30 Day Narrative

107 
FXUS07 KWBC 201231
PMD30D
Prognostic Discussion for Monthly Outlook
NWS Climate Prediction Center College Park MD
830 AM EDT Thu Jun 20 2019
30-DAY OUTLOOK DISCUSSION FOR JULY 2019
For the month of July, a weak El Nino is predicted to continue. There is a 66% 
chance of El Nino continuing through Northern Hemisphere summer, and a 50%-55% 
chance that El Nino will persist through the upcoming fall and winter seasons. 
For discussion of sea-surface temperature anomalies, as well as subsurface 
anomalies, lower and upper-level winds, and convective anomalies, please refer 
to CPC's Seasonal Outlook message for July-Sept. Following a brief period of 
interference from westward-moving modes of tropical variability, the 
Madden-Julian Oscillation (MJO) signal has renewed its eastward propagation and 
the enhanced convective phase is now over the Maritime Continent. Linkages 
between the MJO and CONUS impacts are generally weak in July, so the MJO is not 
forecast to play a significant role in the U.S. monthly temperature and 
precipitation outlooks. Multiple bouts of heavy rain over the past 30-45 days 
led to very high soil moisture and flooding over much of the Great Plains and 
Mississippi Valley. The July 2019 outlooks are based primarily on dynamical and 
statistical model guidance, the latest available official CPC temperature and 
precipitation outlooks for Week-2 and Weeks 3/4, the ongoing El Nino, very high 
soil moisture, heavy rainfall observations during the past 30-days, and July 
climatology.
The monthly temperature outlook indicates that above normal temperatures are 
favored across Alaska, ranging from 33%-40% odds in the northeast part of the 
state to over 60% odds in the southwest part of the state. Contributing factors 
include above normal sea-surface temperatures near the coast, strong historical 
temperature trends, Week-2 and Weeks 3/4 temperatures, most of the NMME model 
suite, and available statistical tools. Above normal temperatures are also 
favored from the West Coast of the contiguous U.S. to near the Continental 
Divide, and across the Gulf Coast and Atlantic Coast states. Probabilities for 
upper-tercile temperatures peak between 40%-49%. Support for this relative 
warmth comes largely from the NMME PAC (Probability Anomaly Calibration), and 
to a somewhat lesser extent most of the remaining inputs of the NMME dynamical 
model suite, in addition to the IMME, statistical models including the CAS 
(Constructed Analog on Soil moisture), historical trends, and the latest Weeks 
3/4 temperature outlook. Below normal temperatures are favored across a broad 
region of the Central CONUS, from Kansas, Oklahoma and northern Arkansas north 
and east into the Upper Great Lakes region. Probabilities for anomalously cool 
temperatures peak between 40%-49%. A significant contributor to these predicted 
below normal temperatures is the very high soil moisture (95th percentile or 
greater) across this area, with approximately half of this region at or above 
the 99th percentile. This broad expanse of near-saturated, or saturated, soils 
has been the result of frequently recurring heavy rainfall. During the past 
30-days, rainfall amounts ranged from 2-8 inches or more above normal. Viewed 
from a slightly different perspective, percent-of-normal precipitation ranged 
from 150%-400% of normal (locally greater). Lower-tercile temperatures are 
favored over the Central CONUS by a majority of models and statistical tools, 
but the exact placement and size of this area of anomalously cool temperatures 
is uncertain. Elsewhere, Equal Chances (EC) of above, near, and below normal 
mean temperatures are forecast.
The monthly precipitation outlook indicates that wetter-than-normal conditions 
are favored from southwestern Alaska northeastward across the Central Interior, 
with maximum probabilities ranging from 40%-49%. This is supported primarily by 
a majority of the last 9 days of CFS runs and the uncalibrated NMME, but also 
the NMME PAC, both GFDL models (FLOR and CM2.1), and to a lesser extent, the 
latest Weeks 3/4 precipitation outlook. Upper-tercile precipitation is also 
favored over a large portion of the Central CONUS, as far south as Texas. As 
was the case in Alaska, maximum probabilities range from 40%-49%. Of the 
statistical tools, the CAS bears the closest resemblance to this predicted 
pattern of upper-tercile precipitation, which also looks fairly similar to 
recent observations of both heavy rainfall and very high soil moisture. The CFS 
precipitation anomaly forecast for July lends some support to this area of 
anomalous wetness. However, it predicts the lion's share of the rainfall to be 
focused farther west, over the Pacific Northwest, the Northern Intermountain 
Region, and the Northern and Central Rockies. A majority of input models for 
the NMME generally predict this corridor of wetter-than-normal conditions, 
though there are variations on the overall theme. The NASA, CMC2 Canadian 
model, and the IMME also extended the favored area of above normal rainfall 
farther west as indicated by the CFS. Finally, there is a slight tilt in the 
odds for drier-than-normal conditions across most of the Alaska Panhandle, and 
west-central portions of the Gulf Coast region. These areas have modest support 
from the CFS, CAS (CONUS), NCAR, GFDL FLOR, and the CMC2 Canadian model. July 
climatology also provides weak support for the relative dryness in the 
west-central Gulf Coast region. Elsewhere, Equal Chances (EC) of above, near, 
and below normal precipitation are favored.
FORECASTER: Anthony Artusa
The climatic normals are based on conditions between 1981 and 2010, following
the World Meteorological Organization convention of using the most recent 3 
complete decades as the climate reference period.  The probability anomalies
for temperature and precipitation based on these new normals better represent
shorter term climatic anomalies than the forecasts based on older normals.
An updated monthly outlook... for Jul will be issued on Sun June 30 2019
These outlooks are based on departures from the 1981-2010 base period.
$$