NOAA Monthly Drought Outlook – February

During the past 30-days, widespread drought improvement was depicted by the Drought Monitor across much of the Southwest, in parts of the Northwest, south-central and northern Plains, and northern New England.

Although the core D3-D4 drought area of the Four Corners region has improved (shrunk) the past few weeks due to cold and unsettled weather that raised WYTD basin average precipitation and SWC (as of Jan. 31) to above normal values, long-term deficits remained, and actual relief from these short-term improvements remain uncertain until the spring snowmelt begins.

In contrast, dryness and drought expansion was limited to parts of the north-central Rockies (eastern Idaho, southern Wyoming, northern Colorado) and southern sections of Texas and Florida.

Abnormal dryness and drought (D1) was rare in the eastern two-thirds of the Nation, confined to small areas in northern and southern Texas, central North Dakota, and southeastern Florida.

An El Niño Watch remained in effect (as of Jan. 10), with El Niño expected to form and continue through the Northern Hemisphere spring 2019 (a 65% chance). However, regardless of the above normal SSTs, the atmospheric circulation over the tropical Pacific has yet shown clear evidence of coupling to the ocean, but late winter and early spring tend to be the most favorable months for coupling, so forecasters still believe weak El Niño conditions will emerge shortly.

But given the timing and that a weak event is forecast, significant global impacts are not anticipated during the rest of the winter, even if conditions were to form. The next ENSO update will be available on Feb. 14.

The Monthly Drought Outlook (MDO) valid for February 2019 predicts continued improvement in the Southwest (southern California and Four Corners Region) where above normal precipitation is expected, especially during the first half of February, and February is normally wet in western portions of the Southwest.

Persistence is forecast for the Northwest; although unsettled (wet) weather is expected during the first week of February, drier weather is predicted for the remainder of the month, thus limiting both improvement and deterioration.

Farther east, the small D1 in southern Texas is short-term, and above normal rainfall during the first half of February should eliminate it. In southern New Mexico and northern Texas, however, the drought is long-term, and with the past 60-day precipitation less than half of normal, it would take significant totals for improvement, hence persistence.

The D1 in North Dakota is frozen in place until the spring thaw, buried under a foot of snow with sub-zero readings. After recent rains and some improvement in southeastern Florida, the remaining D1 along the coast should linger as 6-month deficits remained, and drier weather is predicted there during February.

Elsewhere, no development is anticipated throughout the eastern two-thirds of the lower 48 States as normal to wet conditions prevailed.

Long-term hydrologic drought is expected to persist across the southeastern Alaskan Panhandle as the odds favor subnormal February precipitation. With the El Niño Watch continuing, drought is anticipated to continue across the leeward sides and possibly develop at some windward locations in the Hawaiian Islands. With mixed February precipitation signals for Puerto Rico, the two small D1 areas were left to persist.

West forecast confidence is moderate in the Northwest, moderate to high in California, desert Southwest, and Four Corners region

• In the West, a relatively wet and cold weather pattern the past 30-days brought a decent increase to the WYTD (since Oct. 1) basin average precipitation and Snow Water Content (SWC) in the Southwest, especially to California, Nevada, and the Four Corners region, where most basins were near or above normal as of Jan. 31.
• Basin averages also increased across middle sections of the West (from Oregon eastward to Wyoming), but most remained somewhat below normal.
• To the north (Washington eastward to Montana), no change or a slight decrease in basin average precipitation and SWC occurred as mostly subnormal precipitation fell.
• Overall, however, the WYTD basin average precipitation and SWC were generally in good shape, with the lowest average basin precipitation (70-75% of normal) located in central Idaho, and the lowest average basin SWC (about 50%) was found in western Oregon and southern New Mexico as of January 31.
• As a result, the USDM responded with widespread improvements during the past month in the desert Southwest, California, Great Basin, and Four Corners region, and in portions of the Northwest.
• Some slight deterioration was made in central Idaho, southern Wyoming, and northern Colorado where subnormal precipitation fell during the past 60-days.
• Since February (and winter) is climatologically wet for the Far West, especially since precipitation begins to decrease during the spring while temperatures rise, this month can provide a lot toward how well the Water Year ends up. This is particularly true in California where coastal areas normally receive 17-26% of their annual precipitation.
• Forecast-wise, the 7-day quantitative precipitation forecast (QPF) depicts a robust wet storm for the West, especially in California; the 6-10 day ERF favors below-normal precipitation and temperatures in the Far West but above-normal precipitation in the Rockies; the 8-14 day ERF keeps the cold air in place but enhances precipitation odds in the Southwest; and the updated February LLF tilts toward above-normal precipitation in the Southwest and central Rockies.
• All of these factors suggest continued improvement for California, the central Rockies, and the Four Corners region.
• In contrast, a cold but drier forecast at the medium and 1-month periods in the Northwest, plus lower WYTD basin average precipitation and SWC than basins to the south, point more toward persistence than improvement. Enough precipitation, however, should fall (as snow) during February that should limit drought development in the Northwest and northern Rockies.

High Plains forecast confidence is moderate to high.

• The small area of long-term drought (D1) in central North Dakota should persist until the spring thaw to see if enough moisture from snow melt entered the soil, especially since February (winter) is a dry time of year.
• A blanket of 4-12 inches of snow covered the frozen soils of the Dakotas where the D0 and D1 areas were located. Colorado and Wyoming were discussed in the West region.
• An area to watch in the future was western Nebraska where 30- and 60-day precipitation was less than half of normal – but close to normal at 90-days. Since this is the dry time of year, however, deficits were small, and the forecasts all tilted wet at all time scales.

South forecast confidence is medium to high.

• The South is nearly drought free, except for a few small D1 areas in extreme northern Texas Panhandle and extreme southern Texas.
• A dry climatology, long-term deficits, and short-term dryness (less than half of normal precipitation the past 60-days) favors drought persistence in northern Texas, although the ERFs favor above-medium precipitation (but dry QPF and 1-month LLF = EC).
• In contrast, a wetter pattern in southern Texas in the short- and medium-terms and last week of February (1-month precipitation LLF = EC), plus the D1 is short-term, tilts the odds toward improvement by the end of February.
• Elsewhere, with near to above-normal precipitation anticipated at most time scales and no D0 elsewhere, development is not expected in the South.

Midwest forecast confidence is high.

• There is no drought (D1-D4) over the Midwestern at this time, except for a small area of D0 in northwestern Minnesota that is buried under snow and frozen in place.
• With most locations recording a wet 2018, much of the region blanketed by snow, well above-normal precipitation falling the past 30-days, and all forecasts (from 7-day QPF to 1-month LLF) favoring above-normal precipitation, no drought development is anticipated for the Midwest.
• The spring thaw will determine if enough snow or moisture was left to remove D0 in Minnesota.

Southeast forecast confidence is low to moderate.

• Across the Southeast, only southeastern Florida was experiencing any degree of dryness or drought, and much of this was reduced (improved) when 3-5 inches of rain fell across most of this area during January 20-26.
• Although the El Niño development favors above-normal precipitation here, the short and medium-range forecasts hint at subnormal rainfall and above-normal temperatures, the monthly update had EC for precipitation and good odds for above normal temperatures, and February is climatologically dry, hence persistence for the remaining D1 area.

Northeast forecast confidence is high.

• At present, there is no abnormal dryness and drought over the Northeast. With much of the Northeast blanketed in snow, the past 30-days of precipitation were much above normal, numerous stations observed one of the top five wettest years on record in 2018, the 7-day QPF, 6-10 and 8-14 day ERFs, and favorable chances for above normal February precipitation, drought development is not expected anywhere.

Alaska and Hawaii forecast confidence is moderate to high; moderate for Puerto Rico.

• Moderate to severe drought continues along the southern Alaska Panhandle. As this is primarily a long-term hydrologic drought, and that the updated February precipitation outlook favors subnormal amounts, the drought should continue to the end of February despite slight odds for above normal precipitation the first third of February.
• In Hawaii, subnormal precipitation is typically expected during an El Niño, and with an El Niño Watch currently ongoing during their normal wet winter season, moisture conditions have recently declined, with drought on the leeward sides and D0 across the windwards. This drier pattern is expected to continue during February, so persistence and development is favored for the islands.
• In Puerto Rico, short-term dryness has developed, but signals from dynamical models were mixed, and that it is their normal dry season, thus persistence was drawn for the existing two small D1 areas.