen recently. While it is not a sure sign of a negative NAO, the chances based on this warmth appear to be enhanced.

Precipitation-wise, an El Nino signal of a dry Northwest and wet Gulf Coast are present, but not a wet East Coast. In fact, this forecast indicates that a portion of the Northeast may actually end up slightly drier than normal. While the rest of the model does seem fairly trustworthy, this part does not seem right to me. A moderate El Nino appears likely this winter, and this, combined with a favorable NAO and stratospheric conditions, would make for a snowy Northeast.

It will all become much clearer with time, but for now there remains a few pieces of the puzzle that don't fit quite right.

You can read Brett Anderson's blog and ECMWF posts by clicking here.


Ernesto Dissipates; Redevelopment in East Pacific Likely

Tropical Storm Ernesto dissipated today as it encountered landfall in Mexico, but as it emerges into the open waters of the East Pacific, redevelopment appears likely.

The NHC has outlined this system with a 60% chance of redevelopment into a tropical cyclone. There will be some obstacles in the way, however, with shearing already above 30 knots in Ernesto's path and upper level divergence at a pretty high value. Despite this, the system is maintaining a good form by satellite standards, and it would only take additional convection and strengthening to get the system where it needs to go.

The SHIPS forecasting model has it reaching above 100 knots of wind speed, as seen below.

                TIME (HR) 0 6 12 18 24 36 48 60 72 84 96 108 120
V (KT) NO LAND 20 17 16 16 19 30 43 56 67 78 90 100 106

Note: 'No Land' refers to the strength it can reach with no land interaction.