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As of the May 19th, 2017, release, Week 3-4 outlooks precipitation outlooks are experimental, whereas the temperature outlooks are operational. Both are issued Friday between 3pm & 4pm Eastern Time.
HOME> Outlook Maps> Week 3-4 Outlooks

Week 3-4 Outlooks
Valid: 04 Nov 2017 to 17 Nov 2017
Updated: 20 Oct 2017

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Temperature Probability

Week 3-4 Outlooks - Temperature Probability
Precipitation Probability

Week 3-4 Outlooks - Precipitation Probability

Click HERE for information about how to read Week 3-4 outlook maps

Prognostic Discussion for Week 3-4 Temperature and Experimental Precipitation Outlooks
NWS Climate Prediction Center College Park MD
300PM EDT Fri Oct 20 2017

Week 3-4 Forecast Discussion Valid Sat Nov 04 2017-Fri Nov 17 2017

The global tropics appear to be coming alive recently, with an active Madden-Julian Oscillation (MJO) currently entering the West Pacific concurrent with the ongoing La Nina watch. Further possible tropical impacts on the extratropics exist with the forecast recurvature of Typhoon Lam during the next few days that could yield downstream amplification of flow over the CONUS before the forecast period. Dynamical model guidance during Week 3-4 and evolution from the anticipated Week-2 pattern are the primary drivers of this outlook, with some adjustment for lagged empirical impacts from a robust MJO event in Phase 5 at the time of forecast issuance.

Dynamical model guidance is mixed with its representation of the mid-level circulation, lowering confidence for this outlook. The most consistent features across the forecast guidance are anomalous 500-hPa ridging off the northeastern U.S. and Canadian Maritimes and anomalous troughing in the vicinity of the Aleutians. Across the CONUS the CFS features ridging west of the Rockies and troughing through the Great Lakes, with this general solution tied mostly to an amplified Week-4 pattern. Conversely, the ECMWF and JMA feature weak troughing over the West with the ridging in the east being closer to the Atlantic coastline than the CFS. The ECMWF and JMA each are more stable during Week-4 than the CFS, and lack the amplification of the latter model. SubX model guidance is mixed with its 500-hPa height representations, with the multi-model mean looking nothing like any of the three primary Week 3-4 ensemble suites, further muddying the potential circulation perspective. Generally the ECMWF and JMA models are favored here for their greater consistency with the Week-2 outlook, as the GEFS/CFS appear to be outliers in retrograding anomalous troughing from the Great Lakes into the West late in Week-2.

The temperature outlook features the highest probabilities across northern Alaska, where above-normal values associated with anomalous southerly flow are anticipated, in addition to decadal trends being substantially positive. High probabilities of above-normal temperatures are also forecast across the Northeast where anomalous ridging is generally favored among ensemble guidance. Above-normal temperatures are also favored in the Southwest from model consensus. There are some suggestions of increased odds for cold air outbreaks in the Northern Plains, while the current MJO state strongly tilts odds colder from the Upper Mississippi Valley through Great Lakes. The MJO implications are at odds with the dynamical model guidance, such that equal chances is forecast for these areas, and probabilities for anomalous warmth were reduced in the eastern Great Lakes relative to dynamical model guidance.

Dynamical model guidance is generally forecasting drier-than-average conditions across the entirety of the CONUS, with the exception of the JMA which suggests enhanced moisture from the Northern Plains through Great Lakes and up the East Coast. This JMA prediction of anomalously wet conditions in these areas closely mirrors anticipated conditions from empirical guidance based on the MJO approaching the West Pacific. Above-normal precipitation is forecast focused on the Great Lakes given the JMA and MJO implications for the forecast, with equal chances forecast along the East Coast due to spatial differences between the moisture source in this guidance. Below-normal precipitation is forecast across much of the West through the Lower Mississippi Valley in line with continental flow that is implied by dynamical model guidance.

Anomalously warm SSTs continue to persist around Hawaii, and this pattern is anticipated to continue into the Week 3-4 period. Therefore, above-normal temperatures are favored in this outlook. Dynamical model precipitation forecasts are mixed across the islands, with little in the way of an anomalous mid-level circulation, resulting in equal chances being forecast for precipitation.

Temperature Precipitation
Hilo A80 EC
Kahului A80 EC
Honolulu A80 EC
Lihue A80 EC

Forecaster: Daniel Harnos

The next week 3-4 outlook will be issued on Friday, Oct 27, 2017

These outlooks are based on departures from the 1981-2010 base period

These are two category outlooks and differ from official current three category outlooks currently used for the monthly and seasonal forecasts.

The shading on the temperature map depicts the most favored category, either above-normal (A) or below-normal (B) with the solid lines giving the probability ( >50%) of this more likely category (above or below).

The shading on the precipitation map depicts the most favored category, either above-median (A) or below-median (B) with the solid lines giving the probability ( >50%) of this more likely category (above or below).

In areas where the likelihoods of 2-week mean temperatures and accumulated precipitation amounts are similar to climatological probabilities, equal chances (EC) is indicated.

As of May 19, 2017, the temperature outlook is operational, while the precipitation outlook is still experimental

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Page last modified: May 19 2017
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