February 2017 Review

(On or around the first Monday of each month I’ll review the previous month’s weather over the CONUS. These posts aren’t meant to be especially insightful, but rather to provide a basis of useful maps and other graphs to refer back to when appropriate.)

The following maps show a quick overview of the dynamics averaged over most of February.

The maps below show, in order: the total jet (1a) and the anomalous jet (1b) over the globe; the anomalous 500 hPa heights (1c) over the globe and the anomalous surface temperature (1d) and precipitation (1e) over the CONUS during February.

Fig. 1a: 250 hPa Jet
Fig 1b: Anomalous 250 hPa Jet
Fig. 1c: 500 hPa Height Anomalies
Fig. 1d: Temperature Anomalies
Fig 1e: Precipitation Anomalies

 

Most of the country ended up warm, largely as predicted in my February forecast post. My precipitation forecast was pretty far off though, with significant rain along the West Coast and a small deficit in the southeastern CONUS.

March 2017 Forecast

(This is the second in a series of monthly forecasts, which I will update on (roughly) the last Monday of each month. Each of these posts will be paired with a short retrospective of the past month, which will function as less of an analysis and more of a place to put maps/graphs for future reference.)

February has turned out to be mostly as expected; very warm in the east and less warm in the west. The million dollar question, then, is what happens next month?

Midlatitude Teleconnections

Figure 1, below, shows the AO, NAO, and PNA archives and CFS forecasts for the next three months. I’ve marked March for easy referencing. Visually, the CFS forecast averaged over March seems to yield a fairly neutral AO and NAO, and a negative PNA.

A regime characterized by a negative PNA is often a signal for warmth over the Southeast and cold over the Northwest CONUS.

Figure 1: Teleconnection indices and CFS forecasts

Tropics

The CFS has had a significant MJO event in the forecast for the past two weeks, forecast to begin over the next week. An MJO in its early phases and moving eastward with significant amplitude would favor cold in the eastern and central CONUS and cool in the northwest during the first part of March. The CFS forecast shows weak ENSO forcing and low wave activity through the next 3 months, which implies that the MJO is the dominant forcing mechanism (similar to last month’s forecasts).

The CFS

A 28 day average from the CFS shows warmth over the central CONUS, cold in the Pacific Northwest, and fairly neutral in most other places.

The March 2017 Forecast

Eastern CONUS: near normal temperatures, perhaps a bit below in northern New England and the Delmarva area.

Central CONUS: anomalously warm.

Western CONUS: Pacific Northwest is likely to be anomalously cold, but south of that will probably be near normal.

The PNA is forecast to go negative

The Pacific/North American pattern is forecast to go quite negative over the next month. Take a look at the CFS forecast below.

PNA forecast from the CFS

A negative PNA implies ridging over the east and troughing over the west, which would extend the warmth we’ve seen along the East Coast this winter. Predictably, this corresponds with a CFS temperature forecast that shows precisely that, as well as some incredible warmth over eastern Europe and western Asia.

CFS temperature forecast

If this warmth keeps up during the next few weeks, it’s possible that grapes will begin growing for the season in the East. About half of the nights at the end of February have temperatures at or below freezing in DC, and the possibility of a March frost is quite high. This could have a negative impact on wine yields if the vineyards can’t keep their temperatures high enough.